A new imaging study suggests that the size and shape of the gluteus maximus — the large muscle that forms your butt — may offer early clues about metabolic health and even reveal that you are at risk for developing type 2 diabetes before symptoms appear.

“We found that both glute muscle size and muscle shape vary with age, physical activity, frailty, osteoporosis, and type 2 diabetes,” says lead author Marjola Thanaj, PhD, a senior research fellow at the University of Westminster in London. 

The findings suggest that the gluteus maximus can be a good indicator of metabolic health, adds Dr. Thanaj. 

Researchers Scanned People’s Butts With MRI Machines

The research team used an MRI technique called 3D statistical shape analysis, which allows scientists to create highly detailed models of muscle structure rather than measuring only volume or fat content.

Using data from over 61,000 MRI exams, investigators explored how 86 different factors including age, physical activity, biomarkers, lifestyle habits, and health conditions were linked with subtle changes to the gluteus maximum.

Researchers quantified these changes using “surface-to-surface distance,” a measure of whether a given area of muscle bulges outward or shrinks inward compared with a sex-specific template.

This approach allowed them to pinpoint where the muscle was changing and how those patterns differed across health conditions. 

Butt Changes Were Different in Men and Women With Diabetes

Researchers found key differences in the bottoms of men and women with type 2 diabetes: 

• In men, MRI 3D mapping showed small, very specific “dips” or indentations in the gluteus maximus muscle — a sign that certain areas of the muscle are thinning. Rather than the whole muscle shrinking, these changes appeared in targeted spots, which the researchers say is typical of early muscle atrophy. “These localized areas where the muscle dips inward likely reflect regional atrophy,” Thanaj explains. They may be early indicators of metabolic dysfunction, he adds.
• In women, the pattern looked completely different. Instead of thinning, women showed small pockets where the muscle appeared to bulge outward.
• These outward curves are consistent with fatty buildup inside the muscle — sometimes called fatty infiltration or “fatty hypertrophy” — which can happen when muscle tissue is gradually replaced by fat.

“These opposite signatures indicate that the same disease manifests differently in male and female muscle,” says Thanaj. The study suggests that men are more prone to losing muscle tissue in certain regions, while women are more likely to accumulate fat within the muscle. 

Why Muscle Impacts Diabetes Risk

Type 2 diabetes risk increases steadily as people grow older and less active, lose muscle mass, and accumulate fat.

All these changes contribute to insulin resistance, which is when cells stop responding effectively to insulin. As that resistance grows, blood glucose (sugar) rises, eventually leading to diabetes.

Over time insulin resistance itself contributes to muscle change, intensifying the metabolic cycle that leads to type 2 diabetes.

“I think this study is a reminder that muscle mass is key for metabolic health,” says Marilyn Tan, MD, associate professor of medicine and endocrinologist at Stanford Health Care in California, who was not involved in the study.

“It would be interesting to see how the gluteus maximus changes in people with better or worse glucose control or if other chronic conditions impact the muscle in the same way,” adds Richard Marottoli, MD, geriatrician at Yale Medicine in New Haven, Connecticut, who wasn’t involved in the study. 

Strong Butt Muscles May Help Prevent Diabetes

The key message is that a strong butt may help you stave off diabetes, so put in the effort, says Thanaj.

“Maintaining strong, well-conditioned gluteal muscles appears to be protective against future risk of type 2 diabetes, while early structural changes, especially increased intramuscular fat, may signal emerging metabolic dysfunction,” she says.

If you want to strengthen your butt — and potentially reduce your diabetes risk — cutting the amount of time you spend sitting, maintaining a healthy weight, and getting regular exercise can all help.