Intermittent Fasting (IF)
The Big Idea
Human health thrives with strategic cycles of eating and fasting
Intermittent fasting (IF) is a habit, practiced by various cultures that has become an increasingly popular research topic for weight loss, longevity, and overall health and rightly so. IF is not a diet – no macronutrient 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 a form of intermittent fasting regardless of age, weight, or gender. Note, typically fasting is not recommended for youth, beyond the normal guidance of teaching a healthy approach to eating/fasting windows in a typical day. .
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 initiating the intracellular (meaning within the cell) recycling 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 macronutrients (carbs, proteins, fats) 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. Some of the early findings suggested in research and by ordinary people who practice IF:
Also worth noting these are commonly reported by faster, however, lacking conclusive science:
» mental clarity
» a better relationship with food
» more focus and productivity
» promotes well being
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!). Always be sure to double-check with your healthcare provider prior to starting any new lifestyle modification for specific advice!
» 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:
This is a daily window of fasting and eating. The most common examples are the 16:8 and the 12:12. Below we will dive into the many iterations of TRE.
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 13 hours or more of fasting including regulation of lipids and blood pressure, weight loss, decreased hunger at night, and decreased energy intake. It is an inclusive schedule especially for those who work traditional business hours because it allows for an early start to the day with breakfast and ends 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 while this has yet to be scientifically substantiated, many claims they learn to recalibrate hunger and their conditioned 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 is a 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.
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 initiating some of 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 fasting days each week, or limiting your calories to typically <660kcals for the fasting days. Note, sometimes these days are consecutive, but typically they are not. 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 of 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 hour fast.
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!)
List of Top Science or Studies:
Health benefits of intermittent fasting
Intermittent fasting and weight loss
Intermittent fasting for metobolic health and brain health
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
Don't know which fast is right for you? Read this article
Strategy that combines periods of eating with periods of fasting into a regular schedule.
Combine all your fruits & veggies into delicious juice for a select period of time.
Combines keto dieting principles with routine periods of fasting for enhanced fat loss.
Also known as Fasting Mimicking Diet (FMD), eating specific macronutrients to keep your body in a fasting state.