In this chapter we have reviewed the evidence for physiological anorexia of aging and stressed that its pathophysiology involves both central and peripheral mechanisms. Early satiation in the older person appears to involve signals predominantly arising in the stomach. The increased feeling of satiety in older persons is mainly related to changes in the central feeding drive, in particular a decrease in the opioid rewarding properties for fatty foods. Increased cytokines, secondary to inflammatory conditions which are common in old age, may further increase the anorexia seen in older persons. Leptin, the fat hormone, is an excellent indicator of fat mass in women, in whom leptin concentrations correlate with the MNA. In men, testosterone inhibits leptin, and the fall in testosterone with age results in an increase in leptin concentrations. In males the MNA is not related to leptin concentrations. Finally, we have examined the interrelation of two nutritional screening indices, MNA and SCALES. The two indices were well correlated and were both predictive of poor basic function. We conclude that the MNA is an excellent predictor of nutritional status. These findings suggest that malnutrition is a major predictor of frailty or the "failure to thrive" syndrome in older persons. Depression is a major cause of poor nutritional status in older persons.