Older-adult dieting won't lead to reduced physical function, research suggests
WINSTON-SALEM, N.C. – Unintentional weight loss in older adults often leads to frailty, a decline in physical function and even death. So is it wise for older, overweight women to embark on a weight loss program? New research from Wake Forest University Baptist Medical Center suggests that these women are better off trying to lose weight – even if they regain some of it.
"Our results suggest that losing weight through calorie cutting won't lead to increased disability in older women," said Jamehl Demons, M.D., lead investigator on a project evaluating the effects of weight loss on physical performance.
And even when some of the weight was regained, the women still came out ahead.
"It looks like they are better off than if they had never tried to lose weight," said Mary F. Lyles, M.D., lead investigator on an analysis exploring how dieting affected body composition.
The results of both projects – which are part of the larger Diet, Exercise and Metabolism in Older Women (DEMO) study – are being presented today (May 4) at the annual meeting of the American Geriatrics Society in Seattle.
It is well-known that weight loss – whether it is intentional or unintentional – results in the loss of both muscle and fat. Because people naturally lose muscle as they age, scientists have wondered whether it's safe for older adults to compound this effect by dieting.
"Weight loss without exercise is not widely advocated for older adults because of the potential to lose muscle and reduce physical function," said Demons, an assistant professor of internal medicine -- gerontology.
Her study evaluated 23 obese, postmenopausal, sedentary women with a mean age of 58 who participated in the DEMO study. For five months, their meals and snacks were provided by the study and contained 400 fewer calories than they needed to maintain their weight.
Participants' body composition and physical function were measured before and after the five-month period. Tests of physical function measured knee strength, hand-grip strength, walking speed, aerobic fitness and ability to quickly rise from a chair without using their arms. The women lost an average of 25 pounds, with muscle representing about 35 percent of the total loss.
"Despite the large amount of muscle loss, their aerobic fitness and their ability to rise from a chair showed a trend toward improvement," said Demons. "Their strength and walking speed did not change. This suggests that their weight loss through dieting wouldn't be expected to lead to increased disability."
Losing weight is only part of the equation, however. Most individuals who successfully lose weight tend to regain most or all of it – and little is known about whether the regained weight is fat or muscle. In older adults, regaining a significant amount of fat could be risky because of the potential to end up with less muscle than when they started.
Lyles' project evaluated 30 women from the DEMO study to determine body composition when weight was regained. Body composition was measured before and after the five-month period of calorie restriction. A third measurement was taken 12 months later.
The women lost an average of 25 pounds – about 32 percent of the lost weight was muscle and 68 percent was fat. The women regained an average of 11 pounds. About 27 percent of the regained weight was muscle and 73 percent was fat.
"Weight regain in the year following an intensive weight loss program is accompanied by gain of both fat and lean mass, with relatively more fat gain and less lean gain," said Lyles.
She noted that during the 12 months, the women had returned to their usual diet and exercise patterns, so researchers cannot conclude whether the shifts in body composition were related to the weight loss – or to some natural progression or aging change.
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Both research projects were supported by grants from the National Institutes of Health, and by a grant from the Wake Forest University Older Americans Independence Center.
Co-researchers were Xeuwen Wang, Ph.D., Steve Kritchevsky, Ph.D., Barbara Nicklas, Ph.D., and Leon Lenchik, M.D., all from Wake Forest, and Tongjian You, Ph.D., who is now with the University of Buffalo.
Media Contacts: Karen Richardson, krchrdsn@wfubmc.edu; Shannon Koontz, shkoontz@wfubmc.edu; at 336-716-4587
Wake Forest University Baptist Medical Center is an academic health system comprised of North Carolina Baptist Hospital and Wake Forest University Health Sciences, which operates the university's School of Medicine. U.S. News & World Report ranks Wake Forest University School of Medicine 18th in family medicine, 20th in geriatrics, 25th in primary care and 41st in research among the nation's medical schools. It ranks 35th in research funding by the National Institutes of Health. Almost 150 members of the medical school faculty are listed in Best Doctors in America.
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