How much leptin will go up when you start eating more varies from person to person. And how your brain responds to increased leptin levels also varies from person to person. Clearly, people’s physiologies vary a lot. In some people, when leptin rises, their brain decreases their appetite and increases their NEAT output. In others, the response isn’t nearly so robust.

That being said, most of the time, for most people: The food you eat can change your brain.
Assuming we’re properly nourished, that well-balanced leptin loop will tell us when we’ve had enough. It helps us feel sated and allows us to eat reasonable portions, comfortably. But that nicely balanced loop can become disrupted — quickly — when we eat certain types of food.