Young women, especially those who are overweight, tend to overestimate their levels of physical activity, according to a new study.

After losing weight, however, white women overestimate their physical activity levels to a lesser extent. In contrast, African American women continue to overestimate their physical activity as much as before losing weight, researchers report.

The finding could be useful in helping people keep the pounds off, the study’s lead author told Reuters Health.

“It can be hypothesized that women who overestimate their physical activity may not feel the need to be as physically active,” said Dr. Gary R. Hunter of the University of Alabama at Birmingham.

“This can be important for preventing weight gain since we, as well as others, have previously found that relatively high physical activity levels are important for maintaining weight,” Hunter said.

Black women tend to be less physically active and more likely to be overweight than white women, previous researchers has determined. Studies have also shown that people tend to overestimate when asked how much they exercise. So Hunter’s team set out to compare black and white women’s perceptions about their physical activity.

The study included 20 white and 21 black premenopausal women who were overweight at the start of the study, but who lost weight during the study. The trial also included a control group of 20 white and 14 black women who were not overweight.

The women reported their physical activity levels before and after losing weight.

Most women, regardless of their weight, overestimated how much physical activity they performed, Hunter’s team reports in the June issue of the American Journal of Clinical Nutrition.

“Premenopausal women overestimate physical activity with overweight premenopausal women overestimating physical activity almost twice as much as normal weight women,” Hunter said.

After weight loss, the level of overestimation dropped dramatically in white women, so much so that they were similar to the black and white women who had never been overweight, Hunter noted. But African-American women continued the same level of overestimation even after losing weight, the study found.

“Overestimation seems to be related to muscle function, especially muscular strength,” Hunter said. He noted that fit women tended to overestimate their physical activity less often than women who were not as fit.

There were signs that black women, but not white women, experienced a reduction in physical fitness after they lost weight. Physical activity may have become easier for white women who lost weight, so they may have perceived that they were less active.

Because of the decline in fitness level, physical activity may not have become any easier for black women, which may explain why they continued to overestimate their activity levels, according to the report.

The results of the study “support the concept that exercise training designed to improve fitness and especially strength fitness may be important for increasing free-living physical activity by changing how physical activity is perceived,” Hunter said.

SOURCE: American Journal of Clinical Nutrition, June 2004.