Thursday, June 19, 2008

Brief summary of popular approaches to intermittent fasting

Brief summary of the differences that exist between the various forms of intermittent fasting.

If you're unclear about what intermittent fasting is, read this.

* ADF (alternate day fasting, 36/12 hrs fast/feed). See also The Alternate-Day Diet, which is a milder form of ADF. While I don't think The Alternate-Day Diet is an optimal approach for the fitness enthusiast, Johnson's book is surprisingly good and scientifically accurate. Everything about the title ("turn on your skinny gene") screams faddishness, but I was pleasantly surprised after finishing it. Having read all the quoted studies on ADF myself, I could not find any major misrepresentation of the findings apart from a few too optimistic blurbs about fasting and life extension. I can easily recommend this book for it's summary of the ADF findings. And while the nutritional advice might not be cutting edge, it's certainly not bad or misleading either.

* The Warrior Diet (20/4 hrs fast/feed). WD is actually not intermittent fasting in the strictest sense of the word, since the author allows small meals during the fast (vegetables, fruits). The WD book is somewhat of a cult classic, but the book prefers to quote stories and myth instead of scientifical evidence to supports it's (sometimes ridiculous) claims.

* Eat Stop Eat (24 hrs fasting, 1-2x/week). You can read my review of Eat Stop Eat here. This is a book I highly recommend for those interested in fat loss and the physiology of fasting. Eat Stop Eat has a strong following with many success stories.

* The Fast-5 Diet. (19/5 hrs fast/feed). Fast-5 should be available for free on the Fast-5 website. I shouldn't critique a book that is given a away freely. But let's just say I don't consider reading it the greatest investment of time you can make if you have the most basic understanding of how weight loss works.

* Leangains (16/8 hrs fast/feed)

Within each of these systems, there are more or less specific guidelines regarding nutrition, ranging from the very vague (ADF) to the strict (Leangains).

Leangains is specifically tailored to fitness and strength training, and for those wanting to get as lean and strong as possible. In comparison to other intermittent fasting based diets much more emphasis is put on proper pre- and post-workout nutrition. There are also specific guidelines with regards to calorie cycling, macrocomposition and meal timing.


Anonymous said...


Curious if you would share a bit more on macro percentages. A lot of IFers are also doing low-carb, so I'd be curious to hear your thoughts on that, as well.


Michael said...

I think a couple of things in your post should be clarified.

1. The Warrior Diet is not a 24 hour fast. It is a 20/4 hrs fast/feed. That is just suggested. He allows some flexibility in the fast/feed schedule.

So essentially in terms of timing the Warrior Diet is the same as Fast-5.

The WD is also aimed at athletes as well as typical dieters, and the author specifically says so throughout his work.

2. Eat Stop Eat recommends one or two 24 hour fasts a week.

There is only one behavioural change that the author of Eat Stop Eat recommends - fasting once or twice a week. He believes that should free people from focusing on the typical dietary changes you note.

Martin Berkhan said...

Thanks, Michael. I'll modify the post accordingly.

I've read WD, but I couldn't recall any specific guidelines wrt the fasted/feeding phase - one great meal a day is what I recall reading.

For being aimed at athletes, I found it severly lacking in specific nutritional guidelines, making little to no distinction between casual dieters and different types of athletes, despite the often radically different energy/nutritional needs of either group.

Martin Berkhan said...


training days are generally high(er) in carbs while rest days are low(er) carb.

Note 'generally', since this depends on several factors such as priorities, training volume and activity, gender, body fat % and carb tolerance. Some people get good results from 25-30% carbs on 'high' days, going keto on low days, while others go moderate/high carb on training days and never below 100 g carbs on 'low' days.

Basically it depends, and I'm saving the specifics for the book.

Brian C said...


what do you think of increasing the amount of raw foods in the diet? I think along the same lines as benefit from IF, raw, enzyme rich, alkaline pH foods can also further add to increasing the health of the body. I'm even considering eating raw meat!

Michael said...

Hi Martin,

Yes he has some guidelines for both the fasting and the feasting phase.

