WINSTON-SALEM, N.C. – Dec. 12, 2011 – The holidays are upon us and, for many Americans that means some degree of weight gain and the subsequent New Year’s resolution to diet.
However, shedding the pounds may have some negative consequences on the overall health of older women if the weight loss is not maintained, according to a new study by researchers at Wake Forest Baptist Medical Center.
Published recently in the American Journal of Clinical Nutrition, the study showed that some older women who lose weight gain a lot of their weight back within a year. Importantly, the weight regained is mostly in the form of fat, rather than muscle.
“The body composition of some of the women was worse than before their weight loss,” said Barbara Nicklas, Ph.D., a gerontologist at the J. Paul Sticht Center on Aging and Rehabilitation at Wake Forest Baptist and principal investigator for the study. “When older women lose weight, they also lose lean mass. Most women will gain a lot of the weight back, but the majority of the weight regained is fat.”
For the study, sponsored by the National Institute on Aging, Nicklas and colleagues evaluated 78 postmenopausal women averaging 58 years old, one year after they had intentionally lost an average of 12 percent of their body weight by dieting for another study. The women’s body composition – including change in body weight, muscle and fat – was recorded immediately before and after initial weight loss, then six and 12 months later. There was no weight loss intervention during the year after initial weight loss.
The objective of the study was to determine whether the composition of body weight regained after intentional weight loss is similar to the composition of body weight lost.
At the end of the study, 53 of 78 (68 percent) women at the six-month follow-up and 52 of 68 (76 percent) women at the 12-month follow-up had regained some of their lost weight. Eleven women (16 percent) weighed more at the 12-month follow-up than they did at baseline, and 16 (24 percent) women continued losing weight after the intervention.
A large majority – 75 percent – of those who regained weight gained more than 4.4 pounds at the six-month follow-up, and this number increased to 84 percent at the 12-month follow-up. This subgroup of “regainers” was subsequently used to examine whether lost lean mass from intentional weight loss was recovered during weight regain.
In these participants, researchers found that fat mass was increasing to a greater degree than was lean mass during the postintervention period.
Of the weight lost during the intervention, 67 percent was fat and 33 percent was muscle. Of the weight regained during the entire 12 months of follow-up, 81 percent was fat and 19 percent was muscle. On average, by 12 months after the intervention, 26 percent of fat lost was regained, whereas only six percent of muscle lost was regained.
“Most people will regain their weight after they lose it.” Nicklas said. “Young people tend to regain weight in the proportion that they lost it. But the older women in our study did not appear to be regaining the muscle that they lost during initial weight loss in the same way.”
The long term consequences of losing muscle mass in middle aged and older women is yet unknown, but in combination with the loss in bone density known to occur as we age, the loss of muscle could increase their fall risk, among other things.
“There are certainly a lot of health benefits to weight loss, if you can keep the weight off,” Nicklas said. “For older women who lose weight, however, it is particularly important that they keep the weight off and continue to eat protein and stay physically active so that, if the weight does come back, it will be regained as muscle instead of fat.”
She cautioned that the results from this study were limited to sedentary, abdominally obese, postmenopausal women, and the findings may differ in men or in younger populations. Future studies of weight cycling are needed to determine its effects on muscle strength, quality, and function and body composition in older adults after all weight lost is regained, she said.
“Many health complications associated with overweight and obesity are improved with weight loss,” the researchers wrote. “However, negative consequences (such as loss of muscle mass and bone density) are also associated with weight loss and are detrimental for older adults, which results in a reluctance to recommend intentional weight loss in this population…Because lean mass loss in older adults may be associated with the development of adverse health events and disability, it is important to examine whether the benefits of weight loss outweigh the risks in this population.”
Nicklas’ co-authors are: Kristen M. Beavers, Ph.D., Mary F. Lyles, M.D., Cralen C. Davis, M.S., and Daniel P. Beavers, Ph.D., all of Wake Forest Baptist; and Xuewen Wang, Ph.D., of Washington University School of Medicine, in St. Louis, MO.