I know a personal trainer who says jumping rope is one of the best ways to burn fat. But really, any regular exercise is going to give you results. The minimum amount recommended to get your metabolism revved up is 150 minutes a week - so that translates to 30 minutes a day, 5 days a week. Try mixing it up, on some days walk or run. On other days, do some weight training, other days go for some swimming, etc.
Good Luck!