Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33
DOI 10.1186/s12970-017-0189-4

REVIEW

Open AccessInternational society of sports nutrition
position stand: nutrient timing
Chad M. Kerksick1, Shawn Arent2, Brad J. Schoenfeld3, Jeffrey R. Stout4, Bill Campbell5, Colin D. Wilborn6, Lem Taylor6,
Doug Kalman7, Abbie E. Smith-Ryan8, Richard B. Kreider9, Darryn Willoughby10, Paul J. Arciero11, Trisha A. VanDusseldorp12,
Michael J. Ormsbee13,14, Robert Wildman15, Mike Greenwood9, Tim N. Ziegenfuss16, Alan A. Aragon17
and Jose Antonio18*

Abstract
Position statement: The International Society of Sports Nutrition (ISSN) provides an objective and critical review
regarding the timing of macronutrients in reference to healthy, exercising adults and in particular highly trained
individuals on exercise performance and body composition. The following points summarize the position of the ISSN:
1. Nutrient timing incorporates the use of methodical planning and eating of whole foods, fortified foods and dietary
supplements. The timing of energy intake and the ratio of certain ingested macronutrients may enhance recovery andtissue repair, augment muscle protein synthesis (MPS), and improve mood states following high-volume or intense exercise.
2. Endogenous glycogen stores are maximized by following a high-carbohydrate diet (8–12 g of carbohydrate/kg/
day [g/kg/day]); moreover, these stores are depleted most by high volume exercise.
3. If rapid restoration of glycogen is required (< 4 h of recovery time) then the following strategies should be considered:a) aggressive carbohydrate refeeding (1.2 g/kg/h) with a preference towards carbohydrate sources that have ahigh (> 70) glycemic indexb) the addition of caffeine (3–8 mg/kg)c) combining carbohydrates (0.8 g/kg/h) with protein (0.2–0.4 g/kg/h)
4. Extended (> 60 min) bouts of high intensity (> 70% VO2max) exercise challenge fuel supply and fluid regulation,
thus carbohydrate should be consumed at a rate of ~30–60 g of carbohydrate/h in a 6–8% carbohydrateelectrolyte solution (6–12 fluid ounces) every 10–15 min throughout the entire exercise bout, particularly in those
exercise bouts that span beyond 70 min. When carbohydrate delivery is inadequate, adding protein may help
increase performance, ameliorate muscle damage, promote euglycemia and facilitate glycogen re-synthesis.
5. Carbohydrate ingestion throughout resistance exercise (e.g., 3–6 sets of 8–12 repetition maximum [RM] using
multiple exercises targeting all major muscle groups) has been shown to promote euglycemia and higher glycogenstores. Consuming carbohydrate solely or in combination with protein during resistance exercise increases muscle
glycogen stores, ameliorates muscle damage, and facilitates greater acute and chronic training adaptations.
6. Meeting the total daily intake of protein, preferably with evenly spaced protein feedings (approximately every 3 hduring the day), should be viewed as a primary area of emphasis for exercising individuals.
7. Ingestion of essential amino acids (EAA; approximately 10 g)either in free form or as part of a protein bolus ofapproximately 20–40 g has been shown to maximally stimulate muscle protein synthesis (MPS).
(Continued on next page)* Correspondence: ja839@nova.edu
18
Department of Health and Human Performance, Nova Southeastern
University, Davie, FL, USA
Full list of author information is available at the end of the article© The Author(s). 2017 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

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8. Pre- and/or post-exercise nutritional interventions (carbohydrate + protein or protein alone) may operate as aneffective strategy to support increases in strength and improvements in body composition. However, the size
and timing of a pre-exercise meal may impact the extent to which post-exercise protein feeding is required.
9. Post-exercise ingestion (immediately to 2-h post) of high-quality protein sources stimulates robust increases in MPS.
10.In non-exercising scenarios, changing the frequency of meals has shown limited impact on weight loss andbody composition, with stronger evidence to indicate meal frequency can favorably improve appetite andsatiety. More research is needed to determine the influence of combining an exercise program with alteredmeal frequencies on weight loss and body composition with preliminary research indicating a potential
benefit.
11.Ingesting a 20–40 g protein dose (0.25–0.40 g/kg body mass/dose) of a high-quality source every three to 4 happears to most favorably affect MPS rates when compared to other dietary patterns and is associated withimproved body composition and performance outcomes.
12.Consuming casein protein (~ 30–40 g) prior to sleep can acutely increase MPS and metabolic rate throughout
the night without influencing lipolysis.
Keywords: Position stand, Exercise, Nutrition, Timing, Macronutrients, Performance, Micronutrients, Nutrients

Background
The International Society of Sports Nutrition (ISSN) published the first position stand devoted to the practice ofnutrient timing in 2008 [1]. Consequently, this paper has
been accessed approximately 122,000 times. In the pastnine years, multiple lines of research have explored questions directly related to the timing of nutrients that further
refines information about evidence-based nutritional recommendations. Nutrient timing involves the purposefulingestion of all types of nutrients at various times
throughout the day to favorably impact the adaptive response to acute and chronic exercise (i.e., muscle strengthand power, body composition, substrate utilization, andphysical performance, etc.). Importantly, much of theinterest and available research centers upon outcomes
related to those who are regularly competing in someform of aerobic or anaerobic exercise; however, nutrient
timing strategies may offer favorable outcomes for nonathletic and clinical populations.
From a historical perspective, nutrient timing was first
conceptualized in the 1970s and 1980s with the initial
work that examined the effects of increased carbohydrate feedings on glycogen status and exercise performance [2, 3]. Ivy and colleagues [4] were one of the firstgroups to illustrate that carbohydrate timing can influence post-exercise rates of glycogen resynthesis. While
strategies surrounding carbohydrates were the first to be
explored, there has been a growing body of researchover the last several years that has examined the effectof protein and amino acids, with and without carbohydrates, as a nutrient timing strategy [1, 5].
Due to the volume of research investigating this concept, the need to revise and update the original document is evident. In line with the previous publication,

the updated version focuses on timing considerations fortwo macronutrients: carbohydrates and proteins. Whenconsidering fat, research examining a specific timing
question has yet to take shape. As researchers continue
to explore the manipulation of fat and carbohydrate
intake (e.g., ‘train low, perform high’) [6], it is possiblethat future recommendations may include the timing of
fat intake. It is exciting to note that new research has
begun to examine the impact of timed calcium (a micronutrient) intake on its ability to affect markers of bone
resorption during prolonged cycling exercise [7–10] andanimal models have explored the potential role of timing
iron intake on various health-related outcomes [11, 12].
This research, however, is in its infancy and more studies
are needed to better understand these implications. Furthermore, future versions of this position stand mayneed to consider expanding the document’s scope to include other ergogenic aids. For instance, research related
to caffeine [13], creatine [14–16] and bicarbonate [17]have indicated that timing may affect the acute andchronic response to exercise. Therefore, the primary
purpose of this updated position stand is to refine recommendations made related to the timed consumptionof carbohydrates and protein and how this can potentially affect the adaptive response to exercise.
To expand upon the previous version, the current position stand now discusses research and recommendations
related to meal patterns, timing, and distribution of protein, meal frequency and nighttime eating. It is the contention of the ISSN that these topics also fall under thepurview of nutrient timing. Additionally, non-athletic or
specialized clinical populations may also derive benefit
from these strategies. Throughout each section, an attempt has been made to first highlight outcomes from

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

acute studies before discussing those derived from training
studies spanning several weeks or more.
Carbohydrate

Moderate to high intensity (e.g., 65–80% VO2max) endurance activities as well as resistance-based workouts(e.g., three to four sets using ~ 6–20 repetition maximum [RM] loads) rely extensively upon carbohydrate asa fuel source; consequently, endogenous (liver: ~ 80–
100 g and skeletal muscle: 300–400 g) glycogen storesare of critical importance. It is well documented thatglycogen stores are limited [18, 19] and operate as a predominant source of fuel for up to a few hours during
moderate to high-intensity aerobic exercise (e.g., 65–
85% VO2max) [20, 21]. During resistance training, performing six sets of 12RM leg extension exercise has beenshown to reduce glycogen stores in the vastus lateralis
by 39% [22]. Importantly, as glycogen levels decline, theability of an athlete to maintain exercise intensity andwork output also decreases [19] while rates of tissue
breakdown increase [23, 24]. The simplest guideline to
maximize endogenous glycogen stores is for a highperformance athlete to ingest appropriate amounts ofcarbohydrate relative to their intensity and volume oftraining. Recommended daily intakes of carbohydrate
are commonly reported to be 5–12 g/kg/day, with theupper end of this range (8–10 g/kg/day) reserved for
those athletes that are training at moderate to high intensities (≥ 70% VO2max) upwards of 12 h per week
[25–27]. In the absence of considerable muscle damage,this carbohydrate intake level has been shown tomaximize glycogen storage. Percentage-based recommendations (60–70% carbohydrates of total daily caloric
intake) have fallen out of favor due to their inability toappropriately prescribe required carbohydrate amounts
in athletes eating high amounts of food or in those who
may be following a restricted energy intake.
It should be noted that most of the recommendations
for carbohydrate intake are based on the needs of endurance athletes, and in particular, male endurance athletes.
Moreover, studies have indicated that trained female athletes do not oxidize fat and carbohydrate at the samerates as males and may deplete endogenous glycogenstores to different degrees [28–31]. Perhaps those involved in strength-power sports need a lower intake ofcarbohydrate and instead should focus more on prioritizing their carbohydrate intake in the days leading up tocompetition, but more research is required as this topic
has been critically evaluated in a review by Escobar et al.
[32]. It should be noted that athletes often fail to meet
recommended amounts of energy and carbohydrate;
consequently [33], strategies to replenish carbohydrate
stores may take priority toprepare for maximal performance in the next competition.

