Fat is just more calories stored in the body for later during emergency when there's no food. Fat people are rendering a service, if predators jump out of the woods, the giant slow moving one is the one that gets hauled away, it's been this way for at the very least 800 million years of our evolution, and there's not enough data in the new training samples isolated in the last fourty thousand years, where there's effectively no monsters in the woods. The monsters in the wood could be back at any point and we'll need fat oligarchs to be carried away in our stead.