omg. 15lbs in a week. that can't be healthy long term. it's probably a variation on the meal replacement thing, like the slim fast shakes and such. it'll probably work while you eat what they say, but if you deviate you'll gain the weight back, plus a few extra pounds for company.
if you want to try it, you are welcome to, but those meal replacement things taste awful long term. you're better off eating a variety of fruits and veggies and grains and lean meats while exercising a bit each day. it's probably cheaper too.