person A: I envy people who can eat a lot and not gain weight. It's just not fair.
person B: I think those people don't actually eat that much_comma_ it just seems like it though.
person A: Maybe_comma_ but my brother eats a lot_comma_ if not more_comma_ than me and he barely gains any weight.
person B: If he's taller/bigger than you it would make sense if he doesn't gain any weight