Women trying to lose weight can benefit as much from a moderate physical activity as from an intense workout, according to a new study supported by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health in Bethesda, MD.
Prior studies had focused on short-term weight loss. Data were lacking about the optimal degree and amount of physical activity for long-term weight loss.
The study — “Effect of Exercise Dose and Intensity on Weight Loss in Overweight, Sedentary Women: A Randomized Trial” — appears in the September 10, 2003, issue of The Journal of the American Medical Association (JAMA). [Editor’s note: the study abstract appears at the end of this article.]
The same issue of JAMA also includes an article on recreational physical activity and breast cancer risk. The study, based on data from the Women’s Health Initiative’s Observational Study, found that increased physical activity was associated with a reduced risk for breast cancer in postmenopausal women. Longer duration physical activity gave the most benefit but the physical activity did not need to be strenuous to reduce breast cancer risk.
The exercise dose and intensity trial involved 201 overweight but otherwise healthy women ages 21-45. All received reduced calorie meals in addition to being randomly assigned to one of four physical activity regimens, which varied by intensity and duration.
The regimens consisted of either a moderate- or vigorous-intensity physical activity performed for either a shorter (2½ to 3½ hours per week) or longer (3½ to 5 hours per week) duration. The physical activity consisted primarily of brisk walking, and the regimens used about 1,000 or 2,000 kcal per week.
Women in all four groups lost a significant amount of weight — about 13 to 20 pounds — and maintained their weight loss for a year. They also improved their cardiorespiratory fitness. However, the amount of weight lost or fitness improvement was not different among the four groups.
Effect of Exercise Duration and Intensity on Weight Loss in Overweight, Sedentary Women
A Randomized Trial
John M. Jakicic, PhD; Bess H. Marcus, PhD; Kara I. Gallagher, PhD; Melissa Napolitano, PhD; Wei Lang, PhD
Context: A higher duration and intensity of exercise may improve long-term weight loss.
Objective: To compare the effects of different durations and intensities of exercise on 12-month weight loss and cardiorespiratory fitness.
Design, Setting, and Participants: Randomized trial conducted from January 2000 through December 2001 involving 201 sedentary women (mean [SD] age, 37.0 [5.7] years; mean [SD] body mass index, 32.6 [4.2]) in a university-based weight control program.
Intervention: Participants were randomly assigned to 1 of 4 exercise groups (vigorous intensity/high duration; moderate intensity/high duration; moderate intensity/moderate duration; or vigorous intensity/moderate duration) based on 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% and 30% of total energy intake.
Main Outcome Measures: Body weight, cardiorespiratory fitness, and exercise participation.
Results: After exclusions, 184 of 196 randomized participants completed 12 months of treatment (94%). In intention-to-treat analysis, mean (SD) weight loss following 12 months of treatment was statistically significant (P <.001) in all exercise groups (vigorous intensity/high duration = 8.9 [7.3] kg; moderate intensity/high duration = 8.2 [7.6] kg; moderate intensity/moderate duration = 6.3 [5.6] kg; vigorous intensity/moderate duration = 7.0 [6.4] kg), with no significant difference between groups.
Mean (SD) cardiorespiratory fitness levels also increased significantly (P = .04) in all groups (vigorous intensity/high duration = 22.0% [19.9%]; moderate intensity/high duration = 14.9% [18.6%]; moderate intensity/moderate duration = 13.5% [16.9%]; vigorous intensity/moderate duration = 18.9% [16.9%]), with no difference between groups. Post hoc analysis revealed that percentage weight loss at 12 months was associated with the level of physical activity performed at 6 and 12 months.
Women reporting less than 150 min/wk had a mean (SD) weight loss of 4.7% [6.0%]; inconsistent (other) pattern of physical activity, 7.0% [6.9%]; 150 min/wk or more, 9.5% [7.9%]; and 200 min/wk or more of exercise, 13.6% [7.8%].
Conclusions: Significant weight loss and improved cardiorespiratory fitness were achieved through the combination of exercise and diet during 12 months, although no differences were found based on different exercise durations and intensities in this group of sedentary, overweight women.