Jason Fung

Jason Fung (born in 1973) is a Canadian nephrologist and functional medicine advocate who promotes a low-carbohydrate high-fat diet and intermittent fasting.

Fung disputes the current saturated fat guidelines.

Fung graduated with his medical degree from the University of Toronto, and completed his residency and fellowship in nephrology at the University of California, Los Angeles.

He is the director of the nonprofit organization Public Health Collaboration.

Fung is an author of many low-carbohydrate diet books.

His first book, The Complete Guide to Fasting, co-authored by Jimmy Moore was published in fall 2016 and offered insight to all aspects of fasting culture.

The Obesity Code and The Diabetes Code were subsequently published in 2016 and 2018.

His book The Obesity Code Cookbook was published in 2019.

In 2021, Fung co-authored The Diabetes Code Cookbook with Alison Maclean.

In 2020, Fung co-authored with naturopath Nadia Brito Pateguana The PCOS Plan: Prevent and Reverse Polycystic Ovary Syndrome Through Diet and Fasting.

His book The Cancer Code, published in 2020 advocates intermittent fasting and a low-carbohydrate diet to reduce cancer risk.

Fung's book The Obesity Code received a 31% score for scientific accuracy and an overall score of 60% by Red Pen Reviews.

The reviewer Seth Yoder commented that several of the main claims of the book are poorly supported by science including the idea that elevated levels of insulin are the primary cause of obesity.

Yoder concluded that intermittent fasting may be useful for weight loss, "but most people will not find it as effective as claimed in the book".