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Leading Low Carb Diet Advocate Adds Intermittent Fasting To His Regime

Published on October 2, 2012,

Peter Attia, the co-founder of, has a new post on his blog, The Eating Academy, which explains how he has started to incorporate intermittent fasting into his low carb diet. It is a follow up to a post last year called “What I actually eat”. He calls his new approach IFIK – Intermittent Fasting, Intermittent Ketosis – and it follows up a number of articles we have seen recently on the possible benefits of intermittent fasting, especially in conjunction with a low carb diet…

Peter Attia courtesy of

For reasons I don’t fully understand the most read post on this blog is one I wrote very quickly and with very little thought.  I wrote it in response to a question I’m asked all the time, “What do youactually eat?”  The post, aptly titled, What I actually eat, has more than twice the traffic of the next three most read posts combined. Go figure.

After a full year in “strict” (i.e., no “cheat” days) nutritional ketosis I wanted to experiment with other eating patterns.  I had been reading about intermittent fasting (IF), and had a few discussions and exchanges with Mark Sisson and Robb Wolf about it.  Though I don’t know Brad Pilon or Martin Berkhan personally, I’d also read a few interesting things they had written.

Why the change?

My curiosity was sufficiently piqued to break a golden rule – if it ain’t broke, don’t fix it.

I was very happy after a year of nutritional ketosis, but I did wonder if I could improve on a few things.  For starters, as my cycling season was about to ramp up, I wondered what it would be like to weigh 75 kg (165 pounds) instead of my steady-state weight of about 78 kg (172 pounds).  I know 3 kg does not sound like a lot, but it can make a huge difference when riding up Mount Palomar, assuming one can preserve power output. I also liked the idea of not spending so much time eating.  As you probably know, I’m pretty obsessive about how I utilize the 168 hours in each week and resent anything that takes me away from my family, my work, and my training.  (This includes sleep, which I wish I could figure out a way to thrive without.)

In the end, I think Mark Sisson finally just egged me on enough to agree to at least give it try – even just one day per week.  And with that, I embarked on the next phase of my nutritional odyssey.

I decided, in early May, to start with the following protocol: one meal per 24 hours, twice a week.  On the other 5 days I consumed my usual keto-diet.  On the two IF days I would just eat one meal at around dinner time.  I still consumed normal amounts of liquids (water, coffee, tea) and supplements (see list below), with one exception – on fasting days I doubled the amount of sodium I supplemented via bouillon from 2 gm per day to 4 gm per day.

Like all nutritional changes, this one took some getting used to.  Because I exercise in the mornings, on fasting days I would get pretty hungry by about 10 or 11 am.  Interestingly, though, by about 2 pm, as my blood glucose levels would be between 60 and 70 gm/dL, I would start to feel completely fine.  In fact, by about 5 or 6 pm, just before eating my meal, I found I wasn’t really hungry.  This may have been due to the fact that my B-OHB levels were usually above 3 mM by this time of day.

Why do I call it “IFIK?”

Not surprisingly, after eating 100 gm of protein and 40 gm of carbohydrates in one sitting, my B-OHB levels would fall, often below 0.5 mM, the practical threshold of nutritional ketosis.  Usually within 24 hours I’d be back to my normal levels, generally between about 1 and 2 mM. But, the cycling in and out of ketosis was new to me, hence the phrase “intermittent fasting, intermittent ketosis,” or “IFIK.”  I guess you can see why I didn’t end up in marketing – “if-ik” doesn’t really have a nice ring to it…

More at: What I actually eat, part II – “IFIK”

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