Older-adult Dieting Won't Lead To Reduced Physical Function, Research Suggests

"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.

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.