Nutrient induced thermogenesis

Although first described more than two centuries ago, the increase in energy expenditure associated with feeding (nutrient induced thermogenesis (NIT)) is still incompletely understood. Although the magnitude of the response and the effect of varying the composition of the diet, route and rate of feeding is still the subject of controversy, the importance of taking into account NIT when designing an optimal feeding regimen is well recognised.

What is currently unclear is the effect that injury or sepsis have on NIT. This is of clinical significance because it is precisely this group of patients in whom adequate nutritional support is most difficult to achieve yet most important. Despite significant differences in the metabolic response to feeding, NIT appears to be similar in septic patients and healthy subjects. Excessive use of intravenous glucose in such patients however may lead to marked increases in energy expenditure and stimulation of the sympathetic nervous system and should be avoided.