[stupidcar]

It's not really that counter-intuitive. Presuming humans evolved to cope in situations where food was sometimes very scarce, and had to be acquired through hunting and gathering, likely in competition with other individuals and groups, then being listless and incapable for months as our body's stores of fat and muscle drained away would not be helpful. Far better for the body to expend its store in a few weeks of energetic activity spent searching for replacement food supplies.

I've heard it said that what most people in the developed world describe as "hunger" is really just appetite. A different phenomenon, and an uncomfortable one, but separate from true hunger, which tends to set in after a few weeks, and is more like a psychological impulse to acquire food by any possible means, including violence.