Body Weight and Carb Metabolism

University of Bath20 enrolled

Overview

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 Type

OBSERVATIONAL

Enrollment

Conditions

Exercise Metabolism

Interventions

Moderate-intensity (relative) exercise with glucose ingestion

Eligibility

Sex: ALLMin age: 18 YearsMax age: 60 YearsHealthy volunteers:

Medical Language ↔ Plain English

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

Outcomes

Primary Outcomes

Peak exogenous carbohydrate oxidation rate (g/min)

Time frame: 120 minute

Total exogenous carbohydrate oxidation (g)

Sum of exogenous carbohydrate oxidation in g

Time frame: minutes 30-120 of exercise

Secondary Outcomes

Total exogenous carbohydrate oxidation (g/kgFFM)

Sum of exogenous carbohydrate oxidation (g/kgFFM)

Time frame: minutes 30-120 of exercise i

Whole-body carbohydrate oxidation rate (g)

Sum of whole-body carbohydrate oxidation (g)

Time frame: minutes 30-120 of exercise

Whole-body carbohydrate oxidation rate (mg/kgFFM)

Sum of whole-body carbohydrate oxidation (mg/kgFFM)

Time frame: Sum of minutes 30-120 of exercise

Endogenous carbohydrate oxidation rate (g)

Sum of endogenous carbohydrate oxidation (g)

Time frame: minutes 30-120 of exercise

Endogenous carbohydrate oxidation rate (mg/kgFFM)

Sum of endogenous carbohydrate oxidation (mg/kgFFM)

Time frame: minutes 30-120 of exercise

Whole-body fat oxidation rate (g)

Sum of whole-body fat oxidation (g)

Time frame: minutes 30-120 of exercise

Whole-body fat oxidation rate (mg/kgFFM)

Sum of whole-body fat oxidation (mg/kgFFM)

Time frame: minutes 30-120 of exercise

Plasma lactate concentrations (mmol/L)

Time frame: minutes 0-120 of exercise

Plasma glucose concentrations (mmol/L)

Time frame: minutes 0-120 of exercise

Plasma non-esterified fatty acid concentrations (mmol/L)

Time frame: minutes 0-120 of exercise

Plasma insulin concentrations (pmol/L)

Time frame: minutes 0-120 of exercise

Dietary carbohydrate intake (grams/day)

Time frame: 72-hour food diary in g/d

Dietary sugar intake (grams/day)