Fasting and Growth Hormone Physiology – Part 3

posted in: Fasting, Health and Nutrition | 83

In our previous post (part 2), we took a quick overview of the physiology of fasting.  I’d like to take a more in-depth look at some of the studies that have been done to really try to understand what is actually happening when we fast. Today I want to focus in on human growth hormone (HGH).

HGH is a hormone made by the pituitary gland (the master gland). It plays a huge role in the normal development of children and adolescents as the name implies. However, it also plays a role in adults. HGH deficiency in adults typically leads to higher levels of body fat, lower lean body mass and decreased bone mass (osteopenia).

HGH only lasts a few minutes in the bloodstream.  It goes to the liver for metabolism, where it is converted into a number of other growth factors, the most important of which is Insulin Like Growth Factor 1 (IGF1).

Scientists first harvested HGH from cadavers in the 1950s (eeewww), but only synthesized it in labs in the early 1980s.  Soon afterwards, it became a popular performance enhancing drug. Normal levels of HGH peak in puberty (as you might expect) and gradually decrease thereafter.

Growth hormone is typically secreted during sleep and is one of the so-called counter-regulatory hormones.  HGH along with cortisol and adrenalin tell the body to increase the availability of glucose – so it counters the effect of insulin. High doses of HGH, (or cortisol) will produce higher blood sugars.  These hormones are typically secreted in a pulse just before waking (4 am or so) during the ‘counter-reulatory surge’.  Remember that all hormones exhibit pulsatile secretion to prevent the development of resistance as we covered in a previous post.

Since HGH typically goes down with age, there may be some benefit to giving HGH for its ‘anti-aging’ effects. Perhaps this decrease in HGH-IGF1 may contribute to the decrease in lean body mass both in lower muscle mass, but also lowered bone mass. So, what are the effects of giving HGH in older people?  This was studied in 1990 in a New England Journal of Medicine article.Fasting and HGH

HGH is difficult to measure since it is pulsatile, so IGF1 can be measured as a surrogate. Healthy men with low IGF1 levels were given HGH for 6 months and the effects measured.

Group 1 is the HGH group and Group 2 is the control group that did not receive HGH.  Over 6 months weight overall did not change between the two groups.

But look at the lean body mass.  Compared to the control, the HGH group packed on 3.7 kg (8.8%) more lean mass.  That’s 8 pounds of lean mass!  Fat mass decreased an extra 2.4 kg (5.3 pounds)! Thats a decrease of 14.2%. Even the skin thickness improved.  That’s anti-aging, baby!

In a 2002 JAMA article, similar results were obtained in women as well.  There was a decrease in fat mass and an increase in lean mass.  Sounds pretty great.  So, why aren’t we using it for everybody?  Well, there’s a little thing called side effects.

There was an increase in blood sugars.  This makes sense, since HGH is a counter-regulatory hormone.  Pre-diabetes also significantly increased.  There was an increase in fluid retention as well as blood pressure, too.  Over the long term, there is also a theoretical risk of increased prostate cancer and heart problems (enlarged heart). So, that’s not very good news.Kerndt study

So artificial injections of HGH are out. What if there is an all-natural method of increasing growth hormone? What about, say, fasting?

In 1982, Kerndt et al published a study of a single patient who decided to undergo a 40 day fast for religious purposes.  They measure numerous metabolic indices over that forty days to see what happened.  There is a wealth of data here, but several notable things.  Blood pressure slightly decreased. Glucose goes down.  From 96 initially, it drops to 56.  Insulin goes way, way down.  Starting at 13.5, it quickly drops to 2.91 and stays down.  That is almost an 80% drop!

Glucagon goes from 139 to a peak of 727 or a 423% increase.

But our concern here is HGH.  It starts at 0.73 and peaks at 9.86.  That is a 1250% increase in growth hormone. Even with a relatively short 5 day fast, we are talking about 300% increase.  All this HGH increases without drugs.  Fasting GH2

What about the potential side effects?  Increased glucose? Nope.  Increased blood pressure? Nope.  Higher risk of cancer? Nope.

Other studies have shown the same increase in growth hormone.  In 1988, Ho KY et al studied fasting and HGH. On the control day, you can see that meals (marked M) very effectively suppress HGH secretion.  This is to be expected.  Like cortisol, HGH increases glucose and thus is suppressed during feeding. Fasting is a great stimulus.

During fasting, there is the spike in the early morning, but there is regular secretion throughout the day as well. Hartman et al also showed a 5 fold increase in HGH in response to a 2 day fast.

This HGH is crucial in the maintenance of lean mass – both muscle and bone. One of the major concerns about fasting is the loss of lean mass.  This does not occur. In fact, the opposite happens – there is likely an increase in lean mass. Think about this for a second.

Let’s imagine that we are living in Paleolithic times.  During the summer of plenty, we eat lots of food and store some of that as fat on our body.  Now it is winter, and there is nothing to eat.  What do you suppose our body does.  Should we start burning our precious muscle while preserving our stored food (fat)?  Doesn’t that sound pretty idiotic?

