The stomach lost a lot of weight for no reason may be caused by physiological factors, may also be caused by hyperthyroidism, diabetes and other diseases, the former do not need special treatment, the latter need to be under the guidance of the doctor for targeted treatment, such as general treatment, medication and so on. 1. Physiological factors: the recent decrease in the amount of food and increased consumption or fitness exercise will cause weight and body fat loss, resulting in a thin stomach, is a normal phenomenon, without special treatment. 2. Hyperthyroidism: it can lead to high metabolic state, cause weight loss, and lead to thinning of the stomach; it can be treated with antithyroid drugs such as propoxythiouracil or iodine radiation therapy as prescribed by the doctor. 3. Diabetes mellitus: it can lead to excessive drinking, eating, urination and weight loss, which will cause the stomach to become thin; it needs to be treated by diet control, proper exercise and the use of hypoglycemic drugs such as metformin. In addition, patients with tumors, long-term constipation or functional dyspepsia may also experience a thin stomach after their symptoms improve. It is recommended to go to the hospital if you have lost a lot of weight for no apparent reason.