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5D Adult Body Mass Index (BMI)

Description  | Specific Indicators | Ontario Public Health Standards (OPHS) |  Corresponding Health Indicator from Statistics Canada and CIHI |  Data Sources  | Survey Questions |  Alternative Data Sources |  Analysis Check List |  Method of Calculation |  Basic Categories |  Indicator Comments  | Cross-References to Other Indicators |  Cited References  | Changes Made

  • Proportion of adults, aged 18 and over, that are underweight (BMI <18.5), normal weight (BMI 18.5-24.9), overweight (BMI 25.0-29.9) or obese (BMI ≥ 30.0) according to self-reported height and weight. 

          Note: this indicator excludes pregnant women, lactating women, and persons less than 3 feet tall or greater than 6 feet 11 inches. 

 Specific Indicators

  • Adult Body Mass Index (BMI) 

Ontario Public Health Standards (OPHS)

The Ontario Public Health Standards (OPHS) establish requirements for the fundamental public health programs and services carried out by boards of health, which include assessment and surveillance, health promotion and policy development, disease and injury prevention, and health protection. The OPHS consist of one Foundational Standard and 13 Program Standards that articulate broad societal goals that result from the activities undertaken by boards of health and many others, including community partners, non-governmental organizations, and governmental bodies. These results have been expressed in terms of two levels of outcomes: societal outcomes and board of health outcomes. Societal outcomes entail changes in health status, organizations, systems, norms, policies, environments, and practices and result from the work of many sectors of society, including boards of health, for the improvement of the overall health of the population. Board of health outcomes are the results of endeavours by boards of health and often focus on changes in awareness, knowledge, attitudes, skills, practices, environments, and policies. Boards of health are accountable for these outcomes. The standards also outline the requirements that boards of health must implement to achieve the stated results. 

Outcomes Related to this Indicator

  • Societal Outcome (Chronic Disease Prevention Program): An increased proportion of the population lives, works, plays, and learns in healthy environments that contribute to chronic disease prevention.
  • Societal Outcome (Chronic Disease Prevention Program): There is increased adoption of behaviours and skills associated with reducing the risk of chronic diseases of public health importance. 

    Assessment and/or Surveillance Requirements Related to this Indicator  

  • The board of health shall conduct epidemiological analysis of surveillance the area of healthy weights (Chronic Disease Prevention Program).  

Corresponding Health Indicator from Statistics Canada and CIHI

  • Adult body mass index (BMI)

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Data Sources

Numerator & Denominator: Canadian Community Health Survey (CCHS)
Original source: Statistics Canada
Distributed by:
1. Ontario Ministry of Health and Long-Term Care
2. Statistics Canada
Suggested citation (see Data Citation Notes):
1. Canadian Community Health Survey [year], Statistics Canada, Share File, Ontario Ministry of Health and Long-Term Care.
2. Canadian Community Health Survey [year], Statistics Canada, Public Use Microdata File, Statistics Canada. 

Survey Questions

The Height and Weight module of the CCHS collects self-reported height and weight measures which are used to derive BMI and BMI classification categories.

Note: due to changes to the body weight classification system for adults in 2003, the derived categories changed after the 2000/01 survey.  More information on the differences is included in the Analysis Check List.  

Data Source


Question/ Description

Response Categories




Height and weight - Self-reported


BMI classification for adults aged 18 and over (self-reported) - international standard

Normal weight,
Obese - Class I,
Obese - Class II,
Obese - Class III,
Not applicable,
Not stated



(syntax file available)



(syntax file available)






Are you still breastfeeding?

Don't Know



Maternal Experiences

Are you still breastfeeding?

Don't Know,







Alternative Data Source(s)

The Rapid Risk Factor Surveillance System (RRFSS) has a core module on Body Mass Index (BMI). Note that the RRFSS indicator differs from the Core Indicator as lactating (i.e. breastfeeding) women are not excluded and different age categories are recommended.

