Small breast development may be caused by genetic factors, self-factors, dietary factors, etc. It is recommended to pay attention to nutritional moderation during puberty, moderate intake of protein foods, avoiding dieting, partiality and other situations. 1. Genetic factors: This is due to the maternal or paternal genes, the mammary glands are less, so the proliferation of glands after puberty is not obvious, and it is easy to develop small breasts. 2. Self-factors: If you lose weight during puberty to control your body weight, resulting in malnutrition, or wear underwear that does not match the size of your body and is too tight on the chest to cause compression and other reasons, the development of the breasts will be impeded, which may lead to the development of small breasts. 3. Dietary factors: because the breast is composed of mammary tissue and fat, if you eat too much protein and fiber foods, there will be less fat tissue in the breast, the body fat content is low, thus causing small breast development. In addition, it is recommended to do appropriate chest expansion exercises, aerobics and other sports, which can help breast health.