No gynecomastia does not go away with exercise or dieting. In fact, exercising can make it worse. Sure exercise and dieting will get rid of all the extra fat but the glands will remain as it is. Gynecomastia is not extra fat. It is a glandular structure made up of breast tissue. Moderate amounts of fat around the gland and tummy hide gynecomastia glands but as soon as the fat disappears the gland will be clearly visible over the chest muscles. I have answered this question in detail here.