Stress causes your levels of cortisol to rise. Research shows peak production happens after 3 hours of deep sleep, so make sure you get enough uninterrupted sleep to take advantage of this natural boost. The question of whether protein increases testosterone is a bit murkier. Aging 10 years increases your odds of having low testosterone by 36%, but a 4-inch increase in waist size may increase your chances by up to 75%. If you're obese, you're four times more likely to benefit from testosterone replacement than non-obese men. By contrast, endurance exercises like cycling for hours or running marathons can actually reduce your testosterone level.
