Research published in the journal, Urology states that moderate exercise reduces the incidence of impotence. Men who burned at least 200 calories per day by exercising were less likely to become impotent compared to inactive men. Risk factors for impotence are similar to those for heart disease—both functions involve circulation. Things like smoking, drinking alcohol, lack of activity, poor diet and obesity all increase the chance for impotence.
Urology August 2000;56:302-306.