How fasting reverses type 2 diabetes

While many consider type 2 diabetes (T2D) irreversible, fasting has been long known to reverse diabetes. In a previous post, we considered bariatric surgery. While extreme, these surgeries have proven the point that the metabolic abnormalities that underlie T2D (hyperinsulinemia, insulin resistance) can be fully reversible even after a few short weeks.

Many early studies were done with the heavy-duty Roux-en-Y surgery, which is the heavyweight champions of surgeries. The best weight loss. The most complications.

But even milder forms of bariatric surgery show the same reversibility of T2D. A gastric band is essentially a belt implanted around your stomach. The surgeon keeps tightening the belt so that you can’t eat.

The results of gastric banding versus medical treatment showed a significant and pretty good drop in their fasting blood sugars. In other words, their T2D was reversing in a b-i-g way. Those given medicines alone basically stayed the same. They were no better than before.

Gastric banding a 500 pound patient will still reverse 20 years of diabesity within weeks. One of the main questions is why? There are many hypotheses, but essentially, it is likely the sudden severe restriction of all calories that causes this beneficial effect. I believe this is the same thing as the time tested, ancient healing tradition of fasting. Fasting is the voluntary restriction of food for religious, health, or other purposes (eg. hunger strikes). Is bariatrics simply a surgically enforced fast? I believe the answer is yes.

It’s not a progressive disease

The success of both bariatrics and fasting proves that T2D is not progressive and chronic. It’s in fact a fully reversible disease. Consider this real life example. A lady in her mid 60’s was injecting 120 units of insulin daily along with 2 grams/day of metformin (a type of medication used for T2D). She had T2D for 27 years and had been progressively using higher and higher doses of insulin in an effort to control her blood sugars. However, things were getting worse.

In desperation, she was referred to the Intensive Dietary Management Program. We started her on a regimen that included fasting under strict medical supervision. We started with a full week of fasting and immediately reduced her medications. When she was feeling well, she continued for a second week, then a third. By that time she was off her insulin. We then switched to a LCHF diet along with alternate daily fasting. It’s been over a year now, and she continues to be off all insulin and medications with a HbA1C of 5.9%. Technically, she is no longer diabetic (defined by an A1C of less than 6.4%).

She feels terrific – with more energy now than she has had for over a decade. Her husband was so impressed that he also started our program and has recently come off all his insulin, too.

But wait! The diabetes ‘experts’ insist that T2D was a chronic and progressive disease! How can this lady, with her 27 year history of T2D, suddenly reverse her disease and become non-diabetic? How can this possibly happen?

The answer is fasting

The answer is quite simple. The statement that T2D is chronic and progressive is wrong. The ‘experts’ were being economical with the truth.

But the fact that fasting reverses type 2 diabetes has been known for close to 100 years! One of the most famous diabetologists in the history of the world – Dr. Elliot Joslin wrote about it in the Canadian Medical Association Journal in 1916! In fact, he thought that it was so obvious that fasting was helpful that studies would not even be necessary. This, from the guy that Harvard University used to name its world famous Joslin Center for Diabetes.

What happened to Joslin and fasting for diabetes? Well, back then, medical science had not yet distinguished Type 1 and Type 2 diabetes back then. Fasting is not useful for type 1, and type 2 was still quite unusual back then. After the discovery of insulin in the early 1920’s, all the focus turned to it as the ‘cure’ for type 2 diabetes. While it was a major advance for type 1, it was not quite the panacea for type 2s. However, most of the interest in fasting disappeared as doctors focused on what would be their mantra for the next century – drugs, drugs, drugs. All types of dietary therapy fell into disrepute, since they were really not useful in type 1 diabetes, and have stayed there ever since.

The effect of wartime starvation on T2D also obviously highlights the effect of reducing food consumption on diabetes. During both world wars, the mortality from diabetes dropped precipitously. In the interwar period, as people went back to their accustomed eating habits, it went back up. This, of course, is quite easy to understand. Since T2D is essentially a disease of excessive sugar in the body, reducing intake of sugars and carbohydrates should cause less disease.

Bariatrics or fasting?

Returning to the point that bariatrics is simply a surgically enforced fast, you can directly compare the effects of fasting and bariatrics. One fascinating study assessed patients waiting for bariatric surgery who were given a period of fasting beforehand. The reasoning was that many morbidly obese patients had enormous fatty livers. If you could somehow reduce this fatty liver and reduce their weight somewhat, the risk of surgical complications would be reduced since there is now more room to work within the surgical field.

The reduction in liver size would make working in the abdominal cavity much easier, with better vision. Since many of these procedures are done laparascopically, being able to see better is a huge benefit. Also, with less abdominal distention, abdominal wound healing was significantly improved. Therefore, fasting before surgery makes total sense.

In the meantime, you could compare both sugar control and weight loss during the fasting period and also during the post surgical period. Since bariatrics is considered the heavy weight champ, this was a real David vs Goliath battle (Fasting vs Surgery).

In the graph below, you can see the results. In the first graph, fasting caused 7.3 kg weight loss compared to only 4 kg for surgery. The second graph shows the overall ‘glycemia’ or the total amount of sugar in the blood over the day. During fasting, there was far less sugar in the blood (1293 vs 1478). On both counts you can see that the fasting was actually significantly better than the surgery! Blood sugars came down faster, as did weight. David (fasting) beat Goliath (bariatric)!

If all the benefits of bariatric surgery accrue because of fasting, why not simply do the fasting and skip the surgery? The standard answer is that people cannot do the fasting without the surgical enforcement. But have they ever tried? How do you know that you cannot fast for an extended period of time if you have never tried it? Shouldn’t you at least give it a shot before giving up?

But my main point is again, not to criticize or praise surgery. Rather my point is this. Fasting reverses type 2 diabetes. Rather than the chronic and progressive disease that we have been promised, instead T2D turns out to be a treatable and reversible condition. Both practices of fasting and bariatric surgery prove the point. This is a curable disease. Type 2 diabetes is entirely reversible. This changes everything. A New Hope arises.

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Jason Fung

Dr. Fung has his own blog at intensivedietarymanagement.com. He is also active on Twitter.

His book The Obesity Code is available on Amazon.

His new book, The Complete Guide to Fasting is also available on Amazon.