Pritikin Recipes

This is one of those "I can not remember this and it’s bugging me like crazy" questions. It seems that it started with the letter R and I think it was a fasting liquid diet.
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I am not looking for a diet to use, I’m just asking for the name of the protein drink type diet used back about 10-15 years ago—for a trivia question.

My question again was about popular diets and there have been some great answers