In Nutrition, Reference

December 09, 2011

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Nutrition expert Dr. John Berardi serves up an introductory summary of his research into extended fasting.

Nutrition is a really hot topic in the CrossFit community, but with the debate centering on whether to eat Paleo or Zone, I’m afraid another eating style is completely flying under the radar.

Careful, folks. You don’t want to miss this one.

It’s called intermittent fasting (IF), and while it’s certainly not for everyone, there are athletes in the CF community who would absolutely benefit from playing around with it.

Now, before you pick up your Zone or Paleo toys and go home, here’s the interesting thing: you can still Zone or Paleo while experimenting with IF.

I’ll tell you how.

Dr. Berardi will answer nutrition questions live on Dec. 12 from 11 a.m. to noon EST on the CrossFit Journal's Facebook page.

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24 Comments on “My Experiments With Intermittent Fasting ”


wrote …

Hey everyone - after reading this article, I HIGHLY recommend checking out the free "Experiments with Intermittent Fasting" book linked to in the piece.

The book really delves into the topic in a way we simply couldn't in a short journal article. I think it'll help clear up most of your questions. And prevent any misconceptions about what we learned during our experimentation.

Either way - whether you read only the article - or dig into the entire book - I really look forward to hearing your thoughts and feedback.


wrote …

BTW, here's a link to the free book, which over 150,000 people have read already...


wrote …

I have one question, can I drink just water from time to time during fasting periods? or nothing at all? I am planning on doing 1 day a week as a start. thank you for your help guys


wrote …

Drinking water during the fast is a MUST! I also enjoy a cup of coffee and lots of green tea during fasts. Definitely check out the book if you're going to give this a try. Lots of tips there that'll prevent you from doing harm to yourself.


wrote …

I have been IF-ing since June and I love it. I generally will fast dinner to dinner twice a week. (that is, eat an early dinner Monday and not eat again until a later dinner Tuesday providing me just over 24 hours of 0 calories). during my fast, it is a complete 0 calorie intake. lot's of water (also, occasionally sip on a absolutely zero monster for energy).

also, i have (surprisingly) set many PRs during a fast. thanks Dr. Berardi for your effots, I have been following Brad Pilon for most of my research.


wrote …

I like the idea and have done it for religious reasons in the past and noticed no drop in performance during IF. So IF is not new. The old testament talks about it a good deal and a sort of paleo diet as a matter of fact. The Hebrews of the old testement had to be in great shape because in those times they had several battles and it was a much more physical world. Also try reading "Maker's Diet" by Jordan Rubin IF can hone you mentally, spiritually and yes physically.


wrote …

Dr. Berardi, I just finished reading your book. Fascinating stuff and thank you for sharing it for free.
If I were to follow the Leangains protocol and can train only in the evenings (from 7-9 PM), how would I typically structure my 3 meals?


wrote …

@Srini: thanks for the'd simply have one or two small meals before training and then your biggest meal of the day after training. Of course, you'd still fast for 16 hours every day.

So, here's an example:
Meal 1 (small): 1pm
Meal 2 (small): 5pm
Workout: 7-9pm (use BCAA)
Meal 3 (large): 9pm

Make sense?


replied to comment from John Berardi

Yes, Makes sense. Thanks.


wrote …

Thank you so much for sharing. My husband and i were talking about this last week and deciding if this is something we were interested in. Your study has definitely swayed my decision to trying it, thanks!!


wrote …

JB do you think combining a program like crossfit strength bias and fasting once a week would be "too much"? With the goal of fat loss/strength gains in mind, do you think someone would be successful combining the two?


wrote …

Dr. Berardi,
I haven't yet read your book, but I would like your opinion first.
Would you reccomend IF for someone with type I diabetes who is not that physically active?
Have their been any tests yet on what IF would do for someone with type I diabetes?


wrote …

@Britt: I think that could work well as long as you fast on your rest day, and not on a training day. Beyond that, my only suggestion would be to not get too ambitious right out of the gate.

I prefer starting with one single, one-day fast. Then seeing how you feel. If you like it, you try it again in a few weeks. If that goes well, you start trying to do it weekly.

