International Journal of Sport Nutrition and Exercise Metabolism, 2019, 29, 165-174
https://doi.org/10.1123/ijsnem.2018-0267

SCHOLARLY REVIEW

Dietary Protein for Training Adaptation and Body Composition
Manipulation in Track and Field Athletes
Oliver C. Witard
University of Stirling

Ina Garthe
Norwegian Olympic and Paralympic Committee and Confederation of Sport

Stuart M. Phillips
McMaster University
Track and ﬁeld athletes engage in vigorous training that places stress on physiological systems requiring nutritional support for
optimal recovery. Of paramount importance when optimizing recovery nutrition are rehydration and refueling which are covered inother papers in this volume. Here, we highlight the beneﬁts for dietary protein intake over and above requirements set out in various
countries at ∼0.8–1.0 g·kg body mass (BM)−1·day−1 for training adaptation, manipulating body composition, and optimizing
performance in track and ﬁeld athletes. To facilitate the remodeling of protein-containing structures, which are turning over rapidly
due to their training volumes, track and ﬁeld athletes with the goal of weight maintenance or weight gain should aim for protein
intakes of ∼1.6 g·kg BM−1·day−1. Protein intakes at this level would not necessarily require an overemphasis on protein-containing
foods and, beyond convenience, does not suggest a need to use protein or amino acid-based supplements. This review also
highlights that optimal protein intakes may exceed 1.6 g·kg BM−1·day−1 for athletes who are restricting energy intake
and attempting to minimize loss of lean BM. We discuss the underpinning rationale for weight loss in track and ﬁeld athletes,
explaining changes in metabolic pathways that occur in response to energy restriction when manipulating protein intake andtraining. Finally, this review offers practical advice on protein intakes that warrant consideration in allowing an optimal adaptive
response for track and ﬁeld athletes seeking to train effectively and to lose fat mass while energy restricted with minimal (or no) lossof lean BM.
Keywords: high-quality weight loss, protein recommendations, protein turnover
Dietary protein is widely regarded as a key nutrient forallowing optimal training adaptation (Tipton, 2008) and optimizing
body composition (Hector & Phillips, 2018; Murphy et al., 2015) inathletes including track and ﬁeld athletes. Track and ﬁeld athletics
encompasses a broad spectrum of events including race walking;running (sprints, middle- and long-distance events, and hurdling);
throwing (shot put, javelin, discus, and hammer); and jumping(long jump, triple jump, high jump, and pole vault), all withdifferent ideals for the optimum performance physique (Hirsch
et al., 2016). Most track and ﬁeld athletes are familiar with theconcept of high-quality weight loss (Sundgot-Borgen & Garthe,© 2019 The Authors. Published by Human Kinetics, Inc. This is an Open Accessarticle distributed under the terms of the Creative Commons Attribution License CC
BY 4.0, which permits unrestricted noncommercial and commercial use, distribution, and reproduction in any medium, provided the original work is properly cited,
the new use includes a link to the license, and any changes are indicated. See https://creativecommons.org/licenses/by/4.0/. This license does not cover any third-party
material that may appear with permission in the article.
Witard is with Physiology, Exercise and Nutrition Research Group, Faculty of
Health Sciences and Sport, University of Stirling, Stirling, Scotland. Garthe is with
Norwegian Olympic and Paralympic Committee and Confederation of Sport, Oslo,
Norway. Phillips is with McMaster University, Hamilton, Ontario, Canada. Address
author correspondence to Oliver C. Witard at oliver.witard@stir.ac.uk.

2011), which describes the loss of fat mass while preserving, oreven increasing, fat-free mass (i.e., muscle tissue) during a voluntary period of energy restriction. Many athletes engage in weightloss programs to “make weight” for competition (i.e., combat
sports) or for aesthetic reasons (i.e., gymnasts and divers). However, the “Holy Grail” for most, if not all, track and ﬁeld athletes
during weight loss is to optimize their ratio of strength, power, or
endurance to body weight for a performance advantage.
Since the previous International Association of Athletics Federations consensus statement (O’Connor et al., 2007), the evidence
underpinning nutrition strategies for adaptation and physiquemanipulation in athletes has evolved considerably. In particular,
recent attention has focused on advancing understanding of the roleof protein nutrition in allowing “optimal” training adaptation(Tipton, 2008) and body composition (Hector & Phillips, 2018;
Pasiakos et al., 2015). Accordingly, here we update the latest
evidence-based protein recommendations for training adaptationand promoting, if desired, high-quality weight loss in athletes,with speciﬁc application to track and ﬁeld athletes. In Figure 1,
we provide a theoretical framework for understanding recommended dietary protein intakes for optimal adaptation, as opposed
to offsetting deﬁciency and meeting minimal needs for protein inathletes. The scientiﬁc evidence that underpins this framework is
critically evaluated. To provide practical context, the next sections of
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Witard, Garthe, and Phillips

Figure 1 — Theoretical framework for understanding recommended
dietary protein intakes for optimal adaptation in track and ﬁeld athletes.
AA = amino acid; EAR = estimated average requirement; RDA =recommended daily allowance; BM = body mass.

