Having lost 17lbs in 5 weeks I would say the quickest way to lose weight is to eat significantly less and exercise everyday. Of course, this is not the most healthy option and you do risk depriving your body of the total amount of calories it needs, especially in these winter months but I did it purely as an exercise to see what could be done if I put my mind to it.....
If you wish to lose weight and keep it off then read a thread I started some time back. There were some very good responses, particularly from Aztruck, who explains why it's not such a good idea to starve your body in order to lose weight. Read
Here
My personal opinion is that diets like the Atkins and such are probably doing you more harm than good in the long run. Your body needs carbs so how could it be good to deprive yourself of them? Fat is unhealthy but not giving your body the correct sustenance is bad too. Read up on Rosemary Connelly diets. She insists that the best way to lose weight is to eat less fat and do more exercise and that's basically my view too. If you eat less fat then your body starts using up its fat stores - that's not rocket science and it sounds much healthier than some of these lifestyle diets out there.
Best of luck and remember - it's what's on the inside that really matters.
VFE.