It’s as if you store firewood for a wood-burning oven.  You pack lots of firewood away in your storage unit.  In fact, you have so much, it is spilling out all over your house and you don’t even have enough room for all the wood you’ve stored. But when the time comes to start up the oven, you immediately chop up your sofa and throw that into the oven.  Pretty stupid right?  Why would we assume our body is also so stupid?

The logical thing to do is to start burning the stored wood.  In the case of the body, we start to burn the stored food (fat stores) instead of burning precious muscle.

This has enormous implications for athletes. While studies are few, it is possible that the elevated HGH stimulated by fasting will increase muscle mass as seen in the earlier studies on HGH administration.  This would be an important advantage in elite level athletes, and we are seeing more and more interest in doing this exact sort of protocol.

Brad Pilon
Brad Pilon

The recovery from hard workouts would similarly be improved.  The increased adrenalin during fasting (to be discussed in future) will also allow you to perform a more intense workout.  It will make workouts easier and recovery faster.

It is not by accident that many of the early proponents of training in the fasted state are bodybuilders.  This is a sport that demands, in particular, high intensity training and extremely low body fat for definition.

Martin Berkhan
Martin Berkhan

For example, Brad Pilon, who wrote the fantastic book “Eat, Stop, Eat” is a bodybuilder, as is Martin Berkhan, who popularized the ‘lean gains’ method of fasting.  Somehow, I don’t think that fasting for these two fellows was ‘eating’ their muscle.

So, for all those people who thought that fasting would make you tired, or that you could not exercise during fasting, well, you’re just wrong. Fasting does not ‘burn’ muscle.  There is no ‘starvation’ mode from fasting where you shrivel up into the fetal position on your couch.

Rather, fasting has the potential to unleash the anti-aging properties of HGH without any of the problems of excessive HGH (prostate cancer, increased blood sugar, increased blood pressure).  For those interested in athletic performance, the benefits are even greater.

So, let’s see.  Train harder.  Lose Weight. Faster recovery. Decrease insulin and insulin resistance. Decrease sugars.  All of these benefits are achieved without drugs, supplements or cost.  Yes, like all the best things in life, it’s free. So why is everybody so against it?

Start here with Fasting part 1

Continue with Fasting part 4

Start here with Calories part 1

Watch the lecture – The Aetiology of Obesity 4/6 – The Fast Solution



83 Responses

  1. Ever since I’ve started to fast, I’ve noticed I wake up around 5am almost every night. I wonder if this has to do with that growth hormone pulse around that time.

    • Susan Parker

      Pre-diabetic and overweight I have been utilizing a LCHF ketogenic diet for just over 2 years, ( not perfectly and fell off the wagon a few times.) I dropped a bunch of lbs. Stuck at the same place for months and frustrated in mild ketosis, my caloric intake of fat was good, but It was as if my body had become used to this. A few months ago I began using IF ( 16 hr. and more fasting window) in hopes of strengthening ketosis and increasing weight loss but did not see any results. Using your fasting protocol for a 3 day fast with a few tweaks, ( ate some almond butter the first day, and added butter to coconut oil when I felt hungry, I was able to get into deep ketosis, and dropped 6 lbs. in 3 days. Gained 1 lb. of water back but maintained the weight loss and deeper level of ketosis for the last 3 days of eating. I did experience some
      insomnia, ( Norepinephrine and Epinephrine are released when insulin levels are low) but offset this with the use of sublingual melatonin. Day 2 I felt absolutely wonderful and actually did not want to stop the fast at all. Concerned about protein and muscle loss, I resumed eating my keto diet after the 3rd day, with a slight increase in carbs, ( a bit of green apple and sweet potato), and still maintained my level of ketosis. The increase in HGH is a good thing and I plan to fast more frequently and perhaps for longer periods.

      • Hey wanted to note, that any consumption of calories during the fast breaks it. Even if in full Ketosis. If you are hitting platforms, you might want to dry a water, or dry fast with no calories. Any sort of fat technically breaks the fast – usually at 16 hours in, your body’s Glucose Oxidation inclines around 50%. I would be more interested in that then just the Ketosis portion. There are a myriad of benefits from just abstaining from any source of calories, or fats. A dry or water fast is way better – well from my personal experience at least.

    • Susan Parker

      Norepinephrine and Epinephrine are released when insulin levels are low.

    • It probably has to do with the fact you’re hungry lol.

    • I see all this great information on growth hormone and fasting, but I wonder about growth hormone and the ketogenic diet. I see on a non fast day that hgh doesn’t spike much, but to be clear, is this non fasting growth hormone relation on the chart related to a properly conducted ketone diet lchf style? I was just trying to see how much my hgh would be impacted, because In ketosis and a low animal protein diet(more plant proteins vs animal) should lead to lower insulin in an extended – long term perspective.
      So does hgh go higher on a ketone diet?

