Weight loss requires proper control of the intake of high-fat and high-sugar foods, but excessive dieting may cause malnutrition, endocrine disorders, decreased immunity, psychological and emotional changes. Excessive dieting leads to insufficient intake of nutrients, which may result in decreased muscle mass, hypoglycemia caused by insufficient supply of calories to the brain, nerves and other important organs, and insufficient intake of vitamins, which also affects the normal functioning of the organs. Excessive dieting may cause endocrine disorders. Due to insufficient nutrients, it may cause a decline in the function of endocrine glands and insufficient raw materials for hormone synthesis, which may result in insufficient synthesis of cortisol, a decline in the function of the thyroid gland, and disorders in the secretion of sex hormones, and it may also be manifested as a decline in libido in males, and disorders in menstruation in females. Excessive dieting may cause a decline in immunity, and patients are prone to infections in the respiratory tract, digestive tract and other parts of the body. Excessive dieting may also affect the psychological state, resulting in depression, anxiety and other emotional changes. In short, obese people need to properly control the intake of high-calorie foods, but excessive dieting is not a healthy way to lose weight.