Rita Ora is undergoing a “transformation” with the help of an LA-based health guru. The 31-year-old pop star is said to be more determined than ever to stay in tip-top shape, and she’s turned to a health guru in the US and a personal trainer in London as part of her efforts. A source told The Sun on Sunday newspaper’s Bizarre column: “Rita has always been very much into health and well-being, but lately she has been pushing herself much harder than she has in the past. “She has been saying she wants to undergo a real transformation, and has enlisted the help of a guru in LA who has given her a…