In a 2010 study, American researchers found that 40% of obese male participants had low testosterone. For obese men with diabetes, this number was 50%.
The researchers also discovered that as the men got heavier, their testosterone levels decreased.
Other research suggests that obese men with low testosterone could have problems with fertility. Low testosterone can lead to other issues as well, such as erectile dysfunction, low sex drive, diminished muscle mass, fatigue, and mood changes.