While she’s only 26, she’s already one of the most influential fitness stars in the world. Kayla Itsines started off as a personal coach and turned her company into a million-dollar company since its founding in 2014. Today, the young Australian has over 14 million Facebook fans and 7.5 million subscribers on Instagram. With over a million copies of her eBook sold, a successful online fitness program, her app and other books, Kayla has significant revenue drivers spread across a variety of channels. Since the beginning, she has used customer testimonials in the form of before and after pictures to drive growth—something that is standard practice among fitness influencers.