The best diet is one high in vegetables. If you want a fad diet, try the hunter gatherer diet. It is pretty rock solid.
I am adding green coffee bean extract to my regular eating habits and have upped my workouts. It usually takes two weeks for my metabolism to increase and I usually gain weight in the first two weeks and week three the lbs start to shed off. The coffee bean extract is supposed to double fat burn and seems fairly solid too. Who knows, maybe I will become addicted to it:-)
The single best diet is one you diary what you are eating.