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this review outline the principles of weight loss and expand on whyweight loss is an important goal for many track and ﬁeld athletes
across sprint, throwing, jumping, and race walking disciplines.

Weight Loss Principles for Athletes
The principles of weight loss and weight gain are similar because
both require continuous energy imbalance between energy intake
and/or energy expenditure. Most, but not all, athletes strive
for high-quality weight loss, which can be deﬁned as the lossof fat mass while preserving, or even increasing, fat-free mass
(i.e., muscle tissue) during a voluntary period of energy restriction.
Notable exceptions to this rule include shot put and discus throwers
in which fat mass as well as muscle mass are considered functional
for performance. In general, the already high energy expenditureassociated with structured exercise training in high-performanceathletes means that restricting energy intake is likely the necessary,and perhaps the preferred (Dhurandhar et al., 2015) option, toachieve weight loss in this population. Since weight loss is a resultof a predominance of catabolism in adipose tissue, and the gain ofmuscle mass (i.e., lean body mass [LBM]) is a result of predominance of anabolism in skeletal muscle, this requires the track andﬁeld athlete to practice a meticulously tailored meal plan, combinedwith an adequate and sports-speciﬁc strength training stimulus formuscle growth. Sufﬁce to say, while it would be easier to gain
muscle in an energy surfeit and to lose fat while in an energy deﬁcit,
there are several publications about trained individuals in which theprocess has been shown to occur (Garthe et al., 2011a; Haakonssen
et al., 2013; Longland et al., 2016).

Why Weight Management Is of Importancefor Track and Field Athletes
Both gradual and rapid weight loss practices are commonly
employed across athletic populations. Rapid weight loss (i.e.,
3–10% of body weight over ∼96 hr) is based predominantly on
the loss of bodily ﬂuids caused by passive or active dehydration andis most typically used by weight-class athletes prior to weigh-in(e.g., combat sports). Track and ﬁeld athletes in jumping or

long-distance events, where body weight is closely related toperformance, may also use rapid weight loss as a strategy to takeadvantage of a lighter body weight during competition. Moreover,long-distance runners and race walkers may be well hydrated at thestart of the race but modestly dehydrated at the ﬁnish, due tovoluntary dehydration during the race (Coyle, 2004). Although theprevalence of rapid weight loss strategies among track and ﬁeld
athletes are unknown, the risk of serious health and performance
impairments caused by even moderate dehydration are well documented (Shirreffs et al., 2004), making the relationship between
rapid weight loss and performance a complex concept (Coyle,2004). Track and ﬁeld athletes involved in jumping and throwing
events may be an exception to this rule.
A more gradual weight loss with the goal to maximize the ratioof strength, power, or endurance to body weight is typical for track
and ﬁeld athletes when performance depends on efﬁcient horizontal (e.g., long-distance running) or vertical (e.g., high jump) movements. In these events, excessive “nonuseful” body weight as fat
mass can be a disadvantage for performance. A gradual weight loss
of 0.5–1 kg/week due to a modest increase in energy expenditure
and/or, more likely, a lowered energy intake will primarily comprise of fat mass. This weight loss requires an energy deﬁcit of∼500–1,000 kcal/day, respectively, but understanding that stochastic formulas for weight loss of these rates will vary considerably on
an interindividual basis. However, due to metabolic adaptations
that occur at the onset of weight loss combined with a gradually
lowered body weight, the energy deﬁcit required for weight loss isless during the initial stages of dieting than after 2–3 weeks(Dhurandhar et al., 2015).
While weight loss during the ﬁrst weeks of negative energybalance is largely attributed to changes in glycogen, protein, andﬂuids, long-term weight loss is mainly attributed to changes in fat
mass and to a varying degree loss of LBM (Weinheimer et al.,2010). As a result, the degree of the energy deﬁcit needs to be
individualized. Long periods of energy deﬁcit are inherently
stressful from both physiological and psychological perspectives
and increase the risk of impaired immune function, injuries,
hormonal disturbances, sleep disturbances, loss of bone mass(particularly if calcium and vitamin D intake are inadequate),and other processes detrimental to health and performance causedby relative energy deﬁciency (Mountjoy et al., 2014). Thus,
considering the counterproductive responses related to long-term
energy deﬁciency and the link between body weight and performance in some track and ﬁeld events, ongoing monitoring andevaluation during weight loss by professionals is warranted(Mountjoy et al., 2018). In practice, most track and ﬁeld athletes
reduce the volume of resistance training during a weight-loss
period prior to competition in favor of more event-speciﬁc training.
This removal of resistance exercise as a primary external stimulus
for muscle maintenance combined with negative energy balance islikely to exacerbate the loss of LBM. However, as discussed below,
studies have shown that it is possible, even for the elite athlete, tomaintain LBM during a weight loss intervention (Garthe et al.,2011b; Mettler et al., 2010). The main factors that determine highquality weight loss appear to be an adequate dietary intake of highquality protein distributed evenly and frequently in relation to
exercise and recovery, combined with additional strength training
as stimuli for lean tissue growth.
At the other end of the spectrum, certain athletes, such as thosein power-oriented throwing events, will strive to gain weight by
maximizing LBM, as their performance depends on high absolute
muscle strength and power. Athletes with the goal to gain body

