title: Seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population.
abstract: OBJECTIVE
  To describe seasonal variation in food intake, physical activity, and body weight in a predominantly overweight population.
  
  
  METHODS
  A longitudinal observational study.
  
  
  METHODS
  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.
  
  
  METHODS
  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.
  
  
  BACKGROUND
  US National Heart, Lung and Blood Institute.
authors.affiliation: Division of Preventive and Behavioral Medicine, University of Massachusetts Medical School, Worcester, MA 01655, USA. yunsheng.ma@umassmed.edu
authors.forename: Y
authors.initials: Y
authors.lastname: Ma
authors.forename: B C
authors.initials: BC
authors.lastname: Olendzki
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: A R
authors.initials: AR
authors.lastname: Hafner
authors.forename: D
authors.initials: D
authors.lastname: Chiriboga
authors.forename: J R
authors.initials: JR
authors.lastname: Hebert
authors.forename: M
authors.initials: M
authors.lastname: Campbell
authors.forename: M
authors.initials: M
authors.lastname: Sarnie
authors.forename: I S
authors.initials: IS
authors.lastname: Ockene
mesh_terms: D000328:Adult; D000368:Aged; D001835:Body Weight / Q000502:physiology*; D004032:Diet / Q000706:statistics & numerical data / Q000639:trends; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology*; D012044:Regression Analysis; D012621:Seasons; D017678:Sex Distribution; D013997:Time Factors