Last week we discussed microbes that might make us eat too much. But what about the opposite. Some infections make us want to stop eating. This has practical consequences. If somebody with belly pain in the ER is hungry and can eat (without throwing it all back up!) it makes it unlikely that they have appendicitis or some other surgical diagnosis. Similarly, we are often happy when sick kids look better and are able to eat a popsicle or milk. Being able to eat = discharge from the ER, sometimes.

That leads us to this week’s topic. Anorexia (not eating) during illness– why do we often lose our appetite when we get sick?

The optimal amount of nutrition to provide during illness is an unanswered question in medicine. Some have speculated that anorexia of illness might be a host defense mechanism during infection or might help by changing energy use for various parts of the body.  If true, it is possible that providing fewer than normal nutrients during illness might speed recovery and improve survival. On the other hand, malnutrition or starvation has been associated with mortality in infection.

Writing Assignment

You are a resident doctor taking care of a sick patient in the intensive care unit. Your patient has a fever, but you are letting it go untreated because you think fever might be helpful. The nutritionist has visited your patient and has calculated her energy and nutrition needs that can be given by a nasogastric tube. She calculates a daily energy expenditure of 1800 kilocalories daily. The two senior attending physicians on the team disagree about how much nutrition should be given. Dr. Giacometti thinks giving fewer calories than “normal” is better to rest the gut. Dr. Rubens believes we should give as much calories and protein as possible in order to prevent muscle wasting. They argue briefly and then leave the unit. It is up to you to decide how many calories to give. Do you ask the nutritionist to prepare 1) 1800 calories daily, 2)  2400 calories daily, or 3) 1200 calories daily for the patient? Why?

Reading 1: Self-Medication as Adaptive Plasticity: Increased Ingestion of Plant Toxins by Parasitized Caterpillars

Reading 2: Anorexia Clinical Brief Evolution, Medicine, and Public Health. Alcock J, LeGrand EK. 2014. Nov 5; (1):149.

Reading 3: Underfeeding can benefit critically ill

The complete article referred to in Reading 3: Arabi et al. 2015 NEJM Permissive Underfeeding

Reading 4: Singer: Please sir, could I have some more, the case against underfeeding

Optional Reading – The biggest randomized trial of Tylenol for fever was just published in the New England Journal. Check it out: Young et al. NEJM Acetaminophen for Fever in Critically Ill

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Joe Alcock

Emergency Physician, Educator, Researcher, interested in the microbiome, evolution, and medicine