50 Cent is entering the weight-loss game. The rapper is working on “Formula 50: A 6-Week Total Body Transformation Plan,” his publisher Avery, an imprint of Penguin, told The Post’s Susannah Cahalan. The book is a plan for men and women that focuses on muscle building, nutrition, exercise and mental strength. “It is very important to me to help people make positive changes and take charge of their overall health,” Fiddy said. Last year, he shed 54 pounds to portray a football player suffering from cancer in the movie “All Things Fall Apart,” out early next year. He went from 214 pounds to 160 pounds in nine weeks by going on a liquid diet and running on a treadmill three hours a day. Hopefully, the book’s workout regime won’t be as intense.