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2 weeks ago


Intermittent Fasting (IF)

2 weeks ago

Intermittent Fasting (IF)

2 weeks ago

The Big Idea

Intermittent fasting (IF) is a habit, practiced by every culture across all ages, that has become an increasingly popular research topic for weight loss, longevity, and overall health. IF is not a diet – no calorie restriction! – 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. (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 16/8 fast 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.


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. Since you’re already fasting eight hours while you sleep, only have to delay breakfast by a couple of hours usually.


The 5:2 method fasting includes two non-consecutive fasting days each week or limiting your calories to 500 for the fasting days.

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.) 


20/4 have you fasting for 20 hours consecutively, and eating all your food for the day in a 4-hour window. 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.

36-hour fasts 

This fast happens 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. 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.”


Dr. Edward Group

Though calorie restriction is a proven strategy for weight loss and longevity, not everyone can stick with such an ascetic eating habit. Dr. Edward Group, the founder of, thinks that intermittent fasting is the perfect alternative for ordinary people who still want to improve their health. 

“If you take an ‘all or nothing’ approach to dietary changes,’ he said, “intermittent fasting might help you get the results you want. Indeed, alternating periods of fasting with short periods of eating appears to increase weight loss compared to traditional calorie restriction.”


List of top intermittent fasting studies


Health benefits of intermittent fasting

Intermittent fasting and weight loss

Intermittent fasting for health, aging, and disease 

Insulin sensitivity increases while intermittent fasting

Circadian rhythms and intermittent fasting

Intermittent fasting for cancer, diabetes, and cardiovascular diseases 

Healthier lifestyle through intermittent fasting



Fast Forward Editors 
Your go-to-crew for all things fasting and lifestyle.

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