Body Weight and Carb Metabolism

Study Overview
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Brief Summary
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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.

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

Conditions
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Exercise Metabolism

Intervention / Treatment
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* Other: Moderate-intensity (relative) exercise with glucose ingestion
* Other: Moderate-intensity (absolute) exercise with glucose ingestion


Participation Criteria
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Eligibility Criteria
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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

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

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

What is the study measuring?
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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 |
| --- | --- | --- |
| 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 | 
| 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 |