IGF-1: curious results

This topic contains 9 replies, has 3 voices, and was last updated by  dykask 6 years ago.

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  • Hi,

    I had my IGF-1 measured as I started intermittent fasting. It was 205 ng/mL. Now, 3 months later, after doing between 2 and 3 days of fasting (600 Kcal) every week, my IGF-1 result measured in at 203 ng/mL…

    Any ideas what is going wrong for me. The main benefit I was seeking from IF was a reduction in IGF-1 with the associated health and longevity benefits. This doesn’t seem to have occurred for me.

    Thanks for your thoughts and advice.

    Hi Roy:

    IGF-1 levels are largely determined by the amount of protein in your diet. To lower them, you need to consistently eat less protein. The Longevity Diet recommends that you eat no more than .31 to .36 g. per pound of body weight each day, with a max of 70 g. of protein per day regardless of your weight.

    Thanks for the comment. I’m pretty sure Michael Mosely claimed in the Horizon video that intermittent fasting halved his IGF-1 levels. Maybe just coincidence rather than causation. I’ve now noticed others reporting no drop in IGF-1 levels on this site. Maybe the core principle of one day 500-600 cal fasts is flawed and you really need 4-5 days of proper fasting to get results?

    Hi Roy:

    I am not aware of any poster on this site reporting reduced IGF-1 levels, although several have indicated they had checked their initial levels. They seem to not have returned with their results. Dr. M’s one person five week 5:2 experiment was anything but a clinical trial and I suspect his reported non-weight loss ‘results’ were more reflective of foods he did and didn’t eat rather than the effects of the 5:2 eating pattern.

    If the ‘fasting’ causes lowered protein intake then IGF-1 levels should be reduced. But you don’t need to fast to lower IGF-1 levels, you just need to eat less protein.

    Your choice.

    You might check out Longo’s Longevity Diet for more information. There is a thread on this site that has some discussion of the diet and references some interviews with Longo. https://thefastdiet.co.uk/forums/topic/52-and-the-longevity-diet/


    As an example, please see post by tko: https://thefastdiet.co.uk/forums/topic/test-results-but-not-igf1

    I’ve read Longo’s book and was not hugely impressed – he seems to mostly like to talk about himself. His ideas on diet – high carbs – did not resonate with me. I tend to gravitate to the evolutionary biology school – namely what is our body’s natural evolved diet. To this end, intermittent fasting makes sense (scarce food availability) but high-carbs does not. Longo also espouses a plant-based diet which I find nonsensical from an evolutionary perspective. We have definitely been meat-eaters for much of our past. To this end, there is no, and has never been recorded any, human hunter-gather society that was vegetarian.

    Since my last post I’ve found a study that showed that neither IF nor caloric restriction reduced IGF-1 levels although IGF-1 binding proteins increased in both cases: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017674/

    @royski, Dr. Mosely’s IGF-1 levels went down after a 4 day fast that he did under Dr. Longo’s direction. I assume they when back up later and I’m not aware of any claims made about 5:2 and IGF-1 levels. He simply felt that multiple day fasts were too hard for most people to do and that partly lead to 5:2. 5:2 is primarily about controlling weight.

    As far as low carb diets go, humans probably didn’t do well until they developed agriculture. If the world were to suddenly shift to low carb diet, it would mean worldwide starvation. Most of the world depends on stables like rice. That is actually that biggest problem I have with extremely low carb diets, they simple aren’t sustainable on a large scale.

    I thing there are real problems with extreme diets. Low carb diets are not sustainable, based on questionable nutrition and likely long term increased risks of cardio-vesicular diseases, high carb diets are not completely sustainable either on a world-wide scale and require supplementation for fat soluble vitamins for long-term health. I find a lot of the arguments given in either camp to be largely nonsense. It can sound good but it simply doesn’t match reality. Clinical trails are mixed at best, there isn’t always a clear winner.

    Getting back to IGF-1 levels. I’ve read a lot about fasting and the only claims I can recall about lowering IGF-1 involve multiple days of fasting. IGF-1 isn’t something though that is routinely measured so it is possible there are more ways at reducing it. Most fasting studies seem to focus more on weight and limited blood tests.

