The popular literature sometimes tells women that weight-loss is harder for them, especially exercise-induced weight loss. Different reasons are offered: women’s hormones are different, a woman's body “defends” her body fat more than a man's.
Not so, says a meticulous report from Leeds University. In fact, the paper’s title says it all very clearly: “No Sex Difference in Body Fat in Response to Supervised and Measured Exercise.” The report also finds no significant difference in women vs. men subjects with regard to weight loss, and no increase in food consumption after beginning an exercise program.
The researchers believe they did a particularly good job in the area of “supervised and measured exercise” among 107 male and female subjects. All were overweight or obese at the beginning of the study, and had an average age of about 41.
After enrolling in the study, men and women were both asked to exercise five times a week for 12 weeks. They burned precisely 500 calories per workout. They could choose among the following indoor exercise equipment: treadmill, cross-trainer, rowing machine, or stationary bike. This wasn’t a race; they were allowed to exercise at a modest-but-steady 70 percent of their max heart rate. Mostly because they were smaller, the women had to exercise for an average of 54 minutes to reach 500 calories vs. 43 minutes for the men.
During the 12-week period, researchers also measured each subject’s daily calorie intake. Thus, they had solid numbers for both calories in, and calories out through exercise. They also measured the resting metabolic rate of all subjects.
At the end of the study, the men had lost slightly more weight than the women, possibly because the women gained more muscle. (Both groups gained some muscle, considered an important effect of healthy diets.) Both groups reduced their percent of body fat by 2.45 percent. Perhaps because of the muscle gain, there was no change in resting metabolic rate in either group.
In addition, neither group increased caloric intake, despite the major uptick in weekly exercise. The men continued to consume roughly 2,883 calories a day, and the women 2,469. If these numbers appear high, that’s because the men weighed an average of 213 pounds at the study’s outset, and the women 189 pounds.
There were subtle changes in appetite with the subjects reporting more hunger. However, this was apparently balanced by an increased satiety after meals. The researchers say this paradoxical effect happens because of exercise’s “dual action.” It burns more calories, but also adds to a feeling of satisfaction after meals. Caloric-restriction diets have only one action: They reduce calories in.
“We feel that the current research may correct an unnecessarily negative view of exercise for weight control among women,” the researchers conclude. “When exercise is closely monitored for males and females, there are no sex-biased differences in compensatory response. Exercise should be promoted for weight control for females, as for males.”