Gynecomastia can develop in young boys as well as adult men. Young boys and teens may experience this condition as a result of fluctuating hormones. If this is the case, the problem should resolve itself within a couple of years. Most adults and some minors acquire Gynecomastia due to genetic predisposition to fat and breast tissue accumulation in this area. Weight gain can exacerbate the problem as well.
To be clear, Gynecomastia refers to the amassing of breast tissue, and not solely fatty tissue, in the male breast area. Patients who have excess fat alone in this region are said to have Pseudo-Gynecomastia. Many men have a combination of breast and fatty tissue. There are treatment options to address both of these situations and achieve a flatter, smoother chest.