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:
Table 1: Table of Canadian Body Mass Index Ranges
Less than 20 |
Underweight
zone; may be associated with health problems for some
people |
20 to 25 |
Health weight zone;
good weight for most people |
26 to 27 |
Caution
zone; may lead to health problems in some people |
Greather than 27 |
Overweight
zone; increased risk of developing health problems |
|
Source: Health and Welfare Canada. Promoting
Healthy Weights: A Discussion Paper. Minister of Supply and Services
Canada: Ottawa, Ontario. 1988
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:
Table 2: Table of International Body Mass Index Ranges
*18.5 |
Underweight |
18.6 to 24.9 |
Acceptable weight |
25.0 to 29.9 |
Overweight |
*30.0 |
Obese |
|
Source: Health and Welfare Canada. Promoting Healthy Weights: A
Discussion Paper. Minister of Supply and Services Canada: Ottawa,
Ontario. 1988
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.
[D] Click for larger version, 6 KB Figure 1a. Proportions of Overweight Canadians by Age Groupings, 1996 to 1997
[D] Click for larger version, 6 KB Figure 1b. Proportions of Obese Canadians by Age Groupings, 1996 to 1997
|