I find that a slow progression like this is superior to trying too much, too soon. Hope that helps.


wrote …

@Christopher: Great question.

IF seems to work wonders for type 2, insulin resistant diabetes. And there's even some research showing that IF can slow type 1 progression in rodents (

So there's some good potential in both types of diabetes.

Here's the only thing - I wouldn't recommend type 1 folks trying this on their own, without some guidance from a trained professional.

The long periods between meals, coupled with the short periods with large meals could really change your daily insulin requirements in big-time ways. So you'd want a good monitoring system in place. And someone to help troubleshoot if things aren't feeling right.

Hope that helps.


wrote …

About your (John Berardis) answer to Srini: Is it necessary to use BCAA in the 7-9pm workout? It´s not exactly fasted training?


wrote …

@joachim: I like to use BCAA during training whether fasted or not. The effects of the BCAA (especially leucine) on performance and recovery are pretty important so I like to use between 10 and 15g during every workout.


Zach Even - Esh wrote …

JB so glad to see you here, I'm gonna re-test IM again.

MANY years ago, maybe 8 yrs ago, I read the warrior diet

I dove in easily, was tired of my bodybuilding days of eating every 3 hrs.... after 2 weeks I was easily on a controlled fast till about 8 at night and then overeating till about midnight.

I was 222-225 when I started and VERY FAST got to 202 and felt GREAT!!!

I had 2 cups of coffee during the day (morning and 4 pm) and had maybe some small trail mix and maybe fruit, usually not though, if anything was eaten through the day it was a large salad

I would do this Monday - Thursday, then, friday - sunday I would eat a normal 3 - 4 meals each day.

Energy was high and everything felt GREAT!

After 6 months, I started missing breakfast and missing lunch and overall eating regular through the day.

I quickly gained back to 220..... I think i'm gonna go for 1 - 2 x week IF and will let you know how it goes..... gonna check your report, brutha!

GREAT seeing you here, my man.

Talk soon, fo sho!



wrote …

@Zach, sounds great. Just go slow, man.

You already learned your lesson. There's no need to go extreme and then wind up having that "f*&k it" moment - you know the one where you bail on the plan, go back to old habits, and ending up gaining all the weight back.

Maybe try the progression detailed in the free book. It'll help you ramp up at the right pace. Good luck!


Zach Even - Esh wrote …

JB - U da man, homie, I'm ON it!!! BIG thnx, psyched to see you sharing your knowledge in the CF Journal!

Thnx, Homie



wrote …

Thanks Doc, for another great journal entry!
Very interesting things to think about, hope to see more from you on here.


wrote …

@Andrew: no problem...thanks to you and everyone else in the CF community for the positive feedback!


wrote …

Hi Dr. Berardi, I've been experimenting with IF for about 3 to 4 weeks now and so far I've seen a bit of change in body fat %.

I have been working out in the morning to take advantage of the sleeping hours as fasting hours, but I wait until about 12pm or 1pm to break the fast since my last meal is around 7pm. I usually consume 10g BCAA before the workout, 10g after, and 10g 2 hours after the workout.

Is this schedule bad? Would it be better to switch to the schedule you posted above (1pm small meal, 5pm small meal, workout 7pm, BCAA, 9pm feast) in order to eat a large meal after the workout?


wrote …

@Michael: it's always hard to tell which schedule will work best for which individuals. That's why self-experimentation is always best.

If it were me, I'd stick with the current schedule for another 4 weeks to see what happens. If good things are happening, I'd stick with it. If not, I'd try switching up the schedule as you've outlined.

Couple of important things, though. If your calories in exceed your calories out, neither plan will help you lose body fat. So you'll need to make sure you're eating the right amount of food. (No calorie-counting required though. Just use body weight as an indicator. If it's going down, you're in the right range. If not, you'll need to drop your food volume a bit).

Also, carb cycling is tremendously useful. Try eating higher carbs/lower fat 2x per week while eating higher fat/lower carbs the other 5 days. That'll make a big difference too.

More on this in the book:


replied to comment from John Berardi

Awesome info, thanks doc :)

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