Lie flat on the bed, put your hands on your sides, straighten your legs, and use the strength of your abdominal muscles to lift your legs straight. Slowly, raise them to a right angle to your abdomen, which is 90 degrees. Stay in the air for a few seconds, keep your legs straight as far as possible, then slowly put them down and start doing 10. After that, slowly add a lot, and insist on it for a week will definitely have obvious effects. It is more helpful for thin belly to massage his abdomen clockwise and counterclockwise with his palm around his navel before going to bed at night.