If you look at the replies you'll see the huge variety of responses people have to this, which is absolutely fascinating. I think this might actually be different for different people.
Sure there might be different experiences, but that's what I'm critizising from the article, since it says it IS the same experience for everyone (hunger increases the longer the fast). I do agree I should probably have added an extra "for some/many" or two on my comment though.
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.
I suspect it has to do not with being different people but with gut biome (so it can be different for the same person at different points in time, maybe even something we can change by changing our diet or surroundings).
