Seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population

Objective: To describe seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population. Design: A longitudinal observational study. Setting: Most of the study participants were recruited from a health maintenance organization (HMO) in central Massachusetts, USA. Additional individuals of Hispanic descent were recruited from outside of the HMO population to increase the ethnic diversity of this sample. Subjects: Data from 593 participants, aged 20 - 70, were used for this investigation. Each participant was followed quarterly ( five sampling points: baseline and four consecutive quarters) for 1-year period. Body weight measurements and three 24-h dietary and physical activity recalls were obtained on randomly selected days ( including 2 weekdays and 1 weekend day) per quarter. Sinusoidal regression models were used to estimate peak-to-trough amplitude and phase of the peaks. Results: Daily caloric intake was higher by 86 kcal/day during the fall compared to the spring. Percentage of calories from carbohydrate, fat and saturated fat showed slight seasonal variation, with a peak in the spring for carbohydrate and in the fall for total fat and saturated fat intake. The lowest physical activity level was observed in the winter and the highest in the spring. Body weight varied by about 1/2 kg throughout the year, with a peak in the winter (P<0.001 winter versus summer). Greater seasonal variation was observed in subjects who were male, middle aged, nonwhite, and less educated. Conclusions: Although there is seasonal variation in diet, physical activity and body weight, the magnitude of the change is generally small in this population.