Several nutritional alternatives exist to provide critically ill patients sufficient calories to meet metabolic demands. Intuitively, investigators, nutritionists, and clinicians have pursued the goal of providing high-calorie nutrition support, believing that this would improve outcomes. There is little evidence, however, that meeting caloric goals is of significant benefit. In fact, accumulating data suggest that feeding patients below previously described caloric goals is associated with better outcomes, including decreases in hospital stay, ventilator dependence, use of antibiotics, and even mortality. This suggests that permissive underfeeding could replace the paradigm of meeting measured caloric goals. Prospective evidence to support adoption of permissive underfeeding is lacking, however. Appropriate clinical studies are necessary to prove its safety and efficacy.