It’s simple. If you eat more calories than you burn, you get fat. This is about overeating.
Then, as the stomach gets larger and larger, you need more and more food to feel full.
Vicious cycle.
Obesity and all the medical complications and diagnoses that go with it account for 150 BILLION/year in health care costs and 300,000 premature deaths. Increased costs to the obese individuals average $4,000 per year.
Anybody who claims that the solution to obesity is simple can be dismissed out of hand. If it were simple, the enormous amount of money and effort that have been put into it would have borne fruit.
Here are the specific flaws in your argument.
Your argument presumes that the amount of calories that a person burns is relatively fixed. It isn’t. One’s metabolism may change significantly in response to changes in caloric intake. Some people consume more calories and their metabolism goes up. When some people eat fewer calories, their metabolism goes way down.
Your argument presumes that the amount of food a person eats is relatively easy to consciously control. Satiety and hunger are involuntary bodily processes, similar to heart rate, respiration rate, and eye blinking. In the same way that you could force yourself to blink on a schedule, or choose to hyperventilate, you can force yourself to consciously modify your eating habits. And in the same way, you would feel very uncomfortable and have a hard time maintaining that behavior over the long term.
I don’t know where you’re pulling your “specific flaws” from, but satiation is not involuntary and can be controlled by specific techniques.
For example, if you eat higher protein food, eat more slowly and eat smaller bites you reach satiation earlier.
Heart rate is also something that can be controlled. Deep free divers do it all the time, decreasing their heart rate through training down to about 25 beats per minute.
Essentially, your “specific flaws” can be “dismissed out of hand.”