Obesity has already been linked to heart disease and diabetes. A recent medical study shows that it may also be associated with low testosterone levels, a condition that affects only men, according to a University at Buffalo study.

Results of the study published in the online version of the journal Diabetes Care showed that 40 percent of obese participants had lower-than- normal testosterone readings.

The percentage rose to 50 percent among obese men with diabetes.

The researchers also found that as body mass index -- the relationship of weight to height -- increased, testosterone levels decreased.

"The effect of diabetes on lowering testosterone levels was similar to that of a weight gain of approximately 20 pounds," said Dr. Sandeep Dhindsa, lead author and a UB endocrinology specialist.

Considering that almost one-third of the U. S. population is considered obese, the findings could have significant medical and public health implications, the authors reported.

This is the largest analysis of the association between obesity and low testosterone, and the first to compare prevalence of low testosterone with obesity and diabetes separately and together, according to Dhindsa and his colleagues.

The study also showed that obesity and diabetes may exert independent influences on testosterone concentrations.

The Endocrine Society recommends that men with Type 2 diabetes have their testosterone levels measured.

Dhindsa said the new study indicates that physicians also should consider screening obese nondiabetic men for low testosterone.