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Open Access Research article

Changes in body mass index in Canadians over a five-year period: Results of a prospective, population-based study

Wilma M Hopman1*, Cristine Leroux2, Claudie Berger2, Lawrence Joseph3, Susan I Barr4, Jerilynn C Prior5, Mark Harrison6, Suzette Poliquin7, Tanveer Towheed8, Tassos Anastassiades9, David Goltzman10 and the CaMos Research Group7

Author Affiliations

1 Clinical Research Centre, Kingston General Hospital and Department of Community Health and Epidemiology, Queen's University, Kingston, Ontario, Canada

2 CaMos Methods Centre, McGill University, Montreal, Quebec, Canada

3 Department of Epidemiology and Biostatistics, McGill University, Montreal, Quebec, Canada

4 Human Nutrition, University of British Columbia, Vancouver, British Columbia, Canada

5 Division of Endocrinology, Department of Medicine, University of British Columbia, British Columbia, Canada

6 Human Mobility Research Centre and the Division of Orthopedics, Department of Surgery, Queen's University, Kingston, Ontario, Canada

7 CaMos National Coordinating Centre, McGill University, Montreal, Quebec, Canada

8 Division of Rheumatology, Department of Medicine; Department of Community Health and Epidemiology, Queen's University, Kingston, Ontario, Canada

9 Division of Rheumatology, Department of Medicine, Queen's University, Kingston, Ontario, Canada

10 Department of Medicine, McGill University and Calcium Research Laboratory, Royal Victoria Hospital, Montreal, Quebec, Canada

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BMC Public Health 2007, 7:150  doi:10.1186/1471-2458-7-150

Published: 9 July 2007

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.

Conclusion

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.