A growing body of evidence suggests that age alone may not be the main reason many men experience declining testosterone levels. New research points instead to visceral fat — the deep abdominal fat stored around internal organs — as a potentially more important factor in hormonal decline.
The latest analysis, published in Journal of the Endocrine Society, examined data from nearly 5,000 US men aged 20 to 59. Researchers found that visceral fat was strongly associated with lower testosterone levels, while the relationship with chronological age was considerably smaller within this age range.
Visceral fat lies deep within the abdomen, surrounding organs including the liver, stomach and intestines, and is metabolically active tissue. It interacts with numerous hormonal and metabolic processes, making its accumulation particularly relevant to endocrine and cardiometabolic health.
Visceral fat versus simple aging
After accounting for fat distribution, the study authors found that age had only modest associations with testosterone levels. Men of similar ages could therefore have substantially different hormone profiles depending on differences in visceral adiposity.
Research physiologists Karl Friedl and Adam Potter of the US Army Research Institute of Environmental Medicine concluded that visceral adiposity should be considered a primary fat-related correlate of lower testosterone in US men. Their findings suggest that fat distribution can provide information beyond weight or age alone.
Earlier research has reported similar patterns. A 2007 study involving 1,667 men found that an increase of four to five body mass index points was associated with a decline in testosterone comparable to approximately 10 years of aging, highlighting the relationship between increasing body weight and testosterone levels.
Limits of BMI and waist measurements
Body mass index and waist circumference remain common methods of assessing obesity. However, these measures cannot reliably distinguish between subcutaneous fat beneath the skin, visceral fat surrounding internal organs and lean muscle mass.
As a result, men with similar BMIs or waist measurements can differ considerably in body composition, hormone levels and cardiometabolic risk. A younger man with substantial visceral fat could have lower testosterone despite a seemingly acceptable overall weight, while a muscular older man could have a higher BMI largely because of greater lean mass.
The new analysis therefore highlights the potential importance of looking beyond total body weight. Measures capable of assessing visceral adiposity more directly, including imaging and advanced body-composition techniques, can provide additional information about fat distribution.
How visceral fat may disrupt hormones
Researchers continue to investigate the mechanisms connecting visceral fat with testosterone. One proposed pathway involves insulin resistance, which can interfere with processes involved in normal testosterone production.
Visceral adiposity is also associated with chronic low-grade inflammation. In addition, adipose tissue is involved in the conversion of testosterone into estradiol, potentially contributing to changes in circulating testosterone and the overall balance of sex hormones.
These relationships can potentially become bidirectional. Lower testosterone may contribute to changes in body composition, including reduced muscle mass and increased fat accumulation, while worsening metabolic health may further affect hormonal function.
Implications for treatment and prevention
Clinical guidelines already recognize obesity as an important risk factor for low testosterone and male hypogonadism. The new findings suggest that clinicians may also benefit from considering how body fat is distributed rather than relying exclusively on overall measures of obesity.
The researchers argue that evaluating adiposity patterns and potentially reversible metabolic contributors should be considered when assessing men with low testosterone. Such evaluation can help distinguish broader metabolic factors from situations in which testosterone replacement therapy may be appropriate.
Reducing visceral fat through lifestyle changes, exercise, dietary improvements and, when clinically appropriate, medications may also influence testosterone levels. Weight-loss medications such as semaglutide, marketed as Ozempic and Wegovy, have demonstrated substantial effects on body weight and visceral adiposity in clinical research.
Weight-loss medications, however, are only one component of metabolic care. Long-term nutrition, physical activity, sleep and other health factors can remain important alongside pharmacological treatment.
Previous research has also suggested that testosterone decline with age varies considerably between men. A 2013 study following 1,382 men for five years found that changes in testosterone were associated with potentially modifiable factors including obesity, smoking and depression.
Overall, the emerging evidence highlights visceral fat and metabolic health as important factors associated with testosterone levels. For some men with low testosterone and excess visceral adiposity, addressing underlying metabolic factors may therefore be an important part of evaluation alongside consideration of hormone-specific treatment.
