Intermittent Fasting - Our 6 week IGF-1 check - it works!


Alistair Hall

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My brother Ceri and I have been intermittent fasting since January. Also known as the 5:2 diet, intermittent fasting involves severely restricting your diet for 2 days a week, to 500 calories for women and 600 for men. The aim is to reduce levels of growth hormone IGF-1 so that cell turnover slows and consequently your risk of cancer and other diseases of aging reduce. Ceri first intended to do it for 6 weeks whereas I approached it as a regime I would aim to adopt for life.  As the first 6 weeks was up, we both decided to get our levels of IGF-1 retested to see whether the theory worked in practice.

Just to recap, we had both already had our IGF-1 levels tested, first in October when both of us were following our normal eating pattern and later in early January after an indulgent Christmas.  In October, Ceri’s was already very low: 15.2 nmol/l  (range 12.2 – 32.8) whereas mine was very much in the middle of the range: 21.6 nmol/l (range 11.3 – 30.9). Ceri went overboard at Christmas, putting on half a stone and increasing his IGF-1 level to 24.3 – a big increase. I was more moderate over Christmas and as you would expect, my IGF-1 level went up, but not massively: in January mine had increased to 24.7 – still higher than Ceri’s but less of an increase compared with my October result.

So what were our hopes and fears coming up to the six week check? Well, we had both stuck to the diet, there’s no doubt about that. Ceri approached the whole thing much more scientifically than I did, experimenting with different approaches to spreading his meager calorie allowance across the day. He has a much more ambivalent attitude to food than I do and consequently didn’t find his fasting days difficult at all. I on the other hand LOVE my food and find it very difficult to walk past the fridge without checking in for a small mouthful of something or other. I found my fasting days more difficult, especially to begin with. Ceri was hopeful that his IGF-1 level had lowered and was speculating whether it could go much lower than his original result in October. I wasn’t confident that mine had lowered at all – I had only managed to lose the 3lbs I put on over Christmas whereas Ceri had lost the half a stone he put on as well as another half a stone for good measure.

What a nice surprise to find that my IGF-1 had dropped from 24.7nmol/l to 13.9 nmol/l in just 6 weeks! Ceri’s had also fallen, but surprisingly not back to his previous levels but still a significant drop to 18.9nmol/l.

So where do we go from here? I feel encouraged that the approach is working  - I’m feeling good, my IGF-1 is lower (and if the science is right my rate of ageing has slowed) and I am keen to carry on with intermittent fasting indefinitely. Ceri is less convinced that intermittent fasting has added much to what was his normal approach to eating. He already ate fewer calories during the week hence his low starting IGF-1 levels. He has decided to continue with the intermittent fasting diet, but to raise his fast day calories to 1000 per day – a level he feels is more manageable.

We will both get our IGF-1 levels retested in about 6 months to see what the longer term effects of the diet are, and to see whether Ceri can achieve the same results with a slightly higher calorie intake.

Why the different results after 6 weeks? That is difficult to say but we will describe our slightly different approaches to the diet and to our exercise regimes in a later blog for clues. Watch this space!

Helen and Ceri


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