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Endurance training

The first nutrient timing strategy centered solely upon
the strategic intake of carbohydrate as part of “carbohydrate loading” protocols in the days leading up to prolonged endurance competitions. Initial work by Karlsson
and Saltin in the 1970s reported that a period of highvolume exercise training while consuming limited
amounts of carbohydrates for three to four days followed
by a diet providing > 70% carbohydrate (~ 8 to 10 g/kg/day), while sharply reducing training volume, facilitatedsupersaturation of muscle glycogen and an improved
pace of training for more prolonged periods of time [3].
Sherman and colleagues [2, 34] also demonstrated success at maximizing intramuscular glycogen stores using
similar approaches. Alternatively, Bussau et al. [35] required study participants to ingest high-glycemic carbohydrate (10 g/kg/day) for one day after completing a
Wingate anaerobic capacity test which resulted in a near
doubling of baseline muscle glycogen concentrations. A
similar approach by Fairchild et al. [36] yielded similar
results and highlights the ability to forgo a “glycogen depletion” phase and instead to simply reduce training
volume for three to four days while simultaneously consuming a very high-carbohydrate diet (8–10 g/kg/day)for one to three days to maximize intramuscular glycogenlevels. Overall, the ability of carbohydrate loading strategies to rapidly increase and maximize muscle glycogenlevels is currently unquestioned, and many athletes andcoaches are encouraged to consider making use of such a
dietary regimen in the days leading up to a competitive
event, particularly if their activity will significantly deplete
endogenous skeletal muscle glycogen. It is important tomention that due to noted sex differences related tocarbohydrate metabolism and the supercompensation of
glycogen stores, female athletes may need to significantly
increase total caloric intake over these “loading days” toachieve effects similar to males [31].
The hours leading up to competition are often a highly
prioritized period of feeding and studies have indicatedthat strategic fuel consumption can help to maximize
muscle and liver glycogen levels. Carbohydrate feedings
during this time increase endogenous glycogen stores
while also helping to maintain blood glucose levels. Notably, Coyle et al. [19] reported that consumption of ahigh-carbohydrate meal 4 h before 105 min of cycling exercise at 70% VO2max after an overnight fast significantly
increased both muscle and liver glycogen while also increasing rates of carbohydrate oxidation and utilization ofmuscle glycogen. In addition to increasing stored glycogen, other studies have reported significant improvements
in aerobic exercise performance [37–39]. However, not all
studies have demonstrated a performance-enhancing effect. Nonetheless, it is commonly recommended to consume snacks or meals high in carbohydrate (1–4 g/kg/

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

day) for several hours before higher-intensity (≥ 70%
VO2max), longer duration (> 90 min) exercise. Additionally, and as a measure of practical importance, the need toingest a pre-exercise meal or snacks high in carbohydrate
goes up when the athlete has consumed relatively small
amounts of carbohydrate in the days leading up to a competition or has not allowed for appropriate amounts ofrest and recovery [20, 24].
In the final (< 4) hours before a competition, the athlete’s priority should still be to maximize or maintain optimal levels of muscle and liver glycogen. In this respect,
another priority becomes maintaining a favorable balance with the digestive system and avoiding the consumption of too much food or fluid before competition.
Practically speaking, many endurance events begin in
the early morning hours and finding an adequate balance between rest and fuel must be considered. In thisrespect, two studies have reported that solid or liquid
forms of carbohydrates similarly promote glycogen resynthesis allowing athletes more flexibility when selecting food sources [40, 41]. A certain degree of dogma still
clouds the recommendation to ingest certain types ofcarbohydrate, or avoid carbohydrate altogether, in the
final few hours before an event. The source of this practice stems from initial findings of Foster and colleagues[42] who reported a negative, hypoglycemic response tocarbohydrate ingestion directly preceding (< 60 min) exercise. From these findings, it has been surmised that excessive carbohydrate consumption, and in particularfructose consumption, in the initial hours before exercise
may negatively impact exercise performance perhaps
due to rebound hypoglycemia. Indeed, given the rise ininsulin due to carbohydrate ingestion coupled with upregulation of GLUT-4 transporters from the initiatedexercise stimulus, there may be a decrease, rather thanincrease, in blood glucose at the onset of activity that
could negatively impact performance. However, while anumber of athletes may be affected by this phenomenon,a study by Moseley et al. [43] demonstrated that any “rebound hypoglycemia” response is effectively negated bywhat would be the equivalent of a proper warm-up andthat shifting carbohydrate intake closer (15 min vs.
75 min) to when the exercise bout is scheduled to begin
can minimize the likelihood of these symptoms. A 1997
review by Hawley and Burke summarized the results ofseveral studies that provided some form of carbohydrate
at least 60 min before exercise. They found no adverse
impact on performance. In fact, multiple studies reported performance increases of 7–20% [44]. Moreover,
Galloway and colleagues [45] used a double-blind,placebo-controlled approach to compare performanceoutcomes related to ingestion of a placebo or a 6.4%
carbohydrate beverage either 30 min or 120 min before
a controlled bout of cycling at 90% peak power.

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Ingesting carbohydrate 30 min before exercise led togreater increases in exercise capacity. In contrast, twostudies were completed by Febrraio [46, 47] that required the ingestion of high or low-glycemic carbohydrates 30–45 min before completing bouts of exercisethat spanned 135–150 min at approximately 70%
VO2max. They concluded that performance was similar
for both types of carbohydrate.
The delivery of carbohydrate remains a priority once aworkout or competition commences. Most research has
employed study designs that integrate some form of continuous aerobic exercise, and within these studies it has
been consistently demonstrated that providing carbohydrate (230–350 mL of a 6–8% carbohydrate solution) at
regular intervals (every 10–12 min) can optimize performance and maintain blood glucose levels [48, 49].
Several studies have indicated that the pattern or timingof carbohydrate feedings surrounding endurance exercise may be important. For example, Fielding and colleagues [50] required cyclists to ingest the same dose ofcarbohydrate every 30 min or every 60 min over thecourse of a four-hour exercise bout. When carbohydrate
was ingested more frequently, performance was improved. Two contrasting papers that operate as extensions of this work include work by Schweitzer et al. [51]who concluded that preferentially delivering carbohydrate during the first or second half of a controlled cycling exercise bout offered no enhancement of
performance, while a similar study design by Heesch andcolleagues [52] indicated that providing carbohydrateconsistently throughout or in the latter half of a 2-h cycling exercise bout at 62% of peak power decreased thetime it took to cover a prescribed distance (10-km) whilecycling. It is important to realize that key differencessuch as the duration of the exercise bout, the nature of
the performance assessment (fixed distance vs. time-toexhaustion) and amount of carbohydrate that was delivered all differed between these studies and can help to
explain the differences in outcomes being reported.
A classic paper by Widrick et al. [53] examined theimpact of pre-exercise muscle glycogen status withcarbohydrate feeding throughout a prolonged bout of
exercise. Briefly, participants commenced a 70-km selfpaced time trial with high or low muscle glycogen levels,
which was then combined with either a carbohydrate(9% fructose) or placebo (non-caloric sweetener) beverage regularly (2.35 ml/kg/feeding every 10-km providing
a total of 1.5 g/kg/trial) throughout the exercise bout.
Increased power outputs were recorded when exercise
began with high muscle glycogen levels, and even greater
power was achieved when carbohydrate was frequently
provided throughout the exercise protocol. A similar
outcome was demonstrated by Febbraio and colleagues[54] where they required participants to complete four

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

carbohydrate feedings and exercise conditions in conjunction with a two-hour bout of steady-state (SS) cycling exercise at 63% of their peak power, followed by atime trial using a standardized load. The four feeding
conditions were: a) placebo beverage 30 min before anda 6.4% carbohydrate solution at a dosage of 2 g/kg
throughout SS exercise, b) a 25.7% carbohydrate solution
at a dosage of 2 g/kg 30 min before and placebothroughout SS exercise, c) a 25.7% carbohydrate solution
at a dosage of 2 g/kg before and a 6.4% carbohydrate solution at a dosage of 2 g/kg throughout SS, and d) a
6.4% carbohydrate solution at a dosage of 2 g/kg
throughout the SS exercise bout. As with the findings of
Widrick et al., it was determined that pre-exercise strategies to support glycogen or blood glucose levels increase
exercise performance when carbohydrate ingestion continued throughout the prescribed exercise bouts. Collectively, these findings somewhat prioritize carbohydrate
feeding during the exercise session and could lead someto argue that if pre-exercise carbohydrate feeding strategies are neglected, then delivering appropriate carbohydrate throughout an exercise bout may help offset thepotential for performance decrement. However, one mustcautiously explore this approach as to avoid overwhelming
the gastrointestinal system potentially leading tocramping and discomfort once exercise begins. In thisrespect one should consider the findings of Newell etal. [55] who had 20 well-trained, experienced cyclists
perform four different feeding conditions (no carbohydrate [0 g/h] control, 20 g/h, 39 g/h or 64 g/h) throughout completion of a two-hour cycling bout at 95%
lactate threshold (185 ± 25 watts) followed by completion of a standardized time trial. When carbohydrates
were ingested at a dosage of 39 or 64 g/h, time trial performance was significantly improved compared to thecontrol group. Importantly, no differences in performance
were found between these two feeding strategies suggesting that for those athletes who may not be able to toleratehigher doses of carbohydrates, a moderate regimen ofcarbohydrate feeding throughout a prolonged bout of exercise can still promote similar improvements in performance. Other important considerations related to thepotential ergogenic impact of carbohydrates have been
critically highlighted in recent reviews by Colombani et al.
[56] and later by Pochmuller et al. [57]. In both papers,
the authors contend that the ability of carbohydrate administration during bouts of exercise spanning less than
70 min to operate in an ergogenic fashion is largely mixed
in the literature. It was further suggested that not until exercise durations meet or exceed 90 min does the administration of a ~ 6–8% carbohydrate solution exert a
consistent ergogenic benefit particularly when exercise iscommenced in a fed state as opposed to the fasted statethat is so often studied in this body of literature.

