By John Berardi, PhD
With Krista Scott-Dixon, PhD and Nate Green
By John Berardi, PhD
Nate GreenKrista Scott-Dixon, PhD
© 2018 Precision Nutrition. All Rights Reserved.
All about intermittent
fasting, in under 10 minutes
A quick, easily-digestible
summary of everything I found
in my six months of experiments
with intermittent fasting.
Fast: When things go
I tried several different full-day
fasting variations. Some worked,
some didn't. Here's what I
tried... and what went wrong.
Why do intermittent
There are many reasons to explore
IF. Here's what piqued my curiosity.
Appendix A: Cheat sheet
with our 3 favorite protocols
Want to try intermittent fasting
yourself? Here we summarize
the three methods we like
best and help you choose
which is best for you.
Get to know the
authors a little better
Find out who's behind the book...
and the crazy experiments.
Hi, My name is John.
And I haven't eaten
in 24 hours.
I tried not eating for 24 hours.
I learned a lot, and so can you.
The Daily Fast:
Back on track
Shorter, more frequent fasts
are often considered more
physique-friendly. I test
whether that's true for me.
review: Comparing the
popular IF programs
IF means different things
to different people. Here, I
summarize and compare the
most popular IF styles.
Appendix B: Intermittent
fasting tips & tricks
A summary of the key Intermittent
Fasting concepts and strategies,
as well as the tips and tricks
we cover in this book.
Science or fiction?
Exploring the benefits
of intermittent fasting
What is IF actually supposed to
do, and does it live up to the hype
of its enthusiastic advocates?
and lessons on self-
A summary of my results, with
pictures, along with a discussion of
why self-experimentation is cool,
and how you can try it yourself.
The Weekly Fast:
My first intermittent
Here's my starter IF protocol
and what happened after
the first few weeks.
Additional health, fitness,
& nutrition resources
After reading about my
experience, you may want to
learn more. These additional
health, fitness, and nutrition
resources can get you started.
All about intermittent
fasting, in under 10
Some experts claim short fasts can improve your
health and help you lose fat faster. So we spent 6
months testing the most popular Intermittent Fasting
(IF) protocols ourselves. Find out what IF is, whether
you should do it, and if so — how.
For years, Dr. John Berardi, co-founder of Precision Nutrition, told his
coaching clients to eat every 3-4 hours. That strategy — when combined
with wise food choices, a smart exercise program, and world-class coaching
— helped nearly 100,000 clients drop nearly 2,000,000 pounds of body fat.
Proponents of IF, on the other hand, reject the idea of eating so often.
Many say they’ve gotten healthier and leaner, faster, by deliberately
skipping meals and sometimes going entire days without eating.
The IF research is intriguing, but young. Some animal and human studies
suggest that IF may have benefits, but we don’t have enough long-term data
to know for sure.
With research lagging behind at a snail's pace, but enough anecdotal
evidence to go from, we decided to do what we love at Precision Nutrition:
test stuff ourselves.
Here’s what Dr. Berardi found, in his own words.
Why experiment with intermittent
I’m a professional dieter. In other words, I’ve done nearly every diet or
nutritional protocol that’s around to test its efficacy.
Intermittent fasting has a small yet strong following and enough research to
pique my curiosity.
I wanted to test it myself to see what kinds of physiological and
psychological changes would come from it.
Also, as a competitive, masters-level track athlete and life-long fitness
enthusiast, I wanted to test a new way to drop fat and get extremely lean,
while staying strong and powerful.
What did you test?
Since there isn’t one definitive intermittent fasting protocol, I decided to test
six different methods over the course of six months.
I kept meticulous notes on everything from scale weight, body-fat
percentage, and blood/hormonal markers, to lifestyle markers like energy
levels, cognitive thought, and pain-in-the-ass factors.
Over the course of six months:
Χ My weight dropped from 190 pounds to 170 pounds.
Χ My body fat dropped from 10% to 4% while maintaining most of my lean
Χ I found two intermittent fasting strategies that I could follow indefinitely
with no problem.
Simply put, I hit the goals I set for myself in a way that was easier and less
time-consuming than “traditional” dieting.
What are the big “takeaways”?
I think there are four main takeaways that readers of this book should come
1 | Trial fasting is a great way to practice managing hunger. This is an
essential skill for anyone who wants to get in shape and stay healthy
2 | More regular fasting isn’t objectively better for losing body fat. While
my IF experiments worked quite well, the intermittent fasting approach
(bigger meals, less frequently) didn’t help me lose fat any faster or
better than a more conventional diet approach (smaller meals, more
frequently) might have.
3 | More regular fasting did make it easier to maintain a lower body fat
percentage. Intermittent fasting isn’t easy. However, I did find that using
this approach made it easier for me to maintain a low body weight and a
very low body fat percentage vs. more conventional diets.
4 | Intermittent fasting can work but it’s not for everyone, nor does it
need to be. In the end, IF is just one approach, among many effective
ones, for improving health, performance, and body composition.
So intermittent fasting is good,
but not necessary?
Intermittent fasting can be helpful for in-shape people (who ideally have a
healthy and sane relationship with food) who want to really get lean without
following conventional bodybuilding diets, or for anyone who needs to learn
the difference between body hunger and mental hunger. (And for the latter, I
only recommend the Trial Fast.)
It’s a helpful tool and one I’ll continue to use periodically. But it’s not the
end-all, be-all of nutrition or fitness.
People have been getting in awesome shape — and staying in awesome
shape — for decades without the use of intermittent fasting.
How are IF and “grazing” similar?
Successful nutrition plans, whether they use smaller, more frequent meals
(grazing) or larger, less frequent meals (fasting) all share a few features.
1 | Controlling energy intake. When we consume less energy (i.e. calories)
than we burn, we lose weight (and, ideally, most of that is body fat).
Whether you take in less energy by eating frequent small meals or
infrequent larger meals is up to you.
2 | Focusing on food quality. Fresh, unprocessed, nutrient-dense food is a
must, regardless of which eating style you adopt.
3 | Regular exercise. Exercise is a critical part of the equation.
Once those three have been taken care of, it’s a matter of personal
preference and lifestyle considerations.
Here’s what the rest
of this book will cover.
Hi, My name is John. And I haven't eaten in
I tried not eating for 24 hours. I learned a lot, and so can you.
Science or fiction? Exploring the benefits of
What is IF actually supposed to do, and does it live up to the hype of its
Why do intermittent fasting?
There are many reasons to explore IF. Here's what piqued my curiosity.
Intermittent fasting review: Comparing the popular
IF means different things to different people. Here, I summarize and compare
the most popular IF styles.
The Weekly Fast: My first intermittent fasting
Here's my starter IF protocol and what happened after the first few weeks.
The Twice-Weekly Fast: When things go horribly
I tried several different full-day fasting variati