Jason Fung (b. 1973) is a Canadian nephrologist (kidney specialist) and expert in obesity, type 2 diabetes, and intermittent fasting. Fung’s rigorous research methods, combined with his credentials and decades of professional experience, lend credibility and authority to The Obesity Code. Fung received his medical degree from the University of Toronto and completed his residency and fellowship in nephrology at the University of California, Los Angeles. After years of treating patients in renal failure, Fung shifted his attention to type 2 diabetes. In contrast to his peers, who focused on the symptoms of diabetes (abnormal blood glucose levels), Fung studied the root causes of the disease, namely, excessive insulin secretion and insulin resistance.

The Obesity Code served as the point of departure for several related projects, all of which solidified Fung’s status as a leader in his field. In 2019, he published The Obesity Code Cookbook, which builds on the sample meal plans included in The Obesity Code’s Appendix. In 2021, he co-authored The Diabetes Code Cookbook with Alison Maclean, which is a companion piece to his Diabetes Code of 2018. Fung’s website, The Fasting Method, expands on the content of The Obesity Code with weekly meetings, coaching, and masterclasses about diet and intermittent fasting (only available through paid subscription).