I'm not sure I would call his under eating phase true fasting since he does allow certain foods depending on your needs (like if you are an athlete - and he prioritizes their intake) and generally discourages water fasting (and encourages juices or raw fruits and veggies during the under eating phase) because of what he sees as the catabolic effect of water fasting only.

However when I was heavily into the WD I went all day just on water and did fine.

You are right he is not nearly as focused or precise as you are when it comes to recommendations for athletes, at least not in his book. He does however have a lot of material on his website, a second book, and I believe even offers counseling.

Of the approaches to IF, the WD however is my least favorite because it basically ends your evening (cram in a days worth of food in 4 hours, even when staggered, makes you useless for anything else) and the window he suggests (although he allows for adjustment), in my opinion is to small.

Michael said...

I have lots of raw foods in my diet, including meat (very little in the way of raw vegetables because of the anti-nutrient problem) and haven't noticed any issues. I think it is a boon to my health.

Anonymous said...

great article. Just one question, for someone who is fairly active during the day (rides a bike for an hour or so in round trip and lifts weights a few times a week) how many calories should I be taking in during my evening meals to assure that I do not enter starvation mode? I am pretty thin as it is, so my metabolism must be pretty good. Thanks...I really do worry about this starvation mode thing.

Martin Berkhan said...


I've tried the WD approach as well and my experience mirrors yours, in the way that I often ended up lying on the couch watching tv the rest of the evening after eating (too stuffed to do anything else). I also spent too much mental energy thinking about food planning what elaborate meals I'd eat. Workouts suffered as well, often resulting in abbreviated workouts because I was too drained to adhere to my usual training routine (which subsequently went from low volume to super low volume during WD). A longer feeding window/shorter fast and being able to include pre-workout nutrition took care of a lot of the problems and I abandanoed WD in favour of the 16/8 approach.

Brian C,

I only think there's benefits in eating more raw foods, but I'm doubtful whether a raw food only diet would have such great benefits that the pros (possible extra health benefits) would outweigh the cons (bland foods, hard to adhere to from a practical point of view in social settings) for someone already eating healthy, nutritious foods on a regular basis.


'starvation mode' is just one of the many persistent myths in the fitness/bodybuidling community. It only becomes a possible factor to consider in the most extreme scenarios: think anorexia, prolonged and severe dieting, 'stage ready' fitness/bodybuilding competitors (4-5% body fat for men, 8-9% for women). Your metabolism certainly wont downregulate within one day. I think you'll be fine, trust me.

Steven Sashen said...

Another IF plan is in the book, "The Alternate Day Diet," which is:

Every other day, eat 20-50% of your usual daily caloric intake (depending on whether you're trying for weight loss or maintenance).

Anonymous said...

Lets not forget about the major CRAVINGS you get on the warrior diet. After your gargantuan meal, you're hungry 12 hours later. It SAYS 20 hours fast, 4 hours feeding, but the author implies that it should be in one big evening meal which contradicts the whole 4 hour deal in the first place. Not enough time to fit in a day's worth of food comfortably for sure. And don't get me started on the performance drops that come with the WD.

The WD started out as a great concept with sound principles (it was actually the first diet to open my eyes to IF), but then the author (ori hofmekler) ended up going to extremes by really pushing the vegan food recommendations, then this whole "food order" mess, eventually the crusade against estrogen (which is really impractical), he's become quite the inflexible alarmist nowadays. Nothing is good or OK, everything is bad. He's starting to remind me of Dr. Mercola. The WD has a cult following nowadays.

He also makes several more outrageous claims in his works, but at this point i may just be ranting...

That being said, i like your approach Martin, it is practical, it is precise, and it gets results (your client's before and after photos speak for themselves, unlike WD followers who are in a constant state of starvation due to the small feeding window. His site doesn't even have before/afters.) He says he complains about being a hard gainer after claiming that anyone can gain muscle eating on the WD, if he looked at the way he was eating then maybe he'd have an idea why he is as thin as a toothpick. Have you listened to his radio show? He's a stubborn stubborn fella.

