title: Secular differences in the association between caloric intake, macronutrient intake, and physical activity with obesity.
abstract: To determine whether the relationship between caloric intake, macronutrient intake, and physical activity with obesity has changed over time.
  
  
  
  Dietary data from 36,377 U.S. adults from the National Health and Nutrition Survey (NHANES) between 1971 and 2008 was used. Physical activity frequency data was only available in 14,419 adults between 1988 and 2006. Generalised linear models were used to examine if the association between total caloric intake, percent dietary macronutrient intake and physical activity with body mass index (BMI) was different over time.
  
  
  
  Between 1971 and 2008, BMI, total caloric intake and carbohydrate intake increased 10-14%, and fat and protein intake decreased 5-9%. Between 1988 and 2006, frequency of leisure time physical activity increased 47-120%. However, for a given amount of caloric intake, macronutrient intake or leisure time physical activity, the predicted BMI was up to 2.3kg/m(2) higher in 2006 that in 1988 in the mutually adjusted model (P<0.05).
  
  
  
  Factors other than diet and physical activity may be contributing to the increase in BMI over time. Further research is necessary to identify these factors and to determine the mechanisms through which they affect body weight.
authors.affiliation: School of Kinesiology and Health Science, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Brown
authors.affiliation: University of Alberta, Royal Alexandra Hospital, 10240 Kingsway Ave NW, Edmonton, Alberta T5H 3V9, Canada.
authors.forename: Arya M
authors.initials: AM
authors.lastname: Sharma
authors.affiliation: School of Kinesiology and Health Science, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Chris I
authors.initials: CI
authors.lastname: Ardern
authors.affiliation: School of Kinesiology and Health Science, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Pedi
authors.initials: P
authors.lastname: Mirdamadi
authors.affiliation: School of Kinesiology and Health Science, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Paul
authors.initials: P
authors.lastname: Mirdamadi
authors.affiliation: School of Kinesiology and Health Science, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada. Electronic address: jennkuk@yorku.ca.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Kuk
mesh_terms: D000328:Adult; D015992:Body Mass Index; D004032:Diet / Q000639:trends*; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004041:Dietary Fats / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage; D002149:Energy Intake; D015444:Exercise; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009749:Nutrition Surveys; D009765:Obesity / Q000209:etiology*; D057185:Sedentary Behavior
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins
keywords: Body mass index; Energy intake; Epidemiology; Etiology; NHANES