Intermittent Fasting Primer — 3 Methods Of Intermittent Fasting Explained

Written by Jack

[If you clicked over from an email, I’ll add you to the list to receive the follow up emails. In the meantime this blog post gives you a quick primer on the topic of Intermittent Fasting. Enjoy!…]

Intermittent Fasting has once again become a hot topic in the media. However it’s certainly not new.


It has been popular as a weight loss and health enhancing method off and on for decades.


And obviously it has been around — either intentional fasting or unintentional — for the entirety of human history. Which means humans are well adapted to tolerate and even thrive on periodic breaks for eating.


Now, there are a lot of “methods” recommended for Intermittent Fasting. Yet it all comes down to a very simple definition. Fasting is essentially a stretch of time where you stop eating.


There are a number of benefits to Intermittent Fasting. However the most appreciated for most people is weight loss or weight maintenance.


It’s not a magic weight loss pill though. The research shows that it’s at least as effective as more conventional calorie restriction methods. Yet in the end it comes down to what works for you.


A lot of people like IF because it takes the hassle out of dieting. You don’t need to count calories or macronutrients because the fasting period is a natural limiter that reduces your calories automatically.


It’s not for everyone though. If you obsess over food and you’re constantly hungry you may be better served by other weight loss methods. However you’re still going to need to restrict your calories somehow. There’s no magic bullet unfortunately.


And if you can tolerate periods without eating, there are other interesting health benefits to Intermittent Fasting that I’ll cover in the future.


For now I want to give you a brief overview of what I consider to be the 3 main “categories” of IF that most people gravitate to. Granted there are multiple variations of each of these, but these 3 encapsulate them all fairly well.


The Feeding “Window” Method


This variation of Intermittent Fasting restricts your daily food consumption to a small “window” of time. The most popular application of this is the 16/8 method where you fast for 16 hours and then you’re allowed to eat during an 8 hour window. So for example you may start eating at lunchtime and stop at 8 pm.


Your feeding window can be longer or shorter. However be careful with a window much longer than 9 hours if you want to be sure to create the caloric deficit that will allow you to lose weight.


I think this quote from Nate Miyaki, author of The Half Day Diet sums up the feeding window method perfectly…


“Human beings evolved on a fasting/feeding cycle. We spent the majority of our existence actively tracking, hunting, and gathering our food during the day – often completely fasted or with little ingested food. And then we spent the evening relaxing and feasting on whatever we could catch and gather.”


24 Hour Fast


This one is pretty self explanatory. You simply stop eating for 24 hours. So if you eat supper today at 6:00 pm, you refrain from eating until 6:00 pm tomorrow when you begin eating normally again.


Generally this method is recommended no more than once to twice per week depending on your goals and your body fat percentage.


The 24 hour period is pretty interesting. Obviously it’s very conveniently synchronized with our 24 hour clock. However according Brad Pilon, author of the bestselling book on Intermittent Fasting Eat Stop Eat, it also represents the apex of the hormonal and metabolic benefits associated with fasting.


Yet the nice thing about this method is you are still eating every day. You never go an entire day without food.


Every Other Day


Unlike the 24 Hour Fast, Every Other Day fasting involves an entire day without eating. Basically you skip food for a day, eat for a day, skip for a day, etc…


In my opinion this is the least attractive and most radical form of Intermittent Fasting.


Some variations permit light eating — up to 500 calories — on your fasting days. However I still find it too restrictive to go one day on and then 1 day off. Especially since the scientific evidence seems to support 24 hour fasts once or twice a week to give all the health benefits we’re looking for.


Now like I said… there are countless variations on these “big 3” fasting methods. Each one has it’s own little twist or hook.


The trick is finding one that works for you. The best diet is the one you’ll stick to.


However when it comes to Intermittent Fasting I think it’s best to look at it as a lifestyle rather than a diet. It’s something you can adopt for a lifetime as a tool to improve your health and maintain a healthy weight.


I’ve been incorporating it into my own nutritional approach since 2009. Sometimes I use a Feeding Window approach. Sometimes I use 24 Hour fasts. I’ve even tried 36 hour fasts. And sometimes I don’t fast at all. It depends on how hard I’m training. What my body fat percentage is. And especially on how I feel.


