What you see in the first chart is a steep drop in weight within the first six months on the low-fat and low-carb diets. Then the weight slowly edges up and plateaus. At the two-year mark, the low-carb dieters look almost undistinguishable from the low-fat dieters: there’s only about a 4-pound difference in weight loss between the groups — a difference that's too small to have an impact on health.
This study doesn’t come in isolation. Just about every study comparing prescribed diets over a year shows the same thing: marginal differences among diets and weight losses that are significant at the beginning of the experiment, followed by pounds slowly creeping up and weight plateauing.