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If you walk one mile a day, can you reduce your risk of heart attack and cancer?
Maybe, maybe not
(April 2004)

Healthful Life believes that the evidence indicates that physical activity needs to be of at least moderately vigorous intensity to reduce the risk of heart attacks and cancers of the breast and bowel. We are not persuaded that lesser intensity exercises (moderate to light) will provide health benefits. This may not apply to those over 65 years of age; multiple studies suggest that, in this age group, less vigorous exercise may be effective. Unfortunately, the studies on older persons have been inconsistent. A study in the Journal of the American Medical Association in May 2003 concludes that modest increases in physical activities in older women has remarkable health benefits, but it also shows the problems with the conclusions.

At four centers, a total of 9,518 women age 65 or older were followed for about ten years. The women were divided into four groups: sedentary; sedentary, but then became active; active, then became sedentary; active. The increased physical activity was primarily walking.

The 811 women who became active had a 48 percent reduction in deaths during followup, a 36 percent reduced risk of death from heart attack and stroke, and a 51 percent reduced risk of death from cancer. Those reductions were even better than the reduced risks among women who started active and stayed active. That is a bit surprising.

Those doing quite a lot of walking had about a one-third reduced risk of deaths from heart disease and stroke, but even a very modest amount of walking (at a casual pace for one hour two to three times a week) produced about the same benefit found with more extensive walking. That is also, to say the least, surprising. The same was found with total physical activity - a very small amount resulted in almost the same benefit as a much greater amount; that does not make much sense.

Less benefit of increased physical activity was found among women 75 years of age or older.

Commentary: According to this study, all any older person has to do is walk for one mile a day, two or three times a week, at a normal or casual pace and that will reduce your risk of dying from heart attack,
stroke, or cancer by 35 to 50 percent. That is only thirty minutes of walking a day - it seems almost ridiculous to claim that small amount of physical activity will cut cancer death rates by one-half.

It is also hard to accept that a very modest amount of walking (two to three hours a week of normal or casual pace walking) is as effective as much greater physical activity.

Part of the problem is that the investigators arbitrarily assigned an intensity level to walking that seems to be excessive. That may have thrown off a lot of their calculations.



This is not a persuasive article. Some of the results just do not make sense. Healthful Life does not believe a compelling case for health benefits from non-vigorous activities has been made, even for older persons.

The Healthful Life recommendations are quite clear:

1. Measure intensity in METs (metabolic equivalent tasks). One MET is energy expended or oxygen consumed at rest. Two METs is twice the energy expended at rest; slow pace walking is a 2 MET intensity. Walking at a pace of one mile every twenty minutes is a 3.5 MET intensity and is moderately vigorous.

CLICK HERE for tables of physical activity intensities.

2. The prudent approach to physical activity at work, home, and in leisure time is, if possible, do at least moderately vigorous activity (better than 3 MET intensity) and try to reach at least 12 MET-hours a week. (Walking at a one mile every twenty minutes pace for one hour is 3.5 MET-hours. Doing it four times a week provides 14 MET-hours. Walking at that pace for 30 minutes five times a week provides 1/2 x 3.5 or 1.8 MET-hours x 5 = 9.0 MET-hours).

3. If you can reach 20 MET-hours a week of moderately vigorous or vigorous physical activity, it is even better.

4. If you cannot for personal or health reasons do 12 MET-hours of moderately vigorous physical activity or even if you cannot do any moderately vigorous activity at all, do what you feel comfortable with. The idea is, above all, to avoid being sedentary. If you have been sedentary, it is a good idea to consult with your health care provider before significantly increasing your activity.

5. Physical activities at work, home, and in leisure time all count. Note that lesser intensity and lesser total physical activity may (or may not) be sufficient to reduce heart attack risk in older people.

Gregg, E.W., et al. Relationships of changes in physical activity and mortality among older women. Journal of the American Medical Association. Vol 289 (May 14) Pgs 2379-2386. 2003.

Also see the articles in the Archives “More evidence on the need for moderately vigorous physical activity to prevent heart attacks” and “Exercise and health”.

A member of our Scientific Advisory Board notes “I think you may wish to emphasize even more that the greatest benefit occurs among those who go to some activity from none”. That is an important point.

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