      Hgh = human growth hormkne

    • Christina

      I have only been doing OMAD for a short time, eating just dinner and I also have been waking up between 4:30 and 5am. I’m fine through the whole day as long as I don’t eat. One day I did eat breakfast and lunch and then needed to take a nap. ha. This is great as I use to wake up in the middle of the night, more like 3am to go to the bathroom which I’ve read is associated with high blood sugar level. I sleep more deeply and soundly which I have also read is associated with greater HGH production.

  2. So…how does IF affect the GH levels of people over 60? Is it advantageous to supplement with some arginine or ornithine on fast days?

  3. I really look forwar to each of your posts! Thank you.
    If I have missed some part of your website that already explains the answers to my questions, would you please let us know?

    Were the subjects in the studies you describe in this post all men?

    What is believed about the HGH effects in women? Women of all ages.
    Surely the complexities of cyclic hormonal changes, and overall hormonal differences, matter in this analysis of muscle preservation and growth.

    And,what about hormonal “side” effects of fasting, such as on the HPA axis?

    I would also like to know what has been found in aged people, over age 60 or 65. This is when many of us really tip over into the muscle atrophy zone.

  4. Does the major concern about fasting causing the loss of lean mass perhaps come from people doing JUICE FASTS? – drinking “healthy” sugar all day and preventing HGH spikes?

  5. After reading Fasting Part 2 yesterday, I started a fast today. A few hours after that decision, I walked past my weight room. Should I lift weights today, I thought? As you had explained, my HGH should be going up and maybe that would help me make muscle. Well, no, I thought, it will just make me more hungry. Besides where would the amino acids come from if I’m fasting?

    So, today, you say that it is ok and, possibly, good to workout with weights while fasting. Cool, tomorrow, I’ll start pumping.

    But, still, where do the amino acids come from? Now, if you are going to answer that question in a later post, I can wait – no rush.

    BTW, have you or are you writing a book?

    • Hi Nate

      The amino acids in the the first 24 hours or so will come from the diet. After you have eaten, you have excess circulating glucose and AA. The glucose will get used. The AA will get used for gluconeogenesis, unless you took in absolutely zero proteins in the last 24 hrs, which is not really all that healthy since there are certain essential amino acids.

      After the first 24 hours or so, the rest of the gluconeogenesis substrate comes from glycerol.

      Yes, I am in the process of writing a book due to come out Jan 2016

      • I am a little confused… I have just started an extended fast, and plan to fast for 4 days as this is the first time that I have ever fasted beyond 24 hours. I am consuming nothing but calorie free liquids and salted bone broth.

        But in your response to Nate, you mentioned that “taking in zero proteins is not all that healthy”. Does this only apply to heavy exercisers?

        I was also considering doing some HIIT cardio today but didn’t as I was concerned that the exercise would make me hungrier. Should we be exercising while doing an extended fast? If so… What sort of exercise do you recommend?

        Also… How do you recommend coming off of an extended fast? Will I get sick from returning to my regular low carb diet?

        Can’t wait for your book!!!

        • Sorry – taking zero protein for extended periods (months) is not that healthy. For 4 or 7 or even 14 days, it is OK assuming that you are not malnourished to begin with. HIT is an excellent idea – fasting is an excellent time for exercise due to increased HGH.

          Coming off fasts, it is best to go slow. Gorging will make you feel quite uncomfortable, but not probably dangerous.

          Regarding IR – yes – there is a 70% genetic contribution to obesity. So some people can truly eat whatever they want and never gain weight. I covered this is a previous post on genetics

          • Thank you!! That makes sense.

          • golooraam

            Thank you Dr. Fung
            After reading this, I am doing a 1 (maybe 2?) day water fast and plan on working out both days, one a 1 hour walk with hand weights and tomorrow 50 to 100 pushups… good to know I can keep my workouts in…

  6. I did hit the gym today after 19 h of fasting, and while I hardly have put in their efforts or have their results, at least I got it done today.

  7. For me at least, training in a fasted state is not the problem I thought it could be. One of my weekly gym sessions is after fasting 20 hours into one of my 24-hour fasts and I do not notice any dip in energy levels. My personal trainer says I am noticeably stronger since I switched to low carb / high fat and intermittent fasting and he is increasing the weights I press in resistance training. My lean muscle mass does not seem to have diminished even though my weight has reduced by around 70 pounds over the past couple of years. I am 68 years old.

  8. Thanks to Christoph and John C for sharing your stories.

    Well, I’m in my second fast day. And like others have said, I woke up last night at 4:00 am. My blood sugar was low. (I’m a T1.) I ate two spoonfuls of apricot jam and went back to bed. Normally, increasing my blood sugar to the normal range will relax me and often put me immediately to sleep. Not so this morning. My heart was pounding and my mind was dinking along, even with some subliminal melatonin. Around five, I gave up and got up.

    I’ve lowered my morning basal insulin dose this morning by a quarter unit (3.75 vs 4.00). Besides my basal insulin shots yesterday, I had to take 3 units for high blood sugar. Thus, I took about half as much insulin as a I do on a normal day. Because I plan to do some rather light lifting today, I’ll need to carefully monitor blood sugar and insulin levels.

