As 2015 drew to a close, it’s time to reveal our annual most popular diets list! We use your searches* to determine which diets, programs, books, and supplements are the most talked about, researched, and used for the year and we have to say, there were a few surprises! Popular Diets by Rank 1. Ideal Protein 2. Plexus Slim 3. 17 Day Diet 4.