The 21-day diet is very effective in controlling an individual’s appetite, adjusting the function of the gastrointestinal tract and its role in processing food while losing weight and fat, and controlling the diet. This weight loss method can control the individual’s diet in stages: first, strictly control the individual’s diet to stabilize weight efficiency and prevent weight rebound due to over-eating. Second, restrict the individual’s calorie intake mainly by eating fresh vegetables and fruits instead of normal staple foods to prevent the rebound growth of fat factor. Thirdly, gradually resume an effective diet for the individual. The weight loss method replenishes the nutrients needed by the body in order to maintain the health and normal function of the body, while eliminating all the nutrients that prevent fat burning, correcting the habits of poor diet in the body, and also eliminating inflammatory cells and maintaining the basic power of the body to achieve weight loss.