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Whether or not these results translate to intermittent
sports remains to be thoroughly investigated. A 2011
review by Phillips and colleagues [58] supports the notion that carbohydrate administration throughout intermittent, team-sport activities improves certain types of
performance as well as general indicators of mental
drive and acuity, but evidence regarding benefits ofacute deviations in timing is still lacking. Clarke andcolleagues [59] tested the hypothesis that ingesting isovolumetric amounts of a carbohydrate-electrolyte solution either in two large volumes (7 mL/kg at 0 and
45 min of exercise) or more frequent (every 15 minover the entire course of a 75-min exercise bout) feedings of smaller volumes to achieve the same total dose
can favorably impact metabolic responses. No performance or capacity measurements were made, but the authors did report that either feeding pattern was able tomaintain glucose, insulin, glycerol, non-esterified fatty
acid, and epinephrine levels. More recently, Mizuno
and colleagues [60] concluded that timing the intake ofa carbohydrate gel (1.0 g/kg) did not impact the inflammatory response or exercise performance throughout
completion of two 45-min bouts of intermittent (4–16 km/h) running.
The recovery of lost muscle glycogen operates as a key
nutritional goal, and post-exercise ingestion of carbohydrate continues to be a popular and efficient nutrient
timing strategy to maximize replenishment of lostmuscle glycogen. In what is known as potentially the
first study to examine an actual nutrient timing question, Ivy and colleagues [61] showed that restoration ofmuscle glycogen was 50% faster and more complete overa four-hour post-exercise period when a carbohydrate
bolus (2 g/kg of a 25% carbohydrate solution) was delivered within 30 min versus waiting until two hours after
completion of a cycling exercise bout (70 min at 68%
VO2max followed 6 × 2-min intervals at 88% VO2max).
Subsequent work has since refined conclusions surrounding this topic, namely that the timing of postexercise carbohydrate administration holds the highest
level of importance under two primary situations: 1)
when rapid restoration of muscle glycogen is a primary
goal and 2) when inadequate amounts of carbohydrate
are being delivered. In light of these considerations,muscle glycogen levels can be rapidly and maximally
restored using an aggressive post-exercise feeding regimen of carbohydrates. Ingesting 0.6 to 1.0 g/kg bodymass within the first 30 min of completing a glycogendepleting exercise bout and again every two hours forthe next four to six hours [62, 63], has been shown topromote maximal glycogen replenishment. Similarly, favorable outcomes have also been shown when 1.2 g/kg
of carbohydrate were ingested every 30 min over a 3.5-hperiod [27, 64].

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

Outside of situations where rapid recovery is truly
needed, and daily carbohydrate intake is matching energy demands, the importance of timed carbohydrate
ingestion is notably decreased. However, in no situation
has timed carbohydrate ingestion been shown to negatively impact performance or recovery. If an athlete
participating in heavy exercise is not able, or even notsure if they will be able to appropriately consume therequired amounts of carbohydrate throughout the daythen the strategically timed ingestion of carbohydrate
may accelerate muscle glycogen re-synthesis. When
prolonged endurance exercise is completed, carbohydrate ingestion may also help promote a favorable hormonal environment [65, 66]. Finally, studies in elite
athletes undergoing high volumes of training haveshown that maximal glycogen levels are restored within
24 h if a diet contains ≥8 g/kg/day, and only moderatelevels of muscle damage are present [41]. In support,
Nicholas and colleagues [67] concluded that a daily
carbohydrate intake of 9–10 g/kg/day in six trained
men participating in soccer, rugby, hockey, or basketball, sufficiently replenished muscle glycogen following
consecutive days of prolonged (85–90 min), intense,
interval exercise.

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liver glycogen levels should first consist of following abrief period of reduced training volume in conjunction
with a high daily intake of carbohydrate (≥ 8 g/kg/day).
In the hours leading up to competition, glycogen levels
are best maintained or increased by consuming highcarbohydrate (1–4 g/kg/day) meals or snacks for several
hours before commencement of training or competition.
Athletes are encouraged to continue consuming small
amounts of a carbohydrate solution or small snacks(bars, gels, etc.) to maintain liver glycogen levels and tohelp prevent hypoglycemia. Ingestion of carbohydrate
during endurance type exercise maintains blood glucose
levels, spares glycogen [75], and will likely enhance
performance. Post-exercise consumption of carbohydrate
is necessary and in situations where minimal recovery
time is available, aggressive carbohydrate feeding is
recommended. Although preliminary, initial work inintermittent, high-intensity activities suggest that carbohydrate timing may support metabolic outcomes, while
performance results remain mixed, as do studies involving resistance exercise. For further inquiry, excellent reviews on the topic of carbohydrate and performance areavailable [20, 21, 48, 49, 76].

Resistance training

Carbohydrate + protein
Endurance training

Studies employing resistance exercise that examinedsome aspect of carbohydrate timing are limited. Multiple studies have demonstrated that resistance exercise
can significantly decrease muscle glycogen concentration [22, 68–70], though these decreases are modest incomparison to exhaustive endurance exercise. However,the provision of pre-exercise carbohydrate to individuals performing resistance-style exercise in a moderately
glycogen depleted state may not have an ergogenic effect.
To date, one study has indicated that carbohydrate administration before and during bouts of resistance exercise
can improve performance, but these ergogenic outcomes
were only seen in the second session of resistance exercise
performed on the same day [71]. In contrast, multiple
studies have failed to report an improvement in resistance
exercise performance [72–74]. One study involving preexercise and during exercise delivery of carbohydrate
throughout a bout of resistance exercise has been shownto minimize the loss of muscle glycogen. Briefly, study
participants were given a carbohydrate dose of 1.0 g/kg
pre-workout and a 0.5 g/kg carbohydrate every 10 min
throughout a 40-min resistance exercise bout and foundthat muscle glycogen losses were reduced by 49% whencompared to glycogen changes with ingestion of a placebo
drink; however, isokinetic muscle performance was not
influenced [73].
In reviewing all of the timing considerations related tocarbohydrate intake, strategies to maximize muscle andCarbohydrate + protein combinations are a traditional
strategy employed by endurance as well as strengthpower athletes to increase exercise performance, promote glycogen repletion, minimize muscle damage, andpromote a positive nitrogen balance. A small number ofstudies have examined pre-endurance exercise ingestionof carbohydrate + protein on performance as well as
metabolic outcomes, but very few have directly investigated the impact of altering the timing of when nutrientswere administered. Ivy and colleagues [77] recruited
trained cyclists to complete a three-hour bout of cycling
exercise at an intensity of 45–75% VO2max before exercising to exhaustion at 85% VO2max. In a crossoverfashion, participants ingested either a 7.75% carbohydrate
or a 7.75% carbohydrate + 1.94% protein solution. When
protein was added to carbohydrate, endurance was significantly improved. In a similar fashion, Saunders and colleagues [78] had participants cycle to exhaustion on two
separate occasions (75–85% VO2max) within 24 h while
ingesting a carbohydrate or a carbohydrate + protein solution throughout the exercise bout (1.8 mL/kg every
15 min) followed by a single bolus dose (10 mL/kg) immediately after exhaustion. The carbohydrate + protein
combination resulted in significantly improved performance as well as a reduction in muscle damage. The same
research group [79] used a nutrient gel and again reported
that ingestion of a carbohydrate (0.146 g/kg) + protein(0.0365 g/kg) combination throughout an exhaustive bout

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

of cycling exercise significantly improved cycling performance. While none of these studies directly examined a timing comparison, they all demonstrate that pre-exercise
administration of carbohydrate + protein combinations
can favorably impact endurance performance. Furthermore, the addition of protein (to carbohydrate) has beenshown to increase the speed of glycogen recovery when ashort recovery window is available or if sub-optimal
amounts of carbohydrate have been delivered and can also
help to reduce symptoms of muscle damage [80]. Notably,
no studies have demonstrated that addition of protein tocarbohydrate to a pre-exercise feeding in these amounts
may hinder exercise performance. Similarly, Rustad andcolleagues [81] reported that adding protein (0.4 g/kg/h)
to carbohydrate (0.8 g/kg/h) within 2 h of completing an
initial exhaustive bout of cycling exercise led to a significant increase in cycling performance the next morningwhen compared to ingesting just carbohydrate alone, thus
suggesting improved recovery.
To support recovery upon completion of exercise
bouts that can deplete stored fuels and may cause significant damage to the muscle tissue, post-exercise nutrient timing strategies are of great interest. Ivy et al. [82]required cyclists to complete a 2.5-h bout of cycling(65–75% VO2max) before consuming a combination ofcarbohydrate + protein (80 g carbohydrate + 28 g protein + 6 g fat) or two different doses (High: 108 g ofcarbohydrate + 6 g fat or Low: 80 g carbohydrate + 6 gfat) of carbohydrate immediately after and 2 h after
completing the exercise session. While timing was not
specifically investigated, the carbohydrate + protein
combination led to greater glycogen recovery during thefour-hour investigative window employed by the research team. These findings replicated previous findings[83] by this research group and led them to conclude
that the addition of protein favorably promoted earlyphases of glycogen recovery. Berardi et al. later published two similar studies [84, 85] that also showed thatthe provision of a combination of carbohydrate + protein facilitated greater recovery of muscle glycogen wheningested soon after the completion of a workout and before a subsequent endurance exercise bout.
As more research has been completed on the topic,
the potential benefits of adding protein have been questioned. For example, Jentjens and colleagues [63] failed
to show an improvement in muscle glycogen restoration
with a combination of carbohydrate (1.2 g/kg/h) + protein (0.4 g/kg/h) in comparison to ingesting only the
carbohydrate dose over a three-hour recovery period.
Howarth and colleagues [86] later came to a similar
conclusion regarding the addition of protein and extended these findings also to report that a higher dose ofcarbohydrate (1.6 g/kg/h) did not further promote glycogen resynthesis. Thus, it appears that protein addition

Page 7 of 21

augments glycogen recovery when carbohydrate ingestion is < 1.2 g/kg/h.

