The purpose of this project is to investigate the effects of exercise at different times of day on 72-hour eating behaviour, physical activity and sedentary behaviour in physically inactive adults.

Eligibility and Consent Confirmation:

Prior to the one-week preliminary test, participants will undergo eligibility screening, including measurements of height, weight, and body composition. After the researchers will provide a detailed explanation of the experimental procedures, participants can decide whether to participate in the study. Eligible participants will complete a set of high-intensity bodyweight exercise to familiarize themselves with the exercise. Subsequently, the researchers will explain the use of pedometers and distributed dietary record forms.

During a one-week preliminary test, participants will be instructed to record their physical activity levels measured in steps, sleep duration including wake-up and sleep times, and dietary behaviours through photographs taken (2 weekdays and 1 weekend day) over a period of 7 consecutive days. Participants will be allowed to take part in this study, once they meet the inclusion criteria: 1) an average daily step count of less than 7,500 over the course of the week and 2) a wake-up time no later than 11:00 AM).

Exercise intervention:

Two main trials will be separated by at least one week - exercise in the morning (08:00 to 11:00 AM) or exercise in the evening (18:00 to 21:00 PM).

In both trials, participants will complete the first Visual Analogue Scale (VAS) for subjective appetite upon waking, wear a pedometer and an accelerometer, and record energy intake and physical activity over a 3-day period (the day before exercise intervention, the exercise day and the day after exercise intervention). Upon arrival at the laboratory, participants will complete the second VAS, followed by a 15-minute waiting period before commencing the exercise. Participants will perform high-intensity bodyweight exercise (3 sets with 8 exercises with a cycle of 30 seconds exercise and 30 seconds rest), followed by a 15-minute rest period, after which they will complete the third VAS.

Heart rate and Rating of Perceived Exertion (RPE) will be measured regularly during exercise. Energy balance (e.g., energy intake and spontaneous physical activity) will be assessed using a food diary, Actigraph wGT3x-BT accelerometer (Actigraph Co., Ltd., Pensacola, FL, USA), and pedometer (Realalt, Goldhat Ltd., UK), which will be worn starting from the night two days before the experiment and removed after waking up two days post-experiment.

Inclusion Criteria:

• Aged between 20 and 50 years, with a BMI ranging from 19 to 27 kg/m².
• Classified as having "low" physical activity levels (750 Metabolic Equivalents / week) according to the International Physical Activity Questionnaire (IPAQ).
• Engaged in moderate-intensity exercise for no more than 3 days per week and less than 30 minutes per session in the 3 months preceding the study.
• Maintained a stable body weight (± 3 kg) during the 3 months prior to the main experiment.
• Not taking any medications, supplements, or vitamins that might affect food intake, appetite, physical activity, weight loss, or metabolism.
• Free from cardiovascular and metabolic diseases.
• Not pregnant or planning to become pregnant.
• Not currently on a diet or undergoing any specific dietary interventions (e.g., intermittent fasting, ketogenic diet).
• No injuries or surgical wounds preventing physical activity.
• Regular sleep patterns, averaging 7-9 hours per night, with no shift work.
• No habits of heavy alcohol consumption or smoking.

Exclusion Criteria:

• Personal history of/existing diabetes, cardiovascular disease, metabolic disease or dyslipidaemia.
• Taking medications that may influence lipid or carbohydrate metabolism or immune system function.
• Unable to take part in exercise for any reason (e.g., injury or disability) or a positive response to any questions on the Physical Activity Readiness questionnaire (PAR-Q).