Caloric deficit does work. The problem is that there are two variables that most people have a hard time tracking. Nutrition facts can actually be off by as much as 10%. I think people get so hyper focused on the exact number instead of living a healthier more active lifestyle. 1200 calories for an overweight person is too little. Yeah I said that. They need to eat too keep their metabolism "awake". Then they need to stay active and increase muscle mass that will in turn increase metabolism.