Resistance exercise

A small number of studies are available that examinedthe effect of ingesting carbohydrate + protein before resistance exercise. For example, Kraemer and colleagues[87] had participants ingest a combination of carbohydrate, protein, and fat or an isoenergetic maltodextrin
placebo for seven days before two consecutive days ofresistance exercise. On both occasions, the supplement
was ingested 30 min before beginning the exercise bout,and the multi-nutrient supplement significantly improved vertical jump power and the number of repetitions performed at 80% 1RM. A similar outcome wasreported by Baty and colleagues [88] where they had 34
males complete an acute bout of heavy resistance training (3 sets × 8 reps @ 90% 1RM) while consuming either
a carbohydrate (6.2% carbohydrate) or a carbohydrate +protein (6.2% carbohydrate + 1.5% protein) solution before, during, and after the exercise bout. While performance was not affected, significantly greater levels of
insulin and lower levels of cortisol were found when the
carbohydrate + protein combination was ingested. Moreover, markers of muscle damage (e.g., myoglobin andcreatine kinase) were reduced throughout the first 24 hof recovery when the carbohydrate + protein combination was consumed. These two studies provided a combination of carbohydrate + protein at some point before
the resistance exercise sessions, however these studies
were not designed to examine whether pre-exercise
feeding of carbohydrate + protein was responsible for
improved exercise performance or adaptations.
Tipton and colleagues [89] completed one of the firststudies to directly examine whether the timing of carbohydrates + EAA altered MPS rates. In this investigation,
research participants completed a single bout of lowerbody resistance exercise while ingesting the same combination of carbohydrate (35 g of sucrose) + 6 g EAA
either immediately before or immediately after completion of the exercise bout. Nutrient ingestion immediately
before the exercise bout increased MPS significantly
more than when the carbohydrate + EAA combination
was consumed after the resistance exercise session. A
few years later, however, Fujita and colleagues [90]attempted to replicate their study findings and instead
determined that MPS rates were similar between preexercise and post-exercise ingestion. While many people
use the Fujita paper to discount the pre-exercise period,
it should be noted that significant increases in MPS rates
occurred when nutrients were administered before andafter the resistance training bout in comparison to a
non-energetic control suggesting that nutrient delivery

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

itself, as opposed to timing of delivery, should be a larger
priority. White and colleagues [91] conducted a study to
specifically examine if timed ingestion of carbohydrate +protein timing influenced force production and markers
of muscle damage. For this study, 27 adult participants
ingested either a non-caloric sweetener or a carbohydrate (75 g) + protein (23 g) combination 15 min before
or 15 min after a bout of damaging resistance exercise
and found that neither the nutrients themselves, nor
their timing, influenced changes in force production or
blood levels of muscle damage markers. The results suggest that MPS rates can be acutely increased if a combination of carbohydrate + protein is consumed either
before or after, but changes in force production or
muscle damage may not be impacted by timed ingestionof a carbohydrate + protein combination.
The acute effect of ingesting a carbohydrate + protein
or EAA combination throughout resistance exercise has
been studied [92–96]; however, as with other time periods, no studies have truly examined the question oftiming. In this respect, a series of studies published byBird and colleagues [93–96] has investigated the influence of consuming either carbohydrate or carbohydrate + EAA on measures of acute performance,
hormonal responses and circulating levels of blood proteins associated with muscle damage. In the first study,
32 participants were randomized to ingest either a 6%
carbohydrate solution, a 6% carbohydrate solution + 6 g
of EAA or a non-nutritive placebo regularly throughout
a 60-min bout of resistance training. Findings from thisstudy indicated that serum cortisol levels were reduced
when either a 6% carbohydrate solution or a 6% carbohydrate + 6 g EAA solution were ingested in comparison
to a non-energetic placebo [94]. A later publication fromthis investigation reported that urinary muscle protein
breakdown markers were reduced by 27% when the
carbohydrate + EAA combination was consumed while
the placebo group experienced a 56% increase [95].
A later study by Bird et al. [93] used a ‘triphasic’ approach where they delivered a combination of carbohydrate + amino acids before, during and after a single
bout of resistance exercise. Using a crossover study design, participants also ingested a placebo that consistedof water flavored with a non-nutritive sweetener in similar volumes at the same times. They reported that delivering nutrients (versus none at all) did significantly
increase the volume of exercise completed and reduced
concentrations of serum proteins indicative of muscle
damage. Along these lines, Beelen and colleagues [92]also completed an acute study design that required study
participants to ingest in a fed state a carbohydrate + hydrolyzed casein protein combination at a dose of 0.15 g/
kg body mass before initiating a two-hour resistancetraining session and at 15-min intervals throughout the

Page 8 of 21

bout. Compared to placebo, the carbohydrate + protein
combination significantly lowered rates of protein breakdown and increased fractional synthetic rates of muscle
proteins by 49 ± 22%, resulting in a five-fold increase inprotein balance.
Chronic studies examining carbohydrate + protein
ingestion with resistance training have also been conducted. Bird et al. [96] examined the impact of consuming
a 6% carbohydrate +6 g EAA solution throughout bouts(two bouts per week) of resistance exercise over a 12-weekperiod. Urinary concentrations of 3-methyl-histidine werereduced by 26% when the carbohydrate + EAA combination was ingested, which was significantly different fromthe 52% increase observed in the placebo group. Also, thecross-sectional areas of type I, IIa, and IIb muscle fibers
increased in comparison to the changes seen when solutions containing either just carbohydrate (6%) or EAA(6 g) were ingested. While these findings are encouraging,
the studies are limited by the dosage of EAA provided asother studies have indicated that higher EAA doses (up to12 g) may maximally stimulate MPS. As such, future research in this area should identify if different doses of
EAA or combining a carbohydrate solution with varying
doses of intact proteins consumed during resistance exercise bouts can further impact performance and resistancetraining adaptations. In this respect, when sufficient protein is supplied, it may be that carbohydrate has no additional adaptive benefit. As an example of this, Hulmi andcolleagues [97] showed no benefit in resistance training
adaptations when a combination of maltodextrin carbohydrate (34.5 g) + whey protein concentrate (37.5 g) was
ingested immediately following each workout of a regimented 12-week resistance training protocol as compared
to consuming the protein supplement alone. Cribb andHayes [16] randomized trained male participants to ingest
identical amounts of carbohydrate + protein + creatine either immediately before and immediately after resistancetraining or in the morning and evening during a 10-weekresistance-training program. Changes in strength, hypertrophy, and body composition were assessed, and significant increases in lean body mass, 1RM strength, type II
muscle fiber cross-sectional area, and higher muscle creatine and glycogen levels were found when the supplements
were consumed immediately before and after workouts as
opposed to consuming them in the morning and evening.
While seemingly different than the results of Hulmi, theseresults indicate that close temporal ingestion of a combination of carbohydrate + protein + creatine may afford favorable outcomes relative to resistance training
adaptations and does not necessarily state that a carbohydrate + protein combination is better than simply
ingesting similar amounts of protein. Furthermore,
Cribb and Hayes also provided creatine while the otherstudies did not, which has been shown in multiple

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

investigative scenarios to augment the muscular adaptations seen while resistance training [98–100].
Carbohydrate + protein combinations while resistancetraining are suggested to augment muscle development
via an increased insulin response. Specifically, insulin
promotes anti-catabolic effects in muscle [101], thereby
shifting protein balance to favor anabolism. However,insulin-mediated effects on reducing proteolysis plateau
within a range of ~ 15–30 μIU/mL [102, 103], and theselevels are achieved by consuming a 45 g bolus of whey
protein isolate alone [104]. This would suggest that
post-workout carbohydrate supplementation likely exerts
minimal influence from a muscle development standpoint provided adequate protein is consumed. Towards
this end, Staples and colleagues [105] compared theimpact of a carbohydrate (50 g maltodextrin) + protein(25 g whey protein) combination on rates of MPS observed after completing a single bout of lower-bodyresistance exercise. The authors reported that the carbohydrate + protein combination failed to further stimulate increases in MPSwhen compared to ingesting only
protein. Furthermore, Rasmussen and colleagues [106]found no difference in amino acid balance when 35 g ofsucrose + 6 g of EAA were ingested either 1 h or 3 hafter completion of a bout of resistance training.
In summary, ingestion of carbohydrate + protein (oramino acids) in close temporal proximity to or throughout both endurance and resistance exercise may operate
as an effective strategy to favorably affect performanceof a subsequent exercise bout as well as adaptations
from regular bouts of training. Towards this end, enhancements in endurance performance, as well as improved recovery of reduced muscle glycogen have also
been consistently reported when carbohydrate + protein
combinations have been consumed surrounding exercise
bouts, particularly if lower quantities of carbohydrate areconsumed. However, when optimal carbohydrate is delivered the impact of adding protein (irrespective ofwhen it is provided) appears to offer little to no additional benefit on endurance or resistance exercise performance as well as the recovery of reduced muscle
glycogen. Much like the work on glycogen recovery,
studies involving resistance training and optimization ofadaptations seen from resistance training also point towards a higher priority being given towards the total
amount of protein consumed during the day. Therefore,
if total protein needs are met, the importance of adding
carbohydrate (and even more so in a timed fashion) may
be limited. A key point of discussion, however, lies withwhether or not total energy needs are also being met,
particularly in athletes undergoing large volumes oftraining and more so in those athletes that have highamounts of lean as well as body mass. In these situations, it certainly remains possible that the addition ofPage 9 of 21

carbohydrate to a protein feeding may help the athlete
achieve an appropriate energy intake, which certainly
may go on to impact the extent to which adaptations
occur. For athletes who are likely combining resistancetraining sessions with sport-specific training, theprovision of carbohydrate + protein in close proximity
to each session would be warranted in order to optimize
recovery for subsequent bouts and adaptation.
ProteinEndurance training

