IF 201: A Look at Four Popular Intermittent Fasting Protocols

A Breakdown of the Most Popular IF Variations

Today, we’re going to get in depth about the most popular Intermittent Fasting protocols. Before we begin, in the last article about intermittent fasting, I gave you a brief primer on the practice.  In that article, we covered a definition of IF, as well as some of the general aspects of practice that are consistent among various types of IF.

To briefly summarize, let’s look at what IF is – essentially, abstaining from food for a predetermined period of time, ranging from as little as 16 hours to as long as 36 hours (sometimes longer, just not generally in practices in the fitness industry).

The benefits of IF vary from hormonal management to caloric reduction and decreased hunger, and which benefits are prioritized will be dependent on which “type” of IF you use.

In this article, I’ll give you a complete analysis of the most popular intermittent fasting styles currently discussed in the fitness world, benefits and drawbacks, as well as my own personal experience.

Given that the most obvious difference between each of these methods is the length of the fasting period, that is how I’ve organized them; below, you will find each listed from longest fast to shortest.

Got it?

Great.  Let’s get going.

And the Top Four Intermittent Fasting Protocols Are….


SUMMARY: The feast/fast model, which I’ve been using consistently for close to 8 years, is my own small contribution to the community, and my very own addition to the world of intermittent fasting protocols; although its inception had nothing to do with the benefits of fasting.

Some time around 2004, I noticed that while I was getting a ton of benefit from cheat days in terms of fat loss and mental reprieve, the “digestive aftermath” wasn’t pleasant.  If I cheated on a Sunday, I would pay for it Monday in terms of intestinal distress.  Not only would I be in the bathroom more than I wanted, but my stomach would hurt and eating was a huge chore.

I had come from the old school bodybuilding mentality of, “if you fall off the wagon, get right back on, immediately. The old way of thinking essentially stated that even if you had a cheat meal/cheat day, if you didn’t go back to your regularly scheduled meals, you’d do more harm than good.  In my case, this meant a bowl of oatmeal and several eggs first thing in the morning.  After a night of eating pasta, ice cream, brownies and steak (yes, all at once), this last thing I wanted to do first thing in the morning was eat.

After some time, I discarded the bodybuilding “rules” and started pushing my first meal of the day back by a few hours…then a few more.  Eventually, I stopped eating altogether.

And my results got even better.


BENEFITS: When I started looking into fasting (mainly to justify my not-eating), I came across a few different reasons why the feast/fast worked so well; some had to do with fasting, obviously, but there is some stuff that has to do specifically with the cheat day as well.

Like any style of fasting, removing food for an extended period of time can lead to fat loss, because it often leads to lower caloric intake. Pretty simple.

However, the reason this works well is because it’s coming on the heels of a cheat day.  Again, I’ve written about this before, so I’ll be brief.

The abridged version: when you’re dieting, leptin levels drop, which slows down fat loss. When you overfeed (cheat), leptin levels get bumped back up, increasing rate of fat loss. Scheduling a period of fasting subsequent to a cheat day, therefore, does two things:

  1. Prevents any fat gain from the caloric spillover of eating, oh, I dunno, 14,000 calories worth of ice cream by creating an immediate deficit.
  2. Elevated leptin levels from the cheat prevent stagnated fat loss, allowing the hormonal benefit from the fast to proceed uninterrupted.

More than anything, this is just a practical approach, and was created to alleviate discomfort. I started using this method before looking into science of any kind; it just happened to work.

DRAWBACKS:  There are a few here.

There first is that in order for this to be applicable, you have to have a cheat day—can’t exactly do a feast/fast without the feast.  Some people don’t like cheat days (I know, weird, right?). I made a pretty compelling argument for the inclusion of cheat days, but if you don’t like them, you don’t have to use them.

From there, the main drawback is that you’re really looking at a 32-36-hour fasting period.  If your last meal on your cheat day is before bed (assume 10PM) on Sunday, and you don’t eat at all on Monday, your first meal is breakfast Tuesday morning.  For a number of people, this has proved to be a pretty difficult thing to do.

I believe that with some practice just about anyone can abstain from food for an extended period of time with little discomfort, but for a lot of people, the idea of going without food for a day and a half is a bleak proposition.

For these people, I let them keep the training wheels on for a few weeks: I’ll allow people a small dinner on Monday night, to take the edge off of the hunger.  This won’t detract from any of the hormonal stuff, it just adds in some calories where there weren’t any before.

HOW (AND WHEN) I USE FEAST/FAST: I am a big fan of cheat days, so I use this method nearly every week.  I like my cheat days to coincide with Sundays—because, call me crazy, but I like wings and nachos when I watch football.

