Reducing fat is carried out in the whole body at the same time, but it is only possible when the calorie intake is less than the consumption, and increasing muscle mass is the most effective way to improve the calorie consumption efficiency. In fact, exercising thighs or shoulders can also reduce abdominal (and whole body) fat, because they are a larger muscle group, so exercising them may be more effective than doing sit-ups.

The energy supply of human body is a very integrated whole system. Muscles in any part can't get energy from the recent fat accumulation, but must transport glycogen stored in blood, liver and even whole body fat through blood. The premise of using fat energy is to exercise for at least 20 minutes and keep the heart rate above 55% of the highest heart rate (the highest heart rate is 220 minus age). At this time, the glycogen in the blood and liver is consumed, and the fat can be used.