The role of amino acids and/or protein consumption
with regards to endurance exercise is not well known.
Pasiakos and colleagues [107] had cyclists complete twodifferent bouts of exercise (60 min at 60% VO2peak)
while ingesting a solution containing 10 g of the EAA
with varying levels (1.87 or 3.5 g) of leucine. In response
to EAA ingestion and independent of leucine content,
MPS rates and several signaling proteins related tomuscle hypertrophy (i.e., Akt, mTOR, p70s6k, etc.) weresignificantly increased. While more research certainly
needs to be conducted to better identify the potential
impact and role of protein intake before endurance exercise, the priority for an endurance athlete in the hours
leading up to competition should be focused on appropriate carbohydrate intake to fully maximize endogenous
production of glycogen.
Resistance training

As with endurance exercise, the majority of studies thathave employed some form of protein or amino acidingestion before bouts of resistance exercise have done
so in conjunction with an identical dose during the postexercise period as well. For example, Tipton andcolleagues [108] used an acute resistance exercise andfeeding model to report that MPS rates were similar
when a 20-g dose of whey protein was ingested immediately before or immediately after a bout of lower bodyresistance training. Andersen et al. [109] were one of thefirst to examine the effects of ingesting protein immediately before and immediately after resistance exercise
over multiple weeks. In this study, participants were randomized to ingest either 25 g of a protein blend (16.6 gwhey, 2.8 g casein, 2.8 g egg white, 2.8 g glutamine) or
maltodextrin immediately before and immediately after
each workout over the course of 14 weeks. In the groupthat consumed the protein-amino acid blend, type I andtype II muscle fibers experienced a significant increasein size. Also, the protein-amino acid group experienced
a significant increase in squat jump height while nochanges occurred in the carbohydrate group. Using asimilar study design, Hoffman and colleagues [110] hadcollegiate football players who had been regularly
performing resistance-training ingest 42 g of hydrolyzed

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

collagen protein either immediately before andimmediately after exercise, or in the morning andevening over the course of ten weeks of resistancetraining. In this study, the timing of protein intake did
not impact changes in strength, power and bodycomposition experienced from the resistance-training
program.
When examining the discrepant findings, one must
consider a few things. First, the protein source in the
Hoffman et al. study was mostly a collagen hydrolysate(i.e., not the highest quality protein source); moreover,changes in body composition were determined by dualenergy x-ray absorptiometry (DEXA), which does nothave the same sensitivity to identify subtle hypertrophic
alterations [111] as the histochemical approaches
employed by Andersen et al. [109]. Finally, the study
participants in the Andersen et al. study were consuming
approximately 20% more calories per day (~ 36.6 kcals/
kg/day) than the participants in the Hoffman study (whoconsumed only 30.4 kcals/kg/day) which offers somelevel of explanation for the different outcomes reported
in these two studies. More recently, Schoenfeld and colleagues [112] published the first longitudinal study to
directly compare the effects of ingesting 25 g of whey
protein isolate either immediately before or immediately
after each workout. For this study, 21 resistance-trainedmen (> 1-year experience) followed a 10-week, three day
per week whole-body heavy resistance training program(3 sets of 8 – 12RM) and concluded there were no differences in muscle mass or strength changes when thedose of whey protein was consumed pre- or posttraining. This study is significant as it is the first investigation to attempt to compare pre versus post-workout
ingestion of protein. The authors raised the questionthat the size, composition, and timing of a pre-exercise
meal may impact the extent to which adaptations areseen in these studies. However, a key limitation of thisinvestigation is the very limited training volumes thesesubjects performed. The total training sessions over the
10-week treatment period was 30 sessions (i.e., total of
30 h assuming each session lasted 1 h). One would
speculate that the individuals who would most likely
benefit from peri-workout nutrition are those who train
at much higher volumes. For instance, American collegiate athletes per NCAA regulations (NCAA Bylaw 2.14)
are limited to a maximum of 4 h per day and a 20-htraining schedule per week [113]. Thus, the averagecollege athlete trains more in two weeks than most subjects train during an entire treatment period in studies
in this category.
In one of the only studies to use older participants,
Candow and colleagues [15] assigned 38 men between
the ages of 59–76 years to ingest a 0.3 g/kg protein dose
before or after each workout over the course of a 12-

Page 10 of 21

week resistance training program. While protein administration did favorably improve resistance-training adaptations, the timing of protein (before or after workouts)
did not invoke any differential change. An important
point to consider with the results of this study is the
sub-optimal dose of protein (approximately 26 g of whey
protein) versus the known anabolic resistance that has
been demonstrated in the skeletal muscle of elderly individuals [114]. In this respect, the anabolic stimulus froma 26-g dose of whey protein may not have sufficiently
stimulated muscle protein synthesis or have been of appropriate magnitude to induce differences between conditions. Clearly, more research is needed to determine if
a greater dose of protein delivered before or after aworkout may exert an impact on adaptations seen during resistance training in an elderly population.
Limited studies are available that have examined theeffect of providing protein throughout an acute bout of
resistance exercise, particularly studies designed to explicitly determine if protein administration during exercise
was more favorable than other times of administration.
As discussed previously as part of the carbohydrate +protein section, research by Bird and colleagues [94, 95]
had participants ingest a 6-g solution of EAA throughout a bout of resistance exercise and reported increases
in post-exercise insulin levels and reductions in urinarylevels of 3-methyl-histidine and serum levels of cortisol.
However, when examined over the course of 12 weeks,
the increases in fiber size seen after ingesting a solution
containing 6 g of EAA alone was less than when it was
combined with carbohydrate [96].
The post-exercise time period has been aggressively
studied for its ability to heighten various training outcomes. While a large number of acute exercise and nutrient administration studies have provided multiple
mechanistic explanations for why post-exercise feeding
may be advantageous [115–119], other studies suggest
this study model may not be directly reflective of adaptations seen over the course of several weeks or months[120]. As highlighted throughout the pre-exercise protein
timing section, the majority of studies that have examinedsome aspect of post-exercise protein timing have done sowhile also administering an identical dose of protein
immediately before each workout [16, 109, 110, 121]. Of
these studies, protein [109] or carbohydrate + protein [16]consumption immediately before and immediately after
resistance exercise has been shown to positively affectresistance training adaptations. These results, however, are
not universal as Hoffman et al. [110] reported no impactof timing when 42 g of hydrolyzed collagen protein wasingested before and after several weeks of resistance timing. Of note, participants in the Hoffman study were all
highly-trained collegiate athletes who reported consuming
a hypoenergetic diet. Candow et al. [15] reported that sub-

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

optimal doses of whey protein ingestion (0.3 g/kg, ~ 26 g)
in elderly males (59–76 years) before or after resistancetraining workouts exerted no impact on strength and bodycomposition changes. As mentioned previously, it is possible that the dose of protein may not have been an appropriate amount to properly stimulate anabolism.
In this respect, a small number of studies have examined the impact of solely ingesting protein after exercise.
As discussed earlier, Tipton and colleagues [108] used anacute model to determine changes in MPS rates when a
20-g bolus of whey protein was ingested immediately
before or immediately after a single bout of lower-bodyresistance training. MPS rates were significantly, andsimilarly, increased under both conditions. Until recently, the only study that examined the effects of postexercise protein timing in a longitudinal manner was the2001 work of Esmarck et al. [122]. In this study, 13 elderly men (average age of 74 years) consumed a small
combination of carbohydrates (7 g), protein (10 g) andfat (3 g) either immediately (within 30 min) or 2 h after
each bout of resistance exercise done three times per
week for 12 weeks. Changes in strength and muscle size
were measured, and it was concluded that ingesting nutrients immediately after each workout led to greater improvements in strength and muscle cross-sectional area
than when the same nutrients were ingested 2 h later.
While interesting, the inability of the group that delayed
supplementation but still completed the resistance training program to experience any measurable increase inmuscle cross-sectional area has led some to question theoutcomes resulting from this study [5, 123]. Further andas discussed previously with the results of Candow et al.
[15], the dose of protein (10 g) was likely an inadequate
dose for a population of this age. Schoenfeld and colleagues [124] published results that directly examined
the impact of ingesting 25 g of whey protein immediately before or immediately after bouts of resistancetraining. All study participants trained three times eachweek targeting all major muscle groups over a 10-weekperiod, and the authors concluded no differences instrength and hypertrophy were seen between the two
protein ingestion groups. These findings lend support tothe hypothesis that ingestion of whey protein immediately before or immediately after workouts can promote
improvements in strength and hypertrophy, but the timeupon which nutrients are ingested does not necessarily
trump other feeding strategies.
Reviews by Aragon and Schoenfeld [125] andSchoenfeld et al. [126] critically examined the efficacy
surrounding post-exercise protein administration. The authors suggested that when recommended levels of protein
are consumed, the effect of timing appears to be, at best,minimal. Indeed, research shows that muscles remain sensitized to protein ingestion for at least 24 h following a

