This study's primary aim is to investigate the acute effect of an exercise bout (30 minutes) on appetite and appetite-regulatory hormone responses during energy restriction. The researchers will also test if the exercise bout influences ad libitum energy intake after a period of energy restriction.

The researchers will compare three groups (control, severe-energy restriction, and severe-energy restriction with exercise) to see if exercise bout, during energy restriction, affects appetite, appetite-regulatory hormones, and energy intake in healthy men.

Before the main experiments are conducted, participants will attend a screening visit where the participants will provide consent and complete questionnaires that assess their health, food preferences, and physical activity levels. Researchers will then measure the participants' height, weight, waist circumference, and body composition.

Once the eligibility criteria are confirmed, participants will participate in two treadmill tests to establish their maximum oxygen uptake (V̇O2 max).

After the screening visit, participants will participate in three main experiments, each lasting 24 hours: control, severe energy restriction, and severe energy restriction with exercise. These experiments will be conducted in a counterbalanced design. Each experiment will start around 9:30 AM, following an overnight fast of at least 10 hours. Participants will have a prescribed meal in the evening before each main experiment. After this meal, the participants are only allowed to drink water until the start of the main experiments.

During the exercise trial, participants will begin by running on a treadmill for 30 minutes at a speed estimated to achieve 75% of their V̇O2 peak, followed by a rest period in the laboratory. The same protocol will be followed in the control and severe-energy trials, except that no exercise will be performed. Participants will rest in the laboratory during both the control and energy-restricted trials. In the control trial, the participants will receive 100% of their estimated energy needs; in the energy-restricted trials, the participants will receive only 25%.

The participants will have standardized breakfast and lunch meals at 1h and 5h, respectively. At 24h, participants will be provided an ad libitum buffet meal in a private eating room.

The researchers will assess appetite ratings in each experiment using 100 mm visual analog scales. The researchers will also collect blood samples to analyze ghrelin, peptide YY (PYY), glucagon-like peptide 1 (GLP-1), and potentially other blood-borne measures.

Inclusion Criteria:

• Males aged 18 years or older.
• Have stable body mass for at least six months (within ±2 kg).

Exclusion Criteria:

• Females
• People who are younger than 18 or older than 65 years old.
• Following a special diet (e.g. weight loss, vegetarian or vegan, etc.).
• Have food allergies related to the study.
• Have significant contraindications to exercise (e.g., an injury that would inhibit running).
• Smoking.
• Taking any medications.
• Suffering from metabolic health issues, e.g., history of diabetes, cardiovascular disease, or eating disorders.
• Have any mental health conditions.

The stored data will be pseudonymous and follow the guidelines of the General Data Protection Regulation enforced in May 2018. Hard copies of participant information forms, including consent forms and dietary intake records, will be kept in locked filing cabinets. Keys to the filing cabinets will only be available to the primary investigator. All databases will be password protected and stored on a university computer with firewalls.

Participants' identifiable data will be stored in a locked cabinet. Digital data will be stored anonymously within the server of the University of Glasgow.

This project's Principal Investigator will be responsible for sharing the research data.

Data will be preserved in Enlighten, the official online repository of Glasgow University's research output.

Data will be preserved for 10 years.