Researchers from the University at Buffalo in New York compared 25 obese and 25 lean males, aged 14 to 20, and found that the obese males had up to 50% less total testosterone than the lean males. Testosterone is the hormone produced in the testicles.
The findings, recently published online in the journal Clinical Endocrinology, need to be confirmed with more males, the researchers said.
What the study found
"We were surprised to observe a 50% reduction in testosterone in this pediatric study because these obese males were young and were not diabetic," study first author Dr Paresh Dandona, chief of the division of endocrinology, diabetes and metabolism at the University at Buffalo medical school, said.
"The implications of our findings are, frankly, horrendous, because these boys are potentially impotent and infertile," Dandona said. "The message is a grim one with massive epidemiological implications."
The researchers noted that low testosterone levels also are associated with higher levels of abdominal fat and reduced muscle, which can lead to insulin resistance and then 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," he said. "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 study found an association between obesity and reduced testosterone levels. However, it did not establish a cause-and-effect relationship.
Has he suddenly gone off sex?
The MedlinePlus Medical Encyclopedia has more about testosterone.
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