Gunnar Peterson, personal trainer to stars like Jennifer Lopez, Gwen Stefani and Penelope Cruz, has probably dealt with some real characters. Lately, though, he is taking on a whole new breed. Literally. Hill's Pet Nutrition has teamed up with multiple dog owner Gunnar Peterson to kick-off the 2007 Hill's PetFit Challenge, a weight loss program developed for cats and dogs. Gunnar says, "Many Read more