Patients with liver cirrhosis have protein-energy malnutrition (PEM) and run short of proteins and energy. Protein deficiency leads to hypoalbuminemia, which induces peritoneal effusion and edema. Energy deficiency decreases fat and muscle mass and causes muscle weakness, which decreases the QOL of these patients. A decrease in triceps skinfold thickness (TSF) and arm muscle circumference (AMC), which are indicators of hypoalbuminemia and energy deficiency, and a decrease in respiratory quotient (RQ) affect the prognosis of these patients. Therefore, appropriate nutritional assessment should be performed in order to detect PEM in these patients, and necessary proteins or energy should be supplied. TSF, AMC and RQ are improved by increasing the energy supply to correct its deficiency and by dividing daily food intake (in some cases, adding nocturnal supplementation). Serum albumin levels increase when branched-chain amino acids (BCAAs) are administered after every meal or at bedtime. Consequently, nutritional assessment on PEM, and nutritional therapy based on this assessment are essential for improving the QOL and prognosis of patients with liver cirrhosis.