5:2 / ADF and running

HI runners!

I am starting the 2 day fast diet ( though hate calling it a diet as that isn't really the point) I just wondered if anyone else does this and whether you still run on your down days (when you consume only a max of 500 calories) and how this works for you with training?

So far I have decided to fast on the 2 days a week I don't exercise but I find I have more energy on fasting days than eating days for some reason so just wondered what others do...

Nosy runniff


  • I can manage a run - though probably not a very long one- or a weights session on a fast day. Anything to take your mind off food...
  • if you are not doing it to lose weight .why are you doing it.......

    does it help training..do the days have to be consecutive......

     just be nosey as to why you would want to semi fast....and do those max 500 calories have to be of a certain type or can it be a chocolate bar and packet of crisps


  • The reason for doing it is that there is research showing huge health benefits in terms of reduced risks of cancers, heart disease and increased longevity, plus increased brain function in terms of things like memory. Don't get me wrong, I have half a stone to lose and I won't be sad when this gets rid of it, but that isn't my primary motivation....

    you can find out more about it here if you are interested!


    The 500 calories should be spent on nourishng food. the days need not be consecutive.

    I have done it before, a few months ago, and felt amazing, really energetic...I wasn't running at that time though so just wondered how that fits in.




  • Why do these people never give publication references to back up this stuff?

    When they do and if the science is good then I may pay some attention until then I will view this with a great deal of scepticism

  • I applaud the critical approach groovy, I wish people would apply this more to various health claims..

    The Intermittent fast dies actually has some evidence base - check out Harvie et al in  International Journal of Obesity 35, 714-727 (May 2011) (doi:10.1038/ijo.2010.171) 

    there are also several papers by Chicago group led by Prof Varady about influence of various metabolic factors. 

  • There are lots of publication references to the research at the back of Michael Moseley's book if you are interested. the Horizon documentary also examined the key research.

  • I'm curious too. My hunch says 'incompatible'. This diet utterly flies in the face of everything I've ever read/been advised: small regular meals, snacks to maintain energy levels and avoid blood sugar dips. Got some friends on the 5:2 diet raving like some loony cult members. But they don't run or exercise much at all in fact. I reckon it's hard to do 20+ miles a week on any restrictions. Having said that I feel great (light fast energetic) when I run early morning no breakfast. Only for 6 miles tho, more than that I crash: wobbly legs, nausea etc. I wonder tho if it can work, it does seem to have a basis in proper science and some real converts.
  • in healthy people sugar level remains within normal range -  you need to fast in excess of 60 hours to cause significant drop. I think that the continuous severe calorie restriction leads to slowing down of metabolism and the body going into starvation mode etc - the intermittent nature of 5:2 diet prevents that. 

    Having said that, I am not sure how this diet may be compatible with e.g. marathon  or ultra training. From my limited experience, running on a fast day is fine - though as RosRunner says probably not in excess of 6 miles. However, running first thing in the morning the day after is really hard. 

  • May have a look at the data. Does anyone know if the persons on the diet were compared with a group that just ate around 430 calories less each day. Figures based on supposedly average female needing 2000 calories per day so effectively losing 3000 required calories by intaking only 500 calories on 2 days.

    Only way to lose weight is to burn more calories than you take in. How that's done is up to the individual. If it were me however, and I was hopefully eating a balanced diet and putting on weight the obvious would be portion control to bring calorie intake to less than usage.

    I suspect that above diet is highly unlikely to become anyones staple diet once weight has been lost 

  • Just had a quick look at the obesity journal. I'm no stats person so some stuff I didn't really understand. Bottom line appears to me that study is small, more people dropped out of th 2 day fast than the daily lower intake diet and fewer would continue with the 2 day fast diet than the daily lower intake diet.

    No expert but the 2 day fast diet findings are what I would expect from "fad diets"

  • NHS choices has a nice little article, written recently.

  • For this to work you must surely eat reasonably the other 5 days? Eg you cannot gorge yourself on fried food, chocolate etc for 5 days a week and still expect to lose weight.

    This approach may help me. I (in theory) try to have the odd 'lean' day to try and balance off the weekly calorie total.

    Doing this twice a week will certainly help, combined with a balanced diet the other 5 and a regular exercise programme.
  • KenbroKenbro ✭✭✭

    My in-laws are all doing this diet and are boring me to death about it (nothing worse than the zeal of the newly converted).

    I looked it up on the internet and it seems to have been derived from the reduced calorie diet (ie cutting your calorie intake by 500 calories a day from the recommended amount). The 5:2 diet wasn't originally designed as a weight loss programme, but is now being promoted as one. 

    The one question I do have about the 5:2 diet is why 500/600 calories on a fast day? It seems to have been arbitrarily plucked from the air. Why not 1000 or 1500 calories?


  • RFI Not sure why the 500 calories on fast day but I expect it's to do with what you could reasonably expect someone on a diet to cut down on daily. Basically reduce from 2000 to 1500 cals/day normally so losing 3500 cals/week. On this diet you do that over 2 days and eat the 2000cals/day the rest of the time. 

  • I know quite a few people doing the 5:2 diet now. The thing that makes me laugh is that they keep posting photos of greasy burgers and massive sugary cocktails that they are consuming on their non-fasting days, as though they think that the health benefits of the fasting is going to completely cancel out the rubbish they consume on the non-fast days.


  • KenbroKenbro ✭✭✭

    Since this is a running forum, I don't see why someone trainning 5 days a week would need do be on the 5:2 diet. It seems a bit extreme.  My point is that if you want to be on the diet, would the same benefits be seen with a slightly higher calorie intake.

    From my own point of view, I find that entering a half marathon and increasing the distance of my long run is sufficient to shed a few pounds. 

  • I'm a convert, I've been doing this since the start of September and started my marathon training in October. So far I run up to 8 miles on fast days and it doesn't really affect my running and weightloss so far is 24lbs. This is the only WOE (way of eating) that I manage to stick to even though I plateaued for 4 weeks (christmas time) I didn't give up because it's not a diet.

  • I'm a little disappointed that so many of the comments & views expressed are very narrow minded and are dismissive/rude in tone.

    The science is pretty clear and well documented, all you have to do is look for it, try googling Krista Vardy, her studies on ADF (alternate day fasting) are quite interesting and suggest that intermittent fasting does indeed protect you from the greasy burgers etc on non fast days. (In one study they fed one group "bad" food on their non fast day, this group lost at least as much weight as a group eating "healthy" food and demonstrated the same or better reductions in cholesterol, blood pressure etc)

    The theory from the Horizon program is that our bodies are designed to work well with periods of low food, hunter gathering being somewhat less predictable than visiting your local Sainsbury's!  Periodically lowering food intake appears to offer many health benefits, protecting against heart disease, stroke, high blood pressure, and potentially Alzheimers/dementia.

    I have been on 5:2 for 18 months, run 4 times per week (normally about 24 to 30 miles).  I've always tended to tun fasted to an extent as I mostly go out before breakfast but two of my week-day runs are the following morning after a fast day.  I find no difference to be honest, possibly a few more bad training days when you feel like you have no energy in the  beginning at least, however, I recently did one of my fastest 6 mile morning runs after a fast day.  

    Purely personally I assume that running fasted lie this may stand me in good stead at the end of races as it will teach my body to process fat stores more efficiently.


  • CindersCinders ✭✭✭

    Be interested to hear how Runniff got on given the thread is over a year old.

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