Dr Jason Fung is best known for his advocacy of fasting and low-carb eating. I recently read his latest book, The Diabetes Code: Prevent and Reverse Type 2 Diabetes Naturally, published this year.
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I waffled between a four or five-star Amazon.com review, but settled on four-star because 1) I haven’t read all of the pertinent scientific literature, and 2) I’m not sure how feasible the Fung protocol is for the average type 2 diabetic (or PWD if you prefer).
When I mention diabetes or diabetic hereafter, it’s always type 2 diabetes, not type 1.
This book builds on the success of very low-carb eating as a therapeutic approach to type 2 diabetes. But it goes beyond that by advocating frequent prolonged fasts as a potential cure for diabetes. I’m talking about fasting for 30–36 hours at a stretch, for up to three times a week. On non-fasting days, his patients typically eat a low-carb diet, which makes sense to me. Two week-long sample meal plans are provided. Thus far, none of my patients have asked me about fasting. If the underlying science checks out, I’d seriously consider the Fung approach myself if I had T2 diabetes.
The longest fast I’ve done has been 24 hours. That’s pretty easy for me, probably because I eat low-carb, so my fat-burning cellular machinery is ready for action. In bro-science terms, I’m keto-adapted. I have no idea if fasting 36 hours would be any harder than 24. Maybe it’s easier if you’re obese.
Dr Fung shares many clinical vignettes from his Intensive Dietary Management Program in Canada. He doesn’t mention how many of his patients start the program and then drop out because it’s too difficult.
Why the intermittent fasting? Because it seems to be an efficient way to reverse the fat build-up in the liver and pancreas that cause the high blood sugars of diabetes. That fat build-up, in turn, is caused by high insulin levels, according to Dr Fung’s working theory of diabetes causation.
The author says the following is what causes diabetes and prediabetes. First, remember that dietary carbohydrates cause a release of insulin from the pancreas, in order to dispose of the carbohydrate as an immediate source of energy or for storage in the liver and skeletal muscles as glycogen. If the carb is not needed for immediate energy and if the glycogen tanks in liver and muscle are full, the glucose is converted to fat. That fat is ideally stored in specialized fat cells (adipocytes), but can also be stored in the liver and pancreas (called visceral fat). Excessive fat in the liver and pancreas eventually impairs function of those organs. To prevent this overload, cells have to become resistant to insulin’s effects. Diets rich in highly-processed, refined carbohydrates (especially fructose, sucrose, and starches) over-stimulate insulin release from the pancreas. Over time, this causes not only body fat, but also fat build-up in the liver and pancreas, impairing their function.
Intermittent fasting and very low-carb eating directly and immediately ameliorate the high insulin levels that cause diabetes. The fasting allows for extended periods of low insulin, which helps tissues regain or maintain sensitivity to insulin, he says.
Dr Fung rightfully points out that his program should be done under physician supervision, especially if you take drugs that can cause hypoglycemia. I can see patients taking this book to office visits and asking “Doc, can I try this?” Unfortunately, many doctors won’t take the time to read the book.
I wonder if this manifesto was actually written to convince physicians that what we’ve been doing for years is misguided, and that Fung’s approach is the way to go.
My favorite sentence: “…the very low-carbohydrate diet does remarkably well, giving you 71% of the benefits of the fasting without actual fasting.”
My least favorite sentence was regarding side effects (e.g., hunger pangs, muscle cramps, headaches) when starting fasting: “These side effects are often signs that the body is dumping its toxic sugar load.” No, that’s just good ol’ “induction flu,” more recently called keto flu.
I don’t know if Dr Fung’s causation theory of diabetes is correct or not. Maybe Dr Roger Unger’s glucagon-centric hypothesis is the reality. Ultimately what matters is whether his protocol actually reverses diabetes in significant numbers of folks, and does it safely. If the Fung protocol proves widely effective, and I hope it does, a Nobel Prize in Medicine may be in Dr Fung’s future.
Steve Parker, M.D.
Disclosures: I was given an Advance Reader’s Copy of the book by the publisher’s representative, otherwise I received no financial or other compensation. I don’t know Dr Fung.
Potential conflict of interest: I am a diet book author and blogger who advocates Mediterranean-style eating and low-carb eating for the general public and diabetics.