This means that Mondays, I don’t eat AT ALL. I think this is a good fit for most people – Monday happens to be the busiest day for most people (myself included), and so if ever there was a time where it helped to free up a few hours by not eating, this is it.  Also, since people are busier, they tend not to realize they’re hungry.  Overall, this is a fantastic combo that works very well for most people.

OVERALL IMPRESSIONS:  Again, this is my method, so I can’t really be objective here, but it’s worked well for me in the past, and all of my clients who have tried it.

24-Hour Fast (aka Eat-Stop-Eat)

SUMMARY:  A 24-hour fasting period is essentially what it sounds like: if your last meal is at 8pm on Monday, then you simply do not eat again (at all) until Tuesday at 8pm.  This can be done 1-3 times per week, with 2 being the most common iteration.

It’s impossible to talk about 24-Hour fasts without talking about Brad Pilon and his book Eat-Stop-Eat, which is the definitive book on this style of fasting.  ESE has been around for several years, but Brad continues to publish updated versions with more science whenever he can.  It’s a well-researched book that also happens to be well-written.

Brad was one of the first people talking about IF, and his approach to it is one of “lifestyle, not diet.”  Brad discussed much of this in an interview I did with him, which you can read here.

BENEFITS: The 24-hour fast works well for a number of reasons. The first of these is that it is easily adaptable to any lifestyle, and it’s very hard to screw up.  The only rule is “don’t eat” for 24 hours.  As mentioned above, this is much easier than a 36 hour fast, especially for those new to it.

Secondly, like most methods of fasting, the abstinence from caloric intake for large periods of time is going to be a large part of the reason for success.

For example, if you generally eat 2,000 calories every day, that’s 14,000 calories over the course of a week.

If you remove two of those days, you’re eating 4,000 calories less.  Without any other changes to your lifestyle, you’d be on pace for over a pound of fat per week. Even if you “compensate” and eat a little more on the days you’re not fasting, you are still going to wind up with a fairly substantial caloric deficit.  Add in some exercise, and it’s not hard to see consistent weight loss.

Caloric manipulation aside, this style of fasting works incredibly well because of the effect that fasting has on your overall hormonal environment.

More specifically, when we talk about fasting, we’re really going to talk about two hormones: insulin and growth hormone.

With regard to insulin, it seems that the less often you eat, the less often you raise insulin levels.  This is not surprising, obviously.  It’s even less surprising that this would lead to fat loss, since we know that chronically elevated insulin levels make it very difficult to lose fat.

Therefore, if you’re eating less often, you’re going to have less insulin issues—even if you’re eating the same foods in the same amounts.  (This, by way, is a pretty strong argument against the popular frequent feeding method of 5-6 meals per day).  However, while fasting and infrequent feeding helps to control insulin and keep it low, that’s not enough to stimulate fat loss…unless growth hormone is present.

That is, if insulin AND growth hormone are both low, there isn’t a huge effect on fat loss.  And so, while insulin management is important, growth hormone management is even more important.

Which brings us to the very predictable point: The effect of fasting on growth hormone is incredibly important.

Your body releases GH pretty consistently, but researched has shown increased secretion of growth hormone in three specific instances:

  1. During/immediately after sleep
  2. After exercise (as little as 10 minutes)
  3. During and immediately after a fast

Looking at these three things—all of which are thoroughly discussed in Pilon’s Eat-Stop-Eat—it’s not hard to come up with a “best of all worlds” scenario.

If you produce a lot of GH while sleeping, and you product it while fasting, then the obvious way to combine these is to continue fasting after you wake, allowing for prolonged GH secretion; from there, exercise will allow for increased production in addition to your prolonged secretion.

Overall, this maximizes both the presence of GH and its effect; and in addition, the elevated GH in combination with the low insulin is a deadly one-two punch to your body fat.

Finally one of the main benefits of both this style of fasting and the book itself is the incredible flexibility of the program and the ease with which you can adapt it to your lifestyle—you can fast any day you like, and can move it around at will to suit your social life, which is important.

DRAWBACKS: There aren’t many here.  The main problem that clients of mine seem have here is that 24 hours seems like a long time to go without food; however, this is not unique to 24-hour fasting.

That said, there are some people who seem to have genuine problems with abstaining from food for significant length of time—in particular, people with low blood sugar seem to have an issue.  If you fall into this category, you may want to tread lightly.

