The reasons for small breasts are as follows: 1. Protein and fat intake is reduced. First of all, dieters are mostly vegetarian, meat, protein intake is obviously insufficient, and the chest is mainly fat, so the chest becomes smaller. Secondly, dieters generally eat less.2. Unsuitable underwear. Underwear too small will affect the blood circulation in the chest, too large and unfavorable to the chest shaping, in the long run, the chest may sag and become smaller.3, incorrect exercise posture. Most of the dieters will take running, stretching and other measures, if the action is too violent or posture is not correct will cause chest sagging, long time to go on will be reduced. Normally, you can promote local blood circulation through proper weight gain and breast massage to make your breasts grow.