Benefits of Exercise

We all hear that exercise is good for us. How good is it? How much is needed? Is more always better? In the following, we review several studies on the benefits of exercise, and see what the most current research into the effects of exercise really find.

A study presented in Reference 1 tracked more than 50,000 women in an obesity study, and 68,000 women in a diabetes study, between 1992 and 1998. The average age of the women was approximately 57. At the start, the women were free from diagnosed cardiovascular (blood vessels and heart) disease, diabetes or cancer. They were questioned about physical activity and sedentary behaviors at the start of the study.

They found that for every 2 hours more per day that the women watched TV, they had a 23% increase in obesity (Margin of Error between 17% and 30%), and a 14% increase in risk for diabetes (Risk Ratio of 1.14, Margin of Error between 1.05 and 1.23).

In contrast, standing or walking around at home decreased these risks: for every 2 hours per day standing or walking around the home, obesity was decreased by 9% (Margin of Error - 6% to 12%), and the risk of diabetes was reduced by 12% (Risk Ratio of 0.88, Margin of Error - 0.84 to 0.93). A one-hour brisk walk each day resulted in a 24% reduction in obesity (Margin of Error 19% to 29%) and a 34% reduction in risk of diabetes (Risk Ratio of 0.66, Margin of Error - 0.59 to 0.73).

The figure on the right shows the absolute 10-year risk. That is, if you take 100 people for 10 years, how many of them would develop a BMI above 30? For non-TV viewers, 11 would become obese, wherease for maximum TV viewing, 17 of them would become obese.

The risk for developing diabetes rises from 3 in 100 (over 10 years) for women who don't watch TV, to 6% for women who watch TV more that 40 hours a week. Brisk walking (an hour or more a day) will reduce these numbers by around 34%.

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