There are various reasons for a large small abdomen in adolescent girls. On the one hand, it may be due to increased abdominal fat. On the other hand, improper walking posture is considered to be the cause, such as walking with chest and protruding abdomen, which affects the normal curvature of the spine, while insufficient exercise and underdeveloped muscles can cause the abdomen to bulge. Such people need to maintain good sitting and standing posture, and can do exercises such as sit-ups and swimming on weekdays.