«IT'S CALLED GOSSIP AND OF COURSE IT'S AN OBSESSION OF MINE»

How does Levi Johnston keep to the high-protein diet he needs to prepare for a Playgirl photo shoot? With a rifle.
"Moose meat is very good for you, high in protein and very lean," his trainer, Marvin Jones, tells PEOPLE. "He's an avid hunter, so he has his own." The 19-year-old father of former Alaska Gov. Sarah Palin's grandchild has adopted a 3,500-calorie low-carb diet as part of a grueling regimen to ready him for next month's photo shoot.Johnston works out three hours a day in the gym, six days a week, followed by cardio training and then a rest in the sauna, says Jones. "I'm not trying to give him a body builder's look. He's going to be more toned and more defined," says Jones, 46, who plans on training with him until the first or second week of November. "I'd like to see him with rounder and more muscular shoulders, with a fuller chest. We're going to firm his abs up, [and give him a] smaller waist."