Some of the above is controversial and not understood properly.
Sumo wrestlers sleep twice a day after two heavy meals. So total sleep is quite a lot. Sumo eat nothing until lunch, having risen early and exercised heavily all morning. So that lends credence to the theory of fasting slowing metabolism. However, some recent scientific studies cast doubt on that and there is some evidence that fasting increases metabolism and intermittent fasting is gaining ground as a weight loss method.
Not rubbishing the above at all, just saying it's not all fully understood yet by any measure.
5 years