January 12, 2020

Fasting

My nutritional framework

Nutrition is such a loaded topic—almost a religious or political one—so I’m always looking for ways to explain it that are as free from that baggage as possible.

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I recently read a paper in The New England Journal of Medicine (NEJM): “Effects of Intermittent Fasting on Health, Aging, and Disease.” This review is one of the latest making the case that when you eat (and don’t eat) can have a profound impact on your health. But before looking into this study (we’ll do that next week), we need a framework to put it into context.

Nutrition is such a loaded topic—almost a religious or political one—so I’m always looking for ways to explain it that are as free from that baggage as possible. So far (and this is constantly evolving, so look for this to get better over time) the framework I use to explain eating is based on modifying three parameters or “pulling 3 levers” in various combinations. A few months ago I posted a short video explaining this way to think about nutrition. It comes down to three forms of restriction. Whether it’s what you eat or don’t eat (i.e., dietary restriction or DR), how much you eat (i.e., caloric restriction or CR), or when you eat and don’t eat (i.e., time restriction or TR), virtually all of the dietary schemes you can think of can be distilled into these three elements in some combination (Figure).

Figure. My nutritional framework.

Of the three levers, TR (often, though in my opinion misleadingly, called “intermittent fasting”) possibly contains the simplest dietary prescription: limit your eating to a window of X hours. For example, “Only eat between noon and 8 pm each day.” That’s it. Most people, out of the gate, are already doing something like a 10/14 TRF schedule, even without a modicum of effort (i.e., not eating for 10 hours; eating within a 14-hour window). From here, it’s pretty easy to get to 12/12 (e.g., only eat between 8 am and 8 pm). Then 14/10, and soon enough 16/8. Before you know it, you’ll be amazed by how easy 18/6 feels (e.g., only eat between 1 pm and 7 pm).  

I began experimenting with TRF in earnest in late 2013 and by the end of 2014, I had spent 6 months doing a 22/2 regimen every single day (which works out to basically one meal per day, grazed on over 2 hours). I’ll save the details of that for another time, but the metabolic flexibility I experienced was certainly on par with what I had experienced during my longer journey in nutritional ketosis. For example, though I was only eating one (large) meal per day at dinner, I worked up to doing a 6-hour very tough bike ride on nothing but water in the first half of the day.

Compare this to the thought, planning, and education—for the patient and/or provider—that goes into CR and DR with daily calorie-counting and question(s) around “Is it paleo / keto / vegan / sugar-free?” respectively.

One thing is for certain: if you want to be sick, don’t do any of these things. Eat as much as you want (no CR), of anything you want (no DR), whenever you want (no TR). This is called the “standard American diet.” The further you can get away from this pattern of eating, the better. As I say in the video, always pull one of the levers; often pull two; sometimes pull all three. 

Next week we’ll take a closer look at one of these levers, time restriction, and the recent review on it in the NEJM.

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  1. Awesome article.

    In early 2019, I quit *all* sweet foods (deserts, fruits, juices, colas … the works), and after 2 weeks I cut out all snacking, eating only at mealtime. After 2 – 3 weeks of this, I found my transition to 16/8 TRF was absolutely painless. I believe that the sugar was triggering my appetite.

    Oddly, a month or so later, I started feeling that the act of planning and scheduling 2 meals a day was becoming burdensome, and transitioned to OMAD (one meal a day). This is pretty much the same 22/2 cycle Dr. Attia talks about. Periodically, I may change the feeding time (switching from breakfast to lunch), and go as long as 30 – 32 hours in fasting. On other occasions I switch around from lunch to breakfast; when this happens, the fasting gap drops to 14 or 16 hours, of course.

    In the course of the past year my weight has dropped from 127 kg to 112 kg. My activity level has remained unchanged in this time-frame, so I credit the entire weight loss to TRF. I was (and am) very overweight, so fitter individuals won’t likely experience such a dramatic fall off in weight.

    To summarize:
    DR = no added sugar / high sugar content foods (I still eat carbs – bread, rice potatoes – but not as much as before)
    TRF = predominantly 22/2
    CR = nothing planned, but I have experienced a marked down-regulation of my appetite.

    As Dr Attia likes to point out, [n=1], so YMMV 🙂

  2. At the risk of being pedantic, I wonder if there is a fourth dimension around the mindset behind eating that enables better adherence to the main three levers. Maybe “how you eat”? For instance, being in a mindful, state so that your are getting more “bang for the buck” out of every bite. I’ve noticed that my mindset when approaching my meals has a high correlation with how well I adhere to each of the levers:

    1) CR – Eat less because I experience eat bite as more fulfilling and notice when I experience diminishing returns of pleasure for the next bit. This typically leads to me not going for seconds and being the garbage disposal that I’m naturally inclined to be
    2) TRF – More apt to gut through that last couple hours of my fasting window as I’m mindful of the benefits I’m forgoing if I do. Also related to lever 1, I genuine see the first meal as a reward for self-discipline and forgoing instant gratification
    3) What I eat – Have a more intuitive sense for making adjustments based on recent behaviors. For instance, ate processed food the night before with some carbs, so I’ll eat a more keto-friendly meal tonight.

    • @joey-m, I like this mindset. I am starting to use this myself.

      I only recently attempted a fast and went 41 hours very easily… even while having to prepare meals for my kids and my wife was slow-cooking some delicious food in a crockpot nearly the whole day. I could have gone 48 hours as well, but for some reason I felt like I should eat when I did because of my schedule.

      I also agree with Peter’s sentiment that intermittent fasting is pretty simple to both understand and follow. This makes it infinitely more easy to adhere to.

  3. You recently did a followup on this on Instagram, where you said that you’re currently “going all in on DR,” with no CR or TR, restricting only “all carbohydrates with the exception of vegetables and a couple of berries”, avocados, and nuts. You say you’re pulling “super-hard on this lever,” but you don’t say you’re on keto. Is that because you’re eating enough of even these low-carb foods that you still stay out of ketosis?

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