Dietary Modification
Conditions
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.
Interventions
DIETARY_SUPPLEMENTHigh Fat
High Fat - Carbohydrate (20%), Fat (65%), Protein (15%)
DIETARY_SUPPLEMENTNormal
Normal - Carbohydrate (50%), Fat (35%) and Protein (15%)
DIETARY_SUPPLEMENTNormal + Extra Fat
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.
Sponsors
GlaxoSmithKline
University of Birmingham
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
NONE
Eligibility
Sex/Gender
FEMALE
Age
18 Years to 45 Years
Healthy volunteers
Yes
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| 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
| Measure | Time frame | Description |
|---|---|---|
| 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 Free Fatty Acid concentration | 90 minutes sub-maximal exercise | Area under the plasma concentration versus time curve (AUC) of Free Fatty Acid |
| Change in plasma glycerol concentration | 90 minutes sub-maximal exercise | Area under the plasma concentration versus time curve (AUC) of glycerol |
Countries
United Kingdom
Outcome results
None listed