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Intermittent Fasting (IF)

by | Jun 1, 2020 | FASTING METHODS | 0 comments

The Big Idea

Human health thrives with strategic cycles of eating and fasting Intermittent fasting (IF) is a habit, practiced by every culture across all ages, which has become an increasingly popular research topic for weight loss, longevity, and overall health and rightly so. IF is not a diet – no calorie restriction and it does not dictate which foods to it! – and there are as many ways to practice IF as there are reasons to do it. Almost anyone can benefit from intermittent fasting regardless of age, weight, or gender.

What it is

Intermittent fasting is a strategy that combines periods of eating with periods of fasting into a regular schedule. These eating or fasting “windows”, as they’re called, help your body to burn fat for fuel while enhancing the cellular clean-up process known as autophagy. Water, coffee, tea, and other non-calorific beverages are typically allowed (and recommended) during these fasts.

Since most people aren’t capable of eating during sleep, everybody practices intermittent fasting to some extent. The shortest window of IF begins with a 12-hour fasting window and can be as long as 20 hours or more. Any fasting under 2 days of fasting is considered intermittent fasting. (You’ll find out more about each type in just a bit!)

Though intermittent fasting is recommended for weight loss and positive changes to your body, it is not a diet – no calories are counted, no foods are ‘legal’ or ‘illegal’, and the IF lifestyle is intended to be long term.


With new intermittent fasting benefits being discovered every week, it’s surprising that we were ever recommended to eat 3-5 meals a day. Here are the benefits most often reported in research and by ordinary people who practice IF: 

» increased fat loss
» less bloating
» better digestion
» less hunger
» an improved gut microbiome
» more focus and productivity
» less inflammation
» reduction in type-2 diabetes symptoms
» clearer complexion and improved skin
» a better relationship with food
» mental clarity
» slower aging
» increased autophagy (cellular clean up and renewal)


Though intermittent fasting does have risks, they’re mostly limited to people who are unwell, undernourished, and who have eating disorders. (Remember, we all practice some level of intermittent fasting every time we sleep or go without food!)

  • Pregnant women aren’t advised to practice intermittent fasting because of potential pregnancy complications.
  • Headaches are a very slight but common issue at first
  • Electrolyte imbalances can happen if you go too long without enough minerals – which could lead to dizziness, heart palpitations, and feeling weak. (Doctors recommend taking a multi-mineral tablet and/or adding salt to water during longer fasts.)
  • Hunger is an imminent risk in fasting. But don’t worry – it doesn’t last! Studies report less overall hunger when participants adhere to an IF practice.

How to do it 

There isn’t a right or wrong way to practice intermittent fasting. In fact, there are so many different IF options that just about any person can do it comfortably. Here are the most popular methods:

The 12/12 fast is perfectly balanced: 12 hours fasting and a 12-hour eating window. This daily fasting habit is a perfect intro for beginners who have difficulty going longer periods without food, and it’s very easy, but it is also a sustainable practice for most and is linked to longevity and healthy aging. Since you’re already fasting eight hours while you sleep, only have to delay breakfast by a couple of hours usually.

The 14/10 fast is growing in popularity: 14 hours fasting and a 10-hour window to refeed and enjoy meals.  Similar to the 16:8 fasting schedule, the 14:10 fasting is popular for weight loss, but also for those seeking to experience even more physiological benefits that fasting creates in the body particularly after 12 or 13 hours of fasting including regulation of insulin levels and blood pressure, increase of growth hormone, and a boost in BDNF production. It is a inclusive schedule especially for those who work traditional business hours because it allows for an early start to the day with breakfast and end with an early dinner without much struggle.

The 16/8 fast is loved among those wishing to lose weight, increase lean muscle mass and address metabolic imbalances as well as those hoping to boost performance outcomes. Often referred to as the leangains method, this approach to fasting involves fasting 16 hours consecutively, and eating all your food in an 8-hour window. (Usually 2-3 meals.) This method is typically practiced as a daily habit and useful to help retrain the relationship to food and recalibrate dopamine receptors response to eating.

A 20/4 fasting schedule,  consists of 20 hours of fasting consecutively, and eating all your food for the day in a 4-hour window. A more challenging fasting option it is valuable way to retrain This usually means one big meal per day or one small meal followed shortly by a larger meal.

OMAD (one meal a day)
OMAD means you’re eating only one meal for the whole day. Also known as ‘The Warrior Diet’, OMAD is practiced as a long-term habit and typically requires a work-up period of 16/8s, 20/4s, and 24-hour fasts.

24-hour fasts
These fasts last for 24 hours consecutively. 24-hour fasts start on your last meal for day one, and they end when you eat that same meal on day two – fasting from breakfast to breakfast, lunch to lunch, etc. This allows you to still eat while accessing the fat-burning and rejuvenating aspects of a prolonged fast. (Commonly done one day per week, from dinner to dinner.) 

The 5:2 method fasting is also known as the Fast Diet and includes two non-consecutive fasting days each week or limiting your calories to 500 for the fasting days. It is a very popular method in the UK, and like other fasting methods does not discriminate on what food you can or cannot eat instead focusing on energy balance to manage and restore health.

Also the topic of a best seller book on fasting, this popular method helped make fasting understandable to many skeptics. With great flexibility, the focus of this method is to schedule fasting and eating on a weekly schedule at least once or twice each week, thus ending with dinner on day one and resuming eating with dinner on day two in order to have a 24 our fast. 

36-hour fasts 
Note—this is technically a prolonged fast given it is longer than 24 hours, however given the growing trend of intermittent weekly fasting is catching on in media and among celebrities, it merits mention here for awareness. A 36-hour fast is typically experienced over one day and two nights. It’s started after dinner on day one, continues through all of day two, and ends when you eat breakfast on day three. (Now that’s a real break-fast!)

Key Experts:

Dr. Mark Mattson

Dr. Mark Mattson

Nicknamed the Godfather of Fasting, Dr. Mark Mattson, PhD has spent decades studying the health benefits of intermittent fasting on the brain and body and is considered as one of the world’s preeminent experts on fasting. Dr Mattson is the Adjunct Professor Of Neuroscience at John Hopkins School of Medicine. His well know Ted Talk TEDX Talk “Why Fasting Bolsters Brain Power” generated massive interest in the impact of fasting on cognition and his research continues to further dispel the misconception that fasting is harmful to health and replace it with the understanding of the extensive health benefits of fasting.

“Fasting does good things for the brain. On the days that you don’t eat so much, you will find that you are more productive.”

Dr. Jason Fung

Dr. Jason Fung

Dr. Jason Fung, author of The Complete Guide to Fasting, thinks intermittent fasting is one of the “oldest and most powerful dietary interventions imaginable.” He says that the importance of fasting is written right into our language, even. “Consider the term ‘breakfast’,” he said in a blog post for “This refers to the meal that breaks your fast – which is done daily.”

Instead of being a painful form of punishment, Dr. Fung says, “the English language implicitly acknowledges that fasting should be performed daily, even if only for a short duration.”

About The Author

Fast Forward Editors

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