Effects of fasting on IGF1 – confused!

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Effects of fasting on IGF1 – confused!

This topic contains 16 replies, has 8 voices, and was last updated by  Couscous 7 years ago.

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  • I am confused by, what appears to be, contradicting information on the effects of fasting on IGF1 (Insuline-like Growth Factor 1) i.e. whether fasting increases or decreases secretion of IGF1 and whether increasing or decreasing levels of IGF1 is a good thing.

    In his BBC programme (“Eat, Fast and Live Longer”) Dr Mosley 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), which he said was what he wanted to achieve by fasting.

    However, I came across Dr Jason Fung’s blog (IntensiveDietaryManagement.com) in which he says that fasting INCREASES IGF1 to preserve lean mass during fasting (i.e. to preserve muscle).

    See here: https://intensivedietarymanagement.com/fasting-and-growth-hormone-physiology-part-3/

    Which side of the argument is right, as surely they both can’t be right can they?!

    Hi Robert:

    If I remember correctly, Dr. Fung referenced the Harvie study: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017674/. That is the only clinical study I am aware of that addresses IGF1 levels and it indicates stable or increased levels of IGF1 with the study’s version of 5:2.

    Dr. M’s results were not in any way scientifically based – just a one person result after 5 weeks of eating whatever. The food eaten has an impact on IGF1 levels, and maybe Dr. M ate less food that raises those levels. We cannot know.

    Several posters on this and other sites have reported measuring their IGF1 levels when starting 5:2, but I am not aware of any that have returned with results on either side of the issue.

    I am not aware of any studies that support the ‘other health benefits’ of 5:2 other than those that come with lower weight – better blood pressure, cholesterol and triglyceride levels. But hey, nothing wrong with those results!

    Good Luck!

    Simcoe, don’t you count getting off insulin and steady, low blood sugar results for years “a health result” from 5:2?

    Hi PVE:

    To be fair, I think your husband totally changed his diet and the amount of food he was eating. I have followed your posts quite closely and do not believe you reported that he ate 600 or fewer calories twice a week but otherwise ate just the way he always did.

    Am I right?

    Simcoe, no matter what he eats, it requires fasts to continue keeping his bloodsugars in the normal range. Just losing weight and changing diet will not keep diabetes away. Therefore, it is 5:2 (2 good fasts of 500 cal or less per week) that keeps him healthy. Eating well and staying 68kg only works for a few weeks. The fasts are totally necessary. P

    Hi Simcoe,

    Many thanks for your reply.
    It’s just that both Dr Mosely and Dr Fung seem to have very strong opinions and beliefs about fasting, and when those beliefs are contradictory it worries me slightly.

    You said that you were unaware of any studies that support the ‘other health benefits’ of 5:2, but what about the studies on mice (presented in Dr Mosley’s programme) where calorie restriction seems to prolong their lives significantly? Are those studies irrelevant?

    Hi PVE:

    I have no doubt what he is doing works, but we can agree to disagree that 5:2 alone caused all of the fine results he is enjoying. I’m sure you would not say that if he continued to follow 5:2, but began consistently eating a high sugar and refined carbohydrate diet, he would not have to worry about the return of his Type 2. We both know his Type 2 would be back with a vengeance, 5:2 or no 5:2.

    He was having to reduce his insulin on fast days within weeks of starting 5:2…at 100kg. I can assure you, he is no angel when it comes to food, but is incredibly strict on his fast days. If he does overindulge on eating days, and his bloodtest the next morning is slightly elevated, he skips breakfast and perhaps even lunch and eats a normal dinner. This is how he manages. And I would call it a health benefit of 5:2/fasting, not just weightloss. The diet change is a result of 5:2 also, as it changes ones approach to and tastes for, food.
    Dr M had him stand up and tell others of his success at a luncheon last week.
    Please don’t deny others the hope of using fasting as a non drug mechanism for controlling Type 2 diabetes. P

    Hi Robert:

    You are confusing mice with men.

    One basic confusion is that a 16 hour fast by a mouse equals a 16 hour fast by a human. The general estimate is that a 16 hour mouse fast equals a four or five day water fast by a human.

    Research does show very important ‘other health benefits’ are enjoyed by people that do periodic four or more day water fasts. But I am not aware of research that shows great benefits to humans that don’t eat for just a matter of hours.

    Dr. Mattson believes there may be some benefit to eating in an ‘eating window’, but I am not aware of human studies that back up his belief. He apparently has a human experiment in process but I have not seen the results yet.

