The Impact of Morning or Evening Exercise on Food Intake

The beneficial effects of regular exercise on both physical and mental health are widely known; it is a pivotal component in the treatment and prevention of many metabolic disorders, including obesity. Exercise facilitates weight management, not only by increasing energy expenditure but through its effect on appetite regulation and, therefore, energy intake.

Multiple factors influence the effect of exercise on appetite regulation including body fat , gender, intensity and duration of exercise and levels of habitual physical activity . However, recently interest has grown around the impact time-of-day of exercise may have on appetite regulation . Subjective feelings of hunger follow a strong diurnal pattern, with feelings of hunger peaking in the evening and appearing lowest in the morning . Evening energy intake has been associated with increased total energy intake and body mass index Evening exercise could potentially counteract or lessen the evening hunger sensations and therefore reduce evening and total energy intake. The aim of this study is to investigate any changes in total energy intake, distribution of energy intake, and food preference on the day of and 24 -hours after a bout of moderate-intensity exercise completed in the morning or evening in a group of physically inactive adults. A total sample of 12 physically inactive adults aged 18-60 will be recruited on to the study. The study will take the form of a two-armed randomised controlled crossover trial consisting of two 48-hr overnight stays in the Human Intervention Studies Unit (HISU) at Ulster University, Coleraine, Northern Ireland. The participant information sheet will focus on the effect of morning and evening exercise on ambulatory blood pressure and exercise-induced feeling states to prevent the participants' knowledge of the true purpose of the study from influencing their feeding behaviours. Ambulatory blood pressure will be monitored for at least 24 hours after the exercise session and participants will be asked to complete questionnaires of exercise induced feeling states immediately before and after each exercise session. Participants will be briefed on the true purpose of the study following the study completion. During the visits, participants will be asked to perform 1 hour of exercise at 70% of their maximal heart rate on a motorised treadmill between either 0800-1000 or 1800-2000 on the first full day of the study appointment. Food will be provided ad libitum for the duration of the study. All food intake will be noted and covertly weighed and directly observed through security cameras in the HISU dining room and lounge areas to measure food-related behaviours, such as grazing or bingeing. A 24 hour dietary recall will be conducted at the end of each study appointment to validate recall against observed intake.