The data

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Current estimates are from the 2007-2009 Canadian Health Measures Survey (CHMS),¹⁰ which collected data at 15 sites across the country from March 2007 through February 2009. The survey covered the household population aged 6 to 79 years. Full-time members of the Canadian Forces and residents of Crown lands, Indian reserves, institutions and certain remote regions were excluded. The sample represented approximately 96% of the population. In addition to a questionnaire, the survey involved physical measures (including height, weight, waist circumference, and hip circumference) at a mobile examination centre. The CHMS estimates in this article are based on 3,074 respondents aged 20 to 69 years. Of the households selected, the response rate was 69.6%. One or two members of each responding household were chosen to participate: 87.6% of selected 20- to 69-year-olds completed the household questionnaire, and 83.6% of these respondents completed the physical examination. The overall combined response rate was 51.0%.

Historical estimates are based on the 1981 Canada Fitness Survey (CFS),¹¹ which collected data from a nationally representative sample of the population between February and July 1981. The sample consisted of 13,500 households. The overall response rate for the physical measures component of the survey was 49%. The CFS estimates in this article are based on 10,605 respondents aged 20 to 69 years.

Pregnant women were excluded from both data sources. 

Each survey measured weight to the nearest 0.1 kg, and height, to the nearest 0.1 cm. Waist circumference was measured at the end of a normal expiration to the nearest 0.1 cm at the mid-point between the last floating rib and the top of the iliac crest.^12,13 Hip circumference was measured at the level of the symphysis pubis and the greatest gluteal protuberance.¹²

Body mass index (BMI) was calculated as weight in kilograms divided by height in metres squared (kg/m²); waist-to-hip ratio as waist circumference in cm divided by hip circumference in cm; and waist-to-height ratio as waist circumference in cm divided by height in cm.

Based on categories recommended by the World Health Organization,¹³ Health Canada¹ and Obesity Canada,² respondents were divided into the six BMI-based health risk categories (underweight, normal weight, overweight, and obese class I, II and III) and three categories based on waist circumference: low-risk (men, 93.9 cm or less; women, 79.9 cm or less), increased-risk (men, 94.0 to 101.9 cm; women, 80.0 to 87.9 cm), and high-risk (men, 102.0 cm or more; women, 88.0 cm or more). In accordance with recommended cut-points, respondents were also classified as being at increased/high risk based on waist-to-hip ratio (men 0.9 or more; women 0.85 or more)³ and waist-to-height ratio (0.5 or more for both sexes).¹⁴ 

All analyses were weighted to obtain estimates representative of the Canadian population. Estimates based on the CFS were age-standardized to the 2007-2009 population to account for shifts in Canada's age distribution during this period.

 Statistical analyses were performed using SAS and SUDAAN software. Standard errors, coefficients of variation, and 95% confidence intervals for CHMS estimates were calculated with the bootstrap technique.^15,16 The number of degrees of freedom was specified as 11 to account for the CHMS sample design.¹⁰  Estimates of sampling error for the CFS estimates were based on formulae for simple random sampling with the incorporation of a design effect of 1.5 to account for the complex design of the survey. Significant differences between means and prevalence estimates across surveys were assessed using t-tests.