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Protein and High-Quality Weight Loss in Athletes

weight could be at risk of excessive intake of food and supplements
and may beneﬁt from professional support. The potential for muscle
growth depends not only on nutrition, but also on an athlete’s
genetics and resistance training history. A positive energy balancealone has been shown to elicit an important anabolic effect (Brayet al., 2012), but combining strength training and a positive energybalance results in the most effective gain in LBM (Kreider et al.,
1996; Tipton & Wolfe, 2004).
Although there are few studies on weight gain in athletes, it has
been suggested that an increase in LBM of 0.25–0.5 kg/week may
be a realistic goal for the strength/power-based athlete (Rozenek
et al., 2002) at least over a relatively short-term (12–16 weeks)
period, but this rate would slow drastically with time. To achieve
this gain in LBM, an energy surplus of ∼500 kcal/day is recommended for the track and ﬁeld athlete. However, athletes with along history of heavy strength training may have less potential togain LBM (Garthe et al., 2011b). Therefore, the excess energy
intake in a weight gain intervention should be carefully considered
and monitored as greater rates of weight gain are likely to include
increments in body fat in trained athletes

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Dietary Protein for Training Adaptationin Track and Field AthletesProtein is important for optimizing the physical and likely metabolic adaptations that occur in skeletal muscle, as well as othertissues, in response to exercise (Tipton, 2008), both during states ofenergy balance and energy restriction (Figure 1). The physiologicalbasis for phenotypic changes that take place with either resistanceor endurance-based exercise training stems from changes in thequantity, type, and/or activity of various muscle proteins (Hawley
et al., 2006). The turnover, or remodeling, of all proteins is aconstant and concurrent process. Hence, at any given time, misfolded, older damaged (posttranslational damage) proteins aredegraded through muscle protein breakdown (MPB) and are
replaced with new functional muscle proteins through muscle
protein synthesis (MPS). Muscle protein is gained if rates of
MPS exceed MPB, termed positive net muscle protein balance.
Conversely, muscle protein is lost if MPB exceeds MPS in a state ofnegative net muscle protein balance, as may be the case during
periods of weight loss.
Although an optimum muscle mass may not necessarilyequal maximal muscle mass (Tipton et al., 2007), a prerequisite
for success in predominantly strength/power-based track(e.g., sprinters) and ﬁeld (e.g., long jumpers, shot put, javelin,and discus throwers) athletes is to achieve an optimal power tobody weight ratio. Muscle hypertrophy stems from the remodelingof the contractile myoﬁbrillar proteins in response to resistance
exercise training. More applicable to the endurance-based track andﬁeld athlete such as middle- and long-distance runners, nonhypertrophic muscle adaptation also results from muscle protein remodeling that stems primarily from a protein turnover favoring a
positive net protein balance of sarcoplasmic and mitochondrial
muscle proteins. Although both MPS and MPB processes are
modulated by protein ingestion and exercise, MPS is 4–5 times
more responsive than MPB (Biolo et al., 1997) and changes in
MPB are of far lesser concern. As a result, best practice nutrition
guidelines for muscle adaptation in athletes are primarily based onprotein recommendations for stimulation of MPS. It should also be
noted that dietary and/or nutritional factors that purport to suppress
MPB (i.e., branched-chain amino acids; Borgenvik et al., 2012) are167

