Until recently, it was believed that the immune system was mostly dormant unless the body was under attack in connection with infections. However, it now turns out that the immune system most likely also plays an important role for perfectly healthy people and can affect the body’s production of vital energy sources, says a study from the University of Southern Denmark. Specifically, the immune system causes the liver of the healthy body to produce an energy source called ketone bodies. Says researcher Anne Loft, “We now believe that the immune system affects the production of ketone bodies in fit and healthy individuals and, given the beneficial effects of ketone bodies in various common metabolic disorders, this knowledge can be applied to understand how the immune system is trying to keep the body in equilibrium.”