Ot maybe it's because of all the poison in processed food meant to make people want to eat more of it and also drive down costs with unhealthy filler ingredients and cheaper alternative ingredients
Diet is now a dirty word which has been twisted and broken by marketing execs. the concept of a 8-12 week diet (read: dramatic change of nutritional intake) is laughable as a long term solution.
It has the power to get anyone back down to normal weight. From there they need to make adjustments to not get overweight again. Which will be easier after such a diet, since the habit of eating is already broken, taste buds have reset and the body won't crave energy to maintain his overweight level.