Medicines like semaglutide and tirzepatide help people lose a lot of weight—up to a quarter of their body weight—but they also cause some muscle loss, about as much as you’d normally lose in 10 years of aging.

Some newer weight-loss drugs help people lose a lot of weight—up to a quarter of their body weight—but they might also cause a big drop in muscle, about as much as people usually lose in 10 years of aging, which could make them weaker over time.

If older people lose a lot of muscle while taking weight-loss drugs like semaglutide or tirzepatide, it might raise their risk of weakness, falls, and even earlier death because muscle helps keep the body strong and burning calories.

If you keep your muscle while losing weight with certain diabetes or weight-loss drugs, you might be less likely to gain the weight back after stopping the drug — because more muscle helps you burn more calories even when resting.

If you keep your muscle while losing weight with certain diabetes or weight-loss drugs like semaglutide, you might be less likely to gain the weight back after stopping the drug — muscle could help keep your metabolism healthy long-term.

When adults with obesity take a drug called semaglutide 2.4 mg for about 1.5 years, nearly 9 out of 10 lose at least 5% of their body weight — compared to only about 1 in 3 to half of those taking a sugar pill or another drug, meaning semaglutide works better for weight loss in most people.