Illness Anorexia

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As we discussed in the last post, illness is accompanied by a dramatic decrease in eating, but also an increase in carbohydrate secretion in the gut. These events point towards a coordinated adaptive response to infection and illness that might improve survival when sick. So, should we give our patients less nutrition in the hospital when they are critically ill?

The idea of permissive underfeeding in critical illness was proposed by Zaloga and Roberts (1994). They hypothesized that maximizing nutrition “may adversely affect the host response to injury, especially when given in excess of energy and protein needs.” Supporting the view that calorie restriction during illness is protective, Huang et al 2012 showed that patients with higher illness severity had longer stays in the ICU when feeding was initiated early versus late. In an observational trial, Arabi and colleagues reported that giving higher calories to patients in the ICU was associated with worse outcomes in the ICU (2010). Similar results were found by Krishnan et al. 2003, In a randomized controlled trials, Arabi and colleagues (2011) underfeeding (60%) vs. normal (100%) replacement of calorie needs resulted in improved survival in ICU patients, in keeping with an adaptive function of illness anorexia.

Ed Legrand and I recently summarized why illness anorexia may be an evolved adpative response, and its clinical implications in Evolution Medicine and Public Health, available here.

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