People come in all different shapes and sizes. Some people can eat whatever they like, metabolise carbs and never worry about their weight - others are the complete opposite.
If I saw a thin person tucking into a giant burger and chips, I'd probably think "you lucky sod." If I saw a very obese person doing the same I'd have to wonder why they were happily eating their way to an early grave.
I actually eat a high fat diet including cheese, eggs, oily fish, nuts and avocadoes, minimal meat and loads of salad and vegetables. Sadly I'm one of those people who has to keep carbs to a minimum.