Continuous nasoenteric feeding: bioenergetic and metabolic response during recovery from semistarvation.

The bioenergetic and metabolic response to continuous nasoenteric feeding was examined under balance conditions for up to 22 d in 12 stable undernourished medical patients. Each subject received a fixed inflow of the mixed-fuel formula at rates of one to three times maintenance energy requirement. The pooled results were used to develop a composite profile of physiologic changes during recovery from semistarvation. Body weight, whole-body gas exchange, minute ventilation, thermal and chemical energy losses, and balances of energy, nitrogen, potassium, and sodium changed as a function of formula infusion rate and duration of feeding. These component measurements allowed calculation of such classic bioenergetic efficiency terms as digestible, metabolizable, and net energy as functions of infused energy (IE, kcal.kg fat free body mass-1.h-1: 0.96IE, 0.93IE, and 6.7 [1 - e-0.16IE], respectively) and the energy content of weight gain (means +/- SD; early, 4.2 +/- 3.5 kcal/g, and later, 7.4 +/- 3.6 kcal/g). Continuous nasoenteric feeding provides a unique opportunity to define previously unexplored dietary and metabolic interrelations in humans.