  9. Hi Nate,

    Is tight blood glucose control the correct goal to guide your therapy efforts or is periodically lowering blood insulin the correct therapeutic goal?

    I believe that Dr. Fung is arguing that the latter goal is the correct approach to treating type-2 diabetes.

    • Christoph, yeah, I’m on a crusade to limit the use of the word ‘diabetes’. So, I just use T1 to say I have Type 1 diabetes. I can imagine that T1 would be easily overlooked, because it is not the normal way to write it.

      Diabetes is an old word that was created when the technology used to determine whether or not you had high blood sugar was to taste your urine (eeeww). Our technology has, thankfully, increased tremendously and so has our knowledge of the causes of high blood sugar. Auto immune problems cause T1; insulin resistance, T2; many consider dementia to be T3: then there is high blood sugar during pregnancy.

      I prefer T1, T2, etc over Type 1, etc because of tweeter.

      Lastly, I have a strong opinion that all diabetics should strive for normal blood sugars. Glucose is sticky and gloms onto proteins though out your body – not good. High glucose levels are the leading cause of blindness and foot amputations. Further more, diabetics are much more likely to have heart attacks, develop dementia and get cancer. Ouch!

      • It isn’t that one shouldn’t want lower blood siugars, but what is the best way to get it?

        Rather than, for a T2, inject and/or produce massive quantities of insulin and with it shove sugars into the muscles, organs, and fat cells in pursuit of lower blood sugar, if insulin sensitivity itself is actually obtainable, then it seems to me to be preferrable.

        This may require less tight blood sugar control, and there is evidence that tight blood sugar control efforts can be harmful. Not that good blood sugar is bad, but that not all attempts to achieve stable blood sugar do more good than harm.

        So, one may need to put up with higher blood sugars for a while while working on insulin sensivitivy, then blood sugars can fall long-term without tons of serum insulin forcing an expanding waistline and fatty organs (including pancreas and liver).

        At least that’s how Dr. Fung’s hypothesis treatment methadology goes, I believe: aimed at lowering insulin.

  10. I routines list weights and exercise after 16 to 24 hours fasts with no ill effects. I believe I am actually somewhat stronger due to the fasting.

  11. Jenny Wilkinson

    I read your posts with great interest, so nice to see rational scientific data presented so well.

    I am pretty sure I have high insulin, I am 71, from a family with diabetes but not diabetic myself. Have always had reactive hypoglycaemia and been wary of sugar and carbs. I am always hungry. I searched your site for reactive hypoglycaemia, any comments?

    I would like to lower my insulin but have read that women do not react to fasting in the same way as men. It can mess up hormones and so on. Do you have any data or observations on any difference between men and women to your regimes?

    I fast till lunchtime. Feel fine till I eat, then do not feel so well and eat early evening. Weight not a problem. I look forward to all your posts.

    • I would point out that most of the studies of fasting have included many women as well. Clinically, I see no difference in men and women and fasting.

  12. I’m glad you’re getting more exposure for your ideas, Dr. Fung.

    I don’t know (as in I have thought I knew in the past, and now am uncertain) whether a whole-food, plant-based; low-carb, high-fat; or paleo-style, omnivorous diet is best, but I am certain fasting is beneficial.

    I intend on getting back to it. I had massively slacked off after some initial success.

    If you don’t mind taking the time to answer, do you think the Martin Berkhan LeanGains (also David Zinczenko and Peter Moore The 8-Hour Diet) style of 16 hours fasting/8 hours eating most days can work well, or that isn’t intense enough?

    My thinking is it could be easier for planning purposes: having fresh food on hand and whatnot; and getting into a daily rhythm like that is easier for compliance for some, but don’t know how it compares for results. I thought I heard Dr. Krista Varaday, prominent for her research on alternate-day fasting, is planning some research into 16/8.

    • I think the LeanGains style of fasting works perfectly fine. For some diabetics, with severe insulin resistance, it may not be powerful enough. For somebody just trying to lose a little weight, I think it should be fine. Fasting comes in infinite varieties but usually comes down to – if you do more fasting, you lose more weight.

  13. Bernard P.

    Dr. Fung, after following you for more than a year, watching all your lectures and reading all your blog posts, a question suddently comes to me…

    Since you obviously don’t have any problem with extra weight, do you yourself follow a fasting regimen? Do you fast at some interval as a “preventive” measure?

    • Yes, I generally do 1-2 24 hour fasts per week. If I have overindulged, I may do a few extra to make up. Yes – I do it for preventive measures against diabetes, but also to stimulate growth hormone, to lower insulin and to increase autophagy (to be discussed later).


      • Bernard P.

        Thanks for your reply. I have looked up “autophagy” and you have piqued my interest… I’m staying tuned!


  14. […] important to note that fasting strongly increases levels of growth hormone in humans, by up to 5-fold, which preserves and even increases muscle mass, as well as bone mass. So we see […]

  15. What’s your take on the heart failures reported in fasting studies (such as the ones described at under Dangers and Drawbacks) ?

