The Diabetes Code, in detail
The Diabetes Code is Jason Fung's argument that type 2 diabetes is a dietary disease, not a genetic destiny, and that it is therefore reversible through the right interventions. Fung, a nephrologist who treats kidney failure caused largely by diabetic complications, became frustrated watching patients progress along what medicine treated as an inevitable decline. His book is an attempt to explain why the standard treatment of medicating blood sugar without addressing its underlying cause is inadequate — and often counterproductive.
The core argument is about insulin. Fung contends that type 2 diabetes is fundamentally a disease of excess insulin and insulin resistance, not merely elevated blood glucose. When cells are chronically overloaded with glucose and insulin, they protect themselves by becoming resistant. The body responds by producing more insulin, which worsens resistance, driving a cycle that eventually overwhelms the pancreas. Most conventional treatments lower blood glucose directly while leaving the underlying insulin excess untouched — or even make it worse by adding exogenous insulin.
The solution Fung proposes is two-pronged: significantly reduce dietary carbohydrates, particularly refined ones, and use intermittent or extended fasting to allow insulin levels to drop. He draws on the physiology of fasting to explain why it can achieve what drug treatment cannot — giving cells a period of genuine rest from insulin stimulation long enough to restore sensitivity. He also addresses the dietary advice that has dominated medicine for decades, arguing that the low-fat, high-carbohydrate guidelines promoted since the 1970s have driven the diabetes epidemic.
The book is genuinely useful as an explanation of metabolic disease, and Fung writes clearly without oversimplifying the physiology. The clinical anecdotes are often striking. The weakness is a tendency toward polemical framing that can make nuanced questions feel more settled than they are. Readers who are pre-diabetic, diabetic, or have metabolic syndrome will find the framework actionable. Anyone making changes to diabetes medication should work with a clinician — some of Fung's protocols require supervised monitoring.
The big ideas
- 1.
Type 2 diabetes is driven by chronically high insulin and insulin resistance, not by blood glucose elevation alone. Treating only the symptom leaves the cause untouched.
- 2.
Dietary carbohydrates, especially refined carbohydrates and sugar, are the primary driver of insulin demand. Reducing them directly lowers the disease burden.
- 3.
Fasting — intermittent or extended — lowers insulin levels more effectively than caloric restriction because it removes all food stimulus rather than spreading smaller meals across the day.
