Weight loss during chemotherapy is a result of malnutrition and metabolism abnormality. A few reports have focused on the treatment and prevention of weight and appetite loss in patients with advanced cancer. We evaluated the relationship between weight and appetite loss during chemotherapy by studying the meal intake of patients. In addition, we also investigated whether anorexia is associated with the level of 8-hydroxy-2' -deoxyguanosine (8-OHdG), an oxidation stress marker. The weight loss rate in patients who lack energy intake was significantly higher than that in patients with adequate energy intake. Moreover, the pre-chemotherapy total energy intake, measured according to the hospital meal consumption of patients, was lower among those with than among those without anorexia. The 8-OHdG levels in the patients with anorexia were significantly higher. In conclusion, nutritional management is important for patients even before chemotherapy is started. The 8-OHdG level can be used as an index to evaluate appetite.