The study of postmenopausal women suggests that when they regain weight -- and previous research suggests about 80% of dieters eventually do -- they don’t recover as much lean mass as they lost. As a result, they end up with more fat, even if they’re about the same weight as they were before the diet.
People lose lean tissue as well as fat when they shed pounds, the authors of the new study write. In fact, they write, studies have found that lean tissue represents roughly a quarter of total weight loss. Because the loss of muscle and bone can be especially detrimental to older people, “it is important to examine whether the benefits of weight loss outweigh the risks in this population.”
The scientists analyzed the body composition of 78 non-active postmenopausal women, ages 50-70, before and immediately after they’d completed a five-month-long diet. The researchers then weighed the women six and 12 months after the weight loss trial ended and analyzed the body composition of those who regained at least 4.4 pounds.
Most Regained Some Weight
On average, the women had lost about 12% of their body weight. By the six-month follow-up, about two-thirds of the women had regained some weight; by the 12-month follow-up, about three-quarters had, including 11 women who had gained more than they had lost.
After one year, 84% of the regainers had put on more than the benchmark of 4.4 pounds. Those were the women whose body composition was analyzed.
The women had lost twice as much fat as muscle when they were on a low-calorie diet. But afterward, they regained more than four times as much fat as muscle.
Previous studies of weight cycling were done in younger people, who tended to regain fat and lean tissue in the same proportion as they’d lost it, says researcher Barbara Nicklas, PhD, professor of geriatrics and gerontology at the Wake Forest School of Medicine.
Was It Aging or Weight Gain?
Because her study did not have a comparison group of postmenopausal women who had not lost and regained weight, Nicklas says, she and her co-authors can’t be certain that the shift in the women's lean-tissue-to-fat composition wasn’t simply due to age. She says she’s seeking funding to study that question.
A 2009 paper on body composition changes in men and women 70-79 compared people who had lost at least 3% of their weight and then regained it with those whose weight remained stable. This weight cycling “may contribute to a net loss of lean mass in older men,” the authors concluded, calling for more research.
“We are still trying to figure out what are the natural changes over time of body composition,” Jung Sun Lee, PhD, author of the 2009 report and an assistant professor of gerontology at the University of Georgia, tells WebMD.
The information is especially important because heavy people are living longer than ever before, Lee says, and there are no clear guidelines for treating their obesity.
Some people say it’s best to leave it alone. “There are a few very vocal geriatricians who are totally against an older person losing weight,” Nicklas notes.
But despite the great likelihood that people will gain it back and the suggestion that it will have an unfavorable impact on their lean-tissue-to-fat composition, “I think there are huge benefits to losing weight,” she says. When older obese people deliberately slim down, their osteoarthritis improves, Nicklas says. They can get up out of chairs and climb stairs more easily. Even if they eventually regain all of the weight, she says, it usually takes a few years to do it.
Nicklas and her co-authors published their findings in the American Journal of Clinical Nutrition.