Nutritional support is generally considered an essential component in the management of critically ill patients. The existing guidelines advocate early enteral nutrition, with the optimal timing for the addition of parenteral nutrition to insufficient enteral feeding being the subject of transatlantic controversy. The unphysiologic intervention of artificial nutrition in critically ill patients, however, may evoke complications and side effects. Besides the classically described complications, suppression of autophagy, potentially important for cellular repair and organ recovery, was elucidated only recently. The question whether artificial nutrition in critical illness improves or worsens outcome as compared with starvation has so far not been adequately addressed. This paper provides a critical analysis of the existing literature on ICU nutrition, highlighting important methodological shortcomings of many trials and meta-analyses and underlining the urgent need for high-quality research in this field. Recent adequately designed randomized controlled trials suggest that trophic enteral feeding during the first week of critical illness is as good as full enteral feeding and that early addition of parenteral nutrition to insufficient enteral nutrition does not provide any benefit and worsens morbidity.