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Summary
On episode 460 of 40+ Fitness, Coach Allan sits down with Dr. Jason Fung, a physician, author, and researcher whose books The Diabetes Code, The Obesity Code, and The Complete Guide to Fasting have sold over a million copies, to talk about his new book The Cancer Code, A Revolutionary New Understanding of a Medical Mystery.
Fung explains why the decades-old idea of cancer as a handful of random genetic mutations fell apart once researchers sequenced thousands of tumors and found not two or three mutations but often 80 or more per tumor, differing between patients whose cancers looked clinically identical. He argues cancer is better understood as an evolutionary, almost backward-evolving process, and lays out the traits shared by nearly all cancers: uncontrolled growth, the ability to move (metastasis), cellular immortality, and an inefficient way of generating energy called the Warburg effect.
The conversation also gets practical: why tumor size is the wrong thing to chase, how insulin acts as a growth signal that can feed cancer, and what Fung says is actually worth doing to lower your own risk.
Links
- https://www.thefastingmethod.com
- Episode 77 – Jason Fung – The Obesity Code
- Episode 175 – Fasting for weight loss with Dr. Jason Fung and Jimmy Moore
Key Takeaways
- The old genetic-mutation model of cancer collapsed under its own data. The Cancer Genome Atlas found not 2 to 4 mutations per tumor but often 80 or more, and two patients with clinically identical cancers could have completely different sets of mutations, disproving the idea that cancer is a simple, predictable genetic error.
- Cancer shares four core traits across nearly every type. It grows when normal tissue shouldn't, it moves (metastasizes) when normal cells stay put, it becomes immortal by bypassing the Hayflick limit on cell division, and it burns energy inefficiently through the Warburg effect despite needing a lot of it.
- Tumor size is the wrong thing to chase; metastasis is what kills. Fung says roughly 90% of cancer deaths come from the disease spreading, not from the size of the original tumor, and shrinking a tumor 50% in a drug trial doesn't reliably extend how long someone lives.
- Many approved cancer drugs add strikingly little life. Fung cites data showing that, on average, newer cancer drugs extend life expectancy by about 2.1 months, despite often costing well over $100,000 a year.
- Regulatory shortcuts let weak drugs reach market. The FDA allows approval based on surrogate measures like tumor size or “progression-free survival” rather than requiring proof that a drug extends overall survival, the only outcome that actually matters.
- Insulin acts as a growth signal that can feed cancer. Chronically high insulin, from obesity, type 2 diabetes, or a diet high in refined carbs, tells the body's cells, including insulin-sensitive cancers like breast and colorectal cancer, to grow.
- Diet and smoking dwarf other cancer risk factors. Fung cites population data attributing roughly 35% of cancer risk to smoking and about 30% to diet, far outweighing radiation, pollutants, or plastics.
- Fung uses a seed-and-soil analogy: everyone carries the cancer “seed,” but it needs fertile soil to grow. A high-insulin, high-growth-signal environment (from excess weight or blood sugar) is the soil; removing that environment lowers risk even though the seed is already present.
- Dr. Fung's three strategies to get and stay well: cut out processed foods, especially refined carbohydrates; reduce how often you eat, including through intermittent fasting; and avoid unhealthy habits like smoking while managing chronic stress, which keeps cortisol elevated.
“It's not the size of the tumor that kills you.”
Dr. Jason Fung