Contrary to common belief, aging might not significantly influence testosterone levels.
Research indicates that from around age 35, men’s testosterone levels start to decrease, but the decline is quite slow.
Another important factor, often overlooked, is the location of fat storage in the body.
A recent analysis published in the Journal of the Endocrine Society suggests that visceral fat, or deep-seated fat in the abdomen, could play a more critical role in testosterone suppression compared to other factors.
This type of fat can surround major organs such as the liver, stomach, and intestines, and it has numerous receptors for testosterone, making it particularly responsive to this hormone.
An analysis of health data from nearly 5,000 men in the US, aged 20 to 59, found a strong correlation between visceral fat and reduced testosterone levels.
In this age group, visceral fat appeared to have a more significant impact on testosterone levels than aging itself.
Once fat distribution was considered, age showed only a minor link to testosterone levels within the study’s age range.
Karl Friedl and Adam Potter, research physiologists at the US Army Research Institute of Environmental Medicine, argue that belly fat should be regarded as the “primary adiposity correlate of low testosterone in US men”.
Previous studies have also found that fat-related measures have a more substantial effect on testosterone levels than age in middle-aged men.
For example, a 2007 study involving 1,667 men revealed that a 4 to 5 point increase in body mass index (BMI) was linked to a testosterone decline similar to about ten years of aging.
These findings align with research from 2013 that tracked 1,382 men over five years, concluding that age-related testosterone declines are not inevitable but are influenced by smoking, health conditions, obesity, and depression.
However, using BMI to assess obesity has limitations.
Currently, BMI and waist circumference are the standard measures of excess body weight, but they might not accurately reflect cardiometabolic health.
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While obesity generally correlates with lower testosterone levels, individuals with similar BMIs and waist measurements might have different hormone levels.
For instance, a young man with a healthy BMI might have high hidden visceral fat affecting his testosterone levels.
Conversely, an older, muscular man with less visceral fat might be wrongly assessed as having higher testosterone risks based on age and BMI alone.
In such cases, visceral fat might be a more critical factor.
The exact reasons behind the connection between visceral fat and testosterone production remain unclear, but there are several theories.
Visceral fat can promote insulin resistance, potentially affecting how cells in the testes convert cholesterol to testosterone.
It can also trigger inflammatory pathways that might interfere with hormone signaling, leading to increased 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 indicates that reducing visceral fat through methods such as medications like Ozempic or Wegovy could address low testosterone more effectively 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.
