Repeated weight gain and loss can not only derail diets but also accelerate muscle loss in middle-aged people, a new University of California, San Francisco study finds, as weight-loss drugs revolutionize obesity treatment.
In a study published on July 21, Radiologyresearchers found that even though both groups finished the study with about the same total body weight as they started, those whose weight fluctuated repeatedly lost significantly more thigh muscle over four years than those whose weight remained relatively stable.
“When people’s weight changed cyclically, they lost a lot of muscle along with fat, and the muscle never came back,” said Thomas Link, MD, professor of radiology, who led the study, and co-lead authors Adrian A. Maas, MD, and Gabby Joseph, PhD. “This shows us that understanding how to protect your muscles during weight loss is important for your overall health.”
Although the study was not conducted in people taking GLP-1 drugs, the insights address questions that will become increasingly important as more people enter and exit weight loss therapy, Link said.
See beyond scale
Researchers analyzed MRI scans and health data from 1,433 middle-aged participants in the Osteoarthritis Initiative, a long-term National Institutes of Health-funded study of adults at risk for knee osteoarthritis. While some participants maintained a stable weight over the four-year study period, others experienced repeated weight fluctuations.
Using artificial intelligence to analyze the MRI scans, the researchers measured muscle mass in the thighs, fat within the muscles, and fat around the knees. The differences between the two groups were significant.
People whose weight fluctuated repeatedly lost about four times as much thigh muscle over a four-year period compared to people whose weight remained relatively stable. Taking into account age, gender, baseline BMI, physical activity, diet, and other health factors, weight cyclers lost about 3.7% in thigh muscle mass compared to about 1% in non-cyclers.
The findings also suggest that preserving muscle during weight loss deserves just as much attention as losing fat.
We need a deeper understanding of how weight loss affects our bodies beyond just the number on the scale. ”
Thomas Link, MD, Professor of Radiology, University of California, San Francisco
“Fat loss is just one piece of a larger puzzle that includes how weight loss affects arthritis, muscles, bones, and other factors,” Link said. “As more people take advantage of effective weight loss therapies, we need to think about how those factors fit together.”
sauce:
University of California, San Francisco
Reference magazines:
Mars, A.A. Others. (2026). Association of body weight cycling with MRI-based thigh muscle quality and proximal knee obesity: data from the Osteoarthritis Initiative. Radiology. DOI: 10.1148/radiol.253988. https://pubs.rsna.org/doi/10.1148/radiol.253988
