Canadian Guidelines for Body Weight Classification in Adults

Executive Summary

This technical report describes a body weight classification system for Canadian adults, including the development, uses, interpretation and limitations of the system. The report was developed by Health Canada staff and an Expert Working Group of Canadian researchers and practitioners, and reviewed by leading Canadian organizations. It is intended for health professionals, researchers and educators involved in research and practice related to body weight.

The weight classification system can be used to identify weight-related health risks in populations and in individuals. It is intended for use among Canadian adults age 18 years and older. At the individual level, the system should be used as one part of a more comprehensive assessment of health risk.

The weight classification system provides a scheme for categorizing health risk according to body weight, as measured by body mass index (BMI), and level of abdominal fat, as measured by waist circumference (WC). BMI (kg/m²) is the most useful indicator, to date, of weight-related health risk, and WC is a practical indicator of risk associated with excess abdominal fat.

There is a continuous relationship between gradations of BMI and health risk, and between WC and health risk. However, cut-off points for each of these measures have been established for the purpose of identifying different levels of health risk. These cut-off points are not intended as targets for intervention purposes in individuals.

The following categories of BMI are used to identify levels of health risk (relative to 'normal weight' category) as follows:

View table: Health Risk Classification According to Body Mass Index (BMI)

Health risks associated with the underweight category include undernutrition, osteoporosis, infertility, and impaired immunocompetence. Underweight may also be an indication of an eating disorder or other underlying illness. Health risks associated with overweight and obesity include type 2 diabetes, dyslipidemia, hypertension, coronary heart disease, gallbladder disease, obstructive sleep apnea, and certain cancers.

Waist circumference is also an important indicator of health risk. Sex-specific cut-off points for WC have been established to identify health risk associated with excess abdominal fat.

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For men: WC >= 102 cm (40 in.)
For women: WC >= 88 cm (35 in.)

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A WC above these cut-off points is associated with increased risk (relative to a WC below these values) of type 2 diabetes, coronary heart disease, and hypertension. The WC measurement should be used among those with BMIs between 18.5 and 34.9, to identify additional risk. For BMIs >= 35.0, the WC measurement does not provide additional information on health risk.

The system is recommended for use among Canadian adults, except pregnant and lactating women. There are some limitations to the use of this weight classification system among certain groups. Special considerations are required when applying this system to:

• young adults who have not reached full growth
  
• adults who are naturally very lean
  
• adults with a very muscular body build
  
• older adults (over 65 years of age)
  
• certain ethnic or racial groups

The weight classification system described in this report is an update of the 1988 Canadian Guidelines for Healthy Weights. It is in accord with the weight classification system released by the World Health Organization, which has been widely adopted internationally.