Fasted Evening Exercise: Performance and Compensatory Eating

Effects of Extended Fasting Prior to Evening Exercise on Appetite, Energy Intake and Performance.

This study will compare the appetite, energy intake, and exercise performance responses to a bout of exercise completed in the evening after an extended period of fasting with a similar bout of exercise completed in the evening and the morning, after consuming a carbohydrate-containing meal.

Regular exercise is known to be a successful strategy for improving several facets of health and maintaining body weight. However, many people are not engaging in enough exercise, and some may not be achieving maximum benefits from the exercise that they already do. Performing exercise in the overnight fasted state has been shown to reduce energy intake over the course of a single day, without any compensatory reductions in free-living energy expenditure. Despite these promising findings, it is likely that not every member of the population is logistically able to perform exercise in the morning due to various work, family and social commitments, and exercise in the evening may be a logical alternative for these individuals. Whether the beneficial effects of overnight fasted exercise can be observed at an alternative time of the day (i.e. the evening) is unknown.

Therefore, the investigators are interested in examining the compensatory appetite and energy intake responses following a bout of evening exercise performed after an extended (7 hour) period of fasting. Exercise performance will also be assessed as a marker of voluntary energy expenditure, which if reduced, has the potential to compensate for the reduced energy balance induced by fasted exercise.

Inclusion Criteria:

• Non-smokers.
• Have maintained a stable weight for 6 months (self-reported).
• No history of gastric, digestive, cardiovascular or renal disease (self-reported).
• Female specific: must be using a monophasic, low dose combined OCP (containing less than 50μg oestradiol and a synthetic progestin) OR females with regular menstrual cycles (self-reported).

Exclusion Criteria:

• Have an unusual eating pattern (i.e., extended fasting periods >8h other than overnight - self-reported).
• Severe food allergies, dislike or intolerance of study foods or drinks.
• Currently undergoing a lifestyle intervention (structured diet or exercise)
• Diagnosis of a condition or currently undergoing treatment therapy known to affect glucose or lipid metabolism (e.g., type-2 diabetes, taking statins), or contraindications to exercise.
• Use of medication or supplements that may affect hormone concentrations.
• Excessive alcohol consumption (>14 units/week).
• Intensive training schedule (>10 hours/week).
• Having received a positive COVID-19 test in the 6-month period prior to participation.
• Female specific: currently pregnant or breastfeeding, the use of any hormonal contraception, and the self-reporting of short (<24 d), long (>35 d), or irregular menstrual cycles.