Is bariatric surgery like fasting in type 2 diabetes treatment?

lunch time

What happens when a severely obese, diabetic patient undergoes weight loss (bariatric) surgery? If type 2 diabetes is truly a chronic, incurable progressive disease, then surgery will not alter the natural history.

According to conventional medical wisdom, long standing type 2 diabetics have very high insulin resistance provoking increased insulin secretion from the pancreas. Over time, the pancreas ‘burns out’ and insulin production falls. As the insulin falls, it is no longer able to compensate for insulin resistance and blood glucose rises, triggering the diagnosis of type 2 diabetes.

Once the pancreas burns out, nothing will revive it, meaning that type 2 diabetes is destined to progress and nothing can change that. Since this abnormality is irreversible, the diabetes should continue unabated despite bariatric surgery. Right?

Actually, in virtually all cases, the type 2 diabetes completely disappears!

A reversible disease

SurgeryCuresDiabetes2Type 2 diabetes is entirely reversible, even in patients that weigh 500 pounds. It is reversible even if patients have had their diabetes for twenty or thirty years. Not only is it reversible, but the type 2 diabetes is rapidly reversible. In a matter of weeks, even before any substantial weight loss, the diabetes disappears. Yes. It just goes away.

The 2012 STAMPEDE study was a three-year randomized trial of surgery versus medical therapy. Patients were initially randomized to Roux-en-Y surgery, sleeve gastrectomy, or their usual medications without any surgical treatment. At baseline, the average patient was 48 years old, with a hemoglobin A1C of 9.3% (considered very poor control) and body mass index of 36 (considered obese).

Without surgery, the medical treatment group increased both weight and diabetes medication. Their type 2 diabetes continued worsening, as they required more medication to keep control of their blood sugars.

SurgeryCuresDiabetesBut the surgical results were stunning. Within 3 months, most patients were off all their diabetic medications and maintaining blood sugars in the normal range. Interestingly, the benefits for diabetes appear long before most of the weight loss. A patient undergoing surgery at 400 pounds would likely still weigh over 350 pounds at 3 months. Nevertheless, the diabetes is completely undetectable despite the fact that they are still morbidly obese.

A full 38% of the Roux-En-Y surgical group maintained a hemoglobin A1C < 6% without any diabetic medications whatsoever. Technically, these patients no longer had diabetes. In other words, type 2 diabetes is reversible – even curable! Even the heaviest, most severe type 2 diabetics had disease that is reversible with treatment, but not with standard medications.   The ramifications are enormous. Type 2 diabetes is not chronic. It is not progressive. It is fully reversible, but our current medical paradigm of treatment is not correct.   Adolescents undergoing bariatric surgery enjoy the same success. In one study, patients starting with an average body mass index of 53, classified as super obese maintained a ninety-pound weight loss after three years. High blood pressure resolved in 74% of patients and 66% of abnormal lipids resolved. And Type 2 diabetes? Glad you asked. A stunning 95% of type 2 diabetes was reversed, with a median hemoglobin A1C of only 5.3% by trial’s end. The point once again is that type 2 diabetes is not chronic, not progressive, and not inevitable. It is fully and quickly reversible.

The downsides of surgery

But surgery carries a heavy price. Complications are common with thirteen percent of the participants requiring surgical re-intervention. The most common problem is esophageal strictures requiring dilatation. The esophagus develops scarring. It gradually narrows resulting in difficulty eating. The treatment is to shove progressively larger sized tubes down the patient’s throats to open things up (lovely). This procedure is often repeated over and over.

That surgery can cure type 2 diabetes has been known since 1992. For ten years after weight loss surgery patients, most patients maintained normal blood glucose without the need for any medications. This treatment for diabetes is both rapid and long lasting. Normal blood sugars were achieved within two months and maintained for ten years. So the problem was not the disease. The problem was our treatment and understanding.

The benefits extended far beyond their body weight. Many metabolic abnormalities reverted back to normal as well. Sky-high insulin levels plummeted to normal levels. Blood glucose dropped in half. Fasting insulin, a marker of insulin resistance dropped 73%.

Despite all their successes, I don’t generally recommend these surgeries for a variety of reasons. The most important, though is that we can derive all the benefits without surgery and all of its complications. However, bariatric surgery studies have a very important lesson to teach. Type 2 diabetes, even in the most severe, long-standing and seemingly recalcitrant patient is an entirely reversible disease.

Surgically enforced fasting

Why is bariatric surgery so successful at reversing diabetes where all the medications and insulins fail? Why does it work? There are many theories.

The foregut hypothesis suggests that the surgical procedure itself provides much of the benefit. Perhaps removing part of the healthy stomach or rewiring normal, healthy intestines into an abnormal, artificial man-made configuration somehow improves things. The normal stomach secretes many hormones, including incretins, peptide YY and ghrelin. Removing the stomach reduces all of these hormones, and perhaps others not yet identified.

sleeve-gastrorectomyHowever it soon became obvious that this could not be correct. Gastric banding reverses the type 2 diabetes as effectively as the Roux-En-Y procedure. However, no part of the stomach is removed during lap banding. Reversal of type 2 diabetes did not depend upon surgical removal of any part of the healthy stomach.

The different bariatric procedures do not differ substantially in their ability to reduce insulin resistance. The only variable that matters is how much weight is lost. It did not matter whether you cut the stomach or not. It did not matter if you rewire the intestines or not.

The foregut hypothesis also fails to explain why type 2 diabetes often recurs years later since the stomach does not regenerate the ability to secrete these hormones. This proves what should have been a rather obvious point that the removing healthy stomach (like with the sleeve gastrectomy) doesn’t truly have any benefits.

