Actually - Noblyspoon is only partially right and here is why.
Whey is whey. The differnece between isolate and concentrate is not how much protein is absorbed but how much actual protein there is per gram. Concentrate has fat, lactose and minerals. Isolate doesn't. You may think I am talking semantics but I am not. When you look at a nutrition label of isolate vs concentrate you'll see that per gram of powder a differnce in protein. But why protein is whey protein. Hydrolyzed protein only absorbs better in the research done by the supplement companies marketing it but for the sake of argument lets say it does have a slightly higher absorbtion rate it surely isn't worth the difference in price.
Having said that - concentrate + fruit = remarkable gas for me while isolate does not have the same effect so there are other considerations.
This article is a good one on the different absorbtion rates of various proteins. FYI Milk protein is part whey part casein.
Getting to the point - I'm sure you can find some off label brand that is not as good as IP protein but you would be hard pressed. From what I have seen IP packets make heavy use of soy and conentrate whey and limited use of isolate whey.
This brings me to another point which is quite funny (to me) about how IP markets it's products. They talk about insulin and how critical controlling insulin is and yet the protein they use quite a bit (whey) is the protein which creates the largest insulin response. (
Scroll down about 1/4 of page to see the graph if you aren't interested in learning how insulin actually works) Funny right? Of course it makes sense when you consider that soy and whey protein are the cheapest proteins out there. To take it a step further - they could sweeten their product with stevia but choose not to. I'm not an expert on the pricing between sucrolose vs stevia but stevia does cost more. Again - who cares? I don't. But it seems if it was actually going to be "Ideal" than it wouldn't be artificial. As well as you could easily source organic whey etc ... I could go on.
Make no mistake - what you're paying for with the IP diet is the protocol and the in person coaching/accountability. It's not superior products.