Data Source




Response Categories




Body Mass Index (BMI)

How tall are you without shoes?

height in feet
height in inches
height in centimetres
don't know

2001 - present


How much do you weigh?

weight in pounds
weight in kilograms
don't know

2001 - present


Body Mass Index, Age 18+, Canadian Standard 2003

Acceptable weight

2007 - present


Analysis Check List   


  • In 2003, Health Canada released Canadian Guidelines for Body Weight Classification in Adults, which replaced Canadian Guidelines for Healthy Weights (1988). The 2003 Guidelines extended BMI calculations for the population from ages 20-64 to ages 18 and older, and changed the cut-off points of the BMI categories. In order to follow the new guidelines, BMI and the BMI categories must be re-derived in the 2000/01 CCHS (Cycle 1.1). SPSS syntax and details are provided below.
  • Although calculation of BMI is not recommended for lactating (i.e. breastfeeding) women, the body mass index provided by Statistics Canada in the Share File is calculated for women who report that they are breastfeeding, MEX_05 = 1 (2009 CCHS). These women should be excluded from the analysis unless a comparison to the Ontario Health Survey is required.
  • Include only those aged 18 years and over, and exclude pregnant and/or lactating women.
  • The overweight and obese categories may be combined for analysis and reporting.  The BARC study, which compared BMI based on self-reported versus measured height and weight among RRFSS respondents, found that the validity of BMI estimates was highest when the two BMI classes were grouped together.1  
  • It is recommended that public health units use the Share File provided by the Ministry of Health and Long-Term Care rather than the public use file (PUMF) provided by Statistics Canada. The Share File has a slightly smaller sample size because respondents must agree to share their information with the province to be included; however, the share file has more variables and fewer grouped categories within variables. The Share File is a cleaner dataset for Ontario analysis because all variables that were not common content, theme content or optional content for Ontario have been removed.
  • There may be slight differences between results from the share file and data published on the Statistics Canada website for the Health Indicators because rates calculated for Health Indicators use the master CCHS data file.
  • Not applicable respondents should be excluded; however, it is important to understand who these respondents are from the questionnaire skip patterns to be able to describe the relevant population.
  • Users need to consider whether or not to exclude the ‘Refusal', ‘Don't Know' and ‘Not Stated' response categories in the denominator. Rates published in most reports, including Statistics Canada's publication Health Reports generally exclude these response categories.  In removing not stated responses from the denominator, the assumption is that the missing values are random, and this is not always the case.  This is particularly important when the proportion in these response categories is high.
  • Estimates must be appropriately weighted (generally the share weight for the CCHS) and rounded. 
  • Users of the CCHS Ontario Share File must adhere to Statistics Canada's release guidelines for the CCHS data when publishing or releasing data derived from the file in any form. Refer to the appropriate user guide for guidelines for tabulation, analysis and release of data from the CCHS.  In general, when calculating the CV from the share file using the bootstrap weights, users should not use or release weighted estimates when the unweighted cell count is below 10.  For ratios or proportions, this rule should be applied to the numerator of the ratio.  Statistics Canada uses this approach for the tabular data on their website.  When using only the Approximate Sampling Variability (CV) lookup tables for the share file, data may not be released when the unweighted cell count is below 30.  This rule should be applied to the numerator for ratios or proportions.  This provides a margin of safety in terms of data quality, given the CV being utilized is only approximate. 
  • Before releasing and/or publishing data, users should determine the CV of the rounded weighted estimate and follow the guidelines below:  
    • Acceptable (CV of 0.0 - 16.5) Estimates can be considered for general unrestricted release. Requires no special notation.
    • Marginal (CV of 16.6 - 33.3) Estimates can be considered for general unrestricted release but should be accompanied by a warning cautioning subsequent users of the high sampling variability associated with the estimates. Such estimates should be identified by the letter E (or in some other similar fashion).
    • Unacceptable (CV greater than 33.3) Statistics Canada recommends not to release estimates of unacceptable quality. However, if the user chooses to do so then estimates should be flagged with the letter F (or in some other fashion) and the following warning should accompany the estimates: "The user is advised that...(specify the data) not meet Statistics Canada's quality standards for this statistical program. Conclusions based on these data will be unreliable and most likely invalid". These data and any consequent findings should not be published. If the user chooses to publish these data or findings, then this disclaimer must be published with the data. 
  • Caution should be taken when comparing the results from 2000/01 (Cycle 1.1) to subsequent years of the survey, due to a change in the mode of data collection.  The sample in Cycle 1.1 had a higher proportion of respondents interviewed in person, which affected the comparability of some key health indicators.  Please refer to for a full text copy of the Statistics Canada article entitled "Mode effects in the Canadian Community Health Survey: a Comparison of CAPI and CATI". 
  • 2000/01 CCHS Share File (Cycle 1.1):
    The Ontario Share File for 2000/01 has derived variables for BMI, International BMI categories, and Canadian BMI categories. All three of these variables code respondents aged 12-19 years, aged 65+, and pregnant women as "not applicable".  In order to determine BMI estimates for the expanded population of ages 18+, BMI must be re-derived from height and weight. The syntax file CCHS BMI recode 2000-01.sps, creates a new variable for BMI called bmi_calc and another for the BMI categories called bmi_adult. These variables were derived similarly to those available in 2005 and 2007, and as such, women who were breastfeeding (brfa_03=1) were not excluded. For the Core Indicator, these women should be excluded from the analysis.
  • 2003 CCHS Share File (Cycle 2.1):
    In the Ontario Share File for 2000/01 and 2003, rounding conventions for BMI were different than those used in 2005 and 2007 (one decimal place as opposed to two decimal places).  As a result, those near the cut-off were allocated differently into the BMI categories in 2000/01 and 2003.  The syntax file CCHS BMI recode 2003.sps derives the variables bmi_calc and bmi_adult as above, so that comparisons across years can be made.  Women who were breastfeeding (mexc_05=1) should be excluded from the Core Indicator.
  • All CCHS Share Files:
    In the Ontario Share Files, there are derived variables for BMI.  For Cycle 1.1 and 2.1, this derived variable excludes people who are 7 feet.  For subsequent Cycles, the derived BMI variable includes people who are 7 feet.  To maintain consistency across Cycles, people who are 7 feet should be excluded. 

