A large cross-sectional analysis of nearly 4,500 American men found that visceral fat, the metabolically active fat packed around the abdominal organs, tracks far more tightly with low testosterone than either body mass index or waist size. Among men with identical BMI, those in the top quartile of visceral fat carried roughly 30 percent less testosterone than those in the bottom quartile. A lean, normal-weight man with a hidden visceral fat load can have the same testosterone as an obese man whose fat is mostly subcutaneous. The authors argue that low testosterone is better understood as a phenotype of visceral adiposity rather than of obesity as conventionally measured, and that reducing visceral fat, potentially via lifestyle change or GLP-1 agonists, may treat the root cause more directly than testosterone replacement.
For decades the clinical shorthand has been simple: heavier men have lower testosterone. This study picks that assumption apart and points to a more specific culprit. Using dual-energy X-ray absorptiometry data from the US National Health and Nutrition Examination Survey, researchers at the US Army Research Institute of Environmental Medicine directly measured the visceral fat depot, the fat wrapped around the liver and intestines, in thousands of men and compared it against the two yardsticks clinicians actually use in practice, BMI and waist circumference.
The big idea is that where fat sits matters more than how much a man weighs. BMI cannot tell muscle from fat, and even waist circumference is just a tape measure that lumps together skin fat, muscle, bone and the dangerous fat deep inside. When the team isolated men who looked identical on the bathroom scale but differed sharply in visceral fat, the testosterone gap was striking. Across normal-weight, overweight and obese categories alike, the high visceral fat men had roughly a third less circulating testosterone than their low visceral fat counterparts. Most provocatively, a normal-weight man loaded with visceral fat looked hormonally like an obese man who happened to store his fat under the skin.
The mechanism the authors favor runs through the liver and the pancreas. Visceral fat drives insulin resistance and inflammation, which suppress sex hormone-binding globulin and appear to blunt the testes’ own hormone production. When the team accounted for that binding protein, much of the visceral fat effect was explained, but not all of it, suggesting inflammation and direct gonadal suppression are working in parallel.
There is an important caveat baked into the design. This is a snapshot in time, not a film. It cannot prove that visceral fat lowers testosterone rather than the reverse, and the relationship is almost certainly a two-way street where low testosterone encourages visceral fat and visceral fat further suppresses testosterone. Still, the practical message lands: two men with the same weight can have very different hormonal health, and the difference is buried in their bellies. The authors suggest that targeting visceral fat, rather than reaching first for testosterone gels, may be the more rational route to restoring a man’s own hormone production.
Actionable Insights
The take-home is that fat distribution, not scale weight, is the lever. A man of normal BMI is not automatically in the clear, and a muscular man with a high BMI is not automatically at risk. The effect size is substantial. Within a given BMI band, men in the top quartile of visceral fat had 33 to 36 percent lower testosterone than those in the bottom quartile. In absolute terms, that gap ran from roughly 189 ng/dL in normal-weight men (542 down to 353) to about 165 ng/dL in obese men (468 down to 303). For scale, that within-BMI visceral fat gap is larger than the testosterone difference you get from moving an entire BMI category. A normal-weight man with high visceral fat (353 ng/dL) sits closer to the clinical hypogonadism threshold than an obese man with low visceral fat (468 ng/dL).
Practically: prioritize interventions that preferentially strip visceral fat, which respond well to caloric restriction, resistance and aerobic training, sleep, and, where indicated, GLP-1 receptor agonists. Because functional hypogonadism from adiposity is often reversible, reducing visceral fat may restore endogenous testosterone rather than requiring lifelong replacement. If you have access to a DXA scan, the visceral fat area is a more informative number than your weight.
Context and Source
- Open access Paper: Low testosterone is a phenotype of visceral adiposity.
- Authors and institution: Karl E. Friedl and Adam W. Potter, US Army Research Institute of Environmental Medicine, Natick, Massachusetts, United States.
- Journal: Journal of the Endocrine Society (Oxford University Press on behalf of the Endocrine Society), published 13 July 2026.
- Impact evaluation: The 2024 Journal Impact Factor is 3.1 and the CiteScore is 5, with an SJR of 0.979 placing it in quartile 2 for endocrinology, therefore this is a Low-to-Medium impact journal.