10/16/2009 at 05:10 PM EDT
How does Levi Johnston keep to the high-protein diet he needs to prepare for his upcoming 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 Johnston 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."
Jones says Johnston is committed to the training sessions, which even caused Johnston get sick during his second week of working out.
"I know that's something he wants to do and we're having fun training," says Jones, who is training him in Anchorage, Alaska. "We're looking forward to revealing all his hard work!"