Gynecomastia is an endocrine disorder. It is caused by an increase in estrogen hormone, which is a female hormone in men, or could be a decrease of the testosterone, the male hormone. So it could be caused for either of the things, it could be of many reasons. The mild cases of gynecomastia can be treated by some exercises, for example, push-ups, dumbbells and interval exercises, seating row machine, so that could be used for reducing the fat content in the body and it could treat gynecomastia to some extent. Other things like diet also some impact, because it is also seen in people with lot of fat in the body. So taking less fat, or reducing fat and more protein would definitely help those people with gynecomastia and if you are using creams and lotions for massaging, then taking less fat in the diet and more protein in the diet, would help.