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

Not Applicable

• Conditions: Dietary Modification
• Interventions: Dietary Supplement: High Fat; Dietary Supplement: Normal + Extra Fat; Dietary Supplement: Normal

• Registration Number: NCT02568592
• Lead Sponsor: University of Birmingham

Brief Summary

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

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.

Study Timeline

• Study Start: 2015-03
• Study First Submitted: 2015-05-13
• Study First Submitted QC: 2015-10-02
• Study First Posted: 2015-10-06
• Status Verified: 2016-05
• Last Update Submitted: 2016-05-11
• Last Update Posted: 2016-05-13
• Primary Completion: 2016-06
• Study Completion: 2016-06

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: Female
• Target Recruitment: 16

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.

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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

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Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
High Fat	High Fat	High Fat - Carbohydrate (20%), Fat (65%), Protein (15%)
Normal + Extra Fat	Normal + Extra Fat	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.
Normal	Normal	Normal - Carbohydrate (50%), Fat (35%) and Protein (15%)

Primary Outcome Measures

Name	Time	Method
Rates of fat oxidation during exercise	90 minutes of sub-maximal exercise	Rates of fat oxidation to be measured via indirect calorimetry during 90 minutes of submaximal exercise

Secondary Outcome Measures

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

Trial Locations

Locations (1)

University of Birmingham; 🇬🇧 Birmingham, West Midlands, United Kingdom