If you want to thin your legs and face, it is ok to do aerobic exercise or high-intensity intermittent anaerobic exercise (HIIT), but sit-ups are useless.
The treadmill, spinning bike, elliptical machine and mountaineering machine in the gym are all aerobic exercise equipment. If you don't go to the gym, running, swimming, cycling and other sports that can keep your heart rate at a relatively high frequency belong to aerobic exercise (the best heart rate is 120- 160 times per minute). Aerobic exercise to reduce fat is systemic, that is to say, all body fat is reduced together, including legs and face. If you want to lose weight faster, you should do more leg stretching.