Method of Calculation

Body Mass Index:

Weighted Population aged 18+ (excluding pregnant women and lactating women) by Body Mass Index classification

Total population aged 18+ (excluding pregnant women and lactating women)
 X 100

Basic Categories

  • Age groups for age-specific rates: 18-34, 35-44, 45-64, 65+
  • Sex: male, female
  • Geographic areas: CCHS - all 36 Health Unit areas in Ontario; RRFSS - all participating Ontario Public Health Unit areas

Indicator Comments

  • The Body Mass Index (BMI) is a ratio of weight to height (kg/m2) and is considered to be the most useful indicator of population health risks associated with both overweight and underweight.2
  • This body weight classification system is recommended for use among Canadian adults aged 18 and over, except for pregnant and lactating women.2
  • BMI classifies weight into health risk categories:


BMI category

Risk of developing health problems

Some associated health problems2




Undernutrition, Osteoporosis, Infertility,            Impaired Immunocompetence

Normal Weight

18.5 - 24.9




25.0 - 29.9


Type 2 Diabetes, Dyslipidemia, Hypertension, Coronary Heart Disease, Gallbladder Disease, Obstructive Sleep Apnea, and certain Cancers


    Class I

    Class II

    Class III

30 and over

30.0 - 34.9

35.0 - 39.9

≥ 40.0



Very high

Extremely high

Table adapted from Health Canada's 2003 Canadian Guidelines for Body Weight Classification in Adults, Table 3: Health Risk Classification According to Body Mass Index (BMI)2

