Everything you need to know about intermittent fasting
"Sooner or later, everything old is new again"
—Stephen King
Intermittent fasting has quickly become one of the hottest new eating trends around.
From weight loss, to improving health, and even helping people build better relationships with food, intermittent fasting appears to have all bases covered.
Yay.
But is this amazing new way of eating actually new, or has it simply been re-discovered?
Intermittent fasting is not new. In fact, it's actually one of the oldest ancient secrets of health in existence.
Early philosophers, such as Plato and Hippocrates, long ago talked about abstaining from food to improve health.
“Our food should be our medicine, and our medicine should be our food”
—Hippocrates
Fasting has also long held a place in religious ceremonies, such as Ramadan and Yom Kippur.
In fact one study even says that "although religious fasting is often a time of great spiritual growth, it can also be a time of great improvement to one's physical health".
As it seems there is quite a lot of support, and praise for the intermittent fasting diet.
In the rest of this article I'm going to take you on a start to finish journey through the ancient and fascinating world of intermittent fasting; including the pros and cons.
Settle in, get comfortable, and enjoy the ride.
What is intermittent fasting?
- Fasting = voluntary withdrawal of food for a planned period of time.
Also fyi, the cool kids simply refer to intermittent fasting as "IF". During IF you're choosing not to eat for a period of time. Anytime you aren't eating you're essentially fasting.
Is fasting different than starving?
Yes.
Fasting is voluntary.
Starving (or starvation) is an involuntary loss of food.
Well, if I don't eat won't I go into starvation mode anyway...and die?
Negative ghost rider.
For the majority of people fasting is actually quite safe.
A lot of people say they've gotten healthier, leaner, and increased energy levels by deliberating skipping meals.
If you're still worried about a fasting-induced-death check out this fascinating study of a guy who fasted for over one year, lost close to 300 pounds, and also didn't die.
Wait, who should avoid fasting then?
Disclaimer: Don't mistake this for medical advice. It's not. If you have any concerns about fasting, consult with your physician first.
Cool, now that's out of the way.
People who shouldn't fast include:
- If you're pregnant
- Already underweight
- Have low blood sugar
- Trying to gain weight/bulk up
- Have a history of disordered eating
I'm intrigued. What are the benefits of intermittent fasting though?
The benefits of the intermittent fasting diet are many. Below is a short list of the amazing benefits of IF:
- Simplifies eating
- Promotes weight loss
- Saves time and money
- Helps build healthy habits
- Increases energy throughout the day
- May eliminate need for insulin in diabetics
- Teaches you how to manage short-term hunger
—
“I’ve been doing IF on and off now for about 5 months.
I’m not super strict with it so the weight is coming off a little more slowly but something it’s doing is teaching me better habits , like not eating anything when you get home at night.
Snacking late night has always been a huge vice of mine and I can now say that I have it completely under control.”
Does intermittent fasting work for weight loss?
Yes, but with one caveat.
If you're eating far more food than your body needs, you'll store that food as body fat and gain weight.
With that being said, IF is a great way to help control calories, without doing anything crazy like calorie counting or weighing and measuring every ounce of food like a mad scientist in a lab.
See, fat is simply stored fuel which your body can use for energy during periods of no food. Hmmm, "periods of no food"--sounds a lot like fasting, right?
Anyway, the body evolved to store fat as a survival mechanism (aka, keep you alive when food is scarce).
Below is the non-science version of how this works, and how IF can certainly help you lose weight.
When you eat food your body breaks it down and converts it into usable "energy units". Well, those energy units provide fuel for short term activity. However, if you take in more food than you need what do you think your body does with it?
The body breaks down that food and stores it as energy for future use, of course.
And, how does the body store energy for future use?
By creating body fat.
However, if you stop eating food for a while (ie...fasting) you've essentially cut off that supply of energy (food) which the body uses for fuel.
But, don't worry. The body doesn't panic here.
No, instead the body is calm and relaxed. It's been storing all that extra energy (body fat) for times like this when there is no food coming in.
And this is why IF is great for weight loss. When you fast you're cutting off the fuel source that powers your body; food.
By doing this you convince your body to start breaking down stored body fat to be used as energy. This is good for weight loss.
