[dota_fanatic]

If you hook a hose up to someone’s mouth and nose and measure the ratio of O2 absorbed vs Co2 they expel, the so-called respiratory quotient (RQ), you have a measure of the types of metabolic processing they’re doing, anaerobic vs aerobic.

If someone is in a state of metabolic dysfunction, commonly due to unfit mitochondria, they’ll be unable to utilize energy from fat as well as a young, fit person. Their body is adapted to having access to carbs at all times. Some people call the opposite being “fat adapted”. During a fast, after they’ve burned through all their glycogen, fit mitochondria can still dependably access stores of energy from fat, of which we normally have plenty.

I would bet the people who never stop being hungry during a long fast are experiencing the effects of metabolic dysfunction due to a phenotype acquired from living in the high carbohydrate, frequent access to food environment that is modern living in a first world country, especially if America. I would bet money on measuring a different RQ for the two groups, both normally and during a fast.