Posted: 30/03/2014 at 19:43
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.