If your issue is erectile dysfunction, that is typically a vascular issue with the blood vessels that supply the penis with blood.
High blood glucose and high blood insulin levels damage the lining of all blood vessels, and causes issues with circulation.
Fasting lowers blood glucose and insulin, and up-regulates the healing functions of autophagy and apoptosis - so that the cells in the blood vessels can repair themselves or die off to make room for new cells (epithelial cells in this case).
Fasting and a low carb diet should go hand in hand.