Physical Activity

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"Exercise makes you sexier, more intelligent and all around more attractive". This is the opinion of a group of students polled on their impressions of exercisers versus non-exercisers (University Affairs, April 2001). In the same study, Dr. Kathleen Martin of McMaster University, the principal investigator of the study, remarked that "It seems that perhaps if you are an exerciser you've got somewhat of a halo on you. People attribute all these wonderful qualities to you just knowing that you're an exerciser".

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While these perceptions may be stretching the benefits of exercising, most scientific evidence is supportive of physical activity as a positive determinant of health. Some of the key, summary linkages have been reported by a recent report of the Surgeon General of the United States. These include:

• People who are usually inactive can improve their health and well-being by becoming even moderately active on a regular basis.
• Physical activity need not be strenuous to achieve health benefits.
• Greater health benefits can be achieved by increasing the amount (duration, frequency, or intensity) of physical activity.

More specifically, the benefits of regular physical activity include:

• reducing the risk of dying prematurely
• reducing the risk of dying from heart disease
• reducing the risk of developing diabetes
• reducing the risk of developing high blood pressure
• helping to reduce the blood pressure in people who already have high blood pressure
• reducing the risk of developing colon cancer
• reducing feelings of depression and anxiety
• helping control weight
• helps build and maintain healthy bones, muscles, and joints
• helps older adults become stronger and better able to move about without falling
• promoting psychological well-being

Body Mass Index (BMI)

Many health professionals in Canada consider that obesity has reached or is nearing epidemic proportions in this country. Slightly less attention has been given to the proportions of Canadians who are underweight, but this is recognized as an issue particularly associated with eating disorders. While this is not the appropriate place to detail the health issues associated with weight, we can outline the measure most often employed as an aid in determining whether an individual's weight is in a healthy range - the BMI.

Normally restricted to adults 20 to 64 years of age, excluding pregnant women, BMI is computed by dividing a person's weight (in kilograms) by his/her height in metres squared. The value that has been calculated is then compared with ranges of values to provide an indicator of where one fits in terms of body mass categories. Numerous interactive BMI calculators can now be found on the web. Whatever calculator one uses, the BMI value will be the same. What differs may be the numerical ranges and interpretations of the BMI categories.

The Canadian standard categories from the Health Canada BMI calculator website are as follows:

Employing data from the 1996 to 1997 NPHS, Gilmore (1999) adopted and applied the groupings endorsed by the World Health Organization and the United States National Institutes of Health so as to enhance international comparisons:

Using the latter scheme for the NPHS respondents 20 to 64 years of age: 2% of Canadians (1% men; 4% women) were underweight in 1996 to 1997; 48% (40% men; 56% women) had an acceptable weight; 34% (44% men; 24% women) were overweight; and 12% (13% men; 11% women) were obese. More detailed gender and age breakdowns for overweight and obese Canadians are illustrated in Figures 1a and 1b, respectively.

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Figure 1a. Proportions of Overweight Canadians by Age Groupings, 1996 to 1997

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Figure 1b. Proportions of Obese Canadians by Age Groupings, 1996 to 1997