Dose-Relationship Between Exercise and Weight Loss
News Author: Laurie Barclay, MD
Jan. 12, 2004

There is a dose-relationship between exercise and weight loss, according to the results of a randomized trial published in the Jan. 12 issue of the Archives of Internal Medicine. Even low amounts of moderate exercise, or about 30 minutes of walking per day, may be sufficient to prevent weight gain in sedentary adults.

"From the perspective of prevention, it appears that the 30 minutes per day will keep most people from gaining the additional weight associated with inactivity," lead author Cris Slentz, PhD, from Duke University Medical Center in Durham, North Carolina, says in a news release. "Given the increase in obesity in the U.S., it would seem likely that many in our society may have fallen below this minimal level of physical activity required to maintain body weight."

Of 302 adults screened for the Studies of Targeted Risk Reduction Interventions through Defined Exercise (STRRIDE) trial, 182 met entrance criteria of being sedentary and overweight with mild to moderate dyslipidemia. Age range was 40 to 65 years. These subjects were randomized to one of four groups: no exercise, supervised low-dose/moderate-intensity exercise equivalent to walking 12 miles per week, low-dose/vigorous-intensity exercise equivalent to jogging 12 miles per week or high-dose/vigorous-intensity exercise equivalent to jogging 20 miles per week.

Of the 182 subjects who were randomized, 120 completed the eight-month study. During that time, they were advised to maintain body weight and not to change their diet. Compared with the other groups, the high-dose/vigorous-intensity group had the greatest benefit, and there was a dose-response relationship between amount of exercise and amount of weight loss and fat mass loss.

Weight change was 3.5% loss in the high-dose/vigorous-intensity group, about 1% loss in the two low-dose exercise groups, and 1.1% gain in the control group. Increases in lean body mass were 1.4% in the two vigorous intensity groups and 0.7% in the low-intensity group.

"The higher exercise intensity groups resulted in greater increases in lean body mass, which if confirmed by other studies, could have significant implications," Dr. Slentz says. "This finding suggests that while the amount of exercise determines total body weight change and fat mass loss, exercise intensity would appear to be the primary determinant of gain in lean body mass."

Body fat mass increased by 0.5% in the control group and decreased by 2.0% in the low-dose/moderate-intensity group, by 2.6% in the low-dose/vigorous-intensity group, and by 4.9% in the high-dose/vigorous-intensity group.

"This study revealed a clear dose-response effect between the amount of exercise and decreases in measurements of central obesity and total body fat mass, reversing the effects seen in the inactive group," Dr. Slentz says. "The close relationship between central body fat and cardiovascular disease, diabetes, and hypertension lends further importance to this finding."

Waist circumference increased by 0.8% in the control group and decreased by 1.6% in the low-dose/moderate-intensity group, by 1.4% in the low-dose/vigorous-intensity group, and by 3.4% in the high-dose/vigorous-intensity group. All exercise groups also had significantly decreased minimal weight and hip circumference measurements compared with controls. Dietary intake remained stable in all groups.

"We found that the two low-exercise groups lost both weight and fat, while those in the more intensive group lost more of each in a 'dose-response' manner," Dr. Slentz concludes. "Simply put, the more you exercise, the more you benefit. Just as importantly, the control group of participants who performed no exercise gained weight over the period of the trial."

The National Heart, Lung and Blood Institute supported this study.