The idea that calorie balance will lead to weight regulation over the long term comes from the Caloric Balance Hypothesis, the popular notion that overeating and sedentary behavior causes weight gain.
Since we control our weight by our eating and exercising habits -- which are consciously regulated behaviors -- our weight therefore must be consciously regulated. Any discussion of the physiology of fat metabolism is besides the point. When you are obese, the problem MUST be in your head. You're a glutton, you're a sloth, or you're some combination thereof.
To hammer home this point, let's refer back to the energy balance equation, from which the Caloric Balance Hypothesis derives.
Energy Stored in the Body = Calories In - Calories Out
Weight maintenance, according to this theory, is achieved when you achieve a balance of calories. From the USDA's website:
"How can I move toward a healthier weight? Reaching a healthier weight is a balancing act. The secret is learning how to balance 'energy in' and 'energy out' over the long run. 'Energy in' is the calories from the foods and beverages you have each day. 'Energy out' is the calories you burn for basic body functions in physical activity... Your weight will stay the same when the calories you eat and drink equals the calories you burn."
Since the calories we eat and the calories we burn are clearly under conscious control; therefore, the theory predicts that the fact that we maintain our weight at a relatively constant level over time must also be because we're somehow consciously manipulating calorie balance all that time.
I know it sounds hyperbolic, but I believe that this Black Box concept is the key -- perhaps our ONLY hope -- for solving the obesity epidemic. In other words, without The Black Box, or something like it, our society is doomed to be destroyed by obesity, diabetes and other diet-related chronic diseases. No joke. I 100% believe this. So check it out!