Obese teenage boys are at risk for more than diabetes and heart disease, a new study has found. They also have alarmingly low levels of testosterone - between 40 to 50% less than males of the same age with a normal body mass index.

The study, published this week in the journal Clinical Endocrinology, investigated the effect of obesity on testosterone levels in young males.

It has its origins in earlier research, which showed that type II diabetes and obesity in older men are linked to a high rate (25-33%) of hypogonadism, or low testosterone levels. According to the new study, the rate of hypogonadism in type II diabetic men ages 18-35 is greater than 50%.

In addition, concentrations of free testosterone — testosterone that isn’t chemically bound and thus available to the body — were shown to be negatively related to BMI: The higher the body mass, the lower the concentration.

“This raises the question whether obesity is associated with lower testosterone concentrations, even in younger males,” the study said.

Controlling for age, physical maturity and certain medical factors, 25 obese and 25 lean males between the ages of 14 and 20 were studied.

Blood samples were drawn in the morning to measure both total and free testosterone.

Mean testosterone concentration was 50% lower in obese males. Mean free testosterone concentration was 46% lower.

The results present several problems for those affected, according to Dr. Paresh Dandona, chief of the Division of Endocrinology, Diabetes and Metabolism at the University of Buffalo’s medical school and the study’s lead author.

Obesity can lead to diabetes and heart disease. What’s more, low testosterone can slow or stop sexual maturation — and there’s nothing more hurtful than “a male not having his maleness,” Dandona said.

“It’s alarming, because these guys could grow up to be inadequate in sexual performance and also in terms of fertility,” he said.

The next step is a larger study to confirm the findings as well as investigate more questions, such how the hypothalamus part of the brain is “turned off” when triggering the pituitary gland to produce testosterone — and how it might be turned back on.

The brain’s mechanisms are especially important, Dandona said, because it’s there that the problem begins.

Research has shown that adults who have gastric bypass surgery return to normal testosterone levels. It’s possible that weight loss alone would have a similar effect.

There is no confirmation yet if this holds true for teenaged males.

For cautious parents, the best first step is to be proactive against obesity, doctors say.

“Because that’s the passport to disaster in the long-term,” Dandona said - “diabetes, heart disease and now inadequate sexual maturation.”