not likely to aid training adaptation. The main reason for thisstatement is the recognition that the replacement of damaged or
nonfunctional proteins and the muscle remodeling process isadvantageous (Stokes et al., 2018; Tipton et al., 2018).
As a broad guideline, a daily protein intake between 1.3 and1.7 g·kg BM−1·day−1 is recommended for athletes (Morton &Phillips, 2018; Rodriguez et al., 2009). What appears clear, basedon the most recent evidence-based review and meta-analysis, is that
intakes of protein greater than 1.6 g·kg BM−1·day−1 and possibly ashigh as 2.2 g·kg BM−1·day−1 do not further enhance gains in
LBM in weight-stable trained individuals (Morton et al., 2018).
Moreover, due to the satiating effect of protein compared with othermacronutrients (Veldhorst et al., 2008), it is plausible that excessive protein intakes could displace intakes of other important
nutrients including carbohydrate and be detrimental to training
adaptation (MacKenzie-Shalders et al., 2015). Protein recommendations are now thought to be better expressed on a meal-by-meal,or serving-by-serving basis, rather than daily basis (Murphy et al.,2016; Witard et al., 2016). This approach stems from accumulating
evidence that multiple factors, including the per meal/serving
dose, protein type (i.e., source); meal pattern; and timing (inrelation to training, sleep, and other nutrients) of ingested protein,
as well as the co-ingestion of other nutrients, all modulate theresponse of MPS to ingested protein (Witard et al., 2016). In brief,
based on these studies the dose of protein for track and ﬁeld athletes
to consume on a per serving/meal basis for maximal stimulation of
MPS would equate to ∼0.3–0.4 g/kg BM (Moore et al., 2015).
Consumed over 3–4 feeding occasions, this equates to a daily
protein intake in the region of 1.3–1.7 g·kg BM−1·day−1. While the0.3 g/kg BM target serving represents a safe intake for protein,
this guideline was based on studies that administered isolated intact
proteins, such as whey protein (Moore et al., 2015), gave rise only
to acute measures of MPS (i.e., meal-to-meal), and included noother macronutrients and as such would themselves be considered
optimal only under the speciﬁc conditions employed in the studies.
We and others (Gorissen & Witard, 2018; van Vliet et al., 2015)
contend that the optimal per meal “real world” serving of a proteinrich food for maximal stimulation of MPS may be closer to
0.4–0.5 g/kg BM when we consider real foods, not isolated
proteins, and the coingestion of other macronutrients that would
alter rates of digestion and thus patterns of aminoacidemia tostimulate MPS. Hence, for an 80-kg male sprinter, male long
jumper, or female javelin thrower, this guideline represents an∼30 g protein serving size, with an example meal plan displayedin Table 1. In contrast, but employing the similar rationale,a 55-kg female long-distance runner or race walker would consume∼20 g protein serving, with an example meal plan displayed inTable 2.
In terms of protein type, leucine-rich rapidly digested protein
sources, such as whey protein, have been shown to elicit a greater
stimulation of MPS during training recovery compared with slowly
digested proteins of lower leucine composition, such as soy,micellar casein (high in leucine and more slowly digested), andwheat (Gorissen et al., 2016; Tang et al., 2009). There also isevidence that track and ﬁeld athletes would beneﬁt from distributing their daily protein intake evenly (e.g., 4–5 equally spaced
servings) throughout the day (Mamerow et al., 2014). This strategy
might include a slow-releasing, protein-rich, snack at bedtime(Trommelen & van Loon, 2016). Importantly, in the context of
this review, these protein recommendations are based on scientiﬁcdata generated in weight-stable (i.e., in energy balance) trained, but
by no means elite, athletic individuals.

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Table 1

Example Meal Plan for an 80-kg Male Sprinter, Male Long Jumper, or Female Javelin Thrower

Time

Meal

Foods providing ∼30 g of protein in highlighted meals during the day

08.00
09.30–11.00
11.00
12.30
16.00
17.00–19.30
19.30
22.00

Breakfast
Strength training
Recovery meal
Lunch
DinnerEvent-speciﬁc training
Recovery meal
Evening meal

250-g oatmeal porridge and 200-ml low-fat milk
Water and/or sports drink/bar/gel
300-g Greek yogurt with granola
Omelet of two eggs and cheese, toast/salad
120-g chicken with rice and vegetables
Water and/or sports drink/bar/gel
300-g cottage cheese with apple and berries
100-g tuna in a mixed pasta saladNote. Assuming that a daily protein intake of 1.6 g/kg BM is spread equally between three servings, which equates to a relative per meal protein serving of ∼0.4 g/kg BM or∼30 g of protein expressed on an absolute basis. Carbohydrate-rich foods should be added to meet the individual daily energy needs. BM = body mass.

