Researchers report that higher body fat percentages are linked to lower sperm counts and hormonal changes in men, even among those with a normal body mass index.
Key facts
- •The study examined 1,058 Danish men at the age of 18 years and 9 months.
- •Men with high body fat percentages had an average 23% lower sperm count than those with normal body fat.
- •Body fat was categorized as low (under 8%), normal (8-19%), high (20-24%), and very high (25% or more).
- •Researchers found that BMI is an indirect measure that fails to distinguish between fat mass and lean muscle mass.
- •The findings were published in the journal Human Reproduction on July 29.
A study published July 29 in the journal Human Reproduction indicates that body fat percentage is a more accurate predictor of male reproductive health than body mass index (BMI). Researchers found that men with higher body fat levels often experience lower sperm counts, reduced semen volume, and altered hormone levels, including testosterone. These findings suggest that BMI may overlook men at risk for fertility issues because it does not distinguish between fat and lean muscle mass.
By the numbers
Study Methodology and Findings
The research team analyzed 1,058 Danish men who were 18 years and 9 months old. Using bioimpedance analyzers to measure body fat, they categorized participants into four groups ranging from low to very high body fat. The data showed that men with high body fat percentages had, on average, a 23% lower sperm count compared to those with normal body fat levels. Those with very high body fat percentages showed a 15% lower sperm count. Lead author Nis Brix noted that these associations persist even in men with a normal BMI. The study suggests that assessing body fat composition could help clinicians identify men at risk of reduced fertility who might otherwise be missed by traditional BMI measurements.
Impact of Body Composition on Fertility
Experts not involved in the study emphasized that obesity can impair sperm production, as excess fat tissue may convert testosterone into estrogen. Urologist Philip Werthman described the decline in male fertility as a significant public health signal. Another specialist, Dr. S. Adam Ramin, noted that low sperm counts can sometimes serve as an indicator of broader underlying health issues. While infertility affects approximately 15% of couples in the United States, researchers suggest that men may improve their reproductive health by maintaining a healthy body composition, eating a balanced diet, and managing stress. Other practical recommendations for supporting testicular health include wearing loose-fitting clothing and avoiding prolonged exposure to high temperatures, such as in jacuzzis.
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This article was independently rewritten by ManyPress editorial AI from reporting originally published by Healthline.
