Endocrinological and Physiological Responses to Short-term Reduced Carbohydrate Availability in Males
Condition: Energy Supply; Deficiency; Carbohydrate Availability
Study type: Interventional

Summary: 
      Using a randomised crossover design, nine weight-stable men, aged 18 - 40 years old, will be
      recruited via convenience sampling from the staff and student body of LJMU and local area.
      Participants will be asked to follow two 4-day (~96 hours) periods of tightly controlled
      exercise energy expenditure (15 kcal/kg FFM/day [cycling]) and dietary intake (60 kcal/kg
      FFM/day) to compare a state of 'normal' energy availability (or energy balance; equivalent to
      45 kcal/kg FFM/day) with concomitant 1: normal carbohydrate availability ('Normal'; ~60% of
      dietary intake from carbohydrate) and 2: low carbohydrate availability ('LCHF', ~1.5 g/kg
      carbohydrate per day, ~70 - 80% dietary intake from fat). This approximates the amount of
      carbohydrate consumed by an individual in a state of LEA through consuming 10 kcal/kg FFM/day
      with 50% of intake from carbohydrate, or ~1.5 g/kg/day of carbohydrate. In both experimental
      phases we will measure endocrine, metabolic and physiological parameters.
    

Detailed description: 
      Rationale:

      The primary research question associated with this study is 'What is the impact of an acute
      period of low carbohydrate availability upon associated physiological and endocrinological
      markers in a cohort of healthy males?'

      Extensive research has been conducted since the 1970s to determine the aetiology behind the
      concurrent impairment of reproductive function and low bone mineral density that is commonly
      observed in exercising females (De Souza et al., 2014). This research has determined that
      chronic low energy availability ('LEA' - the energy available from diet after energy used in
      exercise has been subtracted) is the key determining factor for the endocrine and
      physiological responses observed in the Female Athlete Triad (De Souza et al., 2014) model.
      However, whilst the Male Athlete Triad (Nattiv et al., 2021) and RED-S (Mountjoy et al.,
      2018) models identify the likely impact of LEA upon males, equivalent research identifying
      the physiological effects of this state in males is far behind that of females.

      Moreover, whilst low energy availability has been identified as the key driver of the
      physiological dysregulations identified in the Female/Male Athlete Triad and RED-S models,
      much of the existing research has not adequately delineated between the impact of low energy
      availability, per se, and low carbohydrate availability. Recent research suggests that low
      carbohydrate availability, with or without the presence of LEA, may be a driver of the
      physiological dysregulations identified within the aforementioned models. For example, McKay
      et al (2021) have shown altered iron and immune responses and impaired exercise performance
      following 6-days of low carbohydrate (50 - 100 g/day) but ~normal energy availability (40
      kcal•kg FFM-1•day-1), whilst no changes were apparent in a LEA (15 kcal•kg FFM-1•day-1, 60%
      carbohydrate) and a control group. Similarly, Heikura et al (2020) have recently shown that
      over 3.5 weeks, a ketogenic diet impairs markers of bone turnover compared to an
      energy-matched high carbohydrate diet in highly trained athletes.

      Given that exercise and nutritional interventions are key for improving weight-loss and
      health of the general population, understanding how reduced energy and/or carbohydrate
      availability may affect male endocrinology and physiology is of the utmost importance. The
      effects and mechanisms by which low energy and/or carbohydate availability influences male
      physiological function therefore requires further research using well-controlled experimental
      research designs.

      We have recently conducted a study that aimed to understand the broad physiological,
      endocrine and muscular responses to a period of five-days of low energy availability
      (analysis of samples is ongoing). The proposed study therefore now aims to extend the scope
      of our research to investigate the impact of four- days of low carbohydrate availability
      using a low-carbohydrate, high-fat diet in the presence of adequate energy availability to
      address this gap in the literature.

      Objectives:

      Primary:

      To investigate the physiological responses of adult males to low carbohydrate availability
      whilst in energy balance over 4-days (~96 hrs, spanning five testing mornings), in contrast
      to an equivalent period of controlled energy balance with 'normal' carbohydrate availability
      in relation to muscle and endocrine parameters.

