What is Intermittent Fasting and Should You Try It?

Although everyone seems to be buzzing about it lately, fasting is not a new concept. For thousands of years populations have been fasting for religious, self-disciplinary, and health promoting purposes. Fasting, or purposefully going without food for a predetermined amount of time, is gaining popularity in the health community as scientists recognize its benefits. Studies have shown a decrease in rates of diabetes, cancer, cardiovascular disease, hypertension, and even neurological decline when subjects participate in some form of “intermittent” fasting. Intermittent fasting (IF) is the flexible term being used to describe any diet pattern that includes going an extended period of time without eating. There are a lot of methods people use to incorporate a fast into their diets, let’s talk about the why, the how, and any risks you should be concerned if you want to try practicing a little IF yourself.

How does it work?

In short, fasting works because it is calorie restriction, and calorie restriction itself is beneficial. Eating slightly fewer calories than what your body uses each day has been shown to turn on genes that promote longevity. Research hasn’t exactly pinpointed just why, but for some reason, your body does better when it isn’t being overfed. Maybe it allows your body to focus on detoxification, fat cell breakdown, healthy cell replication, and other tasks that tend to be overlooked in an overfed environment. We see this in the island of Okinawa, where people are more likely to live to be 100 years old than any other place in the world. They participate in calorie restriction their whole lives. They eat about 80% of what other people their age and stature are eating on a regular basis. Diseases of aging (heart disease, cancer, stroke, a loss of insulin sensitivity) are almost non-existent in Okinawa. These same benefits are seen with IF. Perhaps less food means less metabolic stress on the body. Going a period of time without your body worrying about digesting food might really give it a much needed break!

What happens when we sleep?

In a way, we all participate in a fast while we sleep. Our bodies are meant to go through a period of time where the processing of calories and nutrients comes to a halt. Your body needs this time to focus its effort into other tasks and uses stored glycogen and body fat as energy. Although the nightly fast is relatively short, we all have the chance to rely on body fat stores for the hours spent sleeping. Using stored energy is good for a couple of reasons. First of all you lose excess weight as you burn it off for fuel for your heart, lungs, brain (yes even dreaming requires energy) and other bodily processes, Secondly, it promotes healthy insulin sensitivity (and other hormone-based functions in the body) when you rely on stored fats as a fuel source. It’s a win-win. On top of that, it’s a way to decrease total calorie consumption in a way that many people find more “doable.”

Speaking of “doable” dieting, the biggest draw of intermittent fasting is that it allows more flexibility and less effort for some people who are trying to cut calories. Instead of having to prepare, pack, and eat 5-6 small healthy meals every day, they can focus their efforts on consuming food for a window of time, then forgetting all about food and calories and nutrients for hours on end. Sound enticing? There are a few different ways to participate in IF, the most popular methods are as follows:


The extended night fast

This method is the easiest way to experiment with IF and simply requires a longer break between dinner and breakfast. For instance eating dinner at 6 and not eating again until 10 in the morning results in a 16 hour fast. If this seems too long, you can experiment with later or earlier times until it feels right for your body. The science behind this method is that you restrict your calorie consumption to a smaller window of time (resulting in less calories being eaten each day) while also synchronixing with your circadian rhythms (also known as your sleep-wake cycle) to support a better metabolism of those calories.

The 5:2 fast

This method allows regular eating for 5 days a week while the other 2 days a week you eat 25% of the calories you would normally consume in a day. This method is just another way of restricting calories without having to do any in-depth menu planning, calorie counting, or other time consuming method.

The weekly/monthly Fast

Perhaps the method people hear the most about, weekly fasts involve choosing one day to go completely without food. This means for the whole 24 hours you don’t consume any calories. This can be done on a weekly basis, or once or twice a month, depending on how the individual feels when fasting.

Bottom line

For some people, this style of eating requires less effort and makes them feel better, although it’s not for everyone. If you are pregnant, diabetic, hypertensive, or have a history of disordered eating do NOT participate in intermittent fasting. Many women who are very active tend to have a difficult time fasting as well. If you are chronically stressed or are starting a new exercise program, IF is probably not something you should jump into right now. Your body has different requirements and will benefit from more regular feedings. If you do want to give IF a try, start slow and find a pattern that works for you. As always, listen to your body and honor how it feels. Remember that there are other ways to be healthy for instance, exercise more, eat more vegetables, cut back on processed foods, all of these will result in metabolic advantages! Fasting is not the only way to be healthy and it definitely is not required for a long, happy life!


Hayley is a Registered Dietician Nutritionist, a part-time yoga teacher, and full-time mother. She is passionate about health, nature, and empowering others to reach their full health potential. She works as a health coach, nutrition writer, recipe developer and group fitness instructor. She is energetic and passionate about delicious food and promoting health of the body, mind, and spirit. She hopes to inspire others to eat closely to the way that nature intended, capitalizing on the amazing benefits of whole, unprocessed foods. Follow her posts for nutrition advice and delicious recipes!

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