[jlhf]

My point was that regardless of what you eat, if you eat more than your body expends, some of the excess will be used to produce fat and you will gain weight. If you lead a sedentary lifestyle and eat 3000 calories of nothing but lean meat per day, you will gain weight.

You are right that different foods (macronutrients, more specifically) have different thermic effects and therefore require different amounts of energy to metabolise. Protein takes more energy to process than fat. This does not change my overall point.