Appendix 1: Obesity in Canada – Estimating the prevalence of obesity – methodology and additional 2007/08 CCHS analyses

Appendix 1. Estimating the prevalence of obesity: methodology and additional 2007/08 CCHS analyses

Using the Canadian Community Heath Survey (CCHS), new analyses presented in this report estimate the prevalence of obesity in Canadian populations stratified by age, sex, geographic location, and income and education levels. Data from the 2007 and 2008 CCHS share files, both separately and combined, were the focus of the new analyses. Data from previous cycles, covering the years 2000/2001, 2003, 2004 and 2005, were also used. Detailed descriptions of the variables used, analyses conducted and resulting limitations are outlined in this appendix.

Canadian Community Health Survey

The target population of the CCHS is all Canadians aged 12 and over (for the 2004 CCHS Nutrition Cycle (2.2), the target population was extended to all age groupsFootnote *). People living on Indian Reserves and Crown Lands, institutional residents, full-time members of the Canadian Forces and residents of certain remote regions were not included in the survey. The survey population is representative of approximately 98% of the total population in the provinces, 90% in the Yukon, 97% in the Northwest Territories and 71% in Nunavut.Footnote 193

Prior to 2007, core component data were collected every two years over a one-year period. Since 2007, data collection has occurred on an ongoing basis across 12-month collection periods. For both the annual data and two-year combined data (2007/08), sampling and bootstrap weights are provided by Statistics Canada such that resulting weighted estimates are representative of the population in the specified period.Footnote 194 Information on approximate CCHS sample size specific to each collection period is provided in Table 3.

Table 3: Sample Size Information for CCHS Cycles Used In Obesity Analyses
  2000/2001 CCHSFootnote 195 2003 CCHSFootnote 196 2004 CCHSFootnote 197 2005 CCHSFootnote 198 2007 CCHSFootnote 199 2008 CCHSFootnote 200
Available survey sample size 130,827 134,072 35,107 132,947 65,946 66,013
Self-report BMI class available 86,000 (ages 20-64) 111,000 (18+) 3,200 (2-17) 7,300 (18+) 11000 (12-17) 114,000 (18+) 4,700 (12-17) 57,300 (18+) 4,900 (12-17) 56,900 (18+)
Measured BMI class available Not available Not available 8,660 (2-17) 11,800 (18+) 480 (12-17) 4,200 (18+) Not available 400 (12-17) 4,100 (18+)


Valid responses for BMI are available for part of the sample, as illustrated in Table 4. All prevalence estimates for obesity are based on the total population for which BMI was available; non-responses and ineligible respondents for whom BMI was not calculated (e.g., pregnant women) were excluded from the analyses. In particular, for the combined 2007/08 obesity estimates, over 8,000 persons from the sample of approximately 132,000 are excluded.

Being female was the characteristic of the sample that showed the highest proportion for whom BMI class was not determined (Table 4), and this was due to the exclusion of pregnant women. Otherwise, characteristics were quite consistent between the sample excluded and the remaining sample.

Table 4: Characteristics of Sample Population and Non-respondents, CCHS 2007/08
  Total Population (n=123,723) Obesity Response not Available (n=8236)
Average age 43 years 42 years
Female 51% 63%
Household income <$20,000/year 9 % 11%
Single, separated, divorced, widowed 29% 29%
Aboriginal peoples 3% 4%

Source: Canadian Community Health Survey 2007/08, Statistics Canada.

Variables used in analyses

In addition to age, sex, province/territory and health region, the following variables were used in the analyses.

Obesity: The BMI is a derived variable calculated by dividing the respondent’s measured body weight (in kilograms) by the square of the respondent’s height (in metres). This calculation is done similarly for self-reported, parental-reported or measured height and weight. Overweight and obese categories for children and youth were developed on the basis of IOTF cut-offs (Cole method)Footnote 23 with specific ranges for children by age and sex. For adults, BMI classes are based on international standards developed by the WHO.Footnote 7

BMI is not calculated for adult respondents with a height of less than 0.91m (3') or more than 2.13m (7'), or for women who either reported being pregnant or did not respond to the question on pregnancy.

Aboriginal Peoples: The variable used in the analyses was based on the question “Are you an Aboriginal person, that is, North American Indian, Métis, or Inuit?”Footnote 193 Footnote 198 Footnote 199

Income Deciles: This variable was derived by Statistics Canada and is based on self-reported household income before taxes. Ten categories with approximately the same percentage of respondents in each group were generated by province/territory according to the ratio of household income to the low income cut-off corresponding to the respondent's household and community size.

Household Educational Attainment: This variable was derived by Statistics Canada and represents the highest level of education attained by any member of the household.