The only other real problem here would be for people who don’t want to miss out on post-workout nutrition but find the need to train on fast days.  This can be alleviated by either moving your workout to the end of the fasting period, or simply scheduling your off days and fast days to coincide.

HOW (AND WHEN) I USE 24-HOUR FASTS: This is a style of fasting I tend to use when I get very busy and have to train in the evenings.

Also, I use this pretty much any day when I have to go out to a large social dinner and am not going to be watching my diet.  For example, if I am going out on a Friday night, I might make my least meal Thursday at 8pm.  Then, at dinner Friday, I’ll get to eat a lot of food, perhaps enjoy dessert, and be fine, even if I go out after and eat again.

OVERALL IMPRESSION: While this type of fasting is suitable for more than “damage control,” it works well for me in an occasional fashion. However, for many of my coaching clients, this is a sort of “every other day” approach that works well with them.

20-Hour Fast (aka Warrior Diet)

SUMMARY:  The Warrior Diet was the first type of structured fasting that I tried.  I initially read about it in an interview with the author, Ori Hofmekler on T-Nation back in 1999. I tried the diet for the first time in 2002.

Simply, the diet is, in theory, a 20-hour fast followed by a 4-hour feeding period; as the name implies this is inspired by the nutritional habits of the warriors of antiquity, who certainly weren’t in the habit of eating six meals per day.

Instead, warriors in cultures ranging from Roman centurions to the Spartan elite subsisted on one to two meals: a large meal in the evening and (sometimes) a small meal in the morning; according to the author, that is.

The diet itself is modeled after this type of eating schedule; however, it’s worth noting that this is often criticized for not being “true” IF.

That is, in most cases, while having a small breakfast and a large dinner will probably work for weight loss, there may only be 8-10 hours between them…which, some people posit, isn’t long enough to get the benefits of fasting.

Moreover, during the fasting part of the day, the diet allows for mild consumption—you’d be allowed to eat a few servings of raw fruits and vegetables, and a few servings of protein (protein shakes included) if needed/wanted. These are kept quite small. Having said that, some fasting purists understandably maintain that Warrior Dieting, should you choose to exercise these options, is not fasting.

In practice, however, most people skip the small meal and simply have one large meal at the end of the day.

BENEFITS:  Much like a 24-hour fast, a 20-hour fast allows you to reap the hormonal benefit of increased growth hormone.  And, like all fasting, generally will result in fewer calories being consumed.

The benefit that is unique to this type of fasting is that you’re generally eating one large meal and, therefore, the make up of such a meal isn’t as important as you might think; as long as you get adequate protein, you can eat “junkier” foods and still do well.

Moreover, having only one meal makes life pretty simple, and less thinking means less screw-ups.

DRAWBACKS:  On the flip side of that coin, once again we’re running into the issue of hunger; and again, this isn’t unique to Warrior Dieting.

The main drawback in my experience comes from the meal itself—trying to get all of your calories in a single meal means that meal is, by necessity, quite large; so large, in fact, that eating it often leads to discomfort.  This is why many people turn to less wholesome foods: getting in 2000 calories of chicken, veggies and rice isn’t nearly as easy as getting it in chicken wings and French fries.

OVERALL IMPRESSION: A generally good dietary practice, and certainly easy to follow.

One criticism often made is that the points are made via story and anecdote, with very little in the way of scientific evidence to support the arguments. While some IF authorities dismiss the Warrior Diet based on that, I feel it should be respectfully acknowledged, given that it was the book that got people talking several years back.

Moreover, while the book does lack in science, it’s truly an enjoyable read. The author has a very engaging writing style and adding to the fun is the fact that he was an editor for Penthouse.

Plus, if that wasn’t cool enough, as mentioned earlier, this diet is based on the eating habits of awesome warriors–including Aragorn, son of Arathorn, Heir to the Throne of Gondor, of the Lord of the Rings fame.


16/8 Fasting (aka LeanGains)

SUMMARY: Popularized by Martin Berkhan, Leangains or 16/8 is a style of IF where the fasting period is 16 hours, and the feeding window is shortened to 8 hours; during this time, users may eat as few meals as they like, with the most frequent iteration being three meals.

Designed specifically with training in mind, and mean to to be used for such, the 16/8 method has specific post-workout suggestions and recommendations, and, in nearly all ways, is the most sophisticated form of intermittent fasting.

Berkhan is great in terms of showing his research, his clients get excellent results, and, if the rumors are true, he is one of the few people aside from myself who liked Final Fantasy 6 better than the inferior but infinitely more popular FF7.

BENEFITS: In addition to having all of the benefits inherent in other types of fasting, the 16/8 methods is a stand out because it offers an advanced level of hormonal management.