  • Some research suggests that health risks may differ in adults over age 65, specifically that the "normal" or healthy range may begin slightly above BMI 18.5 and extend into the "overweight" range. Similarly young adults who have not reached full growth; adults who are naturally very lean; adults with a very muscular body build may not be at the level of health risk indicated by their BMI.  However, for population purposes the current classification system is useful and recommended.2
  • Some racial groups may be more susceptible to health problems associated with obesity than others. More research is needed but for now, the existing body weight classification system is appropriate for all racial/ethnic groups in Canadian society.2
  • These BMI categories should not be used for children and adolescents (age<18 years). Refer instead to "Adolescent Body Mass Index".
  • Since there is individual variability in the risk associated with a specific BMI, a measure of BMI should only be considered as one component of a comprehensive health assessment for an individual.  For example, the classification system can be used to derive prevalence estimates, as well as trends in body weight patterns in a population.2
  • Waist circumference is an additional measure that is often used in combination with BMI. It is an important indicator of individual health risk associated with abdominal fat based on sex-specific cut-off points. The waist circumference measurement should be used among individuals with BMIs ranging from 18.5-34.9 to identify additional risk (such as for type 2 diabetes, coronary heart disease and hypertension). The 2003 Canadian Guidelines for Body Weight Classification in Adults notes that waist circumference is a better and more practical correlate of abdominal obesity and related health risks than the waist to hip ratio measure.2
  • The CCHS has generally relied on respondents to report their height and weight, which is then used to calculate BMI. Self reports tend to yield lower rates of overweight and obesity, as both women and men are inclined to underestimate their weight and overestimate their height.3 Also, as BMI increases more underreporting of weight occurs.3,4 The nutrition survey of the CCHS (2004), which directly measured height and weight, found that the proportion of obese Canadians was much higher compared to the estimates from the self-reported data collected in 2003; 23.1% of Canadians aged 18 or older had a BMI of 30 or more indicating that they were obese, compared to 15.2% from self-reported data.5
  • Some surveys may include lactating women, since women may not have been asked if they were currently breastfeeding (i.e., the Ontario Health Survey).
  • In 2003, Health Canada released the Canadian Guidelines for Body Weight Classification in Adults2, which updated the weight classification system from the 1988 document, Canadian Guidelines for Healthy Weights6 to the international standard. The 1988 document described the Canadian standard for BMI which was defined as: under 20 (underweight), 20-24.9 (acceptable weight), 25-27.0 (some excess weight) and greater than 27 (overweight). The index was calculated for those aged 20 to 64 excluding pregnant women and persons less than 3 feet (0.914 metres) tall or greater than 6 feet 11 inches (2.108 metres).6
  • Based on the CCHS 2005 Share File, the percent of Ontarians aged 18 years and older by BMI category (excluding not stated, pregnant women and lactating women) were as follows: underweight (BMI <18.5) = 2.8%; normal weight (BMI 18.5-24.9) = 47.2%; overweight or obese (BMI ≥ 25.0) = 49.9%.  

Cross-References to Other Indicators

Cited References

  1. Kavsak P, MacRae A, Moran K, Northrup D, Reynolds D. Biological Assessment & Risk Comparison (BARC) Study [presentation online]. RRFSS Workshop; 2007 Jun 20; Toronto, Ontario.  Available from:,%20BARC.ppt.
  2. Health Canada. Canadian Guidelines for Body Weight Classification in Adults. 2003. Available online at:
  3. Shields M, Gorber SC, Tremblay MS. Estimates of obesity based on self-report versus direct measures (Catalogue No. 82-003-X). Statistics Canada Health Reports 2008; 19(2).
  4. Shields M, Gorber SC, Tremblay MS.  Effects of measurement on obesity and morbidity Catalogue No. 82-003-X). Statistics Canada Health Reports 2008; 19(2).
  5. Tjepkema M.  Adult Obesity in Canada: Measured height and weight. Nutrition: Findings from the Canadian Community Health Survey (Catalogue No. 82-620-MWE2005001). Ottawa, Ontario: Statistics Canada, 2005.
  6. Health and Welfare Canada. Canadian Guidelines for Healthy Weights, Report of an Expert Group Convened by Health Promotion Directorate, Health Services and Promotion Branch. Ottawa, Ontario: Health and Welfare Canada, 1988. 

Changes Made


Type of Review

(Formal or Adhoc)

Changes made by


April 20, 2009


Healthy Eating and Active Living subgroup

  • The title of this indicator was changed from "Body Mass Index" to "Adult Body Mass Index" to help users distinguish between the Adult and Adolescent indicators.
  • Age groups were changed to match those from Statistics Canada.
  • All information for this indicator was updated based on the most recent available data.
  • Repetitive information was removed.
  • The indicator comments were revised in accordance with the 2003 Canadian Guidelines for Body Weight Classification in Adults and up-to-date literature.
  • Information on the use of waist circumference in relation to BMI was clarified.
  • Syntax files were revised.

June 29, 2009

Ad hoc

Harleen Sahota on behalf of CIWG

  • Removed an out-of-date point in the Analysis Check List on how the Health Indicators department at Statistics Canada handles 'Not Stated' respondents when using CCHS data.


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