  16. I am curious about something Dr. Fung… Do you think that a baby can be born with IR, or develop it shortly after birth or in childhood? The reason that I ask is because I have been overweight since the age of 5, and don’t feel that I should have been.

    I grew up on a farm and are excellent grass fed meats, our own veggies, raw dairy products (made our own butter and cheeses). Ate the entire animal, including the organs. While we did have cereals and breads/homemade cookies/cakes, etc. Since town was 12 miles away… We weren’t walking to the store and buying junk. We ate very little processed food and seldom had candy or pop. I ate normal portions.

    Plus, I was very active. Lots of chores on the farm, and even young kids were expected to help. No video games, 3 channels on the TV (one of which was French), no computers or smartphones. Entertainment was playing!!

    So… Why was I fat before age 5? By age 21 I was having hypoglycaemic episodes (1.9 mmol/l). By age 45 I was diagnosed with diabetes. I have felt for a long time that there has always been something wrong with me…

    Your thoughts would be very welcomed.

    • I believe many overweight people have some genetic conditions, and the only solution is to be very careful with your diet. Did you try fasting, even intermittent or alternate fasting, already ?

  17. Barb, Dr lustig is the more or less famous pediatric who explains that yes infants have IR. His very popular you tube talk, The Bitter Truth, gives examples of that IR in infants and why it is happening now. Here’s his talk:

    GREAT talk!

  18. Would it be a silly protocol to take a little bolus insulin with meals on the basis that it’s short acting and will flush out of the system soon but could provide some protection against tissue damage, and then stop taking insulin on fasting days to regain insulin sensitivity? Or does that basically make sense?

  19. Hi,
    I was wondering : why do I have migraine almost time I eat to much sugar, and every time I am fasting more than 12 hours. I do not fast on purpose, but when I am not hungry (for example when I ate too much at the previous meal and I skip the meal), when I am sick, when I am on business trip, to have a medical examination…)
    I suspect that this have to do with glucose and insulin? How to improve this?

    • Headaches are quite common when starting fasting. I do not know why. However, with repeated fasting, it often goes away. Staying hydrated, especially with bone broth or mineral water seems to help.

      • Doesn’t bone broth break your fast, technically speaking?

        Dr. Jason Fung: Technically, perhaps. Clinically, it seems to make no difference.

        • Thanks for the reply and for this wonderful fasting series, Dr. Fung! That is certainly good to know. I have some bones in the freezer and may make some bone broth. I’m on day two of a water fast (black tea, black and green tea being the only exceptions) and it is going well. I typically have fasted once or twice a week for 18-24 hours but after reading your posts I have endeavored for a longer fast. No problems so far and am feeling pretty good. I’m a 40yo male, btw.

          Again, thanks for this wonderful resource. I’m trying to convince my father, who is a 65yo type 2 diabetic, to talk with his physician about fasting. He’s on metformin but I fear he will continue to get worse even with currently stable blood sugars. If you have any advice on what he or I might say to his doctor or any resources for his doctor to look at (besides your website of course!) please let me know. I sense that my father’s physician is hesitant about these things and perhaps believes many of the myths that you have detailed.

      • Headaches are common because with fasting all the toxins are released into the blood stream very fast. If you do an enema and drink lots of water – they disappear as you flush them out from your gut.

  20. Claudia

    Hi, Im new to all this fasting protocol/s. I have read all the info that Dr. Fung writes, which I think is amazing! There is something I still don’t understand. If somebody with type 2 diabetes fast, will not be more at risk of having ketoacidosis ending in coma? That part of the human physiology I don’t get. Thank you!

  21. Hi! Dr. Fung, is fasting suitable for who have type 2 diabetes already? Thank you!

    • Yes, but you must be very careful with your medications to avoid low blood sugars. You should only fast with close medical supervision in that case.

  22. Very informative article that makes perfect sense to me and spurs some questions.
    I see in Table 3 above how fasting insulin (FI) dropped from 13 to around 3 in just 5 days. Any data on the long term effects on FI after the fast? Either going back to a “standard diet” or a low carb? And I guess the length of the fasting time will mean longer time for FI to return back up after fast, or the number of shorter time fasts times their length, each over a minimum “starting up” threshold of course. ( making 24 hour fasts only 50% effective ?) Has the long term effect on FI to do with how much visceral fat was removed or consumed during the fasts ?

  23. Imislam

    Hello Mr. Fung,

    I am type 2 diabetes from february, 2015 and reduced my weight 23 lbs (186 to 163 now) in last 2.5 months and a1c reduced from 10.3 to 6.4 by this time. I did extreme exercise and low carb food. Currently on low carb diet (maximum 30 g -60g of carb/day) with lot of fat, vegetable and protein most of my calories. I was having fasting bg few days ago only 94-103 and after meal maximum 110-138. But last 1 week my bg goes up to 114-120 with same diet and exercise. Even, 2 hours after dinner bg was 125-130 but in the morning its showing 118-125 without any breakfast. I am just taking 500 mg metformin every night. How can I lower my morning bg hikes. My doctors says its because of dawn phenomenon or hormonal effect in the morning. Last day before breakfast my bg was 114 then I ran for 2 miles then bg went up to 143.
    my question is
    1. how can I avoid these morning hikes?
    2. How can I avoid after exercise bg hikes, do Ineed to eat any carb before exercise?
    3. Do I need to eat zero carb in dinner to avoid morning hikes?