While something like 24-Hour fasting or Alternate Day Fasting will give you these benefits, these methods are not for daily practice, whereas 16/8 is.  This means that you are going to have a daily increase in GH, which leads to greater effects.

Moreover, daily practice (obviously) means that you’re eating the same way every day; this means that you don’t experience ups and downs in hunger, as with some other forms of fasting.  (Put another way, some people experience difficulty with fasting for 24-36 hours because they do it infrequently; not an issue with daily practice).

Going from there, there is also the benefit of hunger management. A number of studies have recently shown that larger, infrequent meals are better for satiety than small, frequent meals—so you’ll be fuller, longer.

DRAWBACKS: There are very few drawbacks to this style of IF, and these mainly come from scheduling. You see, from everything I’ve seen and read, the LG protocol is MOST effective if the workout is performed in a fasted state, and the meal that breaks the fast is immediately post workouts.

For some, execution can become a little impractical; for most people, adhering to that simple rule forces them to shift the feeding window to inconvenient times.

I find that most of my clients are able to workout either in the morning (roughly 6am, before work) or in the evening (6pm), after work.

Given that we want to have a 16-hour fasting window that ends with the PWO meal and begins an 8-hour feeding window, you can see how either of those times present some issues. For example, let’s look at 6am. In order for this to work as your first meal, your last meal is going to be at 4pm (allowing you to fast for 16 hours for your next feeding window).

Right off the bat, I see three (theoretical) problems arising here.

  • This first is that having your last meal at 4pm can present some social issues, at least if you ever want to have dinner with your friends or family. (The exception is Sunday “dinner” in any Italian household, which for some reason inexplicably begins around noon and ends just after sundown.)
  • The second is that your feeding window is going to coincide almost minute for minute with your workday, making it difficult to eat your meals, let alone enjoy them.
  • The third problem is that a good number of your fasting hours are after your feeding hours have ended. I’ve said in other articles that in my experience, it’s often very clients who try to have  ‘cutoff’ time for eating aren’t successful.

That said, if you’re looking to try 16/8 and can only work out in the AM, it’s certainly doable, just be aware of this going in.  And, of course, this “problem” is really only applicable to certain people.

Like any other style of eating, make it work for you—within the rules of the system.

HOW (AND WHEN) I USE 16/8: This style of fasting fits very well with my life, because I work from home.

For me, it’s very easy to plan my meals and workouts around one another, and making last minute changes isn’t a problem.

Most days of the week—usually Wednesday through Saturday—I do some form of 16/8.  I like to workout anywhere between 12 and 2pm, so I just judge my last meal the night before based on when I’m going to train the next day.  Sometimes I’ll wind up with an 18 hour fast instead of 16, but, again, this is really no big deal.

OVERALL IMPRESSION: Of all intermittent fasting protocols, 16/8 is probably the most sophisticated, in terms of both intention and execution. While most fasting is effective mainly because it prevents you from eating, the Lean Gains style is really about making your hormones your bitch. Which is awesome.

This style of IF is best for serious folks and those who are already lean; and, again, this is the ONLY style of IF that was designed specifically with fitness-oriented people in mind, and therefore yields exceptional results for folks who train consistently.

It’s worth mentioning that Berkhan is one of the guys most responsible for the “IF movement,” and spent years arguing against ideas that many fitness pros (myself included) thought were “fact.”

All in all, he (along with Pilon) is a big part of the reason guys who weren’t talking about IF last year are talking about it this year. So, while he didn’t invent IF, I feel I should give him a wi-five.


That’s about it!  You now have a very firm overview of the most popular types of Intermittent Fasting, as well as the benefits and drawbacks of each.  If you’re looking to try an IF plan, simply choose from those above, and read up on them.

While all of them are effective, the most important thing is to choose the one that fits in best with your lifestyle, and give yourself the greatest advantage.

One final point: specifically because IF is not a diet, it lends itself well to nearly anything that is a diet. That means that you can practice intermittent fasting regardless of your nutritional restrictions or preferences—it doesn’t matter if you’re a low carb-er, a Paleo dieter, lactose free, vegan, or anything in between; you can simply apply the IF system of your choice to your current diet.

This is because intermittent fasting is a way of eating, a nutritional lifestyle that will allow you to reach your goals in an efficient and convenient manner, and then hold onto your physique one you achieve them.

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Comments (2)

Another great article on Fasting. Thank you.

The Feast Fast is what I have had great success with my clients now for the past 5/6 years. I first learnt this principle from John Romaniello. Works great.

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