As the lifestyle medicine movement continues to gain traction and strength, it is critically important that lifestyle medicine practitioners base their recommendations on the best available evidence. This review outlines ways of accomplishing that goal. The core concepts behind lifestyle medicine reside in many different bodies of information. These include nutrition, exercise physiology, behavioral medicine, psychology, and many more. Lifestyle medicine practitioners will need to be knowledgeable in all of these areas. A good place to start is with the evidence-based recommendations put out by major national bodies. The Dietary Guidelines for Americans and Physical Activity Guidelines for Americans also provide comprehensive, evidence-based information regarding these 2 critically important modalities. This review also discusses ways that scientific information is often distorted and how conjecture may sometimes be confused with proof. The review concludes with some recommendations for how lifestyle medicine practitioners can ground their recommendations on sound scientific evidence.