You ignire the fact that human bodies have various systems to keep weight in place. E.g. with a calorie surplus most people will inadvertedly do more small move

You ignire the fact that human bodies have various systems to keep weight in place. E.g. with a calorie surplus most people will inadvertedly do more small movements to burn up to 600kcal/day without even noticing. Without those systems, with just a 100kcal a day, you would gain 5kg of fat a year. All of this is consistent with thermodynamics.