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Table 2

Example Meal Plan for a 55-kg Female Long-Distance Runner or Race Walker

Time

Meal

Foods providing ∼20 g of protein in highlighted meals during the day

08.00
09.30–11.00
11.00
12.30
16.00
17.00–19.30
19.30
22.00

Breakfast
Strength training
Recovery meal
Lunch
DinnerEvent-speciﬁc training
Recovery meal
Evening meal

200-g Greek yogurt and granola
Water and/or sports drink/bar/gel
500-ml smoothie (yogurt and berries)
Two fried eggs and toast/salad
100-g salmon with potatoes and vegetables
Water and/or sports drink/bar/gel
500-ml smoothie with yogurt, fruit, and berries
Ham and cheese sandwich and 200-ml low-fat milk

Note. Assuming that a daily protein intake of 1.6 g·kg BM−1·day−1 is spread equally between three highlighted servings, which equates to a relative per meal protein servingof ∼0.4 g/kg BM or ∼20 g of protein expressed on an absolute basis. Carbohydrate-rich foods should be added to meet the individual daily energy needs. BM = body mass.

Dietary Protein for High-Quality Weight
Loss in Track and Field Athletes
Dietary protein is widely regarded as a key nutrient for manipulating
body composition during weight loss in both nonathletic andathletic populations. The beneﬁts of increasing dietary protein levels
above the recommended daily allowance of 0.8 g·kg BM−1·day−1 onbody composition during weight loss has been extensively investigated in overweight and obese populations (Josse et al., 2011;
Krieger et al., 2006; Longland et al., 2016; Wycherley et al., 2012).
In contrast, the evidence base that currently informs daily protein
recommendations for athletes during weight loss is limited to only
a handful of studies. To date, the most comprehensive review
of protein recommendations during weight loss in athletes was
conducted by Helms et al. (2014). This systematic review of six
published studies concluded that a daily protein intake of 1.8–
2.7 g·kg BM−1·day−1 or 2.3–3.1 g·kg LBM−1·day−1 was estimatedas optimal to preserve LBM and still results in the reduction of fat
mass during energy restriction in lean, resistance-trained athletes(Helms et al., 2014). Noteworthy, however, the fact is that only two(Mettler et al., 2010; Walberg et al., 1988) of the six studies includedin this review (Helms et al., 2014) actually compared matchedgroups of athletes consuming different levels of protein intake orquantiﬁed training. Hence, the practical application of this systematic review to the track and ﬁeld athlete is perhaps best interpreted
on a study-by-study basis.
Of the articles included in this systematic review (Helms et al.,2014), perhaps the study most relevant to strength/power-based
track and ﬁeld athletes was published by Mettler et al. (2010). This

tightly controlled study measured changes in BM, fat mass, and
LBM following a 2-week period of energy restriction in resistancetrained men who consumed ∼60% of their habitual energy intake,while maintaining their normal training schedule (4–5 sessions per
week, including ≥2 resistance training sessions). The control groupof athletes continued with their habitual daily protein intake (1.0 g/kg
BM or 1.2 g/kg LBM) during 2 weeks of energy restriction,
whereas the experimental group increased their protein intake to
2.3 g/kg BM, equivalent to ∼2.7 g/kg LBM or 35% of individual
total energy intake. Energy intake was matched between dietaryconditions. Interestingly, whereas the control group of athletes
lost 1.6 kg of LBM over the 2 weeks of energy restriction, there wasa negligible (0.3 kg) decline in LBM in the high protein-consuminggroup. Given that both groups lost ∼1.3 kg of fat mass, inaggregate, the decline in total BM was greater in the control(3 kg) versus high (1.5 kg) protein group. These ﬁndings wereremarkably similar, both qualitatively and quantitatively, toan earlier study in male body builders (Walberg et al., 1988).
Also consistent with this observation, a recent case study in an elite
female endurance athlete demonstrated an increase in LBM when
protein intake was increased to 2.6 g·kg BM−1·day−1 during∼2 weeks of reduced energy availability (Haakonssen et al., 2013).
Taken together, in terms of practical implications, these datasuggest that strength/power or endurance-based track and ﬁeld
athletes with the goal of preserving or increasing LBM during
weight loss should consume a dietary protein intake in excess of
1.6 g·kg BM−1·day−1 (Figure 1). Moving forward, as is the case forweight-stable athletes, protein recommendations for high-quality
weight loss should move toward expressing recommendations on ameal-to-meal rather than daily basis.

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Protein and High-Quality Weight Loss in Athletes

