June 24, 2019


#59 – Jason Fung, M.D.: Fasting as a potent antidote to obesity, insulin resistance, type 2 diabetes, and the many symptoms of metabolic illness

"We think of all these responses, obesity, insulin resistance, and the beta cell failure, as pathologic. They're actually protective.  . .Your body is actually trying to protect itself against the root cause of the problem which is too much insulin, too much glucose." — Jason Fung

Read Time 41 minutes

In this episode, Jason Fung, nephrologist and best-selling author, shares his experiences utilizing an individualized approach to fasting to successfully treat thousands of overweight, metabolically ill, and diabetic patients, and why being a doctor who specializes in kidney disease gives him a unique insight into early indications of metabolic disease. We also have a great discussion on insulin resistance where Jason makes the case that we should actually think of hyperinsulinemia as the underlying problem. We also discuss the difference between time-restricted feeding, intermittent fasting, and dietary restriction (e.g., low-carb) and how they can be used to attack the root cause of T2D, metabolic syndrome, and obesity. We also have a fascinating discussion about the limitations of evidence-based medicine which leads to a conversation where we compare and contrast the scientific disciplines of medicine and biology to theoretical physics.


We discuss:

  • Comparing scientific disciplines: Medicine and biology versus physics [7:25];
  • The limitations of evidence-based medicine [12:30];
  • Early signs of metabolic disease: How specializing kidney disease gives Jason a unique insight into early indications of illness [20:50]
  • Insulin resistance, hyperinsulinemia, and the overflow paradigm [29:30];
  • Why the common treatments for type 2 diabetes seem to make things worse [42:30];
  • How hyperinsulinemia (not insulin resistance) drives metabolic syndrome [53:15];
  • Insulin and weight gain, and using fasting to empty the cells of glucose [59:30];
  • The two step process of developing type 2 diabetes and how they are both manifestations of hyperinsulinemia [1:03:15];
  • NAFLD and hyperinsulinemia: A vicious cycle [1:08:30];
  • Are the features and symptoms of diabetes actually protective? [1:12:15];
  • Is obesity causing insulin resistance or is it the other way around? [1:17:30];
  • What role does inflammation play in obesity? [1:21:45];
  • CVD and cancer: Diseases of too much growth? [1:27:30];
  • How to reduce proliferation with rapamycin, nutrition, exercise, fasting, and manipulating hormones [1:32:45];
  • Getting patients to fast: How Jason and Peter utilize fasting in their practice, and how their approach differs [1:40:15];
  • Comparing bariatric surgery to fasting as a treatment for type 2 diabetes [1:48:00];
  • Why people think that fasting is bad for you [1:55:15];
  • Time-restricted feeding and intermittent fasting: Defining terms, and how Jason applies them in his practice [1:58:30];
  • A fasting case study: A diabetic patient with a non-healing foot ulcer [2:04:00];
  • Keys to a successful fast [2:12:45];
  • Muscle loss during fasting, and why Jason isn’t worried  [2:24:45];
  • Will fasting help a healthy person live longer? [2:31:30];
  • Does fasting cause gallstones? [2:38:45]; and
  • More.


Comparing scientific disciplines: Medicine and biology versus physics [7:25]

What makes Jason’s perspective unique

  • Peter says what distinguishes Jason from others who like to speak about the benefits (and risks) of fasting is that Jason is on the front lines treating patients
  • Jason agrees, and adds that he’s only interested in what works ⇒ “You can talk all you want about this and that, but if it doesn’t change management, then it doesn’t interest me particularly.”


  • Jason loves the approach to scientific progress in the realm of physics
  • He really looks up to Richard Feynman (as does Peter), Einstein, and Niels Bohr
  • The way they do science is so much better than we do in medicine.
  • In physics, if the theory doesn’t agree with experimental evidence, you have to throw out the theory
  • In medicine, bad theories tend to go round and round and round because they make sense, but nobody’s actually put them to the test
  • In the case of insulin resistance… “the way we think about insulin resistance is sort of totally wrong and that’s why we have the sort of mess that we have

Biology vs. physics

  • Peter: “I’m generally suspect of people who have very, very strong points of view on things in biology or medicine who no longer interact with patients. Doesn’t mean that they’re wrong, but I’m generally suspect because of that.”
  • Biology is harder than physics…. it’s just a lot messier
  • Peter: “Every time I think I’ve really got it figured out, I’ll always meet a patient who proves me wrong.”

