Dallas is a functional medicine practitioner, Certified Sports Nutritionist, and licensed physical therapist who specializes in treating lifestyle-related hormonal, digestive, and metabolic health issues. In 2009, he co-created the original Whole30 program. In 2012, he co-authored the New York Times bestselling book It Starts With Food, and founded his functional medicine practice, mentoring under Dr. Daniel Kalish and enrolling in the Institute for Functional Medicine's certification program. Dallas has presented more than 200 health and nutrition seminars worldwide, is a member of the Paleo f(x) and Fitwall advisory boards, and provides support and lifestyle recommendations to more than 1.5 million people a month.