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> Exercising the willpower to not eat when you're hungry is only a Herculean effort if you've stopped exercising it regularly for a long time.

Addiction mechanics play a role here. It's not just willpower, it's willpower minus addiction. The second variable is absolutely massive, it snowballs over time, and it's why addiction treatments often have more interventions than just willpower.

As such, it's a thousand times more difficult for an obese person to "simply not eat" than it is for a normal person to "simply not eat." To the normal person, not addicted to food, it might seem simple, like the obese person simply lacks willpower, but in the obese person's shoes the normal person would likely end up the same way.

Hence, the obesity epidemic - it sneaks up on you.