What Jason appreciates most about physics

  • Many great theories (e.g., Newton)
  • But then inevitably there are anomalies ⇒ “Anomalies are what drives sort of science forward because you have to come up with a better theory that explains the anomalies
  • Then you come up with a better theory which may have wild predictions but it could supplant the existing theory (i.e. Niels Bohr’s quantum theory supplanted Einstein)
  • This doesn’t happen in medicine, says Jason… instead we have a super laborious process of evidence-based medicine

The limitations of evidence-based medicine [12:30]

Jason explains his frustrations…

  • In medicine, we have a super laborious process
  • We need evidence in order to move things forward
  • Whereas physics moves at “light speed” because it doesn’t demand the sort of evidence base
  • Evidence-based medicine is not a search for truth… it’s a search for consensus
  • This approach makes things move glacially

⇒ For example, fasting…

{end of show notes preview…}

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Jason Fung, M.D.

Dr. Jason Fung is a Canadian nephrologist who one of the most significant clinical practices that utilizes fasting for treatment of metabolic disease in Toronto, Canada.

He has written multiple best-selling books and he co-founded the Intensive Dietary Management program.

Dr. Fung graduated from the University of Toronto and completed his residency at the University of California, Los Angeles.

Disclaimer: This blog is for general informational purposes only and does not constitute the practice of medicine, nursing or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this blog or materials linked from this blog is at the user's own risk. The content of this blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard, or delay in obtaining, medical advice for any medical condition they may have, and should seek the assistance of their health care professionals for any such conditions.


  1. Fantastic podcast! I’m eating one meal a day and fasting for 72 hours at weekends, plus caloric restriction, based on Roy Taylor’s research, to reverse my diabetes at the moment. Things are going very well – I’m on week 8 and aiming for 24 weeks of this to lose all my excess weight. I want to make a point about there being no evidence to support fasting for rheumatoid arthritis. There is in fact. Yoshinori Ohsumi (Nobel prize winner, as I’m sure you know) demonstrated that the autophagy mechanism is defective in people with autoimmune disease, but you can force it to work by fasting. I have had RA since childhood (now 61), and I have managed to get it into remission with a plant-based diet and fasting. I was initial high-carb, plant-based, which resulted in diabetes, so now I’m keto and plant-based, plus a lot of fasting. My DAS28 score is 2.16, in keeping with remission. I have come off the NSAID and one of the DMARDs and now only use 10mg of Methotrexate a week, plus the lifestyle changes to maintain remission. I have also not had an asthma attack since going plant-based 5 years ago.

    • Interesting stuff. Dr. Ben Bikman referenced ceramides as well.

      “Whether obese or not, those with higher circulating insulin levels “…have markedly increased rates of hepatic de novo lipogenesis.” That means their livers are making fat. That fat (triglycerides or triacylglycerol) will be either burned in the liver for energy (oxidized), pushed into the blood stream for use elsewhere, or stored in the liver. Fatty acids are components of triglycerides. Excessive fatty acid intermediaries in liver cells—diglycerides and ceramide—are thought to interfere with insulin’s action, i.e., contribute to insulin resistance in the liver.” Dr. Roy Taylor

  2. I have been waiting for an interview with my two favorite guys! Thank you so much for doing this…not just this episode, but the podcast as a whole. I must say I have never looked forward to Mondays, but now I awake and as soon as I get to work, I peek in to see what amazing experience Dr Attia has curated to expand my mind. Keep on making Mondays worth the wait!

    • This is the hypothesis put forward by Dr Neal Barnard, and I believed it for quite a while. However, I actually developed type 2 diabetes (though I was obviously prediabetic before starting this) on the starch solution. It made me very sick and I was getting progressively worse – retinopathy, peripheral neuropathy, confusion, weight gain and oedema. Prior to going on the starch solution I followed Joel Furhman’s protocol and was doing great on that, apart from feeling ravenously hungry all the time. In the end, I looked more into the science behind keto and realised that actually, the science itself is solid, if you look at the research and not the diets followed by some people doing keto. I went plant-based keto and bought my blood sugars down to normal levels in 7 days – something I’d not been able to achieve in 2 years on the starch solution. My eyesight has returned to normal, the patches of retinopathy have cleared up and the neuropathy is almost all gone, with a tiny amount of numbness left in one big toe. I do believe it’s possible to recover from diabetes on a high-carb plant-based diet for a few people if they are eating a very low amount of calories and can, therefore, lose visceral fat, but for me it was disastrous. A study has shown that you need the right genes to be able to process a high-carb diet – genes which only 50% of people have, which might explain why I and others have been made diabetic by eating a high carb diet. There’s an article about the study here: https://www.dietdoctor.com/study-gene-helped-humans-adapt-to-higher-carb-world-but-50-of-us-dont-have-it?fbclid=IwAR0X8rxCRjbhbPJc3Dtsu0fMl5XghoVp8zo5KOmLunV76LdtaxPcv3qLpWM

      • Very interesting. How long have you been on a plant based keto diet? What changes have you seen in lipids, inflammatory markers or other labs since you’ve been on this diet?

