I'm with Adam with this one.

The initial weight loss from these kind of diets is mainly down to the dieter emptying his glycoegn stores due to him no longer consuming/not consuming enough carbohydrate. This is weight which will simply be gained again once a more natural diet is started.

Basically, the weight loss looks great on the scales, but you're not really ridding yourself of much bodyfat. Carbohydrate and water mainly.