Recently, if you have gained weight instead of eating, it may be caused by diseases, such as malnutrition and hypothyroidism. 1. Malnutrition: If the patient does not eat for a long time, it will cause the body to lack of nutrition, causing malnutrition. If the patient has protein malnutrition, hypoproteinemia will occur, causing generalized edema, as if he/she has gained weight. 2. Hypothyroidism: If the patient does not eat recently, it may cause iodine deficiency, leading to a decrease in the body’s basal metabolic rate and mucous membrane edema. As a result, patients may experience weight gain even if they do not eat. If a patient continues to skip meals and gains weight instead, he or she should go to the hospital for prompt consultation and treatment. Individualized diagnosis and treatment plan will be formulated by the doctor according to the specific condition so as not to delay the condition.