For the critically ill patient who is expected to remain more than 48 h in the intensive care unit (ICU), the need for nutrition is an accepted standard of care. The traditional screening tools used to identify malnutrition on the hospital ward are not adequate for use in the ICU because critically ill patients cannot communicate verbally to provide diet histories. Due to their high catabolic state, all ICU patients are at risk of developing malnutrition if not fed adequately. Since critically ill patients may be so different in terms of pathologies and severity, ‘‘One size does not fit all'' may be the message for nutrition in the ICU.