From a physiological stand point, the whole aforementioned process is actually quite complicated. However, I like my simplified version better because well, it's way easier to understand than any physiology textbook.
So yes, IF can help with weight loss.
Also, if you're a science nerd like I am and need more intermittent fasting/energy metabolism science in your life, then checkout the two studies below:
1. Intermittent fasting and human metabolic health
2. Energy metabolism, fuel selection, and body weight regulation
This is really great info, but what different styles of fasting are there?
Variety is the spice of life. I heard Tony Horton, creator of P90X, say that once and it's always stuck with me. So, you would think that because intermittent fasting involves voluntarily giving up food, that there wouldn't be a lot of variety.
Well...you would be wrong (I mean not YOU personally, but the Royal YOU).
There are actually quite a lot of different styles of intermittent fasting. Some are very practical, while others are a bit out there. We'll take a look at all the different varieties in a second, but just know that THE BIG DIFFERENCE is the length of the fast. The rest of the details are up for grabs.
—
The many different types of intermittent fasting:
16 8 Intermittent fasting →
• Also known as "Leangains"
• Popularized by Martin Berkhan.
• Fast for 16 hours per day, and eat within an 8 hour window
For example:
Eat dinner at 6pm. Then you wouldn't eat breakfast until 10am the next day.
The 16 8 intermittent fasting method is one of the simplest to use in everyday life. I recommend some variation of this style to my clients.
Early Time Restricted Feeding (eTRF) →
• Eat in-sync with the circadian rhythm of the body.
• Eat all your food early in the day, within a 6-12 hour window.
• In the eTRF style of fasting lunch is your last meal.
The idea is that eating later in the day will mess with the natural rhythm of your body. This type of fasting is quite hard for most people to use successfully.
The Warrior Diet →
• Popularized by Ori Hofmekler in the mid 2000's.
• Fast for 20 hours per day/ eat within a 4 hour window.
To be honest, his book titled "The Warrior Diet" was the first book I ever read on intermittent fasting, back in 2008.
The idea is that ancient warriors only at one or two big meals per day, and they were the most feared people on the planet.
I've tried using a Warrior style intermittent fasting approach, but I found it to be quite un-enjoyable to use in my own life.
However, this style of intermittent fasting could work really well for people who chronically eat only 1 or 2 big meals each day, and want to keep eating ultra simple.
Eat Stop Eat →
• Popularized by Brad Pilon.
• Fast for 24 hours, once or twice per week.
• Eat normally the rest of the week
Best practice here is to break up the fasting days, so they aren't back to back.
Eat Stop Eat is the another type of fasting I like to recommend to my clients.
I've found that it fits very well into most people's busy schedules, it's ultra simple, it's only 1 day per week, and it can be done consistently over the long run.
Alternate Day Fasting (ADF) →
• Alternate one day of eating with one day of fasting.
This type of fasting is quite popular in scientific research. However, I personally don't know anyone who has successfully used this style of fasting in real life. Probably because not eating for half of each week is miserable.
You're welcome to try ADF, but I personally don't see it's utility.
5:2 Fast Diet→
• Popularized by Dr. Michael Mosley in 2012.
• Severely restrict calories for 2 days each week.
• Eat normally on the other 5 days
On the calorie restriction days men should eat about 600 calories total, and women should eat about 500 calories total.
The 5:2 fast diet intermittent fasting style is final type of intermittent fasting I like to recommend.
It's simple, it's sustainable, it's enjoyable, and fits well into folks busy schedules.
Extended fasts, 24+ hours →
• Fast for 24+ hours.
There is actually a growing body of science which supports fasts lasting longer than 24 hours.
The current school of thought is that some of the health benefits may not kick in until about that 24 hour mark.
It's not uncommon to hear of people fasting for 36-48 hours, even up to 3 or 4 days.
While the health benefits of longer fasts are worth exploring, I suggest that you save these longer fasts until you're comfortable fasting for 16+ hours at a time.
The 14.37 Fast →
• Fast for precisely 14.37 hours each day.
Okay, I just made this one up.
What I'm saying here is that the aforementioned fasting styles are good places to start; however, there is nothing wrong with coming up with an intermittent fasting approach that works best for you.
