First of all, women's breasts are made up of muscles, mammary glands and fat. If they are thin girls, their breasts are still very big, probably because the mammary glands and some muscles are relatively developed, but most girls' breasts are mainly fat. The fat-reducing exercise only reduces fat, and the metabolism of fat is decreasing on average. Where to be faster and slower is determined by genes, not by exercise methods, but some reasonable exercise methods can still play a certain role in breast enhancement.