A series of elaborate laboratory-based metabolic studies provide a mechanistic link between dietary protein intake, exercise
training, skeletal muscle protein turnover, and the regulation ofmuscle mass during energy restriction. The general consensus isthat the main driver of LBM loss during weight loss is a reduced
stimulation of MPS, with minimal changes in MPB observed
during energy restriction (Hector et al., 2018). This phenomenon
is intuitive given that MPS is an energetically expensive process,requiring ∼4 moles of adenosine triphosphate to add each aminoacid during the elongation process of MPS (Browne & Proud,2002). As such, the attenuated rate of MPS during energy restriction suggests an adaptive mechanism to conserve energy during
weight loss. Accordingly, studies have demonstrated an ∼25%
decrease in fasting rates of MPS during the early (5–10 days) stagesof an energy restricted diet (Areta et al., 2014; Hector et al., 2018;
Pasiakos et al., 2010).
The ﬁndings from several mechanistic studies also indicate thatthe careful planning of dietary protein intake in combination withresistance exercise training provides an effective strategy for track
and ﬁeld athletes to counter the impaired response of MPS during
weight loss (Hector & Phillips, 2018; Pasiakos et al., 2015).
Two recent studies demonstrated that reduced fasting rates of
MPS following energy restriction were offset for the next 48 hr
when young men performed resistance-based exercise (Areta et al.,2014; Hector et al., 2018). Moreover, whereas 21 days of moderateenergy restriction (equivalent to a 20% energy deﬁcit) with a daily
protein intake of 0.8 g·kg BM−1·day−1 resulted in a suppressed
postprandial response of MPS to a 20 g serving of milk, increasing
daily protein intake to twice (1.6 g·kg BM−1·day−1) or thrice(2.4 g·kg BM−1·day−1) the recommended daily allowance restored
postprandial rates of MPS in response to the same 20-g milk serving
to levels observed during energy balance (Pasiakos et al., 2013).
Moreover, a recent study reported a protein dose-dependent increasein the postexercise response of MPS during energy restriction intrained young men (Areta et al., 2014). The highest MPS response
was observed with ingestion of 30 g of protein; however, the increasein MPS was linear from 15 to 30 g with no dose fed above that intake.
Thus, it remains unknown whether the response of MPS is further
increased with a protein dose greater than 30 g during energy
restriction. Nonetheless, taken together these data highlight theinteraction of increased daily protein intake and resistance training
in stimulating MPS response during weight loss.
Few studies have examined the impact of protein type (Hector
et al., 2015) or the meal pattern (e.g., daily protein intake distributed equally between meals or skewed toward the evening meal;
Murphy et al., 2018) of protein intake on rates of MPS during
energy restriction, particularly within an athletic context. Nevertheless, if we assume the recommended protein intake during
energy restriction in track and ﬁeld athletes ranges from 1.6 to
2.4 g·kg BM−1·day−1 (Figure 1), the following calculations can bemade to inform reﬁned protein recommendations on a meal-tomeal or serving-to-serving basis. For the same 80-kg male sprinters, male long jumpers, or female javelin throwers who spread adaily protein intake of 1.6 g·kg BM−1·day−1 equally between fouror ﬁve servings (i.e., three meals and one or two snacks, including a
bedtime snack), this equates to a relative per meal protein serving of∼0.4 g/kg BM or ∼32 g of protein expressed on an absolute basis forthree meals and the remainder of his protein as snacks. Alternately,
if we assume a daily protein recommendation at the high end of thisrecommended range (i.e., 2.4 g·kg BM−1·day−1), this equates toa per meal protein serving of ∼0.5 g/kg BM or a 40-g protein dose.
To this end, these calculations provide only an informed estimate

169

regarding the recommended dose of protein that athletes should
consider consuming on a meal-to-meal basis during energy restriction. However, we contend there is reasonable scientiﬁc evidence
for us to propose, with reasonable conﬁdence, that this target permeal protein dose exceeds the 0.3–0.4 g/kg BM recommendation
set for athletes during energy balance (Tables 1 and 2).
Despite convincing evidence that protein intakes to preserve
LBM are increased in athletes during weight loss, optimizing
protein recommendations for high-quality weight loss in elite track
and ﬁeld athletes also likely depends on several case-speciﬁcfactors. In theory, three general factors determine the level of
LBM loss during energy restriction and should be consideredwhen prescribing protein recommendations for the athlete. First, asevere energy deﬁcit that requires a fast rate of weight loss is
associated with a more pronounced loss of LBM compared with aslower rate of weight loss (Garthe et al., 2011). Second, individuals who inherently possess greater muscle mass are more
susceptible to losing LBM during weight loss compared withthose athletes who possess less (Heymsﬁeld et al., 2011). Third,
the habitual protein intake of the athlete prior to energy restriction
should be considered when setting the target level of protein intake
for the track and ﬁeld athlete during weight loss. In theory, theathlete who habitually consumes a high protein diet, possesses a
signiﬁcant volume of muscle mass, has a high intrinsic metabolic
capacity to degrade amino acids and generate urea, and selectsa more aggressive weight loss strategy should target a daily protein
intake toward the higher (2.4 g·kg BM−1·day−1) end of therecommended range (Helms et al., 2014). Finally, it is likelythat the practice of resistance training is a potent local (i.e., muscle
speciﬁc) stimulus to allow the exercised muscle to retain lean mass
during weight loss. This point is illustrated by data from Longland
et al. (2016) who showed that athletes consuming a protein intake
of only 1.2 g·kg BM−1·day−1 were able to completely ablate theirloss of lean mass, whereas those consuming a protein intake of
2.4 g·kg BM−1·day−1 actually gained a modest but signiﬁcantamount of LBM. We propose that in fact of the two stimuli, thepractice of resistance exercise is going to be far more potent thanincreasing protein intake as a stimulus for promoting retentionof LBM.

