Endocrinological and Physiological Responses to Short-term Reduced Carbohydrate Availability in Males

Investigating the Endocrinological and Physiological Responses to Short-term Reduced Carbohydrate Availability in Males.

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.

Study Overview

• Status: Completed
• Conditions: Energy Supply; Deficiency; Carbohydrate Availability
• Intervention / Treatment: Other: Nutritional/dietary intake manipulation ('Normal'); Other: Nutritional/dietary intake manipulation ('Low')

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.

• Study Type: Interventional
• Enrollment (Actual): 8
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Jose L Areta; Phone Number: +441519046230; Email: J.L.Areta@ljmu.ac.uk
• Study Contact Backup: Name: Harry L Taylor; Email: H.L.Taylor@2019.ljmu.ac.uk

Study Locations

• United Kingdom
  • Merseyside
    • Liverpool, Merseyside, United Kingdom, L3 3AF
      • Liverpool John Moores University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Gender/Sex: Male
• Age:18-40
• Healthy (as determined by pre-participation questionnaires)
• Regularly Exercising/Aerobically trained (3 + times/week, VO2max >50 ml/kg/min), as determined through participant self-identification via recruitment email/verbal communication and baseline assessment of VO2max)
• Weight-stable (within 2 kg) for the past 6-months

Exclusion Criteria:

• Gender/Sex: Female/Other
• Age - < 18 - > 40
• Health - Deemed unable to perform exercise (assessed via PAR-Q)
• Current smoker.
• Medical Condition - Those with any previous diagnosis of; Osteoporosis/low bone mineral density, cardio-vascular disease, Diabetes Mellitus, Cerebrovascular Disease, blood-related illness/disorder, Asthma or other respiratory illness/disorder, Liver Disease, Kidney Disease, gastrointestinal disease, Eating Disorder or Disordered Eating. Those currently taking prescription medication or unwell with a cold or virus at the time of participation.
• Those unwilling to adhere to the study's methodological requirements (including adhering to alterations in diet and training - inc. alcohol abstention) from the day prior to intervention onset (24 hrs pre-intervention) to completion of follow-up assessments (day 5).
• Those following a restrictive diet (e.g. vegans)
• Those with food allergies and/or food intolerances
• Training status - Does not train 3 + times/week (over past 6 months on average) and/or have a VO2max >50 ml/kg/min.
• Any athletes that may be tested for substances on the WADA banned substances list

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: None (Open Label)

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Other: Normal Carbohydrate Availability; Participants will complete a supervised morning cycling session daily (each morning for five days) to achieve a 15 kcal/kg FFM/day exercise energy expenditure, with samples collected pre-, during- and post-exercise. Participants will then be provided (daily) with all subsequent dietary intake for the intervention period. In the Normal Carbohydrate Availability trial arm, participants will be provided with 60 kcal/kg FFM/day of energy intake, to elicit a net energy availability of 45 kcal/kg FFM, with ~60% of this energy intake from carbohydrates. The intervention will last for four days, spanning five testing mornings (i.e. trial begins following fasted baseline assessments on morning 1, finishing with final sample collection on morning 5).	Other: Nutritional/dietary intake manipulation ('Normal'); Energy Intake provision (60 kcal/kg FFM/day) to elicit 'normal' energy availability (45 kcal/kg FFM/day), with 60% from carbohydrates.; Other Names: Normal Carbohydrate Availability
Experimental: Low Carbohydrate Availability; Participants will complete a supervised morning cycling session daily (each morning for five days) to achieve a 15 kcal/kg FFM/day exercise energy expenditure, with samples collected pre-, during- and post-exercise. Participants will then be provided (daily) with all subsequent dietary intake for the intervention period. In the Low Carbohydrate Availability trial arm, participants will be provided with 60 kcal/kg FFM/day of energy intake, to elicit an energy availability of 45 kcal/kg FFM, with ~1.5 g/kg provided from carbohydrate and ~70-80% of energy intake in the form of fat. The intervention will last for four days, spanning five testing mornings (i.e. trial begins following fasted baseline assessments on morning 1, finishing with final sample collection on morning 5).	Other: Nutritional/dietary intake manipulation ('Low'); 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 Names: Low Carbohydrate Availability

