[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/03/16/art.levi.gi.jpg caption="Johnston's latest gig is with Playgirl magazine."]
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.
Full story at People Magazine