And for a very short summation of the small novella I’ve written in other comments, not every calorie has the same amount of nutrition in it.

There are non caloric nutrients in food that are absolutely vital for human health and happiness and when you are deficient in those nutrients your body will compel you to continue eating until you have met your baselines.

Solve the nutritional problem and you will most likely go a long long way towards solving the obesity problem.