The Diabetes Code

Joseph E. Scherger, MD, MPH

Fam Med. 2019;51(3):286-287.

DOI: 10.22454/FamMed.2019.998853

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Book Title:The Diabetes Code

Book Author: Jason Fung

Publication Information: Vancouver, Canada, Greystone Books, 2018, 296 pp., $22.95

Jason Fung, MD uses Ockham’s razor to simplify the management of type 2 diabetes. William of Ockham (1287-1347) was an English friar and philosopher. He is famous for postulating that with complex problems, the hypothesis with the fewest assumptions is usually correct.1 Fung is a nephrologist by training and runs the Intensive Dietary Management Program at the University of Toronto.

Fung formulated a new understanding of obesity by developing the argument that obesity is a hormonal illness of excess insulin.2 With all food consumption, especially carbohydrates, insulin is secreted to drive blood sugar into cells. Insulin is more importantly a fat storage hormone that blocks the burning of fat and causes excess sugar to be turned into fat through lipogenesis. Repeatedly eating carbohydrates causes chronically high insulin levels and the steady accumulation of fat.

Fung stresses the importance of fasting to lower insulin levels enough to begin using body fat for energy. He argues that nutrition for weight loss has been overly focused on what is eaten, and not sufficiently focused on how often we eat. Humans have spent most of their time on earth eating just one meal a day. Eating three meals a day is cultural, and contributes to the epidemic of overweight and obesity, especially with the increased intake of refined carbohydrates.3

In The Diabetes Code, Fung furthers this same argument to show that type 2 diabetes is caused by insulin resistance. Doctors have known this for a long time, but Fung simplifies it for a better understanding of how insulin resistance occurs. The repeated secretion of insulin that causes obesity next leads to insulin resistance as a protective mechanism for chronically high insulin levels. This also results in fatty liver early in the disease process. Insulin resistance results in the high blood sugar of type 2 diabetes. Overcome insulin resistance, and the blood sugar returns to normal and the type 2 diabetes is reversed. Fasting is a key part of this disease reversal process.

The approach to preventing and reversing diabetes described in The Diabetes Code is straightforward. The nutrition is healthy fats, low carbohydrates, and intermittent fasting. Healthy nutrition continues for life with good fats: nuts, seeds, fatty fruits and vegetables such as avocado, quality fish, and meat. This is a version of the Mediterranean diet. All refined carbohydrates and sugars are avoided. Twelve to 16-hour fasting periods are built into the daily routine, and adults eat one to two meals a day. Water is encouraged to stay well hydrated, and coffee and tea are allowed during fasting periods. Any snacks should be healthy fat and low carbohydrate, such as raw nuts. Bone broth or similar foods are used during prolonged fasts to maintain electrolytes.

Obese patients with long-standing insulin resistance often require a prolonged fast to get them started for burning fat, losing weight, and reversing insulin resistance. Fung shows how fat burning does not occur until the insulin levels are low, such as a fasting insulin below 10 mIU/ml. Fung uses longer fasting periods to lower insulin levels, allowing the body to recover from insulin resistance. To avoid hunger from fluctuating blood sugar levels, the patient is first weaned off refined carbohydrates and started on the healthy fat low carbohydrate diet. A minimum initial prolonged fast of 36 hours to 3 days may be needed to start the process of reversing insulin resistance. For morbidly obese patients Fung uses initial fasts of 7 to 21 days. The longest known medically supervised fast is over 1 year in a male weighing more than 460 lbs. Micronutrients, ample water, and electrolytes are provided during the fast, and coffee and tea are allowed.

Fung describes how many of the drugs used to treat type 2 diabetes, while lowering the blood sugar, make the underlying disease worse by increasing body fat and increasing insulin resistance. The biggest culprit here is the use of insulin. In the United States, over 23 billion dollars were spent on drugs for type 2 diabetes in 2013.4 In Fung’s clinic at the University of Toronto, most of the patients with type 2 diabetes have a complete reversal of the disease and are off medications in 3 to 6 months.

With The Diabetes Code, Fung provides a simple lifestyle approach to preventing and avoiding what has become the most expensive of all chronic diseases. The food industry and the drug industry will not be excited by his method, but it is long overdue for the public to curb the epidemic of obesity and diabetes, and lower the costs of medical care. The methods described by Fung should be taught to medical students and residents, and used in family medicine offices as part of a lifestyle approach to promoting health.


  1. Duignan B. Occam’s razor. In: Encyclopaedia Brittannica. Accessed July 27, 2018.
  2. Fung J. The Obesity Code. Vancouver, BC: Greystone Books; 2016.
  3. Lieberman D. The Story of the Human Body; Evolution, Health, and Disease. New York: Random House; 2014.
  4. Palmer E. The top 10 best-selling diabetes drugs of 2013. Fierce Pharma. 2014. -drugs-of-2013. Accessed June 6, 2017.

Lead Author

Joseph E. Scherger, MD, MPH

Affiliations: Eisenhower Health, Rancho Mirage, CA

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