If you want to loose fat, try HIIT (high intensity interval training). You can derive good results from as little as 20 minutes twice a week. If you really want to loose fat quickly combine that with a full body weight workout 3 times a week. The fat burning continues long after the workout is over.
And, of course, nutrition is a large part of fat loss, so change your eating habits also.
Check out the HIIT and weightlifting and nutrition sections of this board for more detailed info.