How did his body manage his fuel reserves? what macromolecules did his body look to first for energy? what did his body do when this resource ran out?

At first the body use carbohydrates as energy (glucose in blood, after that glicogen as reserve polysaccharide in liver and muscle), when body runs out of carbohydrates, it begins burning off the fat inside the body (visceral fat), at last body starts proceed the muscles (proteins) for energy.