I found some interesting biology stuff.

"...is it evolution that evolved the human body that way to prepare for a long draught of food?" Yes. And keep in mind that we inherited our metabolic system from ancestors that long predated mammals, let alone humans--the core machinery that we use is also in bacteria. Our metabolism is heavily biased toward energy storage as a hedge against future food scarcity--and since fat has the highest energy content per unit mass, that allows us to carry maximal energy in the least amount of weight. We store, on average, about 5 times more energy as fat than we do as protein and over150 times more energy as fat than as carbohydrate.

"...why would your body eat away at your lean tissue at the same time it eats your belly fat?" The breakdown of body proteins and their constituent amino acids serves to maintain blood glucose levels during starvation. Several of your tissues have an absolute requirement for glucose--the brain, the renal medulla and red blood cells. So maintaining blood sugar is the #1 priority, and if none is coming in via the diet, then the body breaks down proteins in order to convert amino acid carbon skeletons into glucose by gluconeogenesis. After a couple of weeks, the brain can use ketone bodies from fatty acids, but the other two tissues can't, ever. So even though most energy requirements are being met by breaking down fat, there's always some protein being cannibalized to keep blood sugar levels maintained. The use of fatty acids keeps protein loss down to a bare minimum, but even at that minimum, it's still a continual & gradual loss of body protein. First ones to go are in skeletal muscle, the last to go are the key proteins operating in heart, liver, kidney & brain. Problem is that you eventually reach a point where so much protein is being lost that you start losing vital functions. The average healthy person can last about a month on total starvation, but then that's it. There's tradeoffs in everything--this is one of them.

-- Ted K