title: Changes in body mass index in Canadians over a five-year period: results of a prospective, population-based study.
abstract: BACKGROUND
  The initiation of the Canadian Multicentre Osteoporosis Study in 1996, and subsequent follow-up of the cohort 5 years later, provided longitudinal body mass index (BMI) data for a random sample of Canadians.
  
  
  METHODS
  Height and weight were measured at baseline and 5 years and used to calculate BMI and assign one of six weight categories. Multiple imputation was used to adjust for missing weight at year 5. Data were stratified by age and gender. The proportion of participants moving between categories was generated, and multivariable linear regression was used to identify factors associated with weight change.
  
  
  RESULTS
  Baseline data were available for 8548 participants, year 5 data for 6721, and year 5 weight was imputed for 1827 (17.6%). Mean BMI for every age and gender group exceeded healthy weight guidelines. Most remained within their BMI classification over 5 years, but when change occurred, BMI category was more likely to increase than decrease. Several sociodemographic, lifestyle and clinical characteristics were associated with change.
  
  
  CONCLUSIONS
  Mean baseline BMI tended to be higher than recommended. Moreover, on average, men under age 45 and women under age 55 were gaining approximately 0.45 kilograms (one pound) per year, which leveled off with increased age and reversed in the oldest age groups. These findings underscore the need for public health efforts aimed at combating obesity.
authors.affiliation: Clinical Research Centre, Kingston General Hospital and Department of Community Health and Epidemiology, Queen's University, Kingston, Ontario, Canada. hopmanw@kgh.kari.net
authors.forename: Wilma M
authors.initials: WM
authors.lastname: Hopman
authors.forename: Cristine
authors.initials: C
authors.lastname: Leroux
authors.forename: Claudie
authors.initials: C
authors.lastname: Berger
authors.forename: Lawrence
authors.initials: L
authors.lastname: Joseph
authors.forename: Susan I
authors.initials: SI
authors.lastname: Barr
authors.forename: Jerilynn C
authors.initials: JC
authors.lastname: Prior
authors.forename: Mark
authors.initials: M
authors.lastname: Harrison
authors.forename: Suzette
authors.initials: S
authors.lastname: Poliquin
authors.forename: Tanveer
authors.initials: T
authors.lastname: Towheed
authors.forename: Tassos
authors.initials: T
authors.lastname: Anastassiades
authors.forename: David
authors.initials: D
authors.lastname: Goltzman
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002170:Canada / Q000453:epidemiology; D005260:Female; D006801:Humans; D008019:Life Style; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000453:epidemiology*; D010024:Osteoporosis / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology*; D050177:Overweight / Q000502:physiology*; D011159:Population Surveillance; D012044:Regression Analysis; D012737:Sex Factors; D012959:Socioeconomic Factors