When we are hungry or need endurance, our bodies accumulate fat to store energy. However, where is the best place to store so much energy? Is it piled at the leg end or the arm end? Think of primitive people running around and jumping up and down every day. If fat accumulates on the limbs, it will easily affect the stability of the center of gravity. Brain fat was only accumulated on the legs during the ape-man period, and it is estimated that it was eaten by wild animals when it could not run. When a person stands, the abdomen is the position closest to the center of gravity. Therefore, the "spare energy" of fat accumulation here does not easily affect the change of people's center of gravity, nor does it affect people's running and jumping, and can maintain geometric balance when walking upright. The abdomen is the center of gravity of the human body, and fat radiates outward from the center of gravity. In addition to the abdomen, buttocks and thighs are also prone to accumulation of fat. Suppose a person is infinitely fat, he will approach like a ball, which can ensure the stability of the center of gravity to the maximum extent.

There are two kinds of adipose tissue in human body: stubborn fat containing α -adrenoceptor and ordinary fat containing β -adrenoceptor. The role of α receptor is to inhibit lipase and regulate the supply of muscle energy during exercise. To put it bluntly, it will inhibit the burning of fat. The function of β receptor is to activate lipase, accelerate muscle contraction and promote fat burning. Stubborn fat contains a high density of α adrenoceptors, while ordinary fat contains β adrenoceptors. So stubborn fat is hard to lose.

When short-term exercise produces fatigue, lipase and glucose in liver and adipose tissue will be activated, and muscle glycogen will decompose adrenaline to speed up heart rhythm, blood circulation and fat burning to release heat. But if it is long-term fatigue, such as staying up late, irregular work and rest, great pressure, long-term excessive exercise and so on. , the human body will start the defense mechanism (storing more energy for emergencies and resisting possible longer-term stress), increase α receptor, inhibit lipase secretion, prevent fat from burning, and store more stubborn fat that is difficult to burn. On the road of forming stubborn fat, insulin is also a "hero" and the culprit to accelerate the activity of α receptor! I have said many times before that insulin, a hormone, helps us control blood sugar and store fat. In the period of food shortage, insulin is the most important baby in human life. However, now it has become the chief culprit of our weight gain and a stumbling block to prevent us from losing weight! Stubborn fat is more sensitive to insulin. Insulin can increase the activity of the enzyme responsible for storing fat (specific lipoprotein lipase LSL) and decrease the activity of the enzyme responsible for releasing fat (hormone sensitive lipase HSL), while stubborn fat is much more sensitive to insulin than ordinary fat, which means that stubborn fat often stores more fat and releases less fat than ordinary fat molecules. In addition, estrogen can also increase the activity of α receptor, which explains why women have more stubborn fat than men, and why boys lose weight faster and better!