The harmfulness of not eating to lose weight needs to be analyzed according to the length of time. If you don’t eat for a long time, you are prone to gastrointestinal diseases, endocrine disorders, and in severe cases, anorexia. 1. Gastrointestinal diseases: the normal operation of the body requires food to provide the appropriate calories and nutrients, and the digestive tract will also continue to secrete digestive juices to promote intestinal peristalsis, promote food digestion. If you don’t eat for a long time, it will easily lead to gastrointestinal discomfort and degradation of digestive function. 2. Endocrine disorders: some people do not intake of the appropriate nutrients, easily lead to endocrine disorders, such as the body’s sex hormones, growth hormone secretion will be affected. For example, if women do not eat for a long time, it may cause estrogen and progesterone secretion deficiency, resulting in reduced menstrual flow. 3. Anorexia: Long-term not eating, serious cases can develop into anorexia, due to excessive dieting induced psychological cognitive abnormalities, such as the production of food will have a significant impact on body weight and refuse to eat. Anorexia patients will also be accompanied by physical symptoms, such as insomnia, behavioral abnormalities and emotional instability. Not eating to lose weight is more harmful, it is recommended to combine with exercise to lose weight at the same time, to avoid unscientific ways to lose weight.