Testosterone levels decline globally due to obesity and steroid use

Research presented at the European Society of Human Reproduction and Embryology (ESHRE) annual meeting indicates that testosterone levels in men have dropped by approximately 54% over the last 50 years. This trend, which has intensified since the 2000s, is linked to a significant global decrease in male fertility.

Data from over 118,000 men across Israel, the United States, Brazil, Finland, and Denmark suggest that lifestyle changes are primary drivers. Key factors include rising obesity rates—linked to sedentary behavior and ultra-processed foods—and the use of anabolic steroids for aesthetic or performance enhancement. Experts note that clandestine steroid use can cause the brain to reduce the signals necessary for endogenous testosterone production.

Additionally, a study published in the Journal of the Endocrine Society involving nearly 5,000 men in the United States found that visceral abdominal fat—fat surrounding internal organs—is more strongly linked to declining testosterone levels than aging in men aged 20 to 59. Because visceral tissue contains many testosterone receptors, it is highly sensitive to hormonal variations, meaning men with higher abdominal fat often present lower hormone levels regardless of age.