Testosterone plays a vital role in how the body balances glucose, insulin, and fat metabolism. Studies have shown a correlation between belly fat and lowered levels of testosterone. Evidence developed over the past few years now shows that, while obesity does cause low testosterone, low testosterone causes obesity. A 2008 epidemiological study of 1,822 men by the New England Research Institutes (NERI) concluded that a man’s waist circumference is the single strongest predictor of low testosterone levels. And in women, studies have shown that in the presence of abdominal visceral obesity the usual low-level processes of androgen conversion seen in fat cells is turned off.