[glenra]

Some obese people do eat a lot, but the causality direction is unclear. It's likely they eat a lot in large part because they're obese.

The human body in general is amazingly good at calibrating how much you eat versus how active you are to stay within a pretty consistent weight range - if it weren't, we'd all starve or become morbidly obese in response to tiny inadvertent changes in diet or exercise. But in some people, that calibration mechanism is off - they feel hungrier than they should or their metabolism works slower than it should given their size, and the mismatch leads them to become obese. We don't yet know why and we don't yet know what can be done to reliably change or fix it.

We've almost certainly been underthinking the whole thing.