Page 11 of 21

resistance training bout [127] leading the authors to suggest that the timing, size and composition of any feeding
episode before a workout may exert some level of impact
on the resulting adaptations. In addition to these considerations, recent work by MacNaughton and colleagues [128]reported that the acute ingestion of a 40-g dose (versus20-g) of whey protein resulted in significantly greater
increases in MPS in young subjects who completed an intense, high volume bout of resistance exercise that targeted all major muscle groups. While seemingly a protein
dose question (and not necessarily a timing question perse), these findings are significant from a timing perspective
as the extent to which this higher dose interacts with themuscle’s ability to respond to a subsequent dose of aminoacid or protein (alone or as a mixed meal) feedings remains undetermined. Notwithstanding these conclusions,the number of studies that have truly examined a timing
question is rather scant. Moreover, recommendations
must capture the needs of a wide range of individuals, andto this point, a very small number of studies have examined the impact of nutrient timing using highly trained
athletes. From a practical standpoint, some athletes may
struggle, particularly those with high body masses, to consume enough protein to meet their required daily needs.
Therefore, due to the known sensitization that occurs inskeletal muscle to protein ingestion for ~ 24 h, the pragmatic recommendation is for an athlete to feed as soon as
possible after a workout. In this respect, not eating does
not offer any benefit regarding skeletal muscle hypertrophy and recovery from endurance and/or strengthpower exercise.
Timing and distribution of meals - time of day
considerations

Evidence has surfaced that suggests what part of the day
the majority of calories are consumed may affect one’s
health, weight loss or body composition changes. As astarting point, it is important to highlight that most of
the available research on this topic has largely used nonathletic, untrained populations except two recent publications using trained men and women [129, 130].
Whether or not these findings apply to highly trained,
athletic populations remains to be seen. Keim and colleagues [131] required study participants to complete
two six-week diet periods that delivered similar calories(~ 1950 kcals) and a similar macronutrient composition.
In one scenario, the participants were required to consume 70% of their prescribed dietary intake during themorning meal, while in the other study group participants were required to consume 70% of their prescribed
dietary intake with their evening meals. Changes inweight loss and body composition were compared, andslightly greater weight loss occurred when the majorityof calories was consumed in the morning. As a caveat toKerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

what is seemingly greater weight loss when more calories are shifted to the morning meals, higher amounts offat-free mass were lost as well, leading to questions surrounding the long-term efficacy of this strategy regarding weight management and metabolic activity.
Notably, this last point speaks to the importance ofevenly spreading out calories across the day and avoiding
extended periods of time where no food, protein in particular, is consumed. A large observational study [132]examined the food intake of 867 free-living individuals(375 males and 492 females),and a follow-up study fromthe same study cohort [133] reported that the timing offood consumption (earlier vs. later in the day) was correlated to the total daily caloric intake. These findings
indicate that consuming a greater proportion of one’s
total daily calories earlier in the day was associated withlower daily caloric intake while shifting more of the daily
caloric consumption to evening meals increased one’s
total caloric intake. Indeed, one must cautiously interpret these results as they are not offering any insight
into how these eating patterns may influence body composition changes or even loss of body mass, but nonetheless, provide interesting initial data on how “when”
certain foods are consumed may impact total daily
caloric intake.
Wu and colleagues [134] reported that meals later inthe day lead to increased rates of lipogenesis and adipose
tissue accumulation in an animal model and, while limited, human research has also provided support. Previously it has been shown that people who skip breakfast
display a delayed activation of lipolysis along with anincrease in adipose tissue production [135, 136]. Morerecently, Jakubowicz and colleagues [137] had overweight and obese women consume 1400 cal each day fora 12-week period. A portion of the study participants
consumed 50% of their daily calories (700 kcals) during
breakfast, 35% during lunch (500 kcals) and 15% during
dinner (200 kcals), while the other portion of study participants consumed the exact opposite distribution 15%
for breakfast (200 kcals), 35% for lunch (500 kcals) and
50% for dinner (700 kcals). Approximately 2.5 times
more weight was lost, and significantly greater changes
in waist circumference and body mass index values wereobserved, when the majority of calories were consumed
at breakfast. Also, triglyceride levels decreased by 34%,
greater improvements in glucose and insulin were observed, and feelings of satiety were improved in thegroup that consumed the majority of their calories atbreakfast [137]. While these results provide insight into
how calories could be more optimally distributed
throughout the day, a key perspective is that these studies were performed in sedentary populations without any
form of exercise intervention. Thus, their relevance toathletes or highly active populations might be limited.

Page 12 of 21

Furthermore, the current research approach has failed to
explore the influence of more evenly distributed meal
patterns throughout the day.
Meal frequency

Meal frequency is commonly defined as the number of
feeding episodes that take place each day. For years, recommendations have indicated that increasing meal frequency may serve as an effective way to influence weight
loss, weight maintenance, and body composition. Theseassertions were based upon the epidemiological work of
Fabry and colleagues [138, 139] who reported that mean
skinfold thickness was inversely related to the frequencyof meals. One of these studies involved 379 overweightindividuals between 60 and 64 years of age while theother investigation involved 80 participants between theages of 30–50 years of age. An even larger study published by Metzner and colleagues [140] reported that ina sample of 2000 men and women between 35 and60 years of age, meal frequency and adiposity were inversely related. While intriguing, the observational nature of these studies does not agree with more
controlled experiments. For example, a 2005 study by
Farshchi et al. [141] required individuals over a 14-day
period to consume either a regular, consistent pattern ofsix daily meals or eat anywhere from three to nine meals
per day. The irregular meal pattern was found to resultin increased levels of appetite, and hunger leading one
to question if the energy provided in each meal was inadequate or if the energy content of each meal could
have been better matched to limit these feelings whilestill promoting weight loss. Furthermore, Cameron andinvestigators [142] published what is one of the firststudies to directly compare a greater meal frequency toa lower frequency. In this study, 16 obese men andwomen reduced their energy intake by 700 kcals per day
and were assigned to one of two isocaloric groups: one
group was instructed to consume six meals per day(three traditional meals and three snacks), while theother group was instructed to consume three meals per
day for an eight-week period. Changes in body mass,
obesity indices, appetite, and ghrelin were measured at
the end of the eight-week study, and no significant differences in any of the measured endpoints were foundbetween conditions. These results also align with more
recent results by Alencar [143] who compared the impact of consuming isocaloric diets consisting of two
meals per day or six meals per day for 14 days in overweight women on weight loss, body composition, serum
hormones (ghrelin, insulin), and metabolic (glucose)markers. No differences between groups in any of themeasured outcomes were observed. A review by Kulovitz
et al. [144] concluded that when total energy intake iscontrolled, and when caloric restriction is employed, theKerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

influence of meal frequency on weight loss and improving one’s body composition is secondary to the total
daily caloric intake. Similar conclusions were drawn in ameta-analysis by Schoenfeld and colleagues [145] thatexamined the impact of meal frequency on weight loss
and body composition. Although initial results suggested
a potential advantage for higher meal frequencies onbody composition, sub-analysis indicated that findings
were confounded by a single study, casting doubt as towhether the strategy confers any beneficial effects. However, it is important to note that this “outlier” study was
the only one to include an exercise regimen and only
lasted for two weeks. From this, one might conclude that
greater meal frequency may, indeed, favorably influence
weight loss and body composition changes if used in
combination with an exercise program for a short periodof time. Certainly, more research is needed in this area,
particularly studies that manipulate meal frequency in
combination with an exercise program in non-athletic aswell as athletic populations. Finally, other endpoints related to meal frequency (i.e., glucose/insulin homeostasis, hunger and appetite levels, energy levels, etc.) may
be of interest to different populations, but they extend
beyond the scope of this position stand. The interested
reader is referred to the ISSN’s position stand on meal
frequency [146].
Timing and distribution of protein feeding

An extension of altering the patterns or frequency ofwhen meals are consumed is to examine the pattern
upon which protein feedings occur. Researchers haveclearly illustrated that upon ingestion of a meal containing protein and/or amino acids, serum levels of aminoacids as well as MPS rates will rise and stay elevated forthree to 5 h depending on bolus size [147, 148]. Moore
and colleagues [149] examined the differences in protein
turnover and synthesis rates when participants ingested
different patterns, in a randomized order, of an 80-g
total dose of protein over a 12-h measurement period
following a bout of lower body resistance exercise. Oneof the protein feeding patterns required participants to
consume two 40-g doses of whey protein isolate approximately 6 h apart. Another condition required theconsumption of four, 20-g doses of whey protein isolate
every 3 h. The final condition required the participants
to consume eight, 10-g doses of whey protein isolate
every 90 min. Rates of muscle protein turnover, synthesis, and breakdown were compared, and the authors
concluded that protein turnover and synthesis rates weregreatest when intermediate-sized (20-g) doses of whey
protein isolate were consumed every 3 h. One of the
caveats of this investigation was the very low total doseof protein consumed. Eighty grams of protein over a 12h period would be grossly inadequate for athletes

