Poor Heart Health
Credit: Getty Images

Your blood pressure and cholesterol can tell you how your circulatory system is doing, they can also give you a good idea of your sexual fitness. "Whatever's good for the heart is also good for the penis," says Shindel. Erections are caused by increased blood flow to the penis and kept up by the compression of blood vessels, so poor vascular health can interfere with your functioning down there. The fix? Old-fashioned diet and exercise is your best bet but a trip to the doctor's is also a good idea.