    Can I do exercise (40 min/ day and 5 days/week) with fasting because during fasting my glucose comes from liver to blood that hikes my bg instead to reducing it? What will be the solution?

    I also encourage other people to answer my current problems?
    Thank you.

    • This is exactly what the fasting (IF) will cure but only when waistline reduces I understand. Measure waist instead of weight!

    • Dr. John Koroloff

      I have been on an 18:6 IF fast for about 3 months and record daily blood glucose (mg/dl) and recently fructosamine, A1C, Lipid panel.
      Paradoxical Results:
      Daily BG meter reads end of 18 hr. fast = 115-120 bg/dl (ouch! thats diabetic)
      Yet lab test health paramaters have all have improved.
      body -20 lbs, %body fat -8%, fructosamine, A1C NORMAL/good, Lipid panel NORMAL/good, Resistance exercise show improvement in wt/reps and reduced level of difficulty.
      Conclusion: I think IF increases HGH which increases blood glucose but increase is non problematic because fructosamine/A1, Lipid panel levels remain in Normal/good range.

    • Just an FYI. Have you tried recalibrating your meter or taking a few test in a row to see variation? If the three numbers vary widely, it may be your meter or strips. Just something to check.

  24. […] Continue with Fasting part 3 […]

  25. […] growth hormone (HGH): Levels of growth hormone may skyrocket during a fast, increasing as much as 5-fold (5, 6). Growth hormone is a hormone that can aid fat […]

  26. I am 81 male. 2 years ago I had my blood tested at HDL [health diagnostic labs] and my insulin was 28. It went up over the past 2 years to the high 70’s and fell to the mid 40’s 7 weeks ago. I have had 8 blood tests during this time and will have it tested in 2 weeks. I have been on a strict Keto diet for 16 months. [ 20 gm. cruciferous carbs. total 1600 cal 80% fat, 15 to18 % protein]. a1c = 5.9. All vascular inflammation markers are perfect. I am insulin resistant and have over the past 10 years have gone from 165 to 225 #. Insulin too high to loose fat. The Keto diet is not working. I am on testosterone. I am seeing a bariatric doc and a clinical endocrinologist at UCLA. They are not concerned—I am. After reading your views on IR I am ready for a 5 day water/BB fast. Do you have specific guidance you will share.

  27. pedro ivo

    well, there are solid research too showing the opposite in regards the HGH / IGF 1,
    it is a controversial point that it is almost not discussed… I would like to understand this better…

    Dr. Jason Fung: I think you are confusing Growth Hormone (GH) with IGF-1 (Insulin Like Growth Factor 1). They are quite different Fasting increases GH but decreases IGF-1, as well as insulin.

  28. pedro ivo

    in your text above it is “Perhaps this decrease in HGH-IGF1”, you put they together because igf1 increases or decreases in response to GH levels…
    “HGH only lasts a few minutes in the bloodstream. It goes to the liver for metabolism, where it is converted into a number of other growth factors, the most important of which is Insulin Like Growth Factor 1 (IGF1).’

    “Produced in the liver, IGF-1 mirrors GH excesses and deficiencies, but its level is stable throughout the day, making it a useful indicator of average GH levels.”

    Dr. Jason Fung: While GH may influence IGF-1 levels, other factors do as well, including insulin levels and BMI. Since insulin levels go down with fasting, so does IGF-1 levels even as GH goes up.

    • Good to get this clarified. The connection between HGH and IGF-1 was not clear in the post, and there is absoulutely nothing about IGF-1 in your book “The Complete guide to Fasting.” This I find very strange as IGF-1, as far as I have understood, is a leading biomarker for aging. Prof Valter Longo also highlights fasting and the effect of IGF-1 (it goes down). It is also recognised by many as a driver for many types of cancer.
      You have a small part about mtor in the book, but I think this could be a much bigger part as the title is “a Complete guide…”.
      Also; while we are at it: The book has to much, and repetitive, information about fasting and its effect on insulin, diabetes 2 and weight loss. It should cover more on other Health issues, ieg autoimmune diseases. There have been studies on MS for instance…
      Just some tips for the revised edition on the book:)
      But thank’s a lot for a good book and a lot of good information here!

