Diets are defined in the traditional sense of following a specific eating plan for weight loss/obesity.
Sure, following any of the hundreds of plans that have been promoted in the last few decades may result in some weight loss, but the benefits typically don't last.
Sadly, there is no magic bullet. No, not even those prescription medications that are common these days. Sure, they may result in shedding some pounds, but I've been observing nasty side effects in people that use them, and unless lifestyle changes are made, the pounds will come back.
The average American keeps getting heavier, especially children, and the new miracle diets keep coming, and the average American keeps getting heavier, especially children, and...
I suspect you get my point.