For example: The 12/12 approach (12 hour fast/12 hour eating window), and the 14/10 approach (14 hour fast/10 hour eating window).
Remember, all styles of intermittent fasting simply manipulate the length of the fast.
There is nothing magic about the popularized versions of fasting.
It's infinitely more important to choose a style of fasting that works for your life style and preferences.
How do I manage my hunger during a fast?
First of all, take a deep breath. Listen to the soothing sounds of my voice.
Feeling hungry is not a stage-5 emergency. It's actually not an emergency at all.Feeling hungry is a lot like an ocean wave. First it builds up offshore, then it steadily rolls inward, until it finally breaks up on the rocks or shoreline.
Feeling hungry is the same way.
First you feel hungry, then than feeling eventually breaks up and vanishes.
Ok, now that you know feeling hungry isn't an emergency, here's a hunger emergency fall back plan you can use when you're, well...hungry (just in case):
• Step 1 →
Drink a big glass of water, or a small amount of caffeine.
Hunger and thirst send the same signals to your brain. Sometimes you may just be thirsty, not hungry. If you're still feeling ravenous after you drink the water, take in a small of caffeine in the form of coffee or tea.
Caffeine is an appetite suppressant and will help manage feelings of hunger until it passes all together.
• Step 2 →
Do something to distract your mind
Do any activity which gets you moving.
This could be as simple as going for quick walk, or blasting your favorite music and dancing like a manic to it.
My go-to hunger eliminator dance song is "What Is Love" by Haddaway (Night At The Roxbury style).
What's yours?
So, what can I drink during a fast?
Anything without calories is fine. The key words here being "without" "calories".
Great choices include:
- Water
- Coffee
- Sparkling water
- Tea (herbal, green, black...etc)
Personally I drink sparkling water during my fasts. I like the fizz and the carbonation in the water seems to help curb any hunger pangs I may be experiencing.
Now you may be wondering about diet sodas. Can you drink them during a fast?
Technically...yes, but I don't recommend it.
If you're just chasing the fizz and carbonation (like me) you're better off sticking to sparkling water. Save the sodas as a reward for completing your fast.
Can I exercise during a fast?
This question is being hotly debated right now.
Recent literature shows there may be extra benefit from exercising in a fasted state—both for losing fat, and increasing lean muscle mass.
When I was a younger lad serving as an Army Ranger we would often exercise daily; starting at 6 or 6:30 am.
Well, I was almost always starting these morning exercise sessions in at least a 10 hour fasted state.
Can you guess what happened?
I actually gained about 5-7 pounds of muscle over a few years of doing this. I didn't lose any weight. I didn't wither away and die, and I was actually able to put on a lot of functional muscle mass.
I also know a lot of high level fitness coaches who have successfully used fasted exercise with 100's of their clients. They have amazing weight loss testimonials which help validate that fasted exercise works very well.
With all that being said fasted exercise is potentially powerful weapon to have in your arsenal.
My suggestion is to try it for yourself and observe your own results.
What type of fasted exercise should you perform?
High intensity exercise, lasting between 5-15 minutes, followed by a period of low intensity exercise, lasting 20-40 minutes seems to be the sweet spot.
This could be as simple as a few rounds of sprints, followed by a 30 minute brisk walk.
However, it's important to reiterate that just because fasted exercise is gaining popularity, is not a magic bullet or an excuse for you to eat irresponsibility.
If weight loss is your goal, you still need to control calories.
This study illustrates the point that when calories are accounted for, fasted and non-fasted exercise had similar effects on weight loss.
How do I come out of a fast?
Slowly.
A general rule of thumb is "the longer the fast, the slower you should come out of it."
This may seem counter intuitive, but it's not.
One way I've found that works well is to drink a protein shake as your first food after a long fast.
A protein shake hits your body with a whack of easily digestible calories, which breaks the fast and prime it for real food.
I'm not saying you can't eat real food after a fast though. You certainty can, but eating too much food right after a long fast can cause an upset stomach.
Can I use intermittent fasting if I'm doing Paleo/ Vegan/ on a keto diet/ insert any other diet here...?
Yes.
