Eating 80% full is good for your health, but there must be a premise: adequate food, no hunger and malnutrition. For example, in some parts of Africa, food is scarce, people are generally underfed, and hunger or malnutrition is widespread. It's better for them to eat until seven or eight points are full.
Digestive system damage theory: Eating too much aggravates the work of digestive system such as gastrointestinal tract, which will increase the burden of digestive system and cause digestive system diseases in the long run, so eating 80% full is the healthiest.
Eating eight points depends on when you eat eight points. If you only eat 80% full during the day, especially at noon, and eat dinner late, you will have no strength in the afternoon, and even lead to stomach problems.
People are iron rice steel, and they have the strength to work when they are full.
It depends on when to eat. If it's dinner, and you have to sleep and rest soon after dinner. It is absolutely no problem to eat this meal to 80% full, even for heavy manual workers. If it's lunch, as long as you have physical labor in the afternoon, you'd better eat well if you can. Of course, if you want a healthy body, you should pay attention to the four cornerstones of health: reasonable diet, moderate exercise, smoking cessation and alcohol restriction, and psychological balance. To achieve a reasonable diet, we need our diet to be "complete in variety, sufficient in quantity, appropriate in proportion, and balanced in supply and demand".