Jason Fung

At a glance

• Jason Fung is a Canadian nephrologist (kidney specialist) from Toronto and an author. He is a well-known advocate of low-carbohydrate eating and of intermittent and extended fasting.
• In The Obesity Code (2016) he argues that the hormone insulin plays a central role in obesity, and that when you eat matters as much as how much.
• Further books include The Complete Guide to Fasting (2016, with Jimmy Moore), The Diabetes Code (2018) and The Cancer Code (2020).
• He co-founded the Intensive Dietary Management programme, now The Fasting Method, which coaches people through fasting online.
• Through YouTube and talks he reaches a large audience. Critics find his focus on insulin as the main cause too one-sided; most researchers see calorie intake as decisive.
• For longevity, he matters because he introduced many people to time-restricted eating as a practical way to snack less.
• Takeaway: if you want to try fasting, start with a fixed eating window; if you take diabetes medication, talk to your doctor first.