Back to Menu

MODERATE INTENSITY EXERCISE REDUCES WEIGHT AND ABDOMINAL FAT
(October 2003)

Those are the findings of a very useful study published in the Journal of the American Medical Association, January 13, 2003.  The investigators recruited 173 postmenopausal women, average age 61 years, who were overweight or obese.  They also had excess abdominal weight, their waist circumference classifying them as having abdominal obesity (average circumference 37 inches; above 35 inches is considered abdominal obesity for women).  The women, who at enrollment were sedentary, were divided into two groups, exercisers and non-exercisers. The goal for the exercise group was at least 45 minutes of moderate intensity activity (such as brisk walking) five days a week for a total of at least 225 minutes a week.  In actuality, the women on average exercised three days a week for a total of 176 minutes (still
pretty good compliance - ed).  At the twelve-month followup, the exercisers had modest improvement in all parameters with reduction in weight, waist circumference, body fat, and abdominal fat.  The exercise group was then further divided into three subgroups; those who exercised for 135 minutes or less; those who exercised for 136 to 194 minutes; and those who exercised for at least 195 minutes a week.  There was a direct and impressive relation between the duration of exercise and the amount of loss of total body fat and abdominal fat.  These findings were also correlated with fitness as measured by a treadmill test; the greater the degree of fitness, the greater the total body fat and abdominal fat loss.

The authors concluded "our findings support the important role of exercise in reducing body fat, especially intra-abdominal fat".

Commentary: This is a very good study.  It demonstrates, better than any other, that moderately vigorous exercise can result in significant loss of body and abdominal fat.  It is important to note that participants were encouraged not to change their usual diets.  If a weight loss diet had been combined with exercise, the results would have been even more dramatic.

It is too bad exercise was analyzed only by the duration of activities of at least moderate intensity rather than by duration multiplied by intensity in METs.  One MET is the energy expenditure at rest.  Two METs intensity is twice the resting energy expenditure; slow walking is a 2 MET intensity.  Three METs intensity is three times the times resting energy expenditure; walking at a pace of one mile every 25 minutes is at a 3 MET intensity.  At least three METs intensity was the definition of moderately vigorous in this study; the Healthful Life definition of minimum intensity that can be called moderately vigorous is 3.5 (walking at one mile every 20 minutes is at a 3.5 METs intensity).

for the value of exercise in achieving weight loss and reduction in body fat.

The question then is how much and at what intensity?

In this study, the longer the duration of moderate intensity exercise per week, the better the results.  Healthful Life recommends a minimum 3.5 METs intensity and a minimum total of 12 MET-hours per week.  If your exercise consists of walking at a pace of one mile every 20 minutes, to achieve 12 MET-hours per week would require 3.5 hours a week.

CLICK HERE for a chart showing moderately vigorous and vigorous activities.

CLICK HERE for an article on Exercise and Health for details of our recommendations.

So, remember:

-  the evidence suggests that at least moderately vigorous exercise is needed

- moderately vigorous exercise and a weight loss diet are more effective together than either alone

- the amount of weight loss that can result in very substantial health benefits for overweight or obese people is likely to be at least 5 to 7 percent of initial body weight (still, weight loss of 5 or 10 pounds, even if less than 5 percent, may still be quite effective in lowering blood cholesterol, reducing blood pressure, or preventing diabetes).

Irwin, M.L., et al.  Effect of exercise on total and intra-abdominal fat in postmenopausal women.  Journal of the American Medical Association. Vol 289 (January 15) Pgs 323-330. 2003.

A member of our Scientific Board points out that, although the beneficial results were attributed to exercise alone, no actual analysis of possible dietary changes was made, so it is a little glib to state the results were definitely due only to exercise; it could be a combination of exercise (measured) and dietary change (no change encouraged, but actual intake not measured).

Supported by