Anorexia

During infection it is very common to lose one’s appetite (anorexia) and reduce nutrient intake. Anorexia is one of a group of symptoms collectively termed sickness behaviors, which in turn are a part of the acute-phase response (APR). The APR and its components, including anorexia, fever and iron sequestration, are induced by pro-inflammatory cytokines, e.g. interleukin-6, interleukin-1 and tumor necrosis factor[1, 2]. Whether anorexia in infection is adaptive, or merely a secondary side effect of inflammation, is controversial since one would expect increased food intake is required to meet the nutritional needs of a strong immune response. Uncertainty exists whether to give more or less nutritional support for critically ill patients [3]. However, two recent randomized controlled trials showed improved survival [4] and fewer complications [5] with lower calorie delivery. Animal studies have shown similar results: Listeria-infected mice had higher mortality when force-fed to pre-infection nutrition levels [6]. Evolutionary perspectives