Malnutrition results from inadequate intake or abnormal GI assimilation of dietary calories, excessive energy expenditure, or altered metabolism of energy supplies by an intrinsic disease process.

Both outpatients and inpatients are at risk for malnutrition if they meet one or more of the following criteria:

• Unintentional loss of >10% of usual body weight in the preceding 3 months
• Body weight <90% of ideal for height (Table 6-1)
• Body mass index (BMI: weight/height² in kg/m²) <18.5

Two forms of severe malnutrition can be seen: marasmus, which refers to generalized starvation that occurs in the setting of chronically decreased energy intake without systemic inflammation, and kwashiorkor, which refers to selective protein malnutrition due to decreased protein intake and catabolism in the setting of acute, life-threatening illnesses or chronic inflammatory disorders. Aggressive nutritional support is indicated in kwashiorkor to prevent infectious complications and poor wound healing.