Fatigue during sickness with lack of appetite is likely due to the body prioritizing immune function over processing calories, rather than a simple lack of calories, provided sufficient body fat stores exist.

“So when they're sick, the immune system just the the amount of the the part of your budget that gets consumed by the immune system, you know, expands, right? So this energy this extra energy needs to be stolen from somewhere because you can't eat more to have you know infinite energy. Uh so what where's that energy coming from? So not contracting your muscles because you feel in pain is a good way. Not having to thermmorreulate because you you know cover up another way to conserve energy. and then stopping to care about stuff like becoming asocial and apathic and all of”