I saw a similar story on GMA (maybe the same one?) that stressed that cardio exercise doesn't help you lose weight because you end up making yourself hungrier. Exercise is very important, but things like running can really do a number on your joints. And if you already have bad knees, you should definitely avoid it. I don't really buy into the ideas that you need to be out of breath and sweating like crazy at the end of a work out for it to have been effective.

The point on the story I saw was that weight training gets your heart rate up to a level where you burn fat (as opposed to a really high heart rate during running etc. that builds cardiovascular endurance) while building muscle and is therefore more effective.

I guess the only want to drop a lot of weight quickly is to work out as much as possible and eat less but that is not very healthy for most people. The weight training method sounds like a slower, but healthier and safer way to do it. Either way, we all need to exercise regularly, even if it is just walking for 20-30 minutes at a brisk rate.