Keeping off the excess pounds you lost while dieting can be a challenge, but new research suggests that women past middle age should be extra careful not to regain that weight – often called yo-yo dieting.

In a study published in the American Journal of Clinical Nutrition, researchers at Wake Forest  University School of Medicine evaluated 78 abdominally obese, post-menopausal women who had lost an average of 12 percent of their body weight on a low-calorie diet. 

A year after the diet ended, 76 percent of the women had regained some of the weight they lost. On average, these women lost twice as much fat as muscle during the diet. But a year later, they had regained more than four times as much fat as muscle. 

The researchers didn’t look at whether regaining weight, mainly in the form of fat rather than muscle, affected the health of the study participants, or whether or not the participants lost and regained the weight more than once. However, loss of muscle mass can be problematic for older adults because it may cause them to become less physically mobile, says Barbara Nicklas, PhD, professor of geriatrics and gerontology at the Wake Forest School of Medicine and the study’s principal investigator. “Everyday activities like going up and down stairs might become more difficult for them,” she says.

Middle-aged and older women with arthritis may have even more reason to pay attention to maintaining muscle mass when they’re dieting or regaining weight. According to Jon T. Giles, MD, an assistant professor of medicine in the division of rheumatology at Columbia University’s College of Physicians and Surgeons in New York City, people with rheumatoid arthritis (RA) tend to already have a higher percentage of fat in relation to muscle. “Chronic inflammation causes muscle loss in those patients,” he says. “And since they’re already starting out with low muscle mass, they should emphasize maintaining that muscle during weight loss even more.”

Those with osteoarthritis (OA) need to maintain muscle to help support their damaged joints, says Dr. Giles. “But like older people, they can lose quite a bit of muscle if they’re not doing any resistance exercise while they lose weight.” 

To minimize the loss of muscle both during a diet and if you find yourself regaining weight, it helps to eat high-protein foods and exercise regularly. Dr. Giles recommends looking for a personal trainer who is knowledgeable about arthritis and can teach you exercises that strengthen your muscles while protecting your joints. Focus on doing resistance exercises using, for example, elastic bands, dumbbells, or weight machines. “Start out slow and build up muscle and joint protection over time, then increase the amount of resistance or weight you’re using,” he suggests.