Yesss.
YESss.
And, YESSSSSS.
Ok, that was excessive but you can clearly see the answer is yes.
No matter what diet you're currently into, you can use the intermittent fasting diet simply by adjusting your eating window.
I like to think of intermittent fasting as a diet multiplier, which you can stack on top of your current diet to make it more effective.
What are the biggest mistakes beginners make when starting intermittent fasting?
Let me ask you this:
"What’s your plan when you get really hungry?"
(Hint: we just talked about this. Remember the whole hunger is like a wave speech...?)
If you can’t immediately answer this question, then it’s obvious you haven’t thought through yet it. Not having a plan laid out for when you get hungry is a HUGE MISTAKE...and mistake # 1 that many people make.
See, it’s easy for folks to say ‘Oh yea, I just don’t have to eat for 12 hours and I’ll be doing intermittent fasting.’
It sounds easy, but you’re going to get really hungry.
And trying to figure out what do when you’re ravenous while eyeing up the whole cheese cake in the fridge is recipe for fasting disaster. Before you start fasting you need to think through what you’re going to do when you get super hungry during the fast.
What’s your game plan for dealing with hunger?
To give you a second to think about this I’ll recap my hunger plan…
• Drink a huge glass of sparkling water.
• Wait about 10–15 minutes.
• If I’m still feeling hungry drink a small amount of caffeine in the form of coffee or tea.
• Perform some sort of physical activity to distract the mind from feeling hungry.
Now, what's your game plan?
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Mistake #2 is starting out too fast.
You’ll often hear about people fasting for long periods of time such as 24 hours, or longer. Yes, people do that.
But, if you’re just cutting your teeth into the world of intermittent fasting I suggest starting with a much shorter fasting period.
At first try something like a 10 or 12 hour fast. Once you get the hang of fasting you can slowly increase the length of your fast.
Learning how to fast “correctly” is a skill. And, just like any other skill development, you’ll want to start slow, master the fundamentals, and then progress towards more advanced variations. Intermittent fasting is no different.
Starting with shorter fasts allows you to start building a better relationship with hunger.
I mean, if you’re not used to fasting at all, going without calories for even 10 or 12 hours can feel like an eternity.
The problem is that a lot of people simply freak out when they even feel the slightest bit hungry. Listen, humans have been fasting (either by choice or life’s circumstance) since the dawn of time.
I promise you that if you go for more than a few hours without eating you’re not going to die of starvation.
Your metabolism isn’t going to grind to a screeching halt, and your body isn’t going to start eating your muscles away.
Trust me, feeling hungry isn’t that big of deal (in the short term).
But, this feeling can be uncomfortable; and I get that.
So, to enjoy the long term benefits of fasting you’re going to need to get comfortable being uncomfortable—in this case, getting comfortable feeling hungry.
Shorter fasts allow you to start gaining confidence and getting comfortable while being hungry. Again, once you feel comfortable fasting for 10–12 hours you can start to open up your fasting window.
Personally I feel fine fasting for 16–18 hours, and can do a 24 hour fast without any big prep.
I can do this because I’ve been getting comfortable with feeling hungry for a while now. I didn’t start with 16 hour fasts though. I started with 10 hour fasts, and have slowly opened up my fasting window over many months.
Ok, I’ve beat this point into the ground by now, but to recap:
Don’t start with too long of a fast.
Starting with 10 hours fasting is fine.
You can slowly build up to longer fasting periods.
—
“I usually did 14 hour fasts but this past year I’ve inched up from 16 to 20 and I’ve never felt better.
I love how IF has become a health trend and more and more research is proving what I was already feeling.
My body looks incredible and I feel stronger and sexier than ever!”
How do I tell people I'm doing intermittent fasting without them judging me, or thinking I'm starving myself?
Avoid telling negative Nancy* what you're doing. That way you won't ever get her unsolicted option.
*If you happen to be reading this and your name is Nancy that's just a coincidence.
Another option is to join a support group of other intermittent fasters.
Surrounding yourself with positive people who are doing the same thing as you has been proven to greatly increase success in any endeavor.
You can join whatever intermittent fasting support group you want, but I did a quick search on Google and found 2 that may interest you.
