A unique side-by-side comparison of four popular diets – Atkins low-carb, Ornish low-fat, the Zone and Weight Watchers – has found no difference in each plan's weight loss potential. When the fat-free chips are down, the type of diet doesn't seem to matter nearly as much as whether people actually follow it.From the Dallas Morning News (free registration required).
From hard experience I can say this is totally true. It is calories in versus calories out. That means eat less and move more. Period.