Influence of the Time of Day in the Effect of Caffeine on Maximal Fat Oxidation During Exercise in Women

Study Overview
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Brief Summary
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Caffeine is a natural stimulant with well-recognized metabolic benefits, however, there is a lack of studies investigating the time-of-day caffeine influence to enhance fat oxidation in women. The aim of this study was to evaluate the influence of the time of the day on the effect of caffeine on maximal rate of fat oxidation during aerobic exercise in women.

Detailed Description
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Caffeine is a natural stimulant with well-recognized sports performance benefits. Aside its performance-enhancing effect, caffeine has the potential of increasing fat utilization during aerobic exercise at submaximal intensities, lowering-down the contribution of carbohydrate as a fuel. This property of caffeine may provoke a glycogen-sparing effect in the skeletal muscle and liver for exercise situations where carbohydrate availability may be a challenge. Additionally, the capacity of caffeine to enhance fat utilization during exercise could be of interest for improving health outcomes as it may increase the rate of change in body composition in exercise programs. Maximal fat oxidation rate (MFO) during exercise is a remarkable physiological indicator associated with metabolic flexibility/body weight loss and endurance performance To date, it is unknown if caffeine increases MFO in the same proportion during morning and evening exercise trials in women. For this reason, the aim of the present study was to evaluate the influence of the time of the day on the effect of caffeine on MFO in women. We hypothesised that caffeine would increase MFO during morning and evening exercise and this effect would be of similar magnitude at both times of day.

Official Title
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Influence of the Time of Day in the Effect of Caffeine on Maximal Fat Oxidation During Exercise in Women. A Randomized, Crossover, Double-blind, and Placebo-controlled Study

Conditions
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Dietary Supplement

Intervention / Treatment
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* Dietary Supplement: Acute caffeine supplementation


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: To be non-smokers. To have low caffeine intake (i.e., < 50 mg of caffeine per day in the previous 2 months) To show no previous history of cardiopulmonary diseases or having suffered musculoskeletal injuries in the previous 6 months. To have a regular duration of their menstrual cycle for the previous 6 months. To confirm no existence of any type of menstrual disorders such as dysmenorrhea, amenorrhea, or strong symptoms associated with pre-menstrual syndrome. Exclusion Criteria: -

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 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: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Dietary Supplement: caffeine acute supplementation
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Caffeine intake<br>Test in the morning A dose of 3 mg/kg of caffeine (Bulk Powders, Essex, United Kingdom) was ingested before the beginning of each test. Test in the evening A dose of 3 mg/kg of caffeine (Bulk Powders, Essex, United Kingdom) was ingested before the beginning of each test. | Dietary Supplement: Acute caffeine supplementation<br>* To evaluate the influence of the time of the day (i.e., morning vs evening) on the effect of caffeine on maximal fat oxidation in women.<br>|
| Placebo Comparator: Placebo intake<br>Test in the morning A dose of 3 mg/kg of placebo (Cellulose, Guinama, Valencia, Spain) was ingested before the beginning of each test. Test in the evening A dose of 3 mg/kg of placebo (Cellulose, Guinama, Valencia, Spain) was ingested before the beginning of each test | Dietary Supplement: Acute caffeine supplementation<br>* To evaluate the influence of the time of the day (i.e., morning vs evening) on the effect of caffeine on maximal fat oxidation in women.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| MFO | Maximal fat oxidation during exercise | 2-months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| FATmax | The intensity of exercise that elicits MFO | 2-months | 
| RPE | Rate of percevied exertion during exercise | 2-months | 
| FAT AND CHO oxidation | Fat and carbohydrates oxidation | 2-months |