Many people think that the more cardio you do, the more weight you lose. Cardio does make a difference, but you need a combination of aerobic exercise AND strength training to burn fat and keep it off. Strength training helps by maintaining your muscle mass. You need muscle mass for a strong metabolism and for keeping your metabolism fast. That doesn't mean you have to look like a bodybuilder, but you at least have to maintain or better yet, increase your lean muscle mass. So a combination of aerobic exercise and strength training is the best program for losing weight.
Ideally, you should do strength
training 2 days a week and
cardio 3-4 days a week.