The reasons for ED can be different usually there are several of them. In males of young age is a sexual infection and injury to the pelvic organs. After 40 years the main causes of ED are cardiovascular diseases and diabetes.
At any age alcohol abusers and heavy smokers have 20% more ED and it is more difficult to improve IT. Those who lead a sedentary lifestyle and are fond of high-calorie food develop obesity which leads to erectile disorders. The situation is further worsened by stress. At the same time adipose tissue produces female sex hormones estrogens which suppress the function of testosterone.
Men who are obese are also prone to heart disease which is the main cause of ED after 40 years. Only weight loss can improve the situation. In a strong fit man problems with erectile dysfunction are much less common.