Fasting and Human Growth Hormone

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  • Hi all,

    There seems to be some very conflicting information regarding fasting and production of growth hormone. I’m hoping some of the more scientifically advanced readers could answer this question please.

    In summary, the hormone IGF-1 is very anabolic, builds muscle and new cells etc however it is generally considered best to reduce IGF-1 for those interested in longevity. It is linked to higher rates of cancer and diabetes and general aging. And fasting has been shown to lower IGF-1, obviously this is good.

    This study was using the “fasting mimicking diet” but similar results found across all fasting protocols.

    However… (this bit is my question)..

    HGH (Human Growth Hormone) which has been shown to promote rejuvenation of body tissue has been shown to increase hugely when fasting, one study claimed by 2000% but most studies suggesting it doubles.

    As far as I know IGF-1 is a precursor to HGH, so which one is it? Are we getting the anabolic effects of cell proliferation caused by growth hormone when we fast which leads to the downside of increased cancer risk and premature aging?

    Or have I missed something and I don’t fully understand the relationship between IGF-1 and HGH. Does fasting give us the perfect combo of lowering IGF-1 whilst also giving us an HGH boost?

    Any biologists able to explain further?


    Hi Tom,

    I’m not up to speed on the current research but we do know that fasting causes a drop in blood glucose which triggers growth hormone release. Growth hormone then triggers IGF1 release. I generally thought they mirrored each other as we measure IGF1 as a marker of growth hormone status. Growth hormone is released in pulses where as IGF1 is more constant.

    Whether it is desirable to have low IGF1 I’m not sure. We see it in chronic disease and generally worry if it is low.

    I need to read more on the theory of these fasting benefits. Cortisol, adrenaline, glucagon and growth hormone are all released. I suspect the main benefit is switching off insulin itself.

    Good questions, let me know when you have worked it out!

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