I don't think this willpower explanation quite fits the facts.

I can delay gratification. I can quit coffee cold turkey no problem. I skip breakfast to increase my fasting period. I don't need TV or Internet, I'd rather work on my lifestyle property. I almost never take pain pills, I see myself as stoic, I can do long duration exercise.

I can count calories and force my weight down from 100kg to 74kg by sheer willpower and focus on the issue.

And yet I can't effectively keep the weight off. Because the hunger is 24x7, and my ability to focus on the issue isn't 24x7... I have other things to do in life.