Cardio! Cardio exercises are the only way to lose weight quickly and naturally. Having said that, it is not easy. My fitness out me through a whole range of exercises and I used to leave the gym physically drained. But all that pain was well worth it. I managed to lose substantial amounts of weight in just three months and now I'm fit again. I considered quitting a few times but my instructor gave me good encouragement and I stuck through. Oh and I did I mention she was hot too. :) Exercises such as rowing, swimming and mountain cycling are the best bet.