The effects of enteral tube feeding and parenteral nutrition on appetite sensations and food intake in health and disease

Enteral tube feeding (ETF) and parenteral nutrition (PN) are unphysiologica l methods of feeding. They may not elicit the cephalic phase response becau se part or all of the gastrointestinal tract is bypassed, nutrients are typ ically given in liquid form by a continuous infusion over many hours and of ten overnight while patients sleep. Work conducted in animals, healthy subj ects and patients suggests that nutrients delivered as ETF or PN are less e ffective in relieving appetite sensations than food intake. Distressing app etite sensations may even occur despite the provision by artificial nutriti on of sufficient nutrients to meet requirements. The energy provided by ETF and PN is largely additional to oral food intake in humans eating ad libit um, although the extent to which this occurs may decrease with time; There is a need to establish ways (e.g. nutritional, pharmacological, psychologic al) to suppress appetite sensations and food intake when eating is contrain dicated, and to enhance them when weaning from artificial nutrition is desi rable.