Seasonal Variation in Energy Expenditure, Water Turnover, and Physical Activity in Adults

This prospective observational study will investigate seasonal variation in total energy expenditure, water turnover, and physical activity in healthy adults living in or near Aberdeen, Scotland. Participants will complete two approximately 14-day measurement periods, one in winter and one in summer. Total energy expenditure and water turnover will be assessed using the doubly labelled water method, while physical activity and personal environmental exposure will be measured using wearable devices. The study will examine within-person differences between winter and summer and explore whether environmental factors, including ambient temperature, daylight, and sunlight exposure, are associated with changes in energy expenditure, water turnover, and physical activity.