Methods of analysis

Descriptive analyses were used to estimate the prevalence of obesity across different population subgroups by age, sex, education, income decile, Aboriginal identity, province/territory and health region. Corresponding sample sizes by CCHS year are available in Table 3, which highlights the number of respondents with a valid BMI classification. Non-overlapping 95% confidence intervals were considered as reflecting significantly different point estimates of obesity prevalence. Bootstrapping techniques were used in these analyses to generate confidence intervals, as this technique takes the complex survey design into account. Thus, more accurate estimates of the variability of prevalence values were provided.


New analyses presented in the report have various limitations, depending on the population of subgroups used and the data cycle considered. One caveat when comparing obesity between Aboriginal and non-Aboriginal populations is that the CCHS does not include respondents who reside on reserves or in some remote communities. Therefore, there is no single obesity estimate that includes all Aboriginal peoples.

In addition, the estimates of obesity shown are not age-standardized, and therefore the age differences in obesity among groups or over time are not accounted for. Table 5 illustrates one example of the difference in age-standardized and non-age-standardized obesity prevalence. For the total population, using the four age groups specified to age-standardize the obesity estimate has a very minor impact, of less than half a percent, on the resulting estimate. However, for subgroups with different age and sex distributions, age and sex standardization might be warranted. The focus in this report was to obtain current prevalence estimates.

Analysis was limited to those measures captured by the CCHS. For example, nutrition was captured primarily by fruits and vegetables consumption only, and only in terms of number of times per day and not actual servings.

Table 5: Age-Standardized Obesity Estimates
Age Group 1991 Census Age Distribution 2007/08 CCHS Population Age Distribution Prevalence of Obesity
12 to 24 20.47% 19.21% 6.93%
25 to 44 35.68% 33.58% 16.31%
45 to 64 28.59% 32.71% 20.22%
65 and over 15.25% 14.51% 17.55%
Obesity Prevalence     15.97%
Age-Standardized Obesity (to 1991 population)     15.70%

Source: Analysis of Canadian Community Health Survey 2007/08, Statistics Canada.

As discussed earlier in the report, there are limitations and critiques of the BMI classification system. As noted in Health Canada’s Canadian Guidelines for Body Weight Classification in Adults,Footnote 7 particular caution should be used when classifying people who are very lean or very muscular, some ethnic and racial groups, and seniors.Footnote 201 In addition, research has shown that women are more likely to underestimate their weight and men more likely to overestimate their heights, both of which would result in a more conservative estimate of BMI.Footnote 4

Finally, obesity estimates based on directly measured heights and weights could be calculated for a large representative population for the 2004 CCHS, but only for subsamples in the 2005 and 2008 CCHS. The lack of routine, national, measured obesity estimates has been a noted surveillance information gap. All other obesity estimates are calculated according to self-reported height and weight information which, as discussed earlier in this report, has been shown to underestimate BMI and therefore obesity.

Additional analyses: 2007/08 CCHS

Figure 5 illustrates the prevalence of obesity (self-reported data) in the top and bottom 10 ranked health regions. Obesity prevalence estimates for all health regions in Canada are provided below (Table 6).