    I am very interested in this debate as my husband has had type 2 diabetes for a number of years and the amount of insulin he uses is a concern. I was hoping to eventually get him to join me on 5:2. In my limited time doing 5:2 I would agree with PVE that it has changed my approach to and taste for food which is why I think so many people have had success with it. I was indoctrinated under the old food pyramid which encouraged us to eat lots of carbohydrates and thought I would never be able to cut back on pasta, potatoes and rice. However I am finding it pretty easy to do that at the moment – long may it continue!!

    Hi Jilly:

    You might check this video about fasting and Type 2: https://www.youtube.com/watch?

    And these two threads have much information: https://thefastdiet.co.uk/forums/topic/reversing-type-2-diabetes-the-fastday-lifestyle/



    Dr. Fung’s basic procedure is to water fast patients for 1 to 4 weeks and follow the fast with ADF and a ketogenic diet.

    Good Luck!

    Hi Jilly:

    Looks like I gave the same link twice. Here is the second one: https://thefastdiet.co.uk/forums/topic/type-ii-diabetes/


    Thought I was going to read a thread about IGF1 and not diabetes – nvm.

    I must admit that since starting ADF, mostly with the aim to reduce IGF1 to reduce the chances of cancer, I’ve been half expecting a study to come out and tell me something totally contradictory and probably with bad health consequences.
    Had a sift around the web and there are so many opinions and so little facts from scientific study.
    Worst of all in my sift findings was discovering the FMD diet – ain’t doing that.
    My application of ADF has not been at all rigorous for some time now, but I’m still aiming to reinstate 3 days fasting a week as a way of life and will just take a chance of what is happening to my IGF1 – with the optimistic assumption that it is reduced due to fasting.

    I’m more confused now having read this thread. I thought one could measure how well the 5:2 fast diet was working by taking an IGF-1 test before starting and after a few weeks in. Is that true? If so, by how many points should the IGF-1 level be reduced to show good results? I just had a test last week where IGF-1 = 179ng/mL. Note that I do not have diabetes, but am interested in reducing risk of age related brain illnesses and cancer. Any thoughts?

    Hi hanumanrob,

    Not sure why you would want to track whether 5:2 is working by tracking IGF-1? Too many other variables to take into account, sex , age, physical state, level of stress etc. the actual act of fasting makes some people stress. This releases cortisol. It takes a while to become comfortable with the concept of fasting. Im talking about a true fast not the 500 cal version that most participate in.

    I also dont have diabetes but have been tracking how well 5:2 works simply by measuring my blood glucose levels and when fasting my ketone levels. There are cheap meters available on the market that will measure both BG and ketones. I use a freestyle optium neo. I suppose you could also get bloods taken and measure HbA1C or inflammatory markers like C-RP. The last C-RP I had taken it was below detectible limits, so my plumbing is pretty good at the moment.

    Thanks for the reply. Oh I could have sworn the video or book by Moseley said the IGF-1 blood tests showed how good his health was after doing the 5:2, and I assumed he meant it was some sort of measure how good the diet was working to prevent age related illnesses in brain and elsewhere. I believe in the science, but I have been only doing it a few times a month :(.

    Anyway, it would be nice to say, “well before 5:2 , my X measurement was n, and after 5:2, X is much improved,” i.e. showing the diet is helping my health. (Note: I don’t want Alzheimers nor Dementia like my Nana, and I’m almost 53 now!)

    Good morning hanumanrob, just read your concerns re Alzheimers and Dementia and like your self many are worried about suffering those effects. To date there are no known cures for these but research in many areas continues. I am a great believer in information, (evidenced info that is) so the following may be of some help.
    Google “Google Scholar”. I typed in “Effects of fasting on Dementia Valter Longo”
    A list of research heading appears. One, done in 2016 by Mark Matson and Valter Longo may be of interest-“Impact of Intermittent Fasting on Health and Disease processes” They state, among other things “Tests on mice have “Profound beneficial effects” on many indices of health”. These comments are in relation to research on mice of both Intermittent fasting and Periodic fasting.
    Check out also “How not to Die” by Dr Michael Greger which has a chapter on Brain Diseases and a book called “Blue Zones, The Science of Living Longer” by Dan Buettner, a National Geographic researcher. Both books are about the effects of diet on health and ageing. They may be of some help. As I have said these are for info only, also check out the Active Topics in the Forum link at the top of the page, you may pick up some ideas. Your local Library may have them or get them for you.
    I agree with bigbooty and the comments on fasting and stress etc but we are all different, try different types of fasting, find something that suits you or is achievable. The bottom line is that regular fasting and a healthier diet do seem to have a positive impact on our internal health and who knows may positively impact on Dementia prevention.
    Good luck.

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