Avoid crash diets as they are bad for health and you will gain what you have lost once you take a break.

Crash diets are things people go on in order to wear an old dress or suit for a particular occasion. That's the only purpose that they serve. If you are going to diet, choose a sensible, healthy option that will see a slow, long term weight loss rather than a crash diet. A balanced diet and moderate regular exercise will gently get you toned up, and keep the weight off for good.