Table 6: Prevalence of Self-Reported Obesity by Health Region, Ages 18 and Older, 2007/08
Region Prevalence (%) Significantly different than Canada
Notes: Significantly lower than Canada (-1), significantly higher than Canada (1), not significantly different (0)
Canada 17.1
Eastern Regional Integrated HA, NL 24.4 1
Central Regional Integrated HA, NL 30.6 1
Western Regional Integrated HA, NL 21.3 1
Labrador-Grenfell Regional Integrated HA, NL 29.6 1
Kings County, PEI 32.1 1
Queens County, PEI 21.4 1
Prince County, PEI 24.5 1
Zone 1 (DHA 1 et 2), NS 29.5 1
Zone 2 (DHA 3), NS 23.0 1
Zone 3 (DHA 4 et 5), NS 25.6 1
Zone 4 (DHA 6 et 7), NS 26.1 1
Zone 5 (DHA 8), NS 21.7 1
Zone 6 (DHA 9), NS 20.6 1
Region 1, NB 23.8 1
Region 2, NB 22.4 1
Region 3, NB 20.3 0
Region 4, NB 21.3 0
Region 5, NB 24.5 1
Region 6, NB 19.9 0
Region 7, NB 26.1 1
Région du Bas-St. Laurent, QC 18.1 0
Région du Saguenay - Lac-Saint-Jean, QC 14.5 -1
Région de la Capitale-Nationale, QC 14.7 -1
Région de la Mauricie/Centre-du-Québec, QC 16.5 0
Région de l'Estrie, QC 11.6 -1
Région de Montréal, QC 13.4 -1
Région de l'Outaouais, QC 17.1 0
Région de l'Abitibi-Témiscamingue, QC 20.4 0
Région de la Côte-Nord, QC 16.8 0
Région du Nord-du-Québec, QC 21.7 1
Rég. de la Gaspésie-Île-de-la-Madeleine, QC 18.7 0
Région de la Chaudière-Appalaches, QC 13.6 -1
Région de Laval, QC 13.4 -1
Région de Lanaudière, QC 17.8 0
Région des Laurentides, QC 16.9 0
Région de la Montérégie, QC 18.1 0
District of Algoma Health Unit, ON 26.6 1
Brant County Health Unit, ON 25.5 1
Durham Regional Health Unit, ON 17.4 0
Elgin-St. Thomas Health Unit, ON 19.0 0
Grey Bruce Health Unit, ON 22.7 1
Haldimand-Norfolk Health Unit, ON 24.9 1
Haliburton/Kawartha/Pine Ridge DHU, ON 23.0 1
Halton Regional Health Unit, ON 16.3 0
City of Hamilton Health Unit, ON 20.2 0
Hastings et Prince Edward Counties HU, ON 22.7 1
Huron County Health Unit, ON 24.2 1
Chatham-Kent Health Unit, ON 23.7 1
Kingston/Frontenac/Lennox/Addington HU, ON 19.9 0
Lambton Health Unit, ON 21.5 1
Leeds, Grenville and Lanark DHU, ON 21.2 1
Middlesex-London Health Unit, ON 18.4 0
Niagara Regional Area Health Unit, ON 18.4 0
North Bay Parry Sound District H.U., ON 20.0 0
Northwestern Health Unit, ON 26.1 1
City of Ottawa Health Unit, ON 14.3 -1
Oxford County Health Unit, ON 20.0 0
Peel Regional Health Unit, ON 14.7 0
Perth District Health Unit, ON 19.6 0
Peterborough County-Regional H.U., ON 18.4 0
Porcupine Health Unit, ON 25.3 1
Renfrew County and District H.U., ON 23.3 1
The Eastern Ontario Health Unit, ON 25.4 1
Simcoe Muskoka District H.U., ON 21.3 1
Sudbury and District Health Unit, ON 18.8 0
Thunder Bay District Health Unit, ON 19.9 0
Timiskaming Health Unit, ON 29.6 1
Waterloo Health Unit, ON 21.6 1
Wellington-Dufferin-Guelph H.U., ON 18.8 0
Windsor-Essex County, ON 21.1 1
York Regional Health Unit, ON 11.7 -1
City of Toronto Health Unit, ON 12.7 -1
Winnipeg, MB 16.5 0
Brandon, MB 22.3 0
North Eastman, MB 20.9 0
South Eastman, MB 20.6 0
Interlake, MB 30.6 1
Central, MB 20.8 0
Assiniboine, MB 24.8 1
Parkland, MB 26.4 1
Norman, MB 30.5 1
Burntwood/Churchill, MB 31.1 1
Sun Country, SK 21.4 0
Five Hills, SK 20.3 0
Cypress, SK 24.9 1
Regina Qu'Appelle, SK 26.6 1
Sunrise, SK 24.0 1
Saskatoon, SK 21.8 1
Heartland, SK 26.7 1
Kelsey Trail, SK 29.1 1
Prince Alberta Parkland, SK 23.9 1
Prairie North, SK 21.1 0
Mamawetan/Keewatin/Athabaska, SK 35.9 1
Chinook Regional Health Authority, AB 21.2 1
Palliser Health Region, AB 22.0 0
Calgary Health Region, AB 15.2 0
David Thompson Regional Health Authority, AB 21.1 1
East Central Health, AB 25.0 1
Capital Health, AB 19.0 0
Aspen Regional Health Authority, AB 24.0 1
Peace Country Health, AB 29.2 1
Northern Lights Health Region, AB 27.4 1
East Kootenay, BC 16.7 0
Kootenay-Boundary, BC 17.1 0
Okanagan, BC 14.6 -1
Thompson/Cariboo, BC 20.0 0
Fraser East, BC 16.7 0
Fraser North, BC 11.9 -1
Fraser South, BC 12.0 -1
Richmond, BC 5.3 -1
Vancouver, BC 6.2 -1
North Shore/Coast Garibaldi, BC 10.3 -1
South Vancouver Island, BC 13.8 -1
Central Vancouver Island, BC 16.9 0
North Vancouver Island, BC 14.8 0
Northwest, BC 24.2 1
Northern Interior, BC 17.9 0
Northeast, BC 24.1 0
Yukon 22.4 1
Northwest Territories 23.9 1
Nunavut 22.9 1

Source: Analysis of Canadian Community Health Survey 2007/08, Statistics Canada.

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