Weight gain during chemotherapy is often a good sign, indicating that chemotherapy is currently effective in treating tumors and that the tumors in the body are under control, so the intake of nutrients is reduced and other normal cells in the body can take in enough nutrients to make weight gain. If the weight keeps dropping during chemotherapy, it means the tumor in the body is still growing. If the patient’s gastrointestinal reaction is serious during chemotherapy, the patient will eat less, which may also cause weight loss, but the degree of loss is less than the weight loss caused by tumor, and the weight may still increase after the gastrointestinal reaction disappears.