High Protein Diets for Health andPerformance in Track and Field Athletes
There are a number of long-standing claims that a high protein diet,as advocated here for track and ﬁeld athletes during weight loss, isdetrimental for athlete health (Lowery & Devia, 2009; Martin et al.,2005; Metges & Barth, 2000). However, at present, there is no
scientiﬁc evidence to substantiate the claims that protein will
enhance risk of adverse renal health, particularly within athletic
populations (Phillips, 2017; Phillips et al., 2016; Van Elswyk et al.,2018). Moreover, as opposed to what is often touted as a negative
effect of high protein in stimulating adverse outcomes for bone, a
recent meta-analysis from the U.S. National Osteoporosis Foundation concluded that protein is actually a bone supportive nutrient(Shams-White et al., 2017) particularly when athletes are consuming adequate calcium and vitamin D. In short, track and ﬁeld
athletes who consume a high protein diet during weight loss are notplacing themselves at increased risk of kidney problems or poorbone health.
Perhaps the greater concern for the track and ﬁeld athlete who
embarks on a high-protein weight-loss diet relates to the choice of

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macronutrient to replace with an increased protein intake. Bydefault, dietary carbohydrate and/or fat intake must be adjusted
to accommodate for the increase in protein content of the diet.
According to a meta-analysis, increasing the protein content of anenergy restricted diet at the expense of carbohydrate, rather than fat,results in a greater decline in BM and fat mass during weight loss
(Krieger et al., 2006). However, this meta-analysis was based onstudies conducted in overweight and obese populations. In thecontext of athlete performance, concern has been raised regarding
the impact of reducing carbohydrate availability on maintaining
training quality and subsequent performance during periods ofweight loss. To address this concern, Mettler et al. (2010) standardized carbohydrate intake at habitual levels (3.4 g·kg BM−1·day−1)
and increased protein intake at the expense of fat intake during
2 weeks of energy restriction in resistance-trained men. In addition
to improving body composition, athletes who consumed the highprotein/low-fat diet either maintained or improved their performance on a series of strength-based exercises.
A separate, but related consideration for the track and ﬁeld
athlete in terms of performance during energy restriction concerns
the rate of weight loss. A slower rate of weight loss (0.7% bodyweight loss per week) in elite athletes resulted in more favorable
performance and body composition outcomes than when athletes
embarked on a more rapid weight loss (1.4% body weight loss perweek) program (Garthe et al., 2011a). As a general guideline, track
and ﬁeld athletes are recommended to engage in a slower rate(∼0.5 kg/week) of weight loss and make subtle adjustments toboth their carbohydrate and fat intakes (∼20% of total energy intake)rather than excessively reducing either macronutrient alone whenincreasing the protein content of an energy restricted diet. In theory,
this measured approach will address fears over reducing dietarycarbohydrate or fat intakes to levels that may adversely affect thehealth and performance of the track and ﬁeld athlete.

Amino Acid-Based Supplements forHigh-Quality Weight Loss in Track and
Field Athletes
Anecdotally, there is signiﬁcant interest in the role of protein-based
supplements during weight loss for improved body composition andperformance in athletic populations, including track and ﬁeld

athletes. In this regard, most interest has focused on dietary supplementation with the branched-chain amino acids (BCAA), leucine,isoleucine, and valine. There is ample evidence that ingested BCAA
(Karlsson et al., 2004; Moberg et al., 2016), in particular leucine(Kimball & Jefferson, 2006), result in stimulation of the molecularsignaling pathways that switch on MPS. Recent work also demonstrated that ingestion of 5.6 g of BCAA alone immediately following
a bout of resistance exercise resulted in a moderate (∼27%) increased
stimulation of MPS during recovery compared with a carbohydrate
placebo (Jackman et al., 2017); however, this effect was almost
certainly due to the presence of leucine as the other two BCAA haveno effect in activating cell signaling and stimulating MPS synthesis(Atherton et al., 2010). Similar results also were demonstrated with
the ingestion of leucine or the leucine metabolite β-hydroxy-βmethylbutyrate alone (Wilkinson et al., 2013). However, interestingly the magnitude of this increased stimulation of MPS during
exercise recovery with BCAA ingestion was ∼50% inferior to the
MPS response to ingesting a 20-g dose of whey protein containing
similar amounts of BCAA (Witard et al., 2014). The current
knowledge base that directly investigates the impact of proteinbased supplements, including BCAA, on body composition during
energy restriction is limited and thus future work in the context ofweight loss is warranted.

