Sugar-free means no sucrose, which is a mixture of fructose and glucose, but it does not mean that this food does not contain "carbohydrates", and carbohydrates are also sugar.

Defatting means that the fat content inside is infinitely close to zero. Like skim milk.

Low calorie means that the total calorie per unit of this food is relatively low.

When losing weight, in fact, besides drinking some skim milk, people who lose weight are not advised to eat "sugar-free" and "low-calorie" foods, because people who lose weight don't need these special foods, so they are advised to eat foods with less processing, such as fresh fruits and vegetables, fresh fish and shrimp, which are healthier.