Body Weight and Carb Metabolism

Exploring the Role of Body Mass in Exogenous Carbohydrate Oxidation Rates During Exercise

Whilst theoretically, body size should influence the capacity for intestinal carbohydrate absorption and thus exogenous oxidation rates during exercise, there is currently little empirical evidence to support this hypothesis. Accordingly, current nutrition guidelines for carbohydrate intake during exercise do not take body mass into account. Therefore, there is a need to establish whether body mass is related to exogenous carbohydrate oxidation rates during exercise. If such a relationship is established, this would lay the foundation to revise the current sports nutrition guidelines regarding carbohydrate intake during exercise.

The aims of this study are, therefore, to: 1) establish whether larger individuals display higher rates of exogenous carbohydrate oxidation than smaller individuals; and 2) establish if such a difference can be explained by the higher absolute exercise intensity, and thus the energy demand of exercise. It is hypothesised that larger individuals will demonstrate higher exogenous carbohydrate oxidation rates than smaller individuals, and that this difference will be partly (but not completely) diminished when the absolute intensity of exercise is matched.

Study Overview

• Status: Completed
• Conditions: Exercise Metabolism
• Intervention / Treatment: Other: Moderate-intensity (relative) exercise with glucose ingestion; Other: Moderate-intensity (absolute) exercise with glucose ingestion

• Study Type: Observational
• Enrollment (Actual): 20

Contacts and Locations

Study Locations

• United Kingdom
  • Bath, United Kingdom, BA2 7AY
    • Department for Health, University of Bath

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 60 years (Adult)
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

Trained cyclists or triathletes

Description

Inclusion Criteria:

• Able to cycle continuously for 2 hours at a moderate intensity
• VO2max of between 40-75 mL/kg/min
• Fat-mass index (determined by dual energy x-ray absorptiometry) < 5.5 kg·m-2

Exclusion Criteria:

• Diagnosed disorders of the gastrointestinal tract (e.g. crohn's, colitis etc.)
• People following a low-carbohydrate, high-fat diet
• Pregnant or lactating
• Diagnosed cardiovascular disease
• Possible symptoms of cardiovascular disease
• Diagnosis of diabetes of any type
• Hypercholesterolaemia (total cholesterol ≥ 6.2 mmol/L
• Hypertension (systolic blood pressure ≥140 mmHg or diastolic blood pressure ≥90 mmHg)
• Current smoker
• Family history of coronary artery disease (first-degree relative <60 years)
• Prevalence of vascular disease
• Autonomic neuropathy
• Kidney disease
• Diagnosed pulmonary disease (e.g. chronic obstructive pulmonary disease, asthma, interstitial lung disease or cystic fibrosis)
• Blood borne disease or infection
• Osteoporosis
• Osteoarthritis
• Blood clotting disorders
• Food intolerances/allergies (these may not specifically exclude you- please talk to the investigator)
• Sensitivity or allergy to anaesthetic

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
<70 kg body mass; Cyclists or triathletes with a body mass of less than 70 kg	Other: Moderate-intensity (relative) exercise with glucose ingestion; 120 minutes of cycling at 95% of lactate threshold ingesting 90 g/h of glucose
>70 kg body mass; Cyclists or triathletes with a body mass of less than 70 kg	Other: Moderate-intensity (relative) exercise with glucose ingestion; 120 minutes of cycling at 95% of lactate threshold ingesting 90 g/h of glucose; Other: Moderate-intensity (absolute) exercise with glucose ingestion; 120 minutes of cycling at a power matched to participant in the <70 kg body mass group, ingesting 90 g/h of glucose

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Peak exogenous carbohydrate oxidation rate (g/min)	Peak exogenous carbohydrate oxidation rate (g/min)	120 minute
Total exogenous carbohydrate oxidation (g)	Sum of exogenous carbohydrate oxidation in g	minutes 30-120 of exercise

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Plasma lactate concentrations (mmol/L)	Plasma lactate concentrations (mmol/L)	minutes 0-120 of exercise
Plasma glucose concentrations (mmol/L)	Plasma glucose concentrations (mmol/L)	minutes 0-120 of exercise
Plasma non-esterified fatty acid concentrations (mmol/L)	Plasma non-esterified fatty acid concentrations (mmol/L)	minutes 0-120 of exercise
Plasma insulin concentrations (pmol/L)	Plasma insulin concentrations (pmol/L)	minutes 0-120 of exercise
Dietary carbohydrate intake (grams/day)	Dietary carbohydrate intake (grams/day)	72-hour food diary in g/d
Dietary sugar intake (grams/day)	Dietary sugar intake (grams/day)	72-hour food diary
Dietary fibre intake (grams/day)	Dietary fibre intake (grams/day)	72-hour food diary
Dietary fat intake (grams/day)	Dietary fat intake (grams/day)	72-hour food diary
Dietary protein intake (grams/day)	Dietary protein intake (grams/day)	72-hour food diary
Dietary energy intake (kiloJoules/day)	Dietary energy intake (kiloJoules/day)	72-hour food diary
Dietary energy intake (kilojoules/kilogram/day)	Dietary energy intake (kilojoules/kilogram/day)	72-hour food diary
Dietary carbohydrate intake (grams/kilogram/day)	Dietary carbohydrate intake (grams/kilogram/day)	72-hour food diary
Dietary sugar intake (grams/kilogram/day)	Dietary sugar intake (grams/kilogram/day)	72-hour food diary
Dietary fibre intake (grams/kilogram/day)	Dietary fibre intake (grams/kilogram/day)	72-hour food diary
Dietary fat intake (grams/kilogram/day)	Dietary fat intake (grams/kilogram/day)	72-hour food diary
Dietary protein intake (grams/kilogram/day)	Dietary protein intake (grams/kilogram/day)	72-hour food diary
Total exogenous carbohydrate oxidation (g/kgFFM)	Sum of exogenous carbohydrate oxidation (g/kgFFM)	minutes 30-120 of exercise i
Whole-body carbohydrate oxidation rate (g)	Sum of whole-body carbohydrate oxidation (g)	minutes 30-120 of exercise
Whole-body carbohydrate oxidation rate (mg/kgFFM)	Sum of whole-body carbohydrate oxidation (mg/kgFFM)	Sum of minutes 30-120 of exercise
Endogenous carbohydrate oxidation rate (g)	Sum of endogenous carbohydrate oxidation (g)	minutes 30-120 of exercise
Endogenous carbohydrate oxidation rate (mg/kgFFM)	Sum of endogenous carbohydrate oxidation (mg/kgFFM)	minutes 30-120 of exercise
Whole-body fat oxidation rate (g)	Sum of whole-body fat oxidation (g)	minutes 30-120 of exercise
Whole-body fat oxidation rate (mg/kgFFM)	Sum of whole-body fat oxidation (mg/kgFFM)	minutes 30-120 of exercise

Collaborators and Investigators

• Sponsor: University of Bath
• Collaborators: University of Birmingham

Study record dates

Study Major Dates

• Study Start (Actual): March 1, 2022
• Primary Completion (Actual): April 27, 2024
• Study Completion (Actual): July 27, 2024

Study Registration Dates

• First Submitted: March 2, 2022
• First Submitted That Met QC Criteria: April 14, 2022
• First Posted (Actual): April 15, 2022

Study Record Updates

• Last Update Posted (Actual): September 19, 2024
• Last Update Submitted That Met QC Criteria: September 17, 2024
• Last Verified: September 1, 2024

More Information

Terms related to this study

• Other Study ID Numbers: 6632

Drug and device information, study documents

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