Dr. Jason Fung
Nephrologist · fasting advocate · author of The Obesity Code
A real clinician (nephrology, ~18 peer-reviewed papers) whose flagship claims split sharply: type-2-diabetes remission via major dietary intervention and the hyperinsulinemia-cancer link are genuinely well-supported; his causal-direction claim on insulin resistance, his 'insulin therapy worsens diabetes' claim (a high-stakes patient-safety issue), and his 'calories are irrelevant' framing are not upheld by independent evidence. His claim that fasting uniquely spares muscle mass directly contradicts what we found grading Peter Attia — grading it here found the truth in between: fasting and calorie restriction cause similar, modest lean-mass loss.
Evidence vs. their claims
Across 5 testable claims, where the weight of independent evidence lands — on their side, or against them. Their own research network is excluded as evidence.
Read relative to their stance: when they dispute a claim and the evidence supports that claim, it counts as against them. Each row shows their stance, so you can see which way the evidence cuts.
Conflicts of interest
- Co-founder of The Fasting Method (thefastingmethod.com, formerly IDM Program) — sells paid fasting coaching/courses
- Book royalties across 4 bestsellers directly promoting the fasting/low-insulin thesis
- Notable self-referential tension: has publicly criticized pharma-industry COI in diabetes research while holding an analogous commercial interest in his own fasting programs
Stated factually. Conflicts do not by themselves make a claim wrong; they are context for weighing it.
Claim-by-claim (5)
Grouped by health topic. A person's claims often span several areas — here's where each one lands.
⏳ Longevity 3
Educational only, not medical advice. Verdicts grade the evidence, not the person; see the methodology.