You can go running. Don't run badly every day. You will grow muscles. Jogging at a constant speed of 800- 1000m two or three times a week.

Do sit-ups in two groups a day, 40 in one group, and massage the abdomen after finishing.

In your spare time, you can learn some dances online, and then dance faster, so that you can sweat.

Half an hour's belly hula hoop.

There are also some good sports that are quite effective.

Sit in a chair, hold your head high, straighten your legs and feet. Slowly get off the ground and bend your knees and touch your chest. Then come back, but don't touch the ground with your feet. Adjust your breathing, not too fast, 20 times a day. Every day, you can visit some of them. )