      • Sue, you are aware that foods rich in carbs are not the same as fruits and vegetables correct? You should never go high carb unless you are an athlete.

  3. Great podcast. I had been waiting to hear Jason Fung. I have read his books on diabetes and obesity and recommended them to friends. I live in central México where diabetes is exploding as a problem. Doctors often take very little time here, to explain issues to patients, so I have tried to educate myself in nutrition, to later explain to friends and family what is going on.

    Thanks again for the great content!

  4. Peter another amazing podcast. I too wait for Mondays to see what amazing speakers you have interviewed. This podcast with Jason was very interesting. I am listening to it twice. It changed how I think of Diabetes as a whole and why we treat it the way we do currently. I so wish that this education was common place. We are not doing our patients justice. Some suffer from ignorance of their own disease, because if they knew they could reverse this devastation disease, I believe they would. No one can tell me that someone facing amputations, blindness, possibly dialysis would opt to take more drugs so they could suffer longer. Especially when they learn there is something so powerful that can reverse some major diseases and anyone can do it. I work in Canada and I am not allowed to talk about this with anyone at work. Maybe someday some doctors will actually hear this podcast and learn something new. I have changed to a different WOE that incorporates much of what was discussed and have huge benefits (weight loss, reduced HbA1C, reduced CRP, reduced triglycerides, huge increase in my HDL, loss of 70 pounds, clarity of thought, disappearance of depression, energy, good sleep etc). It’s starting to sound like magic. Sorry but it is. I tried a lot of things in my 65 years to get these outcomes but amazingly “I only had to stop stuffing the suitcase”.

  5. Reading Dr. Fung’s book The Obesity Code is what got me started in the exploration of fasting and low carb. I was incredulous that the science in nutrition was so poor and I had no idea that I was so wrong for so long.

    Thank you both so much for making so much high quality information available.

    I just recently watched Dr. Michael Eades’ presentation on The Incretin Effect and Insulin Resistance from the Low Carb Denver 2019 conference and he posits that the reason the Roux-en-Y gastric bypass works so well is because it bypasses the GIP at the top of the small intestine. Neither of you mentioned the incretin effect so I wondered if you had caught that talk yet.

  6. I fasted for 3 days.. no problem at all. It was going so well I decided to keep going. The fifth morning I woke up with a feeling I was going to vomit, and I did!
    I took it as a sign that my fast was over. Lost 5 lbs. Resumed low carb, lost another pound. After about a week gained 3 lbs back.
    I only have 10-15 lbs to lose and find its an easy way to do it.
    I’ll do it again in a few weeks.

    • Bumping this question – as a layman I’m having a hard time tracking down info on this online. (Not only specific products, but more importantly parsing what this means and how the GABA supplements differ.)

      • I’m also very interested in this question… As I understood it, supplemental GABA didn’t cross the blood brain barrier, so I’m assuming he’s referring to a type that does and I’d love to know a brand!

    • This may be Phenylated GABA, able to pass through the blood-brain barrier (examples: Phenitropic, Phenibut). In April 2019 the FDA removed these supplements from the category of “dietary supplement”. As a result, products containing Phenibut are no longer available.

  7. Would like some comments as to how to treat sarcopenia. I eat a low carb diet and do resistance exercises which help with keeping some musculature but adding some weight seems impossible. I look like a piece of string with knots in it..not very scientific but an accurate description. Perhaps it does not matter as otherwise I seem healthy but it does feel as if I am running just to keep in one place. Ought to add that I follow a TRE plan and had thought to do a 3 day water fast because of its apparent benefit but hesitant because of the sarcopenia and differing advice on the web.

  8. Great Podcast, one of the best so far! It’s very interesting how Peter and Jason with very different approaches to medicine, very different career trajectories and treating two completely different patient populations end up using similar tools.

    Regarding the hyperinsulenimia-adiposity-metabolic derangement arrow of causality I would suggest looking into the research of a fellow Canadian by the name of Jim Johnson (@JimJohnsonSci). He demonstrated in mice that not only hyperinsulinemia comes before adiposity and poor metabolic health, in the mice with imposed low insulin secretion (through genetic manipulation of the mice) the low insulin levels protects against the effects of an obesogenic diet on adiposity, metabolic health and even poor glucose control, i.e., mice with reduced insulin output had better glicemia control than mice with normal insulin output on the same (obesogenic) diet!

