Intermittent Fasting seminar: Part 3

By John Berardi, Ph.D.


Short fasts can accelerate fat loss and make you healthier. But should you do them?  Should your clients?  If so, how?

Intermittent fasting (IF) is the name some people give to the practice of occasionally going for extended periods without eating.

Of course, fasting is nothing new.  Humans have fasted for most of their history, whether it’s during the typical overnight period, during more extended periods of food scarcity, or for religious reasons.

What is new is the clinical research.  Data show that IF, when done properly, might help extend life, regulate blood glucose, control blood lipids, manage body weight, gain (or maintain) lean mass, and more.

Rather than something we’re forced to endure – whether because of food shortage or cultural expectations – IF is becoming something that health and physique-oriented people are seeking out in order to keep their bodies in top shape.

That’s why, in this video series, we’ll teach you all about the hottest trend in the nutrition field.  What it’s all about.  Who it’s for.  And, most importantly, whether you (or your clients) should give it a try.

To learn more about this hot topic, click the play button below.  (Or click here for part 1, part 2, part 4, or part 5).

This video is about 11 minutes long.

To download an audio or a video version of this file, click here.
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In part 2 of this video series we talked about why I got interested in fasting, what the research says about meal frequency, and why we recommend most clients try a one-day fast.

Today, let’s talk about some of the proposed benefits of intermittent fasting and what the research has to say about them.

The benefits of intermittent fasting

As I began exploring the topic, I discovered many online proponents of intermittent fasting.  I even found a host of communities dedicated to sharing intermittent fasting ideas.

The problem?  Most of what I found was evangelism without substance.

Instead of using published or independent research, case studies, or independent trials with a suitable number of test subjects, these evangelists were relying on personal anecdotes, uncontrolled experiments, and dubious hearsay.

That’s why, when I decided to investigate the topic, I began by contacting the top researchers, digging into the scientific literature, and using a more methodological approach.

Here’s what I found to be the benefits of IF.


  • blood lipids (triglycerides and LDL)
  • blood pressure (sympathetic/parasympathetic shift)
  • inflammation (CRP, IL-6, TNF, BDNF, and more)
  • oxidative stress (protein, lipid, and DNA damage)
  • risk of cancer


  • cell turnover and repair (called autophagocytosis)
  • fat burning (fatty acid oxidation later in the fast)
  • growth hormone (later in the fast)
  • metabolic rate (later in the fast via epi/norepi)


  • appetite control (PYY and ghrelin)
  • blood sugar control (increasing insulin sensitivity)
  • CV function (ischemic injury to the heart)
  • chemotherapy (higher doses tolerated more frequently)
  • neurogenesis/plasticity (neurotoxin protection)

That’s a pretty impressive list of benefits.  However, there are still some important questions for future research to answer.

For example, are these benefits unique to intermittent fasting?  Or are they simply a function of eating less (which is what usually happens when fasting)? This is an important distinction.

The other issue is that most of the research has been done in rodents. Forgive me for pointing out the obvious, but rats are not humans. Only when more human research is done will we know the full extent of the benefits.

The most popular fasting programs

I’m kind of an impatient guy when it comes to getting answers. I don’t want to wait a decade or more for the research to be completed. Our clients want to feel better, look awesome, and be healthy now.  So I dug into the most popular intermittent fasting programs, the ones with the most positive feedback.

Here’s a listing of the ones that seem to have the most scientific and user-driven support.

Alternate-day fasting

(36-hour fast/12-hour feed)

With this plan you simply eat every other day.

So on Monday, you’d eat within a 12-hour window, say, 8 AM to 8 PM. Then you’d fast overnight on Monday, and all day/overnight on Tuesday. You’d eat again from 8 AM to 8 PM on Wednesday. And so on.

Alternate day fasters are encouraged to make good eating choices, but they’re allowed to eat what they want on the non-fasting days.

Eat Stop Eat

(24-hour fast, 1 or 2 times per week)

On this plan, you fast for a full 24 hours once or twice per week, eating sensibly (higher protein, minimizing processed foods, etc.) the rest of the week.

It’s flexible: You can choose whichever 24 hours you want.

Want to fast from breakfast to breakfast? That’s cool. Just eat breakfast on Monday, and don’t eat again until breakfast on Tuesday. Want to fast dinner to dinner? That’s cool too. Eat dinner on Wednesday, and don’t eat again until dinner on Thursday.


(16-hour fast/8-hour feed)

This brand of fasting is based on an 8-hour feeding period followed by a 16-hour fast.

However, it also layers a few other food rules on top: The diet should be high in protein, should cycle carbohydrates, should include fasted training, and should use nutrient timing (eating the bulk of your calories during the post-exercise period).

On this plan, you fast from, say, 9 PM on Monday night until 1 PM on Tuesday afternoon. If you’re going to exercise, you’d do so just before 1 PM on Tuesday, with 10 g BCAAs (branched chain amino acids) during training. After training, you eat 2-3 meals before 9 PM, with your biggest meal coming right after exercise. The fast begins again on Tuesday evening until Wednesday at 1 PM, and repeats every day.

Warrior Diet

(20-hour fast/4-hour feed)

On this plan, you would either fast, or eat very small amounts of specifically recommended foods, for the first 20 hours of each day, working out during this period of under eating.

Then, you would eat the majority of your daily intake within a 4-hour over feeding window. After that 4-hour over feeding period, you would repeat the under eating/fasting for the next 20 hours.

Generally, most people place their 4-hour over feeding window at the end of the day, as it’s more convenient for family dinners and after-work training sessions. However, modifications can be made based on individual and scheduling differences.

Meal skipping


Some IF proponents believe we should behave like our evolutionary ancestors did. As humans evolved to get their food and exercise randomly, so should we.

This brand of IF includes eating unprocessed “evolutionary friendly” food (think Paleo-diet type), randomly cycling daily calorie intake, and randomly skipping a breakfast or dinner meal once or twice a week. The rules are very flexible. (It is random, after all.)

Wrap-up and today’s takeaways

That’s it for part 3 of Intermittent Fasting: Science or Fiction?

Here are today’s key points.

  • Fasting’s new popularity is part research support, part online evangelism.
  • The benefits of fasting seem numerous.
  • However, most of the research has been done in rodents.
  • Several popular fasting programs have emerged.
  • If you’re interested in hearing about the ones I test drove, check out part 4.
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