Disordered nutrition is common in Crohn's disease and is multifactorial. Regular and systematic monitoring of at least a minimum set of nutrition data is an essential component of care of children and adults with Crohn's disease. However, even in children, monitoring of growth and development may be deficient. Multiple macro- and micronutrient deficiencies are common in Crohn's disease, especially in those with extensive small bowel deficiencies or after multiple surgical resections. Body composition analysis may show differences from simple starvation, and metabolic effects of inflammation are increasingly being recognized. Nutritional support is part of the management of all patients with Crohn's disease, but nutritional intervention with defined formula liquid diet is an effective specific anti-inflammatory therapy. Although meta-analysis of published trials suggest that steroids are more effective than defined formula liquid diets, objective evidence from whole gut lavage fluid analysis and from faecal excretion of radiolabelled leukocytes shows unequivocal benefit of elemental diet based on measuring parameters of tissue damage. Enteral feeding with liquid diets should be considered in patients with incomplete small bowel obstruction, severe painful perianal disease, failure of corticosteroids in active Crohn's disease, borderline intestinal failure and in children with active Crohn's disease or with growth failure.