First of all, you should understand a proper term: basal metabolic heat, referred to as BMR, refers to the heat that a person must consume in order to maintain the normal operation of various organs in the body in a coma. In short, if the food you eat every day, if the calories can't reach your BMR (that is, dieting), then your brain will think that you may be in a state of food shortage, such as famine, and then your brain will send a signal. Store the body fat, because fat is very important for protecting body organs (such as keeping warm or buffering when the body is hit), and it is also necessary to consume fat to provide energy in the case of continuous "famine". Because the brain chooses to store fat, it will consume muscle, and because muscle is much heavier than fat, this is why when your intake is lower than BMR, you will lose a lot of muscle. Then, if you continue dieting, especially over-dieting, the gap between your daily calorie intake and BMR is so great that even if you consume muscles, you can't fully maintain the operation of your body organs, and organs will begin to fail.

According to protein, no matter whether you eat normally or go on a diet, you will consume it, but if you go on a diet, most of protein will provide fat to prevent fat consumption, and only a small part of protein will provide it to muscles, so muscles are consumed by the body because they are not fully absorbed by protein.