Low testosterone is a phenotype of visceral adiposity.

Context: Low testosterone in men is associated with obesity. However, body mass index (BMI) and waist circumference (WC), the most common measures of obesity, do not account for fat distribution. Visceral adipose tissue (VAT) may be the more precise metabolic determinant of androgen suppression. Objective: To determine if visceral adiposity better explains variations in testosterone levels than BMI or WC. Design and Participants: This was a cross-sectional analysis of 4948 US men, aged 20-59, from the 2011-2016 National Health and Nutrition Examination Survey (NHANES). All participants had morning total testosterone measurements and 4492 had valid VAT measures from dual-energy X-ray absorptiometry. VAT discordance phenotypes were defined as the lowest vs highest quartile of VAT within BMI and (WC) categories. Main Outcome Measures: Serum total testosterone and sex hormone-binding globulin. Results: Visceral adiposity was strongly and inversely associated with total testosterone. Although VAT, BMI, and WC showed similar overall explanatory value, visceral adiposity identified substantial differences in testosterone among men with similar BMI or WC. Within each BMI category (normal-weight, overweight, and obese), men with high VAT had 33-36% lower testosterone than men with low VAT. Within WC strata, corresponding reductions were 25-39%. Normal-weight men with high VAT had testosterone levels comparable to obese men with low VAT. Conclusion: Visceral adiposity, rather than BMI- or WC-defined obesity, is the primary adiposity correlate of low testosterone in US men. Testosterone deficiency in some men appears to be a phenotype of visceral fat biology rather than obesity per se.