In my medical practice I find that the best type of exercise for losing weight is swimming. I find that patients who are overweight generally do not tolerate either heat of the pounding on the joints produced in running. Swimming provides excellent cardiovascular benefit while being extremely easy on the joints and back. It also works all of the muscle groups. Also, since one is in the water, the heat intolerance is vastly improved. Start swimming!

In addition to the good answer that Phildoc gave in regards to swimming, I would like to add that just about any sport that you enjoy could constitute the most effective way to lose weight...and I've tried an awful lot. It is easier to stick to a program if you enjoy the exercises. In MY experience I have found running to be the most efficient calorie burner, and since the goal is to burn calories, this was the one I found I enjoyed the most. Now bang for your buck swimming is probably a better exercise for you in terms of taxing of the joints, but it really takes practice to be able to get a good workout from it, myself and those I know who have tried to swim as a cardiovascular workout have had difficulty maintaining pace and technique. As a personal opinion I have found running to be the ultimate exercise, there may be exercises that are more difficult but running is about as hard as you can work and still keep going for a long enough time to burn substantial calories, it allows me to stay "in the Zone" and it's at my doorstep so nothing is more convenient. As I said, this is just an opinion, for you it could just as easily be biking (excellent for the joints), Tennis, Hockey, Elliptical Trainer (also excellent for the joints) or just about anything that YOU enjoy! But as I said, If your joints can take it, and you enjoy it, running is a more effficient calorie burner than all listed.

Cardio: running, walking, dancing! Try this for 1 month and you'll see HUGE results from 10, 15 20lbs being lost! But eat less too! And keep this up or nothing will happen!

The best cardio exercise for loosing weight is one that you enjoy the most. If you don't enjoy it then you are less likely to do it. I will say that the "quickest cardio exercise to loose weight " is running or jogging. You burn the highest amount of calories in the shortest amount of time. If running and joggin is hard on the joints, then a spinning class is always an excellent way to "push your cardio" Elliptical trainers are fantastic and sculpt the lower body, just make sure that you push yourself hard enough. Hiking is also a fantastic way to burn those calories.. also fun!! Make sure that you do cardio for at least 45-60 minutes a day 4 times a week if you are really wanting to drop the lbs! Good Luck!