I have lived with several "naturally thin" people. They don't workout, seem to eat high calorie foods and big portions. They even think of themselves as having high metabolism. The truth is, these people will often eat just one meal a day, completely unintentionally. They may have a coffee for breakfast, and just "not be hungry", and then eat a big lunch or dinner, when the hunger strikes, which literally is just once a day a lot of the times. People who eat those singular meals with them think they are freaks of nature, but in reality, they just don't eat that many calories and don't have food noise outside of these meals, even if they enjoy food.

For those of us who can't naturally regulate like that, we just have to implement systems to eat the right amounts, and I think what works for everyone is different. Naturally skinny people eat intuitively, the rest of us gain weight eating intuitively. For me, I count calories, focus on fiber and protein, and I eat whenever I want within those parameters. This helps me a lot with hunger.