Phil Maffetone is an author, health practitioner, and coach with decades of experience helping everyone from amateurs to world-class athletes optimize their health and performance. In this episode, Phil explains the importance of developing the aerobic system, defines maximum aerobic function (MAF), and explains how to determine your MAF heart rate. He then demonstrates how to integrate that into a training protocol which is designed to help people move faster at a sub maximum heart rate and increase fat utilization as the primary source of fuel—emphasizing the importance of nutrition on one's capacity to oxidize fat. Phil also extracts training insights from the amazing feats of world-class marathoners, explores the impact of a low-carb diet on one’s capacity for high intensity exercise and anaerobic performance, and explains the downstream effects of being “overfat.”   We discuss:   Phil’s background in running, and training insights from a six-day race (2:30); The difference between being “fit” and being “healthy” (11:00); Defining the aerobic and anaerobic systems, and why VO2 max doesn’t predict performance (18:15); Defining maximum aerobic function (MAF), determining your MAF heart rate with Phil’s 180 Formula, and why a strong aerobic system is crucial to health and performance (24:00); Using the MAF test to track and improve your aerobic fitness (37:30); How increasing your sub-max pace at a given heart rate can increase your maximum pace (40:00); The impact of nutrition on one’s ability to use fat as fuel while exercising (43:00); Phil’s nutritional approach with patients, the concept of “carbohydrate intolerance” (51:45); Assessing the impact of a low-carb diet on high intensity exercise and anaerobic performance (58:00); Extracting insights from world-class marathoners (1:04:45); How being “overfat” affects health and performance, and ways to decrease excess body fat (1:13:30); and More. Learn more: https://peterattiamd.com/ Show notes page for this episode: http://peterattiamd.com/PhilMaffetone Subscribe to receive exclusive subscriber-only content: https://peterattiamd.com/subscribe/ Sign up to receive Peter's email newsletter: https://peterattiamd.com/newsletter/ Connect with Peter on Facebook | Twitter | Instagram.