Your bodies absorbsion of nutrients and yes calories is not a system in a vacuum. Nor it’s decision to store excess calories as fat. There’s a wide range of how much different types of foods affect different people. I had a friend who would eat (we counted) 4000 calories a day and couldn’t get over 120lb. Turns out they had a soy allergy and their bodies didn’t absorb the food.
Simplifying it to calories in calories out is a generalism of a generalism.
Simplifying it to calories in calories out is a generalism of a generalism.