September 1st 2003

MODERATE EXERCISE AS EFFECTIVE AS VIGOROUS EXERCISE IN INITIAL WEIGHT LOSS WHEN COMBINED WITH DECREASED CALORIE INTAKE

CHICAGO—Exercising longer or with greater intensity will not significantly increase the amount of weight lost for women who are dieting and exercising, according to an article in the September 10 issue of The Journal of the American Medical Association (JAMA), a theme issue on medical education.

According to background information in the article, an estimated 60 to 65 percent of adults in the United States are overweight. Exercise is an important component of interventions targeting overweight and obese adults, and is important for improving short-term weight loss when combined with changes in dietary intake; and is one of the best predictors of long-term weight loss. However, the optimal amount of exercise necessary to enhance long-term weight loss has not been established. But it has been believed that a higher dose and intensity of exercise may improve long-term weight loss.

John M. Jakicic, Ph.D., of the University of Pittsburgh, Physical Activity and Weight Management Research Center, Pittsburgh, and colleagues examined the effect of exercise of varying duration (moderate vs. high, about 150 min/week to 200 min/week) and intensity (moderate vs. vigorous) on weight loss and cardiorespiratory fitness following 12 months of treatment in overweight adult women.

The study was a randomized trial conducted from January 2000 through December 2001 involving 201 sedentary women (average age, 37 years); average body mass index (BMI) 32.7 (a 5'4" woman with a BMI of 33 would weigh 192 lbs.), in a university-based weight control program. Participants were randomly assigned to 1 of 4 exercise groups based on the estimated energy expenditure (1000 kcal/wk vs. 2000 kcal/wk) and exercise intensity (moderate vs. vigorous). All women were instructed to reduce intake of energy to between 1200 and 1500 kcal/d and dietary fat to between 20 percent and 30 percent of total energy intake.

Of the randomized participants, 184 completed 12 months of treatment. "Average weight loss following 12 months of treatment was statistically significant in all exercise groups (vigorous intensity/high duration = 8.9 kg [19.6 lbs.]; moderate intensity/high duration = 8.2 kg [18.1 lbs.]; moderate intensity/moderate duration = 6.3 kg [13.9 lbs.]; vigorous intensity/moderate duration = 7.0 kg [15.4 lbs.]), with no significant difference between groups. [Average] cardiorespiratory fitness levels also increased significantly in all groups (vigorous intensity/high duration = 22.0 percent; moderate intensity/high duration = 14.9 percent; moderate intensity/moderate duration = 13.5 percent; vigorous intensity/moderate duration = 18.9 percent), with no difference between groups."

"Weight loss was significant within all groups, but there was no significant effect of either exercise duration or exercise intensity on changes in body weight between groups," the authors write.

"The results of this study have implications for prescription of exercise for sedentary, overweight adults engaging in weight loss efforts. Our results suggest that moderate to high levels of exercise used in combination with a decrease in calorie intake resulted in 8 percent to 10 percent reductions in body weight following a 12-month intervention. Moreover, participants randomized to vigorous exercise intensity did not have greater weight loss than those randomized to a similar dose of exercise performed at a moderate intensity," the researchers write. "However, when data were analyzed based on the amount of exercise performed, greater levels of exercise were associated with a greater magnitude of weight loss following 12 months of treatment. Thus, interventions should initially target the adoption and maintenance of at least 150 min/wk of moderate intensity exercise, and when appropriate, eventually progress to exercise levels consistent with the Institute of Medicine's recommendation of 60 min/d."
(JAMA. 2003;290:1323-1330. Available post-embargo at jama.com)

Editor's Note: This study was supported by a grant from the National Institutes of Health and the National Heart, Lung and Blood Institute.

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