  29. pedro ivo

    thank you, it is a good explanation… so it is possible measure GH by other means… not only trough IGF-1 levels… one hipothesis was that the GH maybe decreases in the fasted state, and would increase dramaticaly in the refeeding, but is not, increases in the fasted state itself, correct? thanks

  30. […] – Fasting increases HGH secretion in the body by up to 1000%. That staggering figure is backed by multiple studies. HGH plays a huge role in athletic performance and is crucial for building and maintaining lean […]

  31. […] fasting” is a great way to enhance your growth hormone levels. There have been many scientific studies on how fasting increases HGH levels and how HGH causes […]

  32. […] sehr guter Beitrag zu diesem Thema ist übrigens auch auf der Seite Intensive Dietary Management zu […]

  33. […] who did try intermittent fasting revealed increased human-growth hormone levels, weight loss, stabilized insulin levels, brain repair and strengthening, anti-aging, fat loss, […]

  34. Art Deco

    Very interesting article, I had no idea that HGH became elevated during fasting or the role it played in healing the body.

  35. I have been inspired to start fasting after watching BBC’s Horizon programme “East, Fast and Live Longer” (by Dr Mosley).
    A lot of your posts, Dr Fung, make perfect sense to me and both the available research and common sense tell me that this should work.
    However, I am slightly confused by this post about IGF1.
    Dr Mosley in his programme was talking about elevated levels of IGF1 being one of the risk factors contributing towards many types of age-related diseases (such as cancer). After starting his fasting regime, Dr Mosley’s IGF1 levels dropped by half (after 5 weeks of following the 5:2 regime).
    However, you Dr Fung propose quite the opposite idea in this post: that fasting INCREASES IGF1 to preserve lean mass.
    I am confused! Is IGF1 supposed to drop or increase when fasting?

  36. […] we are clearing out all our old, junky proteins and cellular parts. At the same time, fasting also stimulates growth hormone, which tells our body to start producing some new snazzy parts for the body. We are really giving […]

  37. I started fasting in February 2016 and by early June 2016 I’ve lost 42 lbs–absolutely amazed me–Sure at first it was hard but as Dr. Fung very eloquently explained in his wonderful book “The Obesity Code” most people have never fasted before so I wasn’t used to it-but the hunger pangs ultimately disappeared and ultimately I continued to a 24 hour daily fast (just having dinner every evening-and tea in the morning and carbonated water at lunch). I still eat at special occasions (birthdays, holidays etc) but I know that I can go right back to fasting and maintain my weight easily

  38. […] Hormônio do Crescimento ou GH – jejum é uma forma natural para aumentar a produção de GH. O GH auxilia na recuperação de exercícios de alta intensidade, assim como aumenta o […]

  39. Levels of HGH have been measured as high as 1000x higher than average in people fasting for several days, but what about intermittent fasting ? How high does HGH get ?

  40. […]  The increase in Human Growth Hormone activates the body’s own fat loss system, by increasing lean muscle gains.  Lean muscle burns more calories than fat – leading to not only a leaner body, but one […]

  41. […] we are clearing out all our old, junky proteins and cellular parts. At the same time, fasting also stimulates growth hormone, which tells our body to start producing some new snazzy parts for the body. We are really giving […]

  42. […] we are clearing out all our old, junky proteins and cellular parts. At the same time, fasting also stimulates growth hormone, which tells our body to start producing some new snazzy parts for the body. We are really giving […]

  43. I am a type 2 diabetic And I am in day 6 of a planned 14 day fast. So far I am doing great. I have lost about 9 pounds. My a.m. fasting sugars the first day were 101. The p.m. sugars were 66. I did not take in any insulin. Day 2 I quit metformin. Day 3 Ketones were 4.2mmol/l and sugars were in 70s. I feel great. Morning of day 5, sugars were 84. p.m. 95. Day 6 a.m. sugars were 101. I took one metformin and we will see what happens. I was wondering what could be causing the increased sugars starting with day 5? Any ideas? I thought that maybe it was due to an increase of HGH or even the sugar dump process from the stored fat. Would be interested to know if this is common.

  44. […] обмена. С другой стороны, голодание приводит к выработке гормона роста, указывающего нашему организму, чтобы тот начал […]

  45. […] Fasting and Growth Hormone Physiology – Part 3 – Intensive … – The effect of fasting on Growth Hormone is discussed and the benefits of training in the fasted state. […]

  46. […] Fasting and Growth Hormone Physiology – Part 3 […]

  47. Hi Dr Fung,

    Always been a big fan of your work and especially this one.
    I’m interested in boosting HGH levels from a bodybuilding point of view.

    What would you recommend to be the most optimal fasting protocol to maximise muscle gains?

    Thanks and I look forward to your reply, doctor!

  48. I’m quite confused because the article below suggests HGH and IGF-1 go in tandem. So it’s a “Faustian bargain” whether you want short-term muscle and cognitive enhancement, or longevity. See

  49. Hello, dear Sir,

    This is Josie. Thanks for your time and patience.

    Shenzhen Unique-Peptide Biotechnology Co.,Ltd, specialized in generic peptide, cosmetic peptide and active pharmaceutical ingredient peptide and raw powder producing. Custom Peptide Synthesis service is also provided.

    The best wholesale price will be offered to all resellers and distributors around the world.

    1. Your order can be shipped from our France/USA/Australia warehouse, no need to worry about customs problem.
    2. A professional, stable logistics team to ensure safe customs pass and fast shipping.
    3. GMP Lab certificate and HPLC, MS and COA test reports are available.

