The feeling of fullness at the end of a meal is primarily driven by the stretching of the stomach. Which is why people who have their stomach stapled feel fuller faster, and so eat less per meal.
Fat, with its extremely high calorie density, is some of the least satiating food you can eat.
This oversimplifies it a bit, because there are multiple signals and sensations related to satiety and hunger. The mechanics of snacks are different from meals because you will never get "full" from eating snacks, although you may cease being "hungry".
You are oversimplifying it. Calorie density is not the only factor related to satiety.
Blood sugar, insulin, the combination of foods eaten, fibre levels, all contribute to satiety. And in this context adding more fat and less carbs to your diet does increase satiety
Fat, with its extremely high calorie density, is some of the least satiating food you can eat.
This oversimplifies it a bit, because there are multiple signals and sensations related to satiety and hunger. The mechanics of snacks are different from meals because you will never get "full" from eating snacks, although you may cease being "hungry".