Kayla Itsines ( it-SEE-nəs; born 21 May 1991) is an Australian personal trainer, author and entrepreneur. She is the co-creator of a series of fitness ebooks titled Bikini Body Guides, and a meal-planning and workout app, Sweat with Kayla. In 2016, Sweat with Kayla generated more revenue than any other fitness app. In March 2016, Time named Itsines one of the 30 most influential people on the Internet, noting her success at leveraging social media to promote her brand. As of October 2016, Itsine…