Belly Fat, Not Age, May Be The Bigger Driver of Low Testosterone

Aging may not impact your testosterone levels as much as you might think.

From the age of about 35, studies suggest that circulating levels of this sex hormone in men usually begin to decline.

But it's only very gradual.

There's another overlooked factor that could have a bigger impact: where fat is stored in the body.

According to a new analysis, published in the Journal of the Endocrine Society, visceral fat, or deep fat in the abdomen, may be the more precise metabolic determinant of testosterone suppression.

This specific type of fatty tissue can wrap around vital organs like the liver, stomach, and intestines, and it has many receptors for testosterone, making it especially sensitive to this circulating hormone.

In a review of health data from nearly 5,000 men in the US, aged 20 to 59, the presence of visceral fat was strongly associated with testosterone suppression.

In fact, in this age bracket, it seemed to influence testosterone concentrations significantly more than chronological aging.

After accounting for fat distribution, age showed only modest associations within the study's age range.

The two review authors, research physiologists Karl Friedl and Adam Potter, of the US Army Research Institute of Environmental Medicine, conclude that deep belly fat should be the "primary adiposity correlate of low testosterone in US men".

Visceral adipose tissue area and total testosterone in US men aged 20–59 years, adjusted for age and body mass index (BMI). (Friedl & Potter, Journal of the Endocrine Society, 2026)

Previous research has similarly found that among middle-aged men, fat-related measures exert a greater influence on testosterone levels than age.

For instance, a 2007 study of 1,667 men found that gaining 4 to 5 body mass index (BMI) points was linked to a decline in testosterone, and this was comparable to roughly 10 years of aging.

Such results also broadly align with research from 2013, which tracked 1,382 men over the course of five years.

The study authors concluded that age-related declines in T levels are "not inevitable", but instead are explained by smoking behavior and health status, particularly obesity and depression.

But using BMI to measure obesity also has its flaws.

Today, BMI and waist circumference remain the most common measures of excess body weight, but they aren't necessarily the best measures of cardiometabolic health.

While obesity is largely consistent with lower testosterone levels, men with similar BMIs and waist circumferences can still demonstrate substantially different levels of this hormone.

It's possible, for instance, that a young man with a BMI in a healthy weight range has a high percentage of hidden visceral fat, and this may be impacting his testosterone levels.

By contrast, an older, muscular man with lower visceral fat could be deemed to have a higher risk of testosterone issues just because of his age and BMI score.

In cases like these, visceral fat levels may be the more important consideration.

It's unclear why testosterone production is so closely linked to visceral fat, but researchers have a few ideas.

Deep fat in the abdomen can promote insulin resistance, and this, in turn, may cause a downstream impact on how certain cells in the testes convert cholesterol to testosterone.

Visceral fat can also stimulate inflammatory pathways that could disrupt the body's hormone signaling pathway, increasing the conversion of testosterone to estradiol.

"Current guidelines appropriately recognize obesity as a risk factor for low testosterone, but our findings suggest that adipose distribution, particularly visceral adiposity, may provide additional information beyond total body mass alone," explain Friedl and Potter.

Related: Where You Carry Your Body Fat Is Directly Linked to Brain Aging in First-of-Its-Kind Study

This means that interventions that reduce visceral fat, including drugs like Ozempic or Wegovy, may address the issues of low testosterone more directly than testosterone replacement therapy alone.

"These observations underscore the importance of characterizing the underlying adiposity phenotype and considering reversible metabolic contributors before initiating testosterone therapy," the study authors conclude.

The study is published in the Journal of the Endocrine Society.

This article was fact-checked by Clare Watson and edited by Clare Watson. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.