Indeed, I've known a few people in my life who say "I can eat as much as I want and I never seem to gain any weight". But then when I actually accompany them,

Indeed, I've known a few people in my life who say "I can eat as much as I want and I never seem to gain any weight". But then when I actually accompany them, it's mostly that they don't overeat. "As much as they want" is a portion that is aligned with their body.