Page 13 of 21

performing high volumes of training as well as those
who are extremely heavy (e.g., American football players,
sumo wrestlers, field athletes, etc.). A follow-up study
one year later from the same research group determinedmyofibrillar protein synthesis rates after randomizing
participants into three different protein ingestion patterns and examined how altering the pattern of protein
administration affected protein synthesis rates after about of resistance exercise [150]. Two key outcomes
were identified. First, rates of myofibrillar protein synthesis rates increased in all three groups. Second, whenfour, 20-g doses of whey protein isolate were consumed
every 3 h over a 12-h post-exercise period, significantly
greater (in comparison to the other two patterns of protein ingestion) rates of myofibrillar protein synthesis
occurred. In combining the results of both studies, one
can conclude that ingestion of intermediate protein
doses (20 g) consumed every 3 h creates more favorable
changes in both whole-body as well as myofibrillar protein synthesis [149, 150]. Although both studies
employed short-term methodology and other patterns or
doses have yet to be examined, the results thus far consistently suggest that the timing or pattern in which
high-quality protein is ingested may favorably impact
net protein balance as well as rates of myofibrillar protein synthesis.
An important caveat to these findings is that supplementation (in most cases) was provided in exclusion ofother macronutrients over the duration of the study.
Consumption of mixed meals delays gastric emptying
and thus may result in different metabolic effects. Moreover, the fact that whey is a fast-absorbing protein
source [151] further confounds the ability to generalize
results to traditional mixed-meal diets, as the potential
for oxidation is increased with larger dosages, particularly in the absence of other macronutrients. Whether
acute MPS responses translate to longitudinal changes
in hypertrophy or fiber composition also remains to be
determined [120]. In addition to these aforementioned
studies, extensive work by Arciero and colleagues has
directly examined the combined effect of meal frequency
and timing along with the distribution of protein intake
with [129, 130, 152–156] and without [157, 158] exercise
training in both short-term (3 months) and longer-term(> 1 year) interventions using a “protein pacing” model.
Protein pacing involves the consumption of 20–40 gservings of high-quality protein, from both whole foodand protein supplementation, evenly spaced throughout
the day, approximately every 3 h. The first meal is consumed within 60 min of waking in the morning, and thelast meal is eaten within 3 h of going to sleep at night.
Arciero and colleagues [129, 130] have most recently
demonstrated increased muscular strength and power in
exercise-trained physically fit men and women using

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

protein pacing compared to ingestion of similar sized
meals at similar times but different protein contents,
both of which included the same multi-component exercise training during a 12-week intervention.
In this respect and in consideration of alterations in
the time between protein feedings, one must also consider the impact of the “muscle full” effect introduced by
Millward et al. [159] and later refined by Atherton et al.
[160] where it was speculated that a sensing mechanism
was present in muscle that governed overall rates ofmuscle protein growth. In support of this theory one
can point to the well characterized changes seen in peak
MPS rates within 90 min after oral ingestion of protein[160] and the return of MPS rates to baseline levels inapproximately 90 min despite elevations in serum aminoacid levels [161]. Thus if efficacious protein feedings areplaced too close together it remains possible that theability of skeletal muscle anabolism to be fully activatedmight be limited. While no clear consensus exists as tothe acceptance of this theory, conflicting findings exist
between longitudinal studies that did provide protein
feedings in close proximity to each other [16, 110, 153],
making this an area that requires more investigation. Finally, while the mechanistic implications of pulsed vs.
bolus protein feedings and their effect on MPS rates
may help ultimately guide application, the practical importance has yet to be demonstrated.
Pre-sleep protein intake

Eating before sleep has long been controversial [162–164].
However, methodological considerations in the original
studies such as the population used, time of feeding, andsize of the pre-sleep meal confounds any conclusions thatcan be drawn. Recent work using protein-centric beverages consumed 30-min before sleep and 2 h after thelast meal (dinner) have identified pre-sleep protein consumption as advantageous to MPS, muscle recovery, andoverall metabolism in both acute and long-term studies[165, 166]. For example, data indicate that 30–40 g of casein protein ingested 30-min prior to sleep [167] or via
nasogastric tubing [168] increased overnight MPS in bothyoung and old men, respectively.
Likewise, in an acute setting, 30 g of whey protein,
30 g of casein protein, and 33 g of carbohydrate consumption 30-min pre-sleep resulted in elevated morning
resting metabolic rate in fit young men compared to a
non-caloric placebo [169]. Similarly, although not statistically significant, morning increases in resting metabolic
rate were reported in young overweight and/or obese
women [170]. Of particular interest is that Madzima etal. [169] reported that the respiratory quotient (RQ) themorning after pre-sleep nutrient intake was similar forthe placebo and casein protein trials, while bothcarbohydrate and whey protein producedincreasedRQ

Page 14 of 21

compared to placebo. This infers that casein protein
consumed pre-sleep maintains overnight lipolysis andfat oxidation. This finding was verifiedwhen Kinsey et al.
[171] designed a study using the microdialysis technique
to measure interstitial glycerol concentrations overnightfrom the subcutaneous abdominal adipose tissue following
30 g of casein or a flavor and sensory-matched noncaloric
placebo in obese men. It was concluded that pre-sleep
casein did not blunt overnight lipolysis or fat oxidation.
Similar to Madzima et al. [169] who compared pre-sleep
ingestion of either casein or carbohydrate, Kinsey et al.
[171] also concluded that pre-sleep casein did not resultin elevated insulin the next morning along with decreased
ratings of hunger in an overweight population. Of note, itappears that previous exercise training completely ameliorates any rise in insulin when eating at night before
sleep [172] and the combination of pre-sleep protein andexercise has been shown to reduce blood pressure andarterial stiffness in young obese women with prehypertension and hypertension [173].
To date, only two studies involving nighttime protein
have been carried out for longer than four weeks. Snijders
et al. [174], randomly assigned young men (22 ± 1 years
old) to consume a protein-centric supplement (27.5 g ofcasein protein, 15 g of carbohydrate, and 0.1-g of fat) or anoncaloric placebo every night before sleep while also
completing a 12-week progressive resistance exercise
training program (3 times per week). The group receiving
the protein-centric supplement each night before sleep
had greater improvements in muscle mass and strength
over the 12-weeks. Of note, this study was non-nitrogenbalanced and the protein group received approximately
1.9 g/kg/day of protein compared to 1.3 g/kg/day in theplacebo group. More recently, in a nitrogen-balanced design using young healthy men and women, Antonio et al.
[175] supplemented participants with 54 g of casein protein for eight weeks either in the morning (any time before
12 pm) or in the evening (90 min or less before sleep) andcompared changes in body composition, strength performance outcomes. All subjects maintained their usual
exercise program. The authors reported no differences inbody composition or performance between the morningand evening casein supplementation groups. A potential
explanation for the lack of findings might stem from thealready high intake of protein by the study participants before the study commenced. However, it is worth notingthat although not statistically significant, the morninggroup added 0.4 kg of lean body mass compared to 1.2 kgin the evening group even though the habitual diet of the
trained subjects in this study was reported to be 1.7 to
1.9 g/kg/day of protein. Thus, it appears that protein consumption in the evening before sleep represents anotheropportunity to consume protein and other nutrients. Certainly more research is needed to determine if timing perKerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

se, or the mere addition of total daily protein can affectbody composition or recovery via nighttime feeding.

Conclusions
Nutrient timing is an area of research that continues togather interest from researchers, coaches, and consumers. In reviewing the literature, two key considerations should be made. First, all findings surrounding
nutrient timing require appropriate context because factors such as age, sex, fitness level, previous fueling status, dietary status, training volume, training intensity,
program design, and time before the next training boutor competition can influence the extent to which timing
may play a role in the adaptive response to exercise. Second, nearly all research within this topic requires further
investigation. The reader must keep in perspective thatin its simplest form nutrient timing is a feeding strategy
that in nearly all situations may be helpful towards thepromotion of recovery and adaptations towards training.
This context is important because many nutrient timing
studies demonstrate favorable changes that do not meetstatistical thresholds of significance thereby leaving thereader to interpret the level of practical significance thatexists from the findings. In this respect, it is the positionof the ISSN that when a strategy may either help or havea neutral effect and fits within that individual’s dailyschedule and ability to comply, then from a purely practical perspective, it is worth employing. It is noteworthy
that differences in real-world athletic performances canbe so small that even strategies that offer a modicum of
benefit are still worth pursuing. One must rememberthat the overarching purpose of any nutritional strategy
is to enhance the adaptive response to acute and/or
chronic exercise. In nearly all such situations, this approach results in an athlete receiving a combination ofnutrients at specific times that may be helpful and has
not yet shown to be harmful. This perspective also has
the added advantage of offering more flexibility to thefueling considerations a coach or athlete may employ.
Using this approach, when both situations (timed or
non-timed ingestion of nutrients) offer positive outcomes then our perspective is to advise an athlete to follow whatever strategy offers the most convenience orcompliance if for no other reason than to deliver vitalnutrients in amounts at a time that will support thephysiological response to exercise.
Finally, it is advisable to remind the reader that due tothe complexity, cost and invasiveness required to answer
some of these fundamental questions, research studies
often employ small numbers of study participants. Also,
for the most part studies have primarily evaluated men.
This latter point is particularly important as researchers
have documented that females oxidize more fat whencompared to men, and also seem to utilize endogenous

