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.

The role of dietary carbohydrates in weight loss has received considerable attention in light of the current obesity epidemic. The authors investigated the association of body mass index (weight (kg)/height (m)(2)) with dietary intake of carbohydrates and with measures of the induced glycemic response, using data from an observational study of 572 healthy adults in central Massachusetts. Anthropometric measurements, 7-day dietary recalls, and physical activity recalls were collected quarterly from each subject throughout a 1-year study period. Data were collected between 1994 and 1998. Longitudinal analyses were conducted, and results were adjusted for other factors related to body habitus. Average body mass index was 27.4 kg/m(2) (standard deviation, 5.5), while the average percentage of calories from carbohydrates was 44.9 (standard deviation, 9.6). Mean daily dietary glycemic index was 81.7 (standard deviation, 5.5), and glycemic load was 197.8 (standard deviation, 105.2). Body mass index was found to be positively associated with glycemic index, a measure of the glycemic response associated with ingesting different types of carbohydrates, but not with daily carbohydrate intake, percentage of calories from carbohydrates, or glycemic load. Results suggest that the type of carbohydrate may be related to body weight. However, further research is required to elucidate this association and its implications for weight management.

We declare no competing interests. We thank our colleagues throughout the Burns Network in England and Wales for their collaboration towards this Correspondence.

Background-The effect of dietary carbohydrate on blood lipids has received considerable attention in light of the current trend in lowering carbohydrate intake for weight loss.

Objective-To compare the effects of a low-glycemic index (GI) diet to the American Diabetes Association (ADA) diet on glycosylated hemoglobin (HbA1c) among individuals with type 2 diabetes.Subjects/Methods-Forty individuals with poorly controlled type 2 diabetes were randomized to either a low-GI or an ADA diet. The intervention, consisting of eight educational sessions (monthly for the first six months and then at months 8 and 10), focused on either a low-GI or an ADA diet. Data on demographic, diet, physical activity, psychosocial factors, and diabetes medication use were assessed at baseline, and 6-and 12-months. Generalized linear mixed models were used to compare the two groups on HbA1c, diabetic medication use, blood lipids, weight, diet, and physical activity.Results-Participants (53% female; mean age= 53.5 years) were predominantly white with mean body mass index of 35.8 kg/m 2 . While both interventions achieved similar reductions in mean HbA1c at 6 months and at 12 months, the low-GI diet group was less likely to add or increase dosage of diabetic medications (odd ratio=0.26, p=0.01). Improvements in HDL cholesterol, triglycerides, and weight loss were similar among groups.Conclusions-Compared to the ADA diet, the low-GI diet achieved equivalent control of HbA1c using less diabetic medication. Despite its limited size, this trial suggests that low-GI diet is a viable alternative to ADA diet. Findings should be evaluated in a larger randomized controlled trial.