How can I intermittently fast and still enjoy breakfast with my kids?
Two options jump to mind.
Option 1 is to simply drink tea or coffee in the morning, while you grace your kiddos with your presence.
Option 2 is try something like a once a week 24 hour fast, and then eat normally the rest of the week.
Maybe you could turn that day into a fun family fasting challenge.
Actually, a third (bonus) option is to try something closer to the Time Restricted Fast (eTRF). You could eat breakfast with your kiddos, have a big lunch, and start to wind down the food intake in the early afternoon.
Although I suspect if your kids want breakfast, they probably want dinner as well. This option may sound better on paper than it is in practice...
Look, the bottom line is that if eating breakfast with your kids is high on your priority list that's fantastic. You don't need to give that up just to fast.
Experiment around with different fasting windows and see what works best for you and the family.
How do I use IF if my work schedule is constantly changing?
If you work a constantly changing schedule, you may want to consider using something like the 5:2 Fast Diet approach.
Here you would eat normally on the days you work, regardless of when they fall, and then restrict calories on your off days.
How do I use the intermittent fasting diet but still go out with friends and maintain my social life?
I mean, are you going out every single night with friends?
Probably not.
How about trying something along the lines of the Eat, Stop, Eat approach we discussed earlier.
In this approach you fast for one full day, once per week. You could use this complete fasting day on the day after you go out with friends.
For example: If you go out on Friday and Saturday nights consider doing a full 24 hour fast on Sunday. It will also help clean your system from any junk you may have eaten over the weekend.
Another option is to use something resembling the 5:2 Fast Diet. With this approach you just eat normally for 5 days, and restrict calories on 2.
If you go out on Fridays and Saturdays consider using Monday and Thursday as your calorie restricted days.
With a little forethought you can enjoy the benefits of both intermittent fasting and a healthy social life.
Who knows, maybe intermittent fasting will give you something interesting to strike up a conversation around as well...
Does chewing gum break a fast?
If you're chewing gum with a boat load of sugar in it, then ya, probably.
But how many calories do you actually get from chewing gum?
Five calories a stick...maybe?
Don't worry about the trival minutia here. If chewing a piece of gum allows you to fast for an extra hour or two, then go for it.
Don't worry about the 5 calories you may (or may not) get from chewing gum.
Besides chewing gum is hard work for your jaw. Those calories are almost certainty instantly burned up to fuel the act chewing.
So, after talking this out together let's just plant our flag in the sand, and give this answer a hard no.
No, chewing gum will not break your fast.
Chew away.
Your style of writing is amazing, but what other intermittent fasting resources do you recommend?
First of all, thank you for the kind words. I really appreciate that.
There are a lot of great resources out there regarding intermittent fasting. I've read many of them, and I always learn something new.
Note: I've not only read a lot about intermittent fasting, I've also done a lot of self-testing, as well as successfully used the principles of IF with my personal training clients since 2007.
This article is my attempt to explain what I've read, AND seen work in real life with real people.
To that end, here are the intermittent fasting resources that have helped shape my thinking. I highly recommend them all.
IF Resources (websites/articles):
- Leangains.com
- Eat Stop Eat.org
- Anything by Dr. Fung (dietdoctor.com)
- Precision Nutrition experiments with IF
IF Resources (books):
- Fast Diets For Dummies, by: Pat Flynn and Dr. Kellyann Petrucci
- The Warrior Diet, by: Ori Hofmekler
- Eat, Stop, Eat, by: Brad Pilon
- The Complete Guide to Intermittent Fasting, by: Dr. Fung
- The Obesity Code, by: Dr. Fung
Final thoughts/wrap up of IF
We covered quite a bit in this article.
If you're still down here with me, thank you for your time.
Intermittent fasting is an amazing journey. However, there are many different paths a person can take. I hope this article will help you find yours.
The big takeaways are:
- When you're just starting out, start with shorter length fasts. You can always work up to longer fasts.
- Remember the 14.37 fast? Don't be afraid to get creative and create a framework of fasting which works for you.
- Have a plan in mind for when you get really hungry.
Those are the big takeaways.
If you need more specific pearls of wisdom go back and re-read that specific section of the article.
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