What is Intermittent Fasting? Explained in Human Terms

Brunette With Apple on PlateA phenomenon called intermittent fasting is currently one of the world’s most popular health and fitness trends.

It involves alternating cycles of fasting and eating.

Many studies show that this can cause weight loss, improve metabolic health, protect against disease and perhaps help you live longer (1, 2).

This article explains what intermittent fasting is, and why you should care.

What is Intermittent Fasting?

Intermittent fasting is an eating pattern where you cycle between periods of eating and fasting.

It does not say anything about which foods to eat, but rather when you should eat them.

There are several different intermittent fasting methods, all of which split the day or week into eating periods and fasting periods.

Most people already “fast” every day, while they sleep. Intermittent fasting can be as simple as extending that fast a little longer.

You can do this by skipping breakfast, eating your first meal at noon and your last meal at 8 pm.

Then you’re technically fasting for 16 hours every day, and restricting your eating to an 8-hour eating window. This is the most popular form of intermittent fasting, known as the 16/8 method.

Despite what you may think, intermittent fasting is actually fairly easy to do. Many people report feeling better and having more energy during a fast.

Hunger is usually not that big of an issue, although it can be a problem in the beginning, while your body is getting used to not eating for extended periods of time.

No food is allowed during the fasting period, but you can drink water, coffee, tea and other non-caloric beverages.

Some forms of intermittent fasting allow small amounts of low-calorie foods during the fasting period.

Taking supplements is generally allowed while fasting, as long as there are no calories in them.

Bottom Line: Intermittent fasting (or “IF”) is an eating pattern where you cycle between periods of eating and fasting. It is a very popular health and fitness trend, with research to back it up.

Why Fast?

Humans have actually been fasting for thousands of years.

Sometimes it was done out of necessity, when there simply wasn’t any food available.

In other instances, it was done for religious reasons. Various religions, including Islam, Christianity and Buddhism, mandate some form of fasting.

Humans and other animals also often instinctively fast when sick.

Clearly, there is nothing “unnatural” about fasting, and our bodies are very well equipped to handle extended periods of not eating.

Brunette Holding a Clock and Waiting to Eat

All sorts of processes in the body change when we don’t eat for a while, in order to allow our bodies to thrive during a period of famine. It has to do with hormones, genes and important cellular repair processes (3).

When fasted, we get significant reductions in blood sugar and insulin levels, as well as a drastic increase in human growth hormone (4, 5).

Many people do intermittent fasting in order to lose weight, as it is a very simple and effective way to restrict calories and burn fat (6, 7, 8).

Others do it for the metabolic health benefits, as it can improve various different risk factors and health markers (1).

There is also some evidence that intermittent fasting can help you live longer. Studies in rodents show that it can extend lifespan as effectively as calorie restriction (9, 10).

Some research also suggests that it can help protect against diseases, including heart disease, type 2 diabetes, cancer, Alzheimer’s disease and others (11, 12).

Other people simply like the convenience of intermittent fasting.

It is an effective “life hack” that makes your life simpler, while improving your health at the same time. The fewer meals you need to plan for, the simpler your life will be.

Not having to eat 3-4+ times per day (with the preparation and cleaning involved) also saves time. A lot of it.

Bottom Line: Humans are well adapted to fasting from time to time. Modern research shows that it has benefits for weight loss, metabolic health, disease prevention and may even help you live longer.

Types of Intermittent Fasting

Intermittent fasting has become very trendy in the past few years, and several different types/methods have emerged.

Here are some of the most popular ones:

  • The 16/8 Method: Fast for 16 hours each day, for example by only eating between noon and 8pm.
  • Eat-Stop-Eat: Once or twice a week, don’t eat anything from dinner one day, until dinner the next day (a 24 hour fast).
  • The 5:2 Diet: During 2 days of the week, eat only about 500-600 calories.

Then there are many other variations.

I am personally a fan of the 16/8 method (popularized by Martin Berkhan of LeanGains), as I find it to be the simplest and the easiest to stick to.

In fact, I pretty much naturally eat this way. I am usually not very hungry in the morning, and don’t feel compelled to eat until about 1 pm.

Then I eat my last meal somewhere between 6-9pm, so I end up instinctively fasting for 16-19 hours every day.

Bottom Line: There are many different intermittent fasting methods. The most popular ones are the 16/8 method, Eat-Stop-Eat and the 5:2 diet.

Take Home Message

As long as you stick to healthy foods, restricting your eating window and fasting from time to time can have some very impressive health benefits.

It is an effective way to lose fat and improve metabolic health, while simplifying your life at the same time.

You can find much more info on intermittent fasting here: Intermittent Fasting 101 – The Ultimate Beginner’s Guide.