What is Intermittent Fasting?

In my quest to find the “diet” that is right for me I came across something that is known as “intermittent fasting” (IF) or “leangains”. I use the term “diet” very loosely because IF is more of an eating lifestyle. When most people think of a diet, they think of some calorie restricted diet that will help them lose weight or get shredded. In truth, diet can be applied to both those who want to lose body fat or put on some lean mass. When it comes to losing or gaining it comes down to calories in vs. calories out. If you consume less calories then you expend in a day, you will be at a calorie deficit and will (hopefully) lose weight. If you are at a calorie surplus, or eat more calories then you expend in a given day, you will put on mass (ie muscle or fat, but hopefully more muscle than fat). Sorry to stray, let’s get back to IF and Leangains!

According to Wikipedia, Intermittent fasting (IF) is a pattern of eating that alternates between periods of fasting (usually meaning consumption of water and sometimes low-calorie drinks such as black coffee) and non-fasting.[1] There are many different variations that people have made to IF – Leangains, The Primal Blueprint, The Warrior Diet, Eat Stop Eat. To make things a little simpler intermittent fasting describes any diet that includes a period of fasting and a period of non-fasting, even if the diet involves consuming a limited amount of calorie-containing beverages such as coffee, tea, or diet soda during the fasting period.

One of the main variations in each IF diet is the duration of the fasting phase. When you see these different variations, you will probably notice shorthand such as “20/4”, “16/8” and “15/9”. This shorthand is used to denote the repeating pattern of 20 hours of fasting followed by a 4 hours of non-fasting, which is commonly referred to as your ‘eating window’. “Fast-5” is a book promoting a regimen equivalent to “19/5”. Let’s take a look at these different approaches in a little more detail.

Approaches to Intermittent Fasting

The Warrior Diet

The Warrior Diet is based on a daily feeding cycle of ‘undereating’ during the day and ‘overeating’ at night. The pattern used by The Warrior Diet is 20/4 – that is 20 hours of fasting followed by a 4 hour eating window. Many IF proponents say that the Warrior Diet really isn’t a true fast because its author allows small meals consisting of vegetables/fruits during the fast. The downside to this diet is that there is no real science or research to support the claims made by the author. Instead it uses stories, which are anecdotal at best.

The Fast-5 Diet

The Fast-5 Diet has a 19 hour fast and a 5 hour eating window. Fast-5 is a way of “losing weight and maintaining a healthy weight” that is based on a lifestyle change, not a specific diet.


Leangains, by Martin Berkhan, is an IF protocol that is tailored more towards people that have more fitness and strength training goals when it comes to dieting, body composition, and muscular maintenance/development. It has a 16 hour fasting window followed by an 8 hour feeding window. Leangains is for the crowd that wants to get as lean and as strong as possible and most importantly, be able to maintain that leanness. Martin Berkhan gives very specific guidelines regarding nutrition, calories, macros, and everything in between to help you get the best results possible. I will talk more about Leangains in my next article.

What are the Benefits of Intermittent Fasting?

Burn More Fat

Energy expenditure and macronutrient intake (carbs, proteins, fat) are the most important factors when it comes to losing fat. By reducing your calories below your expenditure rate it is possible to get really lean and lose body fat without becoming a ‘cardio bunny’, or someone that does an insane amount of cardio. Research has shown that fasting can help shift stubborn fat and explains why people can get exceptionally lean without cardio work.

Lack of Hunger

I know what you are thinking – how can you possibly not get hungry after fasting for 18, 19, or even 20 hours?? It seems impossible, but your body is a pretty tricky little machine. Let’s see if I can explain this correctly. The fasting period begins after your last meal of the night and continues into the next day. Because of this you will skip your breakfast. By doing this, you are able to eat bigger more satisfying meals. According to Martin Berkhan “Contrary to popular belief, the fasting phase has a suppressive effect on hunger. Hunger pangs may come, but they disappear quickly, to be replaced by a sense of well being and total absence of hunger.”

Within a few days of starting the diet, your body’s hormones, notably the hunger hormone, ghrelin, get used to the new eating pattern and adjust accordingly so you no longer feel hungry in the mornings. I have been on the Leangains protocol for about a week and I have already noticed this shift. I’m not hungry at all. Ever. This is coming from a guy that was eating 6-7 smaller meals every 2.5 to 3 hours beginning at 4:30 in the morning. Needless to say, I feel much better and my meals are more enjoyable.

Increase in Mental Focus and Concentration

I am a desk jockey. I sit at my computer for 80% of my work day. So naturally one of my main concerns when starting Leangains was if I was going to turn into a work zombie and be tired and sluggish while in the fasted period. Not a problem at all. Research shows that during a fast, your body releases catecholamines. Catecholamines are produced by your central nervous system and are responsible for the release of the hormones epinephrine and norepinephrine. Some typical effects are increases in heart rate, blood pressure, blood glucose levels, and a general reaction of the sympathetic nervous system. Mental focus is increased, productivity goes up, and you’ll feel more involved in whatever you’re doing. Most people find this particularly pronounced during the last 4 hours of the fast.

Intermittent fasting provides a lot more benefits than the ones that I have covered. It also balances out your energy levels, improves mood, and really helps me personally not worry about meal timing. I don’t need to get in my meals every 2-3 hours, which is so nice!

Is Intermittent Fasting the Right Diet For You?

As a former “grazer” I was skeptical that you could “skip” meals or fast without suffering brain fog, brain fog and muscle loss. I mean, one of the most popular nutritional recommendations of today is to graze, or eat 5-7 small meals per day. I had really good results grazing, it just seemed like I was always eating and carrying my meals with me so I wouldn’t miss one and completely blow my diet. At the end of the day, it all comes down to calories in and calories out. What you need to determine is the best way and the most convenient way for you to get those calories in. Getting them out, going to the gym is the easy part. But you know what they say, abs are built in the kitchen. It’s the diet part of getting lean and shredded that is the toughest part to master.

There is a lot of research going on surrounding the pros and cons of IF, and I am paying attention. While the research is ongoing and takes time, my suggestion is don’t sit around and wait on the research. Forget what science hasn’t yet proven. Establish best practices in your own exercise and nutrition habits, right now. Figure out your TDEE, and macros and build your diet around your nutrition and fitness goals. Then once you have that you can tweak your diet to your heart’s content. Start living better today. Control your food intake, use a diet that isn’t so restrictive that it causes you to develop binging habits and an unhealthy relationship with food.


[1] – http://en.wikipedia.org/wiki/Intermittent_fasting

About The Author

Brian E. is from southern California and has worked for names like GNC and Vitamin Shoppe as a supplement expert and consultant. He currently lives in Utah and is studying marketing.

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