New study findings conducted by researchers from the University of Westminster’s School of Life Sciences show that the shape of the gluteus maximus, or the main buttock muscle, changes with age, lifestyle, frailty, osteoporosis, and even type 2 diabetes (T2D). The study authors, who will present their findings at the Radiological Society of North America (RSNA) meeting, noted that the study also found that these changes look different in women and men.1
What is the Role of Gluteus Maximus?
Gluteus maximus is one of the largest muscles in the body, followed by gluteus medius and gluteus minimus. The gluteus maximus is used when standing, walking, running, or climbing, which are movements that need force to move forward. It also helps extend the thigh bone out and away from the body and keeps hips balanced and the trunk upright when sitting down.2
“In a healthy-functioning individual, the gluteus maximus has the potential to be the most powerful and largest muscle in the body,” Jane Konidis, MD, physiatrist at Mayo Clinic in Rochester, Minnesota, said in a news release. “But several factors can cause dysfunction in this muscle, leading to reduced or delayed activation. Factors causing this dysfunction can include prolonged sitting, hip flexor muscle group overactivity, and pain from local or distal injuries. Many people have ‘flat butt’ syndrome from sitting for so long.”3
The study authors noted that the gluteus maximus plays an essential role in metabolic health, and changes in the shape of the muscle in the buttocks could be associated with T2D.1
How Does Type 2 Diabetes Change the Shape of the Gluteus Maximus Muscle?
In the study, researchers used MRI 3D mapping, including a total of 61,290 exams from the UK Biobank database, to create detailed anatomical models to allow a better view of the gluteus maximus.1
“Unlike past studies that mainly looked at muscle size or fat, we used 3D shape mapping to pinpoint exactly where the muscle changes, giving a much more detailed picture,” Marjola Thanaj, PhD, study coauthor, and senior research fellow at the University of Westminster’s Research Centre for Optimal Health, said in a news release.1
The research team also examined how MRI analysis can capture the structure and makeup of the gluteus maximus. Using imaging, physical measurements, demographics, biomarkers, medical history, and lifestyle information from the UK Biobank data, researchers evaluated 86 variables to see how each relates to changes in muscle shape over time.1
Researchers found sex-specific shape patterns in the muscle linked to T2D, suggesting that muscle shape and not size could reflect underlying metabolic differences. Specifically, the results demonstrated that men with T2D tended to have muscle shrinkage, while women showed enlarged muscle likely caused by fat infiltration. Among participants classified as frail, men showed extensive muscle shrinkage, while women had smaller, more localized changes.1
“People with higher fitness, as measured by vigorous physical activity and hand grip strength, had a greater gluteus maximus shape, while aging, frailty, and long sitting times were linked to muscle thinning,” Thanaj said.1
The findings suggest that men and women respond biologically to the same disease in different ways. The study authors noted that changes in the shape of the gluteus maximus could signal functional decline and metabolic issues in individuals with T2D; however, further research is needed on sex-specific responses to insulin tolerance.1
REFERENCES1. Shape of your behind may signal diabetes. News release. EurekAlert! November 25, 2025. Accessed November 25, 2025. https://www.eurekalert.org/news-releases/11065312. Gluteal Muscles (Glutes). News release. Cleveland Clinic. Updated October 2, 2025. Accessed November 25, 2025. https://my.clevelandclinic.org/health/body/gluteal-muscles-glutes3. Got glutes? Part 1 — The role of the gluteus maximus and healthy activation patterns in core stabilization. News release. Mayo Clinic. October 10, 2023. Accessed November 25, 2025. https://www.mayoclinic.org/medical-professionals/physical-medicine-rehabilitation/news/got-glutes-part-1-the-role-of-the-gluteus-maximus-and-healthy-activation-patterns-in-core-stabilization/mac-20555692
