Which diet?

So after indulging myself to a piece of that red velvet cake, I went to my belly dancing class...hoping that the few calories I had would burn away. Are there really tested diets that work? I wonder too. I once stumble a page of diet reviews with user ratings, in the list were the popular methods used by celebrities such as the lemon cleanse to those I've never heard of like the Neolithic diet which suggests eating raw food only...like those times when the fire wasn't yet known to man. Well, I don't really know which one works well, but perhaps a combination of diet, workout and some more diet would really help.