Unintentional weight loss is a well-validated indicator of malnutrition (White et al., 2012). The signifi cance of weight change is evaluated after the percentage of usual body weight lost in a given period of time is calculated (Box 1.3). Usually, weight changes are more refl ective of chronic, not acute, changes in nutritional status. The patient’s weight can be unreliable or invalid due to hydration status. Edema, anasarca, fl uid resuscitation, heart failure, and chronic liver or renal disease can falsely infl ate weight.