General Conclusions
Tables 3 and 4 provide an overview of the “knowns” and “unknowns” regarding protein recommendations for training adaptation and body composition manipulation in track and ﬁeld athletes.
In summary, optimal levels of protein intake in athletes clearlyexceed the current protein recommended daily allowance ofbetween 0.8 and 1.0 g·kg BM−1·day−1. As outlined, dietary protein
intakes in the range of 1.3–1.7 g·kg BM−1·day−1 are optimal forathletes who are maintaining their body weight. In contrast, athletes
wishing to undertake high-quality weight loss are advised toengage in resistance exercise and consume dietary protein intakes
in quantities above 1.6 g·kg BM−1·day−1 and closer to 2.4 g·kg
BM−1·day−1 to promote the retention and potentially increase
LBM. Leucine is a key and critical amino acid for stimulating
the cell signaling pathways that control MPS and should beemphasized in protein sources consumed postexercise to trigger
a rise in MPS during weight loss. There are beneﬁts to consuming

Table 3 Protein Recommendations for Training Adaptation and Body Composition Manipulation in Track and Field
Athletes
What we know from scientific literature and how this knowledge may be translated into everyday practice for track and fieldathletes(a) The optimum daily protein intake for the weight stable track and ﬁeld athletes exceeds the protein RDA (0.8–1.0 g·kg BM−1·day−1) set for the generaladult population.
(b) The optimum daily protein intake for track and ﬁeld athletes with the goal of weight maintenance or weight gain ranges from 1.3 to 1.7 g·kg
BM−1·day−1 (refer to Table 1).
(c) The optimum per meal/serving of protein for track and ﬁeld athletes with the goal of weight maintenance or weight gain ranges from 0.3 to 0.4 g/kg
BM per meal (refer to Table 1).
(d) Very high protein intakes of >2.5 g·kg BM−1·day−1 offer no adaptive advantage.
(e) The optimum daily protein intake for track and ﬁeld athletes with the goal of high-quality weight loss exceeds 1.6 g·kg BM−1·day−1 and may be as
high as 2.4 g·kg BM−1·day−1.
(f) Track and ﬁeld athletes who consume a high protein diet (e.g., 2.4 g·kg BM−1·day−1) during weight loss are not at increased risk of kidney problems orpoor bone health.
Note. RDA = recommended daily allowance; BM = body mass. High-quality weight loss is deﬁned as the loss of fat mass while preserving, or even increasing, lean bodymass.
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171

Table 4 Future Research Directions in Dietary Protein for Training Adaptation and Body Composition Manipulationin Track and Field Athletes
What research has yet to discover

Priority areas for future research(a) The optimum per meal/serving of commonly consumed protein-rich Studies designed to characterize the dose–response of MPS to ingested
foods for maximal stimulation of MPS during exercise recovery. protein-rich foods rather than isolated intact protein sources such as whey andsoy protein.
(b) The longer term beneﬁts of higher protein intakes on high quality Individual or small group case studies in elite athletes with a more realistic
weight loss in track and ﬁeld athletes.
level of weight loss (e.g., 20% vs. 40% energy deﬁcit) over a longer period of
training (>2 weeks).
(c) The optimum per meal/serving of protein during weight loss in track Studies designed to characterize the dose–response of MPS to ingested
and ﬁeld athletes.
protein during energy restriction in athletes.
(d) The impact of protein source and timing on body composition during Studies should determine rates of MPS after manipulating the daytime patternweight loss in track and ﬁeld athletes.
of animal- and plant-based protein foods during energy restriction in athletes.
(e) Individual variability in body composition responses to dietary
Studies should explore genetic and epigenetic factors that predict bodyprotein manipulation during weight loss in track and ﬁeld athletes. composition responses during energy restriction.
(f) Event-speciﬁc protein needs in track and ﬁeld athletics related to body Individual or small group case studies across all track and ﬁeld events.
composition manipulation.

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Note. MPS = muscle protein synthesis.

food-based protein sources due to their nutrient density (Phillips
et al., 2015), which would be beneﬁcial for track and ﬁeld athletes
especially those who are on energy-restricted diets.
Acknowledgments
The manuscript preparation and editing was undertaken by O. C. Witard,
I. Garthe, and S. M. Phillips. All authors approved the ﬁnal version of thepaper. We also would like to thank all volunteers who participated inresearch projects, providing valuable data and information. O. C. Witard
reports having received honoraria from PepsiCo. S. M. Phillips reports
having received funding, honoraria, and travel expenses from the U.S.
National Dairy Council, funding from PepsiCo, and funding from theDairy Farmers of Canada.

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