If you take plenty of crystal Meth & smoke crack, you'll lose plenty of weight. The only downfall is that you'll end up dead or addicted & living off the street.
If you don't want that, then just a proper diet & exercise is needed. No trainer needed, trainers are just for the weak people that can't motivate themselves and too lazy to do their own research or pick up a magazine or two for tips. Long and short of it, eat less, exercise more.