Body composition, rather than masculine physical traits, linked to aging markers in middle-aged men

“The findings do not support the hypothesis that greater morphological masculinization reflecting higher androgen exposure is associated with accelerated biological aging.”

BUFFALO, NY — October 28, 2026 — A new research paper was published in Volume 18 of Aging on October 6, 2026, titled “Body composition, but not morphological masculinity, is associated with biological aging markers in middle-aged men.”

The study found that masculine physical characteristics were not independently associated with biological aging markers in middle-aged men. Instead, body composition, particularly fat-free mass percentage and body fat distribution, showed stronger relationships with inflammation and growth hormone levels. However, these associations disappeared after adjusting for adiposity, suggesting that body fat may help explain the observed relationships.

The research was led by first and corresponding author Agnieszka Żelaźniewicz, affiliated with the University of Wroclaw.

Aging involves changes in hormonal regulation, immune function, metabolism and body composition. In men, testosterone influences the development of masculine physical characteristics, muscle mass and reproductive function. However, its relationship with biological aging remains unclear, with evidence suggesting both potentially beneficial and harmful effects depending on physiological conditions.

Some evolutionary theories propose that greater investment in reproductive characteristics may come at the expense of long-term bodily maintenance. According to the limited soma hypothesis, resources devoted to reproductive competition could reduce those available for cellular repair and maintenance, potentially accelerating aging.

Traits such as broad shoulders, muscularity, facial proportions and physical strength are influenced to varying degrees by androgen signaling. If developing and maintaining these characteristics carries long-term physiological costs, men with more pronounced masculine traits might be expected to show signs of accelerated biological aging.

To investigate this hypothesis, the researchers studied 176 generally healthy middle-aged men, with an average age of approximately 53.8 years. They examined whether physical characteristics associated with androgen exposure were related to inflammatory and endocrine markers commonly used to assess aspects of biological aging.

The researchers measured shoulder-to-hip ratio, waist-to-chest ratio, facial width-to-height ratio, jaw width, fat-free mass, handgrip strength and torso strength. They also assessed the second-to-fourth digit ratio (2D:4D), which has been investigated as an indirect marker of prenatal androgen exposure.

These characteristics reflect different developmental processes and are influenced by genetics, nutrition and lifestyle. They therefore cannot be considered direct measures of testosterone exposure.

Biological aging was evaluated using inflammatory markers, including high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). These molecules are associated with chronic low-grade inflammation, often called inflammaging, which is linked to several age-related conditions.

The researchers also measured endocrine markers, including soluble alpha-klotho, growth hormone (GH), insulin-like growth factor-1 (IGF-1), dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Circulating testosterone was assessed separately to examine its relationship with the same aging indicators.

Initial analyses revealed several associations involving body composition. Men with a higher percentage of fat-free mass generally had lower inflammatory marker levels and higher growth hormone concentrations. Conversely, a higher waist-to-chest ratio was associated with greater inflammation, suggesting a relationship between body fat distribution and inflammatory activity.

After correcting for multiple statistical comparisons, the strongest remaining associations involved fat-free mass, waist-to-chest ratio, inflammatory markers and growth hormone. Other masculinity measures, including facial characteristics, digit ratios and muscle strength, showed no consistent relationships with biological aging indicators.

However, these relationships changed after accounting for potential confounding factors. When the researchers adjusted for adiposity, age, cortisol levels, physical activity, smoking history and chronic diseases, morphological masculinity measures no longer independently predicted biological aging markers.

This suggests that the initial associations involving body composition may largely reflect differences in body fat rather than the long-term physiological costs of masculine development. Importantly, the findings do not demonstrate that increasing muscle mass or reducing adiposity directly changes the rate of biological aging.

The researchers also used principal component analysis to identify broader patterns among the physical characteristics. Three components emerged, representing body masculinity, muscular strength and digit ratios associated with prenatal androgen exposure. Together, these accounted for approximately 65% of the variation in the measured traits, while facial masculinity did not form a separate component.

None of these broader masculinity measures independently predicted biological aging markers after adjustment for relevant factors. This indicates that combining several physical characteristics did not provide a reliable indicator of biological aging in the study population.

Testosterone showed a similarly complex pattern. Higher circulating levels were associated with greater fat-free mass, broader shoulders relative to the hips and lower waist-to-chest ratios. Initial analyses also identified some associations between testosterone and inflammatory markers, generally suggesting lower inflammation at higher testosterone concentrations.

Nevertheless, testosterone did not independently predict biological aging markers after accounting for confounding factors and multiple testing. These results provide little support for the hypothesis that greater testosterone exposure necessarily accelerates biological aging in middle-aged men.

The findings also highlight the distinction between body composition and masculine appearance. Fat-free mass is closely related to skeletal muscle and metabolic function, while abdominal adiposity is associated with chronic inflammation. These relationships may be more relevant to aging-related physiology than facial proportions or physical features established during development.

“These associations most likely reflect the well-established relationship between adiposity, inflammation, and biological aging rather than the costs of developing sexually dimorphic traits.”

The study contributes to an ongoing debate about testosterone, reproductive investment and healthy aging. Although some evolutionary hypotheses predict biological costs from greater androgen-related development, testosterone also supports muscle maintenance, physical performance and metabolic function. Its effects may therefore depend on age, body composition, health status and other physiological factors.

The research has important limitations. Its cross-sectional design cannot establish causality or determine whether masculine traits predict future aging trajectories. Testosterone was measured only once, which may not reflect long-term hormone exposure. The study also assessed selected inflammatory and endocrine biomarkers rather than comprehensive measures such as epigenetic aging clocks.

Additionally, participants were generally healthy middle-aged men from a relatively homogeneous population. The findings may not apply to younger men, older adults or individuals with significant chronic diseases. Longitudinal studies incorporating repeated hormone measurements and broader aging indicators will be necessary to clarify these relationships.

Overall, the study found no evidence that greater morphological masculinity or higher circulating testosterone independently predicts accelerated biological aging in middle-aged men. Instead, adiposity may better explain the observed relationships between body composition and aging-related biomarkers. The findings highlight the importance of metabolic health and body composition when investigating the complex biological processes underlying male aging.

Paper DOI: https://doi.org/10.18632/aging.206427  

Corresponding author: Agnieszka Żelaźniewicz - agnieszka.zelazniewicz@uwr.edu.pl  

Abstract video: https://www.youtube.com/watch?v=jQa9XRsvrIU

Keywords: androgen signaling, inflammaging, endocrine aging, klotho, life-history trade-offs

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