    If this subject of hyperinsulinemia is something you would like to continue exploring on this podcast Dr. Jim Johnson would be a great guest IMHO.

  9. Chris Masterjohn has some great (old) videos on how insulin/diabetes is caused by the body making the best of out of a bad situation (energy overload).

  10. Excellent podcast!!! I love that Dr. Fung simplifies the science in a way that’s easy for most people to understand. Thank you for having him on!

  11. This was an amazing podcast. Dr. Fung is an excellent educator. His analogies (the firewood/sofa, suitcase stuffing) are brilliant and really bring home the central concepts. Thank you, Dr. Attia, for this informative interview (and for your sock drawer analogy). (:

    Maybe you could get a Prolon discount going for members?

  12. This intense, conversational podcast really made the concepts that I have read about come alive. I really appreciate how well the interview was laid out, the audio quality, and the pace. A big thank you to both docs for devoting your lives to improving the lives of others.

  13. Fung invitation robs the podcast of the last credibility. Fung is very clearly a fraudster.

      • Yes, please tell us about all the people with fraudelent type 2 diabetes that Dr. Fung has frauded into think they have had their T2D put into remission.

  14. Layman here. Would have been interested to hear something about nicotine, and its close relationship to insulin, blood sugar, & diabetes.

    My amateur understanding and source of puzzlement:

    1. nicotine is sometimes called an “insulin suppressant,” because it supposedly reduces insulin secretion from pancreas; also

    2. nicotine is often cited as a source of “insulin resistance,” and associated with T2D , because it raises blood sugar.

    3. if you reinterpret “insulin resistance” as hyperinselimia, how can #1 and #2 both be true at the same time?

  15. I really enjoyed the podcast and it inspired me to try a 3 day water/coffee only fast for the first time. As a side note, I have been doing 18/6 TRE in combination with strict KETO for 48 days and had lost 25 lbs. I found the fast to be easy and felt very good the whole way through with no hunger. However, my blood glucose levels were much lower during the fast. In fact, on day 2 I had a blood glucose reading of 35! I didn’t stop the fast because I felt very good. What are the possible explanations for such a low blood sugar reading. I do not have T2D but am 27% bodyfat. Could I be producing sufficient insulin to drive blood glucose down that low on day 2 of a fast? Why wouldn’t glucogon be activated to raise my blood sugar? How common is symptom free hypoglycemia during fasts? Thank u in advance. My physician couldn’t explain it.

  16. Dr. Fung claims that ingestion of Stevia causes an insulin response similar to sugar but i see nothing in the show notes about this claim. I am providing a link to a randomized, double blind, placebo-controlled crossover study, the results of which counter this claim to conclude there is no difference between Stevia and placebo in insulin response. (I was curious because i sometimes have dark chocolate with stevia after dinner).


  17. OB/GYN here. Fantastic lecture. Broadly applicable concepts, of most interest to me for my patients with PCOS and those with estrogen-sensitive gynecologic malignancy (i.e. endometrial cancer). A couple of thoughts:

    There is a comment made at some point that gestational diabetes seems to be a distinct clinical entity from type 2 diabetes. I wanted to add some information (and confirm that statement). Gestational diabetes in its pure form (i.e. not pre-existing type 2 found during pregnancy) is driven by placenta-derived insulinase (which breaks down insulin) and human placental lactogen (decreases insulin sensitivity) . We (OB/GYNs) are fastidious about strict glycemic control during pregnancy—often more so than endocrinologists—because of the short-term risks of maternal hyperglycemia and fetal macrosomia (increased risk of polyhydramnios, cord prolapse on rupture of membranes, sudden fetal death, shoulder dystocia and subsequent fetal neurologic injury, postpartum hemorrhage, etc.). Increased maternal glucose levels cause stimulation of the fetal pancreas, causing abnormal fetal growth and neonatal hypoglycemia. Exogenous insulin does not cross the placenta and will decrease maternal serum glucose without adversely affecting fetal growth, which is why it is our drug of choice for treatment of GDM. A placentally-derived disease process is supported by a nearly immediate return to normal serum glucose levels after delivery, and by decreased insulin needs late in the third trimester as placental function wanes. For what it’s worth….

    Thanks for the lecture and plenty of food for thought!

  18. show notes say <<>>

    I don’t think de novo lipogenesis means making glycogen. Did you mean to say trigliceride here? or am I missing something.

    • Hmmm, comment thingie didn’t like my angle brackets. The quoted passage is

      “””Insulin is responsible for de novo lipogenesis (meaning if you have a lot of carbohydrates/glucose, it will build it into glycogen)”””

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