      Secondary:

      To investigate the wider physiological responses of adult males to low carbohydrate
      availability (whilst in energy balance) over 4-days (~96 hrs, spanning five testing
      mornings), compared to an equivalent period in controlled 'normal' carbohydrate availability
      in relation to whole-body physiological and metabolic status as well as body composition
      changes.

      Study Methods:

      Using a randomised cross-over design, participants will complete two interventions that will
      elicit conditions of 'normal' (NEA) and 'low' (LEA) carbohydrate availability whilst in
      energy balance, with a 10-day washout period in between conditions. Body composition changes
      and markers of bone turnover and reproductive health will be assessed, along with further
      physiological parameters.

      Sample Size:

      Sample size was determined based upon the primary outcome measure of Free Circulating
      Testosterone, the least sensitive primary outcome measures of the study.

      The findings of Koehler et al (2016) were used to estimate required sample size for this
      study. Koehler et al (2016) reported a non-significant (P >0.05) change in Testosterone
      following four days of Low Energy Availability (with exercise) at 15 kcal/kg FFM/day (LEA +
      Ex: Pre 5.27 ± 0.46, Post 4.46 ± 0.96 ng.ml-1), compared to a control group with exercise (C
      + Ex: Pre 4.98 ± 0.47 Post 4.92 ± 0.53 ng.ml-1). However, a large effect size for the
      reduction in testosterone concentrations for LEA + Ex compared to C + Ex (d = 1.36) was
      observed/calculated. Therefore a post-hoc power analysis was conducted, revealing a power
      (1-β err probability) of 0.759 for the sample size of N = 6. To replicate these findings with
      greater statistical power (α err prob 0.05, 1-β err prob > 0.9) would require 8 participants,
      with 9 participants required to factor for a potential 10% dropout rate in participants
      commonly observed.

      Quality:

      The research plan has been reviewed internally within the research team at Liverpool John
      Moores University. The researcher's associated with this study and associated with the review
      of the study protocol are all members of staff (or a PhD Student) within the Liverpool John
      Moores University Research Institute for Sport & Exercise Sciences (RISES). In the 2014 RISES
      (LJMU) submitted 34.75 FTE (full time equivalent) to Unit of Assessment 26 (UoA26) and
      attained a GPA (Grade Point Average) of 3.57. Placed second on GPA in the UoA, RISES became
      the leading centre for Sport and Exercise Science Research Quality in the UK (4* - 61% of all
      activity world leading, 3* - 36% of all activity internationally excellent standard). RISES
      submitted the largest volume of 4* outputs (n=60) in the UoA, had 90% of the impact activity
      rated at 4* and had 100% of the environment rated as 4*. Importantly, out of 1,911
      submissions in all 36 UoA's RISES came 11th in the entire UK for GPA achieved at REF2014,
      putting RISES (LJMU) amongst Oxford, UCL, LSE and Cambridge in the league tables for this
      metric. This makes RISES perfectly qualified to assess this research project.
    

Intervention name(s): Nutritional/dietary intake manipulation ('Normal'); Nutritional/dietary intake manipulation ('Low')
Intervention type(s): Other; Other
Intervention description(s): Energy Intake provision (60 kcal/kg FFM/day) to elicit 'normal' energy availability (45 kcal/kg FFM/day), with 60% from carbohydrates.; Energy Intake provision (60 kcal/kg FFM/day), with 1.5 g/kg of carbohydrate and 70-80% fat intake, to elicit 'low' carbohydrate availability in energy balance (45 kcal/kg FFM/day).
Other intervention name(s): Normal Carbohydrate Availability; Low Carbohydrate Availability
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Participants will complete two five-day trial-arms in randomised order, with an ~10-day washout period between interventions.
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Bone turnover markers; Testosterone; Glucose; Glycerol; Ketones; Insulin; Leptin; Ghrelin; Triglycerides; Triiodothyronine; Thyroxine; Resting Metabolic Rate (RMR); Free fatty acids; Blood pressure; ß-CTX; P1NP