Another natural assumption is that loss of fat mass, both subcutaneous and visceral, leads to the beneficial effects of surgery. We often imagine that fat cells, as a store of energy, just sit around doing nothing all day long, like a sack of potatoes, but it’s not really true. Adipocytes actively secrete many different types of hormones.

For example, fat cells secrete the hormone leptin, an important regulator of body weight. As fat mass rises, leptin secretion increases, signaling brain receptors to lose weight. In obesity, the body becomes resistant to the leptin’s weight losing effects. Adipocytes also convert testosterone into estrogen, leading to the familiar phenomenon of ‘man boobs’ in obesity. So adipocytes are not metabolically inert, but active hormonal players.

If adipocytes help sustain obesity and type 2 diabetes, then their removal should normalize the hormonal environment. But there are two problems with this theory. First, type 2 diabetes disappears within weeks – long, long before any substantial loss of fat mass. Second, surgical removal of fat does not provide any metabolic benefit.

Liposuction removes subcutaneous fat but not the visceral fat found in and around the organs. One study of liposuction removed 10 kg (22 pounds) of subcutaneous fat, yet failed to provide any metabolic benefit. There was no significant improvement in the blood sugar readings or any measurable metabolic markers. The only benefits were cosmetic.

Visceral fat is a far greater health risk. Unfortunately, this tendency to gain weight around the abdomen is very common. People with this ‘beer belly’ often have skinny arms and legs, but a protuberant abdomen. Bariatric surgery preferentially removes this visceral fat, where liposuction only removes subcutaneous fat. This partially explains why bariatric surgery leads to metabolic improvement even before all of the weight is lost.

There is no real magic here. The mechanism of benefit is the simplest and most obvious. All different types of bariatric surgery work because they have one thing in common – a sudden severe caloric reduction. Simply put – Bariatrics is surgically enforced fasting. All the benefits accrue because of the fasting. A study directly comparing the two shows fasting is actually superior to surgery in both weight loss and blood sugar reduction. Fasting produced almost twice the weight loss of bariatric surgery.

So here’s the crucial question. If all the benefits come from fasting, why not do the fasting and skip the surgery entirely? Fasting can produce results without postoperative complications, cost, or the need for expensive hospitals, equipment or specially trained surgeons. In essence, fasting is ‘bariatric surgery, without the surgery’. Medical Bariatrics.

But my point is not to criticize or praise surgery. There is one essential lesson to be learned from surgical studies. Type 2 diabetes is not a chronic and progressive disease. This is a colossal deception. Instead type 2 diabetes is an entirely preventable and reversible disease. Even the heaviest patients with the most intractable obesity can reverse decades of type 2 diabetes within weeks. Further, the cure does not require invasive surgery, only a deeper knowledge of its root causes. This changes everything. A new hope arises.

Jason Fung


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  1. Raul
    My name is Raúl, i'm a doctor from Mexico and recently i'm diving into this "new" paradigm of fasting. I've been lookinf for clinical trials comparing fasting modalities versus bariatric surgery but i failed to find them. And you said in your article "A study directly comparing the two shows fasting is actually superior to surgery in both weight loss and blood sugar reduction. Fasting produced almost twice the weight loss of bariatric surgery." Then I would like to read those articles and see where we're standing and the grade of evidence that we have til today. Thanks
  2. Carol
    I think you’ll find this whole interest in Fasting started with the work of Dr Roy Taylor in Edinburgh Scotland. He influenced Jason’s work. Dr Robert Cweys (sp) also talks about how when he was fasting patients for bariatric surgery he noticed their fatty liver went away. Fascinating I think.
  3. Josy
    HI, Thank you for all your interesting writings. I'm a bit confused, so maybe you, or someone else, can answer my question. If bariatric surgery is basically enforced fasting, both approaches boil down to an extreme calorie restricting diet, right? Given that "we all know calorie restricting diets don't work long-term" and that weight is gained back,... What can we say about long-term effects of fasting? I know for sure that many people shed hundreds of pounds before even considering bariatric surgery. What is going to help them keep it off after yet another prolonged fast? And, if it's basically the same, would the alternative to surgery be: 300 kcal IF, i.e., one meal per 24 hours for life? Hope to hear from you, kind regards, Josy
  4. chita
    To hear about fasting for life or about eating only one meal per 24 hours can feels scary or not doable. I understand. I can share my experience with fasting for 30 years . I am a female , 53 years old who was never fat, sick or needed any medication ever . I am married, have two kids, work normal traditional life . I am not on low calorie restricting diet . I eat every day my normal size dinner that has no calorie restrictions plus I have my grapes ( or any other fruits ) , ice creme ...until I feel full and satisfied . I don't feel any kind of deprivation because I am free to eat whatever i want. During the day I live my active life. There is no need for food breaks or for obsessive thoughts about the food since I will eat after all work is done .I will eat full meal in the evening when I have time for digestion. Yes, Fasting is a lifestyle that prevents you from being sick and obese.
    Long term fasting gives me happy - diseases free life so why should I stop live this way ? :)
  5. Donald Kelly
    As alluded to above, it seems that bariatric surgery is more like enforced severe caloric restriction than fasting. Why does it work when caloric restriction doesn't?
  6. Bill Roberts
    Fasting means not eating for extended periods of time, Why does Dr Fung call Bariatric surgery the same as fasting, I thought surgery patients eat on a more coventional timely schedule but smaller portions. Which to me means it is not fasting. Sounds more like a very low calorie diet rather than a fasting diet. Am I wrong?

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