In general, we consider for an average female the breast to be made up of half fatty tissue and half glandular tissue. The younger the patient the more glandular tissue they will have and the older the patient the less glandular tissue and more fatty tissue the patient will have. Therefore, if there is weight gain, depending on where the patient gains their weight, the breast may increase in size after a breast reduction. In most cases as long as the patient has a stable weight, this is unlikely to occur.