Researchers have confirmed that obesity is linked to low testosterone levels in men. Results of the Hypogonadism in Males (HIM) study, which involved more than 2000 men aged 45 and over, revealed that the prevalence of lower-than-normal testosterone levels was 40% in obese men and 50% in obese diabetic men. In comparison, 26% of normal weight men were found to have subnormal testosterone levels.  The study also showed that the mean free testosterone concentration of diabetic men was significantly lower than that of non-diabetic men, with free testosterone levels dropping by 7.8 pg/ml/decade in non-diabetic and 8.4 pg/ml/decade in diabetic men. "The effect of diabetes on lowering testosterone levels was similar to that of a weight gain of approximately 20 pounds," says study author Sandeep Dhindsa, MD, an endocrinology specialist in the University of Buffalo Department of Medicine. "In view of the fact that almost one-third of the U.S. is obese, these observations have profound pathophysiological, clinical, epidemiological, and public health implications."