Sometimes I like fasting. Sometimes I can’t bear the thought of it. And that’s the best indication of whether it’s right for you at any given time.


In fact Brad Pilon, the author of Eat Stop Eat, has become a really good friend of mine. And even he recommends abandoning a fast if you are suffering or struggling with it on any given day. You have to listen to your body and do what works and what is sustainable for a lifetime.


The cool thing is it’s easy for you to start experimenting with fasting and finding a method that works for you. You can start tonight. You don’t need any fancy ingredients and it certainly isn’t rocket science.


Although personally I really like knowing what’s happening in my body and what the science says about what I’m doing. That’s why I’m a fan of Brad and Nate. They both do a great job of explaining their take on fasting in a way that’s both thorough and easy to understand.


Bottom Line: Find what’s right for you and what you can stick to.

About the author


My grandfather gave me my start in fitness. He said he just wanted to keep me out of trouble. But he shaped the person and the coach I am today. Sport quickly became the center of my life.

I competed in Laser Class sailing at an international level, as well as skiing, football, hockey and more. My first coaching passion was alpine skiing where I spent 20 years as a coach, instructor and ski school director.

But my greatest passion has always been helping people get fit. I’ve devoted my life to study and intense personal practice. I’m a firm believer in practicing what I preach, and in testing my theories on myself. I’m obsessed with the world of health, fitness and nutrition.

Then a few years back I stumbled — grudgingly — on Crossfit. To be honest I started out as a “hater” who believed the negative hype. But after giving it a try, I became increasingly hooked. I dabbled for a couple years, and then in the Spring of 2016 I really started taking it seriously.

I now consider myself a Crossfit Masters Athlete. I’m immersed in it completely. And I want to share my journey here at Smooth Is Fast.

NCSA-CPT, NCCP 3, CSIA Lvl 4 Course Conductor, CSCF 3,
Biosignature Certified, MAT Lower Body Certified, AKC Certified Coach


    • Hi Randi. Yes, you can definitely drink as much no-calorie liquids as you want. Just be careful of artificial sweeteners since there is pretty good evidence pointing to health harming effects and even disruption of insulin sensitivity.

        • Hey Roy. Technically they are not “no” calories. But they are so low that you can go ahead and enjoy them while fasting as long as you are not adding anything to them.

  • I have read about fasting benefits including 2 or 3 day fasting once a month which apparently has several health benefits.
    I have a high burn rate (79 years old) and weight gain is no issue, my interest is general health benefits and I would be interested to have your take. I was once over weight (4 meals a day and beer!) and went on egg and toast for breakfast, Apple and orange lunch and light salad and meat or fish for dinner. Result, lost 14 pounds in 3 weeks and lost all interest in food after 3 days so diet was no longer a problem (anorexia?!). Then lost 14 pounds in the next 6 months

    • Hi Richard. A lot of folks use Intermittent Fasting purely for the health benefits rather than weight loss. Brad’s book is the best overview of the science relating to the health benefits.

  • Hi! Jack,
    Just to share, fasting is our common practice. At least twice aweek we fast. Our fasting duration usually ftom dawn till dusk…about 12 hours. And once a year we fast for one whole month. ..but what i want to tell you I don’t lose weight with the fasting..maybe intermittent fast would help.

    • Hi Noriah. Weight loss inevitably comes down to creating a caloric deficit. If you do want to lose weight as a result of your fasting, most likely you’ll need to take a look at what and how much you are eating during your “feeding” days.

    • Hi Jo. As with any specific medical condition, you should always run any nutritional changes by your medical practitioner to be sure. There is certainly research suggesting IF can help with Type-2 diabetes and with weight management. I’m not familiar with the research with regards to thyroid function specifically.

  • I have always been led to believe that fasting is not a good thing as far as weight loss is concerned as it makes your metabolism slow down in order for your body to hold on to the fat/energy it has stored. Your article on IF does not seem to support this?

    • Hi Leonard. This is a very popular myth, but there is no scientific research to support it. In fact the research shows that even in fasts up to 72 hours there is no measurable decline in metabolic rate. If you are signed up for the email series, I cover this topic in the second email.

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