By Dr Ananya Mandal, MD
It is common knowledge that some weight is regained after weight loss, but in older women many of those regained pounds return as fat mass rather than muscle mass, according to a new study.
The study included 78 women, average age 58, who had lost about 25 pounds during a previous diet study. The women in the study were sedentary, and their average body mass index (BMI) at the start was 33. BMI is a calculation based on height and weight, and a BMI of 30 is considered obese. Looking at data on the regainers, the researchers found a change in body composition. The researchers evaluated the women's body weight, lean mass and fat mass before the diet, right after weight loss, and six and 12 months later.
“A third of the weight lost was muscle,” said Dr. Barbara Nicklas, a gerontologist at the J. Paul Sticht Center on Aging and Rehabilitation at Wake Forest Baptist Medical Center in Winston-Salem, N.C. “The proportion of weight they gained back as muscle was 20 percent.” That left them with more fat and less muscle.
At one year, the researchers zeroed in on 68 women for whom complete records were available. Fifty-two (76 percent) had regained some weight, including 11 who weighed more than at the study's start. Sixteen were still losing weight. The study was published Dec. 13 in the American Journal of Clinical Nutrition.
The finding may not apply to women who are less overweight, Nicklas said. She suspects the results would also apply to older men, but perhaps not to younger men or women. “Some research shows (younger people) regain their weight in the same muscle-fat proportion they lost (it),” she said. There is a possibility, Nicklas said, that a higher proportion of fat with the regained weight may simply reflect normal aging.