Ok i'm done raving and insulting now. Great site, keep it up it is amazing.

Boldizar said...


Quick question: will eating fish or coconut oil during the fasting stage interfere with it? I've read some evidence that neither raises blood sugar.

(I drink coconut oil for medical reasons and fish oil because of joint issues from daily jiu-jitsu.)


Amar said...

What do you think of Protein Pulse Feeding, & how does it relate to intermittent fasting?

Martin Berkhan said...

Well, the condensed eating window used in IF setups is one form of protein pulse feeding in that you're getting large amounts of aminos within a short time frame. Whether that has any great benefits compared to more evenly spaced protein feedings is up for speculation.

There are studies on older folks showing better nitrogen balance with pulse feeding, but then again protein metabolism changes with age.

Anonymous said...

Hi Martin

Just curious that do you recommend to do fasted training everyday ? I mean , why do you still use one or two meal pre-workout plan ,if IF is better ?

fr00t said...

You suggest prioritizing solid calories over liquid ones. Is this for any reasons other than satiation?

Anonymous said...

Hey Martin,
I'm trying to shed fat but I really don't want to lose the muscle that I've worked hard to get. Will takeing BCAA's (Scivation Xtend) during the fasting period, effectivley help me retain muscle without negativly impacting my fat loss? I can't see how it could hurt, but really I want to make sure that it will acctually help. Any thoughts would be appreciated. Thanks Martin, keep up the good work.

Terp said...

I'm just wondering how you arrived at 16/8 for the leangains approach, rather than, say, 15/9 or 18/6, for example. I read the Eat Stop Eat approach and they often cite studies that show a lot of the magic happens, insofar as fat burning processes start to increase at an increasing rate after 18 hours and then start to level off (and then diminishing returns thereafter) at 24 hours.

Perhaps 16 hours of fasting was arbitrary, but I suspect otherwise. ;)

So, why is 16 hours pareto optimal and 18 hours is not?

Anonymous said...

@fr00t - your comment caught my eye, not sure if I read that recommendation on this site, but just wanted to throw my two cents out in response to your question...You should always prioritize solid calories over liquid ones. In nature, there are not a whole lot of available liquid calories (milk, fruit juice?), so I am assuming that by liquid calories, you mean some type of protein shake, which is a product, and not actual food. Solid calories = real food (plants and animals - which is what humans were designed to eat for fuel) Sorry if my assumption on the shakes is incorrect

Natacha said...

I am having some problems calculating my macros. Is there any rules depending on fat%, gender, age, activity level etc. to help me find out my approx. needs? Or even better, is the book out already?


Anonymous said...

i have read through the guide and im still not sure if this is something you do every day or a few times per week

Anonymous said...

I just finished reading the updated warrior diet and he's made changes. So now instead of the 20/4 under eating/overeating. He says that since his diet is mainly tailored to athletes that he doesn't recommend 'under eating' for longer than 16-18 hours now. He still does allow basically 4 small meals during the 'under eating' phase which can only contain preferably vegetables in the form of juice, a piece of fruit(small), or a small amount of protein. I use to wake up, eat a plain greek yogurt, deep green salad(farmers market greens) for lunch, an apple pre-wo, and then protein shake of about 50g post-wo to kick off overeating. It's worked for me and I've dropped 8 lbs. in 2 weeks. I'm going to give leangains a try too though because it seems that you can tailor it more towards whatever your currently doing(cutting, maintain, bulking) whereas WD is more for fatloss.

Lee said...

Hi, I'm new to this but very interested although I'm not a true body builder, just someone who enjoys training.

Is there another protein alternative to whey or BCAA supplements? And should I make any adjustments to take into account that I am 52 years old (although think I am 32!)?

Thanks - interesting stuff.

Anonymous said...


Dan Nguyen said...

Thank you Thank you for posting this. This will be my tool to dispel other naysayers about IF'ing and dieting in general.

My name is Martin Berkhan and I work as a nutritional consultant, magazine writer and personal trainer.

Welcome to the Internet's leading resource on intermittent fasting and all things related.

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