    It sounds like a major driver for IGF-1 is protein. More protein drives up IGF-1 and insulin. Dr. Longo recommends no more protein than 0.81g / kg of body weight. (0.36g / lb) <== very strange units …

    Hi @dykask,

    Thanks for the reply. I have a few comments to your various points:

    1. Dr. Mosely reported in his video and book that after his “unsustainable” 4 day fast, his IGF-1 came back to its previous level, but that following the 5:2 diet for 3 months his levels halved i.e. same effect as the 4 day fast.

    2. I’m not so sure protein affects insulin as much. Whilst having a high IGF-1 reading after 3 months of 5:2 (203 ng/mL) at the same time I had very low fasting insulin – 2.5 uiU/ml (normal range 2.0-19.6). So if it was proteins that caused my high IGF-1, they did not affect my insulin. Alternatively, it’s not proteins that are raising my IGF-1 but something else. Does anyone have any ideas?

    3. This is a long discussion but in brief: human physiology is essentially unchanged since our pre-agriculture hunter-gatherer ancestors (i.e. 10,000 years in no time for evolutionary change). Therefore, our bodies are adapted to the diet prevalent for most of our evolutionary past and this is very very low sugar, low carb, high fat and moderate protein (let’s call this the Natural Diet). What people call a normal diet is “extreme” compared to our Natural Diet. To say that a Natural Diet leads to malnutrition and cardiovascular disease is not supported by facts – just look at any native population, they have no cardiovascular disease. (Incidentally, one of the highest rates of heart attacks is in India, a mainly vegetarian society).

    As for sustainability, humanity took the path of exceeding the planet’s natural capacity to feed it when it adopted agriculture, and has been pushing the boundaries ever since (e.g. Haber-Bosch process for making ammonia, hence fertilizer). If we decide we need more protein in our diets, man will figure it out (just look at what’s going on now with biosynthesis of proteins). People have been predicting that population will outstrip food production since at least the 1700’s (see famously the Malthusian catastrophe: https://en.wikipedia.org/wiki/Malthusian_catastrophe). In any case, the sustainability question is beside the point to the question of health – the diet best adapted for our health may require man-made solutions to feed the world, but that’s the devil’s bargain we made when we adopted agriculture to allow larger populations…

    Regards and thanks again for engaging with this subject.

    Hi Roy:

    As you seem interested in IGF-1, here is a link I posted on another thread that deeply explores the relationship between protein intake and IGF-1 levels: https://patents.google.com/patent/US9237761B2/en

    @royski – Metabolism is very complex. Protein has been clinically show to increase or even drive insulin spikes. I don’t reading much about fasting levels of insulin and protien. Protein also drives the PI3K-Akt-mTOR pathway and impacts IGF-1. I’m not clear why you think your fasting insulin levels should mirror your IGF-1 levels. They are two different things.

    As far as physiology goes, you are talking about just theories. Diet has huge impacts on physiology, just look at how obesity has grown in the last 50 years. Over a couple hundred generations of humans, the one more adapted to agriculture are likely the ones that survived. No proof either way but what people likely eat 10,000 years ago is largely different that what we have access to today, so it doesn’t make much difference.

    I find a lot of value in reading apposing viewpoints. Personally I find veganism and ketogenic diets suffer from the same problem, the diets are so extreme that on their own they lack key nutritional components. It is clear that neither approach is natural and they are both completely unsustainable if the diets were adopted worldwide.

    A quick search on the book does show numerous mentions of IGF-1. To get the same results you would probably have to be following the actual diet/exercise done and then you might not even get the same results because your body is likely somewhat different than Dr. Mosely’s. It is worth nothing that his bodyfat was pretty high when he started at 28%. He moved down to an okay 21%, but that is still plenty of fat. That could be another factor. 25% drop in bodyfat is a lot in a few months.

    Finally you have your measurements. In your case you feel something you are doing isn’t working. If you want to change it you need approach it with an open mind. When you blow of protein consumption as a possible factor than you might be losing the game before you even start.

    FYI – I do zero calorie fasts. I don’t personally see eating 600 calories on a fast day as really fasting. I find now it is much easier to not eat anything than to just try to get by on a small amount of food. Eating drives hunger and a lot of hormonal changes too.

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