Page 15 of 21

fuel sources to different degrees [28–30]. Furthermore,
the size of potential effects tends to be small, and whensmall potential effects are combined with small numbersof study participants, the ability to determine statisticalsignificance remains low. Nonetheless, this consideration
remains relevant because it underscores the need formore research to better understand the possibility of thegroup and individual changes that can be expected when
the timing of nutrients is manipulated.
Practical applications
 In many situations, the efficacy of nutrient timing is











inherently tied to the concept of optimal fueling.
Thus, the importance of adequate energy,
carbohydrate, and protein intake must beemphasized to ensure athletes are properly fueledfor optimal performance as well as to maximize
potential adaptations to exercise training.
Prolonged exercise (> 60 – 90 min) of moderate tohigh intensity (65–80% VO2max) relies heavily uponendogenous carbohydrate stores, and timing strategies
to maximize these stores (carbohydrate loading or
glycogen supercompensation strategies) have beenshown to facilitate recovery and offset these changes.
High-intensity exercise (particularly in hot andhumid conditions) demands aggressive carbohydrate
and fluid replacement. Consumption of 1.5–2 cups
(12–16 fluid ounces) of a 6–8% carbohydrate
solution (6–8 g carbohydrate per 100 mL of fluid)has been shown as an effective strategy to replace
fluid, sustain blood glucose levels and promote
performance. The need for carbohydrate
replacement increases in importance as training andcompetition extend beyond 70 min of activity andthe need for carbohydrate during shorter durations
is less established.
Rapid ingestion of high amounts of carbohydrates(≥ 1.2 g/kg/h) for four to 6 h soon after exhausting
exercise can rapidly stimulate replenishment ofmuscle glycogen.
Adding protein (0.2–0.5 g/kg/h) to carbohydrateincreases the rate of glycogen resynthesis wheningesting < 1.2 g/kg/h of carbohydrate. Moreover,
the additional protein may minimize muscle
damage, promote favorable hormone balance andaccelerate recovery from intense exercise.
For athletes completing high volumes (i.e., ≥ 8 h) of
exercise per week and subsequently requiring theneed to continually and rapidly replenish endogenous
glycogen stores, the single most effective strategy tomaximize endogenous glycogen stores is theconsumption of a daily diet high in carbohydrate(8–12 g/kg/day).

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

 The use of a 20–40-g dose of a high-quality protein













source that contains approximately 10–12 g of the
EAA maximizes MPS rates that remain elevated forthree to four hours following exercise.
Protein consumption during the peri-workout period
is a pragmatic and sensible strategy for athletes,
particularly those who perform high volumes of
exercise. Not consuming protein post-workout(e.g., waiting for several hours post-exercise) offers
no benefits.
The impact of delivering a dose of protein (withor without carbohydrates) during the peri-workout
period over the course of several weeks may operate
as a strategy to heighten adaptations to exercise.
Key factors that may influence the overall outcomes
include one’s total daily protein intake, anindividual’s training status and when their lastdose of protein was consumed.
Like carbohydrate, timing related considerations
for protein appear to be of lower priority than theingestion of optimal amounts of daily protein(1.4–2.0 g/kg/day).
In the face of restricting caloric intake for weight
loss, altering meal frequency has shown limited
effects on body composition. However, more
frequent meals may be more beneficial whenaccompanied by an exercise program. The impactof altering meal frequency in combination with an
exercise program in non-athlete or athlete
populations warrants further investigation. It isestablished that altering meal frequency (outsideof an exercise program) may help with controlling
hunger, appetite and satiety.
Nutrient timing strategies that involve changing the
distribution of intermediate-sized protein doses(20–40 g or 0.25–0.40 g/kg/dose) every three to 4 hbest supports increased MPS rates across the day
and favorably enhances body composition andphysical performance outcomes. One must also
consider that other factors such as the type of
exercise stimulus, training status, and consumptionof mixed macronutrient meals versus sole protein
feedings can all impact how protein is metabolized
across the day.
When consumed within 30 min before sleep,
30–40 g of casein may increase MPS rates andimprove strength and muscle hypertrophy. In
addition, protein ingestion prior to sleep may
increase morning metabolic rate while exerting
minimal influence over lipolysis rates. In addition,
pre-sleep protein intake can operate as aneffective way to meet daily protein needs while
also providing a metabolic stimulus for muscle
adaptation.

Page 16 of 21

 Altering the timing of energy intake (i.e., total

calories over the course of a day) may improveweight loss, body composition changes, and healthrelated markers, particularly when a greater
proportion of calories are consumed during
breakfast and to a greater extent when this meal
provides higher amounts of dietary protein.
Availability of data and materials
Not applicable.
Authors’ contributions
CMK prepared and compiled the draft for initial review and incorporated all
suggested edits into the final draft. BJS, SMA, and JRS completed an initial
review and provided significant edits and additional content before review
and approval of other authors. All other authors reviewed, suggested edits,
and approved the final manuscript.
Ethics approval and consent to participate
This paper was reviewed by the International Society of Sports Nutrition
Research Committee and represents the official position of the Society.
Consent for publication
Not applicable.
Competing interests
CMK consults with and receives external funding from companies who sell
supplemental protein, has received remuneration from companies fordelivering scientific presentations at conferences and writes online, print andother media on topics related to exercise, nutrition and protein for relatedcompanies. Has served as an expert witness and provided testimonies
related to exercise, supplementation, and nutrition.
BJS has no conflicts to report.
SMA has received grants to evaluate the efficacy of dietary supplements andhas previously served on scientific advisory boards for a sports nutrition
company.
JRS has received grants to evaluate the efficacy of dietary supplements andhas previously served on scientific advisory boards for a sports nutrition
companies.
BIC writes and is compensated for various media outlets on topics related tosports nutrition and fitness; has received funding for research related todietary supplements; serves on an advisory board for a sports nutrition
company and is compensated in product donations.
CDW has received external funding from supplement companies to doresearch, served on multiple advisory boards for supplement companies, andhas served as a consultant, advisor, and spokesperson for various nutrition
companies.
LT has received external funding to evaluate the efficacy of dietary
supplements and has previously served in a consulting role for sports
nutrition companies.
DSK works for a contract research organization that does conduct clinical
trials for dietary supplement and pharmaceutical companies.
ASR has received grants to evaluate the efficacy of dietary supplements andserves on the scientific advisory board for sports nutrition companies.
RBK has received externally-funded grants from industry to conduct researchon protein and protein containing supplements, serves as a scientific andlegal consultant, and is a university approved scientific advisor for Nutrabolt.
DSW has received grants to evaluate the efficacy of dietary supplements,
serves on a scientific advisory board for a sports nutrition company, and as
scientific consultant, and has received remuneration from a company fordelivering scientific presentations at conferences.
PJA consults with and receives external funding from nutrition supplementcompanies; has received remuneration from health and wellness companies
for presenting at conferences; serves as an advisory board member ofgoverning organizations in healthcare and nutrition supplement companies;
serves as a paid consultant to the nutrition supplement industry; serves as
Founder and CEO of PRISE LLC a health and wellness consultant company
that owns the GenioFit App.
TAV has received grants to evaluate the efficacy of dietary supplements.

Kerksick et al. Journal of the International Society of Sports Nutrition (2017) 14:33

MJO is on the advisory board for Dymatize Nutrition and has received
external funding from companies who sell nutritional supplements.
RW serves as Chief Science Officer for Post Active Nutrition, St Louis MO.
MG has received external funding and nutritional product from companies
who sell protein supplements and has received remuneration fromcompanies for presenting scientific based nutritional supplement andexercise research at professional conferences.
TNZ has received external funding from companies who sell protein
supplements, has received remuneration from companies for deliveringscientific presentations at conferences, and authors online articles related toexercise, nutrition and protein. He has also served as an expert witness andprovided testimonies related to exercise, supplementation and nutrition.
AAA has no conflicts to report.
JA is the CEO and co-founder of the ISSN. The ISSN is supported in part by
grants from raw good suppliers and branded companies.

Publisher’s NoteSpringer Nature remains neutral with regard to jurisdictional claims inpublished maps and institutional affiliations.
Author details
1
Exercise and Performance Nutrition Laboratory, School of Health Sciences,
Lindenwood University, St. Charles, MO, USA. 2IFNH Center for Health &Human Performance, Department of Kinesiology & Health, Rutgers University,
New Brunswick, NJ, USA. 3Health Science Department, Program of Exercise
Science, CUNY Lehman College, Bronx, NY, USA. 4Institute of Exercise
Physiology and Wellness, University of Central Florida, Orlando, FL, USA.
5
Performance & Physique Enhancement Laboratory, Exercise Science
Program, University of South Florida, Tampa, FL, USA. 6Human Performance
Lab, Department of Exercise Sport Science, University of Mary Hardin-Baylor,
Belton, TX, USA. 7Department of Athletics, Florida International University,
Miami, FL, USA. 8Applied Physiology Laboratory, Department of Exercise andSport Science, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA.
9
Exercise & Sport Nutrition Lab, Human Clinical Research Facility, Department
of Health & Kinesiology, Texas A&M University, College Station, TX, USA.
10
Exercise and Biochemical Nutrition Laboratory, Department of Health,
Human Performance, and Recreation, Baylor University, Waco, TX, USA.
11
Human Nutrition and Metabolism Laboratory, Health and Exercise Sciences
Department, Skidmore College, Saratoga Springs, NY 12866, USA.
12
Department of Exercise Science and Sport Management, Kennesaw State
University, Kennesaw, GA, USA. 13Department of Nutrition, Food and Exercise
Sciences, Institute of Sport Sciences and Medicine, Florida State University,
Tallahassee, FL, USA. 14University of KwaZulu-Natal, Biokinetics, Exercise andLeisure Studies, Durban 4000, South Africa. 15Post Active Nutrition, 111 Leslie
St, Dallas, TX, USA. 16The Center for Applied Health Sciences, Stow, OH, USA.
17
Department of Family Environmental Sciences, California State University,
Northridge, CA, USA. 18Department of Health and Human Performance, Nova
Southeastern University, Davie, FL, USA.
Received: 12 July 2017 Accepted: 14 August 2017

7.

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