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in blood bone turnover markers: ß-CTX (Bone Resorption)	Analysis of changes in blood-borne bone (re)modelling marker ß-CTX (Bone Resorption) following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood bone turnover markers: P1NP (Bone Formation)	Analysis of changes in blood-borne bone (re)modelling marker P1NP (Bone Formation)	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: Testosterone	Analysis of changes to circulating testosterone concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in resting substrate utilisation	Analysis of changes in resting substrate utilisation. Assessed using indirect calorimetry.	Days 1, 3 and 5 of each intervention
Changes in sub-maximal Exercise Energy Expenditure	Analysis of changes in sub-max exercise energy expenditure and substrate utilisation at standardised exercise intensities. Assessed using indirect calorimetry.	Days 1, 2, 3, 4 & 5 per intervention
Changes in sub-maximal exercise substrate utilisation	Analysis of changes in sub-max exercise energy expenditure and substrate utilisation at standardised exercise intensities. Assessed using indirect calorimetry.	Days 1, 2, 3, 4 & 5 per intervention
Immune function	Analysis of changes to saliva-based markers of immune function	Days 1, 2, 3, 4 & 5 per intervention
Changes in Initial Orthostatic Hypotension (IOH)	Analysis of changes in IOH, assessed via blood pressure finometry and questionnaire	Pre- and post-intervention (days 1 and 5) for both intervention
Change in Profile of Mood States	Analysis of changes in Psychological/mood, assessed via the POMS-40 questionnaire	Pre- and post-intervention (days 1 and 5) per intervention
Change in subjective hunger	Analsis of changes in subjective hunger, assessed via visual analogue scales	Days 1, 2, 3, 4 & 5 per intervention
Change in sexual drive/libido	Analysis of subjective sex-drive/libido changes, assessed via visual analogue scale	Pre- and post-intervention (days 1 and 5)
Physical activity energy expenditure (PAEE)	Analysis of PAEE alterations, assessed via wrist-worn accelerometers (acti-watch)	Continuous monitoring during intervention period (5-days)
Sleep duration and quality	Analysis of sleep alterations, assessed via wrist-worn device and sleep diary (collectively quantified by analysis of sleep duration, sleep latency, time of sleep onset, no of wakes during night, subjective sleep quality visual analogue scale)	Continuous monitoring during intervention period (5-days)
Changes in Body Composition: Body Mass (kg)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Body Mass Index (kg/m^2)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Fat Mass (kg)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Body Fat Percentage (%)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Fat Free Mass (kg)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Skeletal Muscle Mass (kg)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Total Body Water (l)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Total Body Water (%)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Extra-cellular Water (l)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Extra-cellular Water (%)	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in Body Composition: Extra-cellular Water/Total Body Water ratio	Analysis of body composition changes - assessed using bio-electrical impedance analysis (BIA)	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: Ketones	Analysis of changes to circulating ketones concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: Glucose	Analysis of changes to circulating glucose concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: Free fatty Acids	Analysis of changes to circulating free fatty acid concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: Insulin	Analysis of changes to circulating insulin concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: Cortisol	Analysis of changes to circulating cortisol concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: HDL	Analysis of changes to circulating HDL concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: LDL	Analysis of changes to circulating LDL concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: glycerol	Analysis of changes to circulating glycerol concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: Leptin	Analysis of changes to circulating Leptin concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Changes in blood metabolites/hormones: IGF-1	Analysis of changes to circulating IGF-1 concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention
Alterations to skeletal muscle glycogen	Assessment of alterations in skeletal muscle glycogen content	Days 1 & 5 per intervention (pre-post)
Alterations to Intra-muscular lipid profile: lipid droplet content	Assessment of alterations in lipid droplet content	Days 1 & 5 per intervention (pre-post)
Alterations to Intra-muscular lipid profile: lipid droplet morphology	Assessment of alterations in lipid droplet morphology	Days 1 & 5 per intervention (pre-post)
Alterations to Intra-muscular lipid profile: lipid droplet associated proteins	Assessment of alterations in lipid droplet associated proteins	Days 1 & 5 per intervention (pre-post)
Resting Metabolic Rate	Analysis of changes to Resting Metabolic Rate (kcal/day) following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 3 and 5 of each intervention
Changes in blood metabolites/hormones: Triiodothyronine (T3)	Analysis of changes to circulating T3 concentrations following short term energy balance with a) normal carbohydrate availability and b) low carbohydrate availability	Days 1, 2, 3, 4 & 5 per intervention

Collaborators and Investigators

• Sponsor: Liverpool John Moores University
• Investigators: Study Director: Jose L Areta, Liverpool John Moores University

Study record dates

Study Major Dates

• Study Start (Actual): May 4, 2022
• Primary Completion (Actual): December 9, 2022
• Study Completion (Actual): December 9, 2022

Study Registration Dates

• First Submitted: March 2, 2021
• First Submitted That Met QC Criteria: September 20, 2022
• First Posted (Actual): September 22, 2022

Study Record Updates

• Last Update Posted (Actual): October 17, 2023
• Last Update Submitted That Met QC Criteria: October 16, 2023
• Last Verified: October 1, 2023

More Information

Terms related to this study

• Keywords: Insulin; Blood pressure; Glycerol; Glucose; Leptin; Testosterone; Triglycerides; Ketones; Ghrelin; Bone turnover markers; Thyroxine; Free fatty acids; Triiodothyronine; P1NP; Resting Metabolic Rate (RMR); ß-CTX
• Other Study ID Numbers: 22/SPS/026

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No