Exercise Substrate Utilisation and Endurance Performance Following Short-term Manipulation of Dietary Fat Intake

Study Overview
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Brief Summary
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The capacity to burn fat as fuel for exercise may have important implications for sporting performance, with dietary fat intake positively influencing this ability. Endurance performance and the ability to burn fat will be measured in women runners following the consumption of 3 diets varying in the amount of fat and carbohydrate.

Detailed Description
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Dietary fat intake positively influences the ability to burn fat during exercise in women but not men, whereas carbohydrate intake negatively influences fat oxidation in both sexes. The independent nature of dietary fat intake as a predictor of the ability to burn fat in women suggests that in conditions of adequate carbohydrate intake providing additional fat may increase fat oxidation in women whereas it does not in men. It is of interest to explore if indeed women are responsive (i.e., increase in fat oxidation) to short-term increases in dietary fat intake induced by overfeeding (adequate carbohydrate) or if as appears to be the case in men reduced carbohydrate intake as typically employed in high-fat, low carbohydrate dietary studies is also a prerequisite for enhancing fat oxidation in women, and whether this translates into a difference in exercise endurance performance.

Official Title
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Exercise Substrate Utilisation and Endurance Performance Following Short-term Manipulation of Dietary Fat Intake in Women

Conditions
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Dietary Modification

Intervention / Treatment
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* Dietary Supplement: High Fat
* Dietary Supplement: Normal
* Dietary Supplement: Normal + Extra Fat


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BMI >17.0 < 25 kg/m2 Good General Health Accustomed to vigorous physical activity Run > 2 times per week V̇O2max >50ml/kg/min Weight Stable > last 6months Non Smoker Pre-menopausal, and either eumenorrheic and regularly menstruating, or using monophasic hormonal oral contraceptives for > 3 months. Exclusion Criteria: Currently taking part in another scientific/clinical study Taking any prescription drug / supplement thought to influence metabolism Following unusual dietary practices (such as intermittent fasting or low carbohydrate diets) Pregnant Breast Feeding

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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Female

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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Design Details

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


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: High Fat<br>High Fat - Carbohydrate (20%), Fat (65%), Protein (15%) | Dietary Supplement: High Fat<br>* High Fat - Carbohydrate (20%), Fat (65%), Protein (15%)<br>|
| Experimental: Normal<br>Normal - Carbohydrate (50%), Fat (35%) and Protein (15%) | Dietary Supplement: Normal<br>* Normal - Carbohydrate (50%), Fat (35%) and Protein (15%)<br>|
| Experimental: Normal + Extra Fat<br>Normal + Extra Fat - Carbohydrate (50%), Fat (65%), Protein (15%). Carbohydrate and protein intake identical in absolute amounts to NORM (Normal), with an additional 30% extra energy coming from fat. | Dietary Supplement: Normal + Extra Fat<br>* Normal + Extra Fat - Carbohydrate (50%), Fat (65%), Protein (15%). Carbohydrate and protein intake identical in absolute amounts to NORMAL, with an additional 30% extra energy coming from fat.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Rates of fat oxidation during exercise | Rates of fat oxidation to be measured via indirect calorimetry during 90 minutes of submaximal exercise | 90 minutes of sub-maximal exercise | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| 5km running performance | Time to complete 5km on a treadmill | Immediately following measurement of Primary Outcome measure | 
| Change in plasma glucose concentration | Area under the plasma concentration versus time curve (AUC) of glucose | 90 minutes sub-maximal exercise | 
| Change in Free Fatty Acid concentration | Area under the plasma concentration versus time curve (AUC) of Free Fatty Acid | 90 minutes sub-maximal exercise | 
| Change in plasma glycerol concentration | Area under the plasma concentration versus time curve (AUC) of glycerol | 90 minutes sub-maximal exercise |