Because the principle of weight loss is that the daily energy intake is less than the energy consumed. A mooncake (about 100g) has an energy of about 475 calories, a bowl of porridge (white porridge, 300g) has an energy of about 150 calories, so the energy you take in every day is about 625 calories. For a 60kg person, the normal daily energy requirement is about 1500 calories. So obviously your intake of energy (625 calories) is less than your consumption of energy (1500 calories), every day if you adhere to this, you can lose weight.

But you have to consider the question, can you stick to it every day? If you stick to it for a month (which you probably won't), and then can't stand it anymore and go back to your normal diet or even eat a lot of food and drink, your weight will rebound quickly and be much bigger than your previous weight. There's also the fact that with such a small amount of energy intake per day, over time, you'll get a waxy complexion and endocrine imbalance.

In summary, if you really want to be thin for a long time, you should insist on more exercise, eat a normal diet, and eat less unhealthy high-calorie foods such as deep-fried barbecue, increase your energy consumption through exercise, and reduce your energy intake by eating healthy foods, which will make you lose weight and have a fit body.

Good luck with weight loss.