Sleep in a trash bag, don't eat, jog constantly in a rubber suit go to the sauna spit in a bottle. That's about all you can do... I don't suggest it though. It's all water so it'll come right back on.
That's not gonna happen unless you chop off half your body... or stop eating and exercise nonstop... and both would result in death one way or the other.
You CAN way around 90-ish if you eat less (like, TONS less calories) and exercise. Jogging helps.