Dont trust your eyes. You dont see people eating fatty foods at McDonalds. You see them eating a shitload of sugar, salt, and a little bit of fat and proteine.

If fat would make people fat, why are americans the mos obesive nation? Your diets, relatively speaking, consist of less fat than most european diets.

But way way more sugar. In the states, sugar is in everything, including most hamburgers, bread slices and soft drinks.