Young boys and adult men who are obese have about half the levels of the male hormone testosterone than their normal-weight peers, new research shows.
The University at Buffalo research, published online in the journal Clinical Endocrinology, suggests obesity not only puts young boys and men at greater risk for diabetes, stroke, heart disease, and cancer, but it may also leave them more vulnerable to impotency and infertility.
"We were surprised to observe a 50 percent reduction in testosterone in this pediatric study because these obese males were young and were not diabetic," said lead researcher Dr. Paresh Dandona, chief of the Division of Endocrinology, Diabetes and Metabolism in the UB medical school. "The implications of our findings are, frankly, horrendous because these boys are potentially impotent and infertile. The message is a grim one with massive epidemiological implications."
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To reach their conclusions, Dandona and colleagues tracked 25 obese and 25 lean males — ages 14 to 20 years. The investigators checked their blood levels of testosterone and estradiol, an estrogen hormone. In addition to identifying negative reproductive consequences for those with low levels of testosterone, the researchers found the obese study participants had higher levels of belly fat and reduced muscle — factors that predispose them to developing insulin resistance, which contributes to diabetes.

"These findings demonstrate that the effect of obesity is powerful, even in the young, and that lifestyle and nutritional intake starting in childhood have major repercussions throughout all stages of life," Dandona said.
"The good news is that we know that testosterone levels do return to normal in obese adult males who undergo gastric bypass surgery. It's possible that levels also will return to normal through weight loss as a result of lifestyle change, although this needs to be confirmed by larger studies."
The UB researchers now plan to study whether weight loss programs can restore testosterone levels in obese teen males.
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