Current and predicted prevalence of obesity in Canada: a trend analysis.

Background: The prevalence of obesity has increased over the past 3 decades, with a disproportionate growth in excessive weight categories (body mass index [BMI] 35.0-39.9 and BMI ≥ 40.0). The objective of this paper is to present the data for the past and current prevalence of adult obesity in Canada, together with future estimates.

Methods: We calculated BMIs for adults aged 18 years and older who were not in long-term care using data from Canadian health surveys administered between 1985 and 2011. Calculation of the BMIs was based on self-reported heights and weights. The weight categories were as follows: normal (BMI 18.5-24.9), overweight (25.0-29.9), obese class I (30.0-34.9), obese class II (35.0-39.9) and obese class III (≥ 40.0). Outcome measures were prevalence of adult obesity according to BMI categories, nationally and provincially. We used regression analysis models to predict future prevalence of adult obesity up to 2019.

Results: Between 1985 and 2011, the prevalence of adult obesity in Canada increased from 6.1% to 18.3%. Furthermore, since 1985, the prevalence of obesity in classes I, II and III increased from 5.1% to 13.1%, from 0.8% to 3.6%, and from 0.3% to 1.6%, respectively. Taking into account regional variations, we predict that, by 2019, the prevalence of obesity in classes I, II and III will increase to 14.8%, 4.4% and 2.0%, respectively, and that half of the Canadian provinces will have more overweight or obese adults than normal-weight adults.

Interpretation: We found significant increases in the excessive weight categories of obesity, with continued increases predicted for all provinces up to 2019. Provincial variations in obesity prevalence were also significant. To address these projected increases and any subsequent burden on the health care system, a concerted effort must be made by the provinces to focus on the prevention, management and treatment of obesity in Canada.