Founder of extreme fitness program P90X Tony Horton has been following a vegan diet for more than two weeks. “I’m in the midst of a little vegan experiment,” Horton announced last week via a video on Instagram. Horton revealed he committed to follow a vegan diet for two weeks but chose to extend his “experiment” indefinitely. “So far so good,” Horton said. “I feel amazing!” The extreme athlete has been using vegan protein powder from fitness food company Shakeology, which he said made transitioning to a vegan diet easier for him. This month, a host of celebrities have announced that they are adopting a vegan diet—including Orange is the New Black star Danielle Brooks, musician Ne-Yo, and reality star Kylie Jenner.