A new study using 3D MRI scans has found that the shape of the gluteus maximus—the large muscle in your buttocks—changes in different ways as people age or experience health problems like type 2 diabetes, osteoporosis, frailty, or even just long periods of sitting. Interestingly, these changes are not the same for women and men.
The study was presented at the Radiological Society of North America (RSNA) annual meeting and used advanced imaging to understand how the shape of this powerful muscle is linked to overall health.
Researchers used a technique called 3D MRI mapping, which processes many MRI scans to build a detailed, three-dimensional model of the muscle. This helped them go beyond looking at just muscle size or fat content. They could now see exactly where and how the muscle shape changed.
Dr. Marjola Thanaj, a senior research fellow at the University of Westminster, explained that past studies mainly focused on how big a muscle was or how much fat it contained. “We wanted a deeper picture,” she said. By mapping the shape of the gluteus maximus in detail, the team was able to find new patterns—especially those linked to metabolic conditions like type 2 diabetes.
The gluteus maximus is one of the largest muscles in the body. It plays a big role not only in movement but also in metabolic health, said Dr. E. Louise Thomas, lead author and professor of metabolic imaging at the University of Westminster.
Using data from 61,290 MRI scans in the UK Biobank database, the researchers studied how the shape of this muscle changed in connection to 86 different health and lifestyle factors. This included data on physical activity, hand grip strength, medical history, and how much time people spent sitting.
One of the key findings was that people who were more physically active and had stronger hand grip strength also had healthier muscle shapes. On the other hand, older adults, people with frailty, and those who spent long hours sitting showed signs of muscle thinning.
The differences between men and women were also very clear. In people with type 2 diabetes, men showed muscle shrinkage. But in women, the gluteus maximus muscle appeared enlarged, which the researchers think might be due to fat building up inside the muscle.
Frail men experienced general muscle shrinkage, while in women, frailty only caused changes in smaller parts of the muscle. These differences suggest that men and women may react differently to the same health conditions, especially when it comes to how the body handles insulin and blood sugar.
The researchers believe that changes in the shape of the gluteus maximus could be an early sign of declining physical function and metabolic health, especially in people with type 2 diabetes. They hope that future studies will explore how these shape changes relate to insulin resistance and other early warning signs of disease.
In short, your butt muscles may be telling a story about your health—and thanks to modern 3D imaging, scientists are getting better at reading it.
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