Is Rising Obesity a Causation for Low Testosterone Levels among American Men?

Andrea Werdecker, University of Marburg
Allan Mazur, Syracuse University
Ronny Westerman, University of Marburg

The testosterone of men in industrial societies peaks in their twenties and tends to decline with increasing age. Apart from this individual-level decline, there have been reports of a secular (age-independent population-level) decline in testosterone among American and Scandinavian men during the past few decades, possibly an indication of declining male reproductive health. It has been suggested that both declines in testosterone (individual-level and population-level) are due to increasing male obesity. Using an unusually large and lengthy longitudinal dataset (991 US Air Force veterans examined in six cycles over 20 years), we investigate the relationship of obesity to individual and population-level declines in testosterone. Over twenty years of study, longitudinal decline in mean testosterone was at least twice what would be expected from cross-sectional estimates of the aging decline. We have not identified the reason for secular decline in testosterone, but we exclude increasing obesity as a sufficient or primary explanation.