    We with a keen hope to establish long-tern business relationship with you.

    Looking forward to your reply soon.
    Thanks a lot.

    Skpye: josie_6210

    Email: [email protected]

    WhatsApp/ Viber : +86-13763063935

    Shenzhen Unique-Peptide Biotechnology Co.,Ltd,

    1 ACE-031 98%purity 1mg/vial
    ACE-031 85%purity 1mg/vial
    2 ACTH 1-39 2mg/vial
    3 Adipotide/FTPP 2mg/vial
    4 AICAR 50mg/vial
    5 Alarelin 10mg/vial; 5mg/vial
    6 AOD 9604 2mg/vial
    AOD 9604 5mg/vial
    7 BPC-157 5mg/vial
    8 CJC-1295 no DAC 2mg/vial
    9 CJC-1295 (DAC) 2mg/vial
    10 DSIP Delta Sleep Inducing 5mg/vial
    11 Epithalon 10mg/vial
    12 EPO 3000iu/vial
    13 Follistatin 344 85%purity 1mg/vial
    Follistatin 344 95%purity 1mg/vial
    14 Fragment 176-191 2mg/vial
    Fragment 176-191 5mg/vial
    15 GDF-8 95% purity 1mg/vial
    GDF-8 85% purity 1mg/vial
    16 GHRP-2 5mg/vial
    17 GHRP-6 5mg/vial
    18 Gonadorelin 2mg/vial
    19 GW501516 10mg/vial
    20 HCG 5000iu/vial
    21 Hexarelin 2mg/vial
    22 HGH 191 AA (Pharm Grade) 99%purity 10iu/vial
    HGH GMP 98%purity 10iu/vial
    23 HMG 75iu/vial
    24 IGF1-DES 1mg/vial
    25 IGF1-LR3 0.1mg/vial
    IGF1-LR3 1mg/vial
    26 Ipamorelin 2mg/vial
    Ipamorelin 5mg/vial
    27 Lipopeptide 100mg/vial; 10mg/vial
    28 Melanotan I 10mg/vial
    29 Melanotan II 10mg/vial
    30 MGF 2mg/vial
    31 NA-Epithalon amidate 100mg/vial
    32 NA-Epithalon 100mg/vial
    33 NA-Selank / amidate 30mg/vial
    34 NA-Semax 120mg/vial; 60mg/vial; 30mg/vial
    35 NA-Semax amidate 120mg/vial; 60mg/vial; 30mg/vial
    36 Oxytocin 2mg/vial
    37 Pal-Ghk 10mg/vial
    38 PEG-MGF 2mg/vial
    39 PT-141 (Bremelanotide) 10mg/vial
    40 Selank 5mg/vial
    41 Semax 30mg/vial
    42 Sermorelin 2mg/vial
    43 SNAP-8 10mg/vial
    44 Tesamorelin 10mg/vial; 5mg/vial; 2mg/vial
    45 Thymalin 10mg/vial
    46 TB-500 2mg/vial
    TB-500 5mg/vial
    47 Thyrotropin TRH 20mg/vial
    48 Triptorelin/ GnRH 100mcg/vial
    49 Raw Powder of the above Based on your requirement
    50 Cosmetic Peptide Based on your requirement
    51 Custom Peptides Synthesis Based on your requirement

    Skpye: josie_6210
    Email: [email protected]

    WhatsApp/ Viber : +86-13763063935

    Shenzhen Unique-Peptide Biotechnology Co.,Ltd

  50. Michelle Uhlig

    Dear Dr. FUNG Thank you in advance for the wonderful work you ate dping and changin poeples lives…
    I would like to see an article specifically about woman’s imbalanced hormones and what effect fasting has on it, especially reproductive and thyroid hormones as I have an underactive thyroid gland (pituary gland aswell).

    I would like to ask a few questions about this theory about the Paleolithic times… but first, is it save for a toddler to fast? I question this because of an article I read somewhere that says that children should not be fasting because of some growth hormone. If then, it is NOT save, what happenend to them during the “winter months” in paleolithoc times??
    Can children safely maintain a ketogenic diet then?

    What are the pro’s and cons of this in children?

    In the more than every so often case of ADD and Adhd these days I would like to see if the KETO diet may not be a way out for these affected children… the wheat and sugar in childrens diets can not be excluded maybe and see a positive chabge in behaviour.

  51. I have just recently discoved fasting this year, at first as a means to weight control, but after the first fast I discovered there was so much more to it and so much I could get back from it.
    I feel like I have discovered a magic pill or food source, but of course that would break my fast 🙂
    Nothing I have tried in the past has given me more excitement than this, I am reading up on it like crazy.

    I have tried sharing this with friends and family, but have now given up. I got the usual stuff about it not being natural and bad for you, yet in the bigger scheme of things this was more natural through our path of evolution over 1000,000’s of years than the constant 3 meal a day and all that constant insulin.

Leave a Reply