95% of all diets fail. Why? When you go on a low-calorie diet, your body thinks it is being starved, so it slows down your metabolism. Dieting can actually train your body to store fat more efficiently!
When you stop any drastic diet, your metabolism is now less efficient, so you will tend to gain the weight back even faster, even if you’re eating less than before.
With a low-calorie diet you also lose muscle and fat in almost equal amounts, but your rebound weight gain is all fat, not muscle, and this will slow your metabolism even more.