Background: Although the broad health benefits of exercise are well-documented, the benefits for weight loss vary, and this may be due, in part, to compliance. The time-of-day that people exercise could have an influence on the efficacy of exercise for weight loss, through improved compliance and/or physiological benefits. However, there is currently no evidence to support a ‘best’ time-of-day for exercise to maximise efficacy. This abstract describes a protocol to compare the effects of morning vs evening exercise on weight loss and selected health outcomes.
Aims: To determine whether morning or evening exercise is more beneficial for weight loss and health benefits.
Design: A target sample of 95 insufficiently active, overweight adults aged 18-60 years will be recruited for a 12-week intervention and randomised to one of three groups: i) morning exercise; ii) evening exercise; or iii) waitlist control. Exercise groups will be prescribed self-paced brisk-walking or running on a treadmill for 50 minutes. There will be 5 supervised sessions per week for the first 4 weeks, followed by 8 weeks of combined supervised and unsupervised sessions. Physiological and physical tests, and questionnaires will be administered to participants at baseline, mid- and post-intervention, and at 3- and 6-month follow-up. These include: body composition analysis, dietary intake and eating behaviour, objectively measured physical activity, use of time, resting metabolic rate, cardiorespiratory fitness, sleeping behaviour, chronobiology, exercise enjoyment, and blood lipid profiles.
Preliminary data will be available for the conference.
Conclusion: If, by manipulating the time-of-day at which exercise is prescribed, we can identify favourable changes in the way people restructure their time, adhere better to the programme, and improve their diet and associated eating behaviours, recommendations could be developed to promote exercise at a certain time-of-day. This is the first study of its kind, addressing a critical gap in the literature.