This is actually bad science. It was the result of one experiment in the 60s or 70s in mice that showed that fewer calories and more exercise = weight loss.
THIS HAS NEVER EVER EVER BEEN REPRODUCED. Reproducibility is a key part of running scientific experiments. If you or someone else cannot reproduce the same experiment with the same result, it generally means that the original experiment is flawed. No one else has ever been able to show that eat less, move more means weight loss.
Actually, I'm going to have to respectfully disagree with you on this one. There was
a recent study done by the National Institutes of Health that showed that the
type of diet selected almost doesn't matter, and that it's the total number of calories consumed that has the most effect on weight loss.
Now that being said, I think that the reason some people have such a hard time keeping at a healthy weight has very little to do with the calories in vs. calories out math, and more to do with the fact that people eat for a variety of reasons that have nothing to do with biological need or hunger.
Our bodies evolved during times when food resources weren't as reliable as they are not, and people were much, much more active. As a result, our bodies were optimized to store fat so we'd have reserves during the lean times. These days, at least in most first-world countries, it's a rare thing that people starve because of drought, crop failure, or economic disasters. Cheap food is plentiful, and so are modern conveniences like washing machines, cars, and self-propelled lawn mowers, so we don't have to work as hard to make it through the day.
Going back to the original post, I think what's going to be important for you not to regain lots of weight when you stop using CD is to make the transition gradually, while you ramp up your activity levels as well.