What is intermittent fasting?

Dr. Becky Gillaspy, author of Intermittent Fasting Diet Guide and Cookbook, answers questions about this trending lifestyle choice and what you need to know. 

In a sentence or two, can you explain what intermittent fasting is?

Intermittent fasting is a simple strategy for promoting better health and weight loss. In its most basic form, it requires you to do nothing more than split your day between a period of eating and not eating (fasting).

Is intermittent fasting a new diet trend?

​​​​Fasting has been practiced for millennia for health and spiritual reasons. What is new is the use of fasting for weight loss. It is a perfect complement to any diet style, from vegetarian to keto.

What biological benefits does intermittent fasting have on the body?

​​​​Intermittent fasting has grown in popularity due to the weight loss benefits it provides. However, it also has a host of health benefits. It can lower blood sugar, decrease inflammation, improve brain function, reduce cardiovascular risk factors, and make your metabolism more adaptable.

There are so many different styles/schedules of intermittent fasting. Could you give us a very brief description of what they are and who would benefit most from each style?

12:12

Those who are new to intermittent fasting can get their feet wet with 12:12 fasting. With this entry-level method, you'll consume all of your daily calories within a 12-hour eating window and fast for the other 12 hours of the day. For instance, finish dinner at 7 p.m. and break your fast with breakfast at 7 a.m.

16:8

A 16:8 fasting routine is one of the most studied and popular forms of intermittent fasting. Fasting for 16 hours of the day yields weight loss and health results and can be performed by simply skipping breakfast.

20:4

Those with a stubborn metabolism or who are looking to break out of a weight loss plateau may find that fasting for 20 hours of the day does the trick! With this form, you eat all of your calories for the day within a 4-hour window.

One Meal A Day (OMAD)

OMAD fasting could also be called 23:1 fasting because you restrict your eating window to one hour of the day. This can be an effective strategy for breaking a weight loss plateau. However, the limited eating window makes it hard to get all of the calories and nutrients needed to prevent a slowing of your metabolism. For that reason, it is best used as an occasional strategy to throw your metabolism a curveball.

Alternate Day

Alternate day fasting has been the subject of many studies, with promising benefits. As the name suggests, this style of fasting is performed by alternating between fasting and nonfasting days. You can completely abstain from calories on your fasting day or follow a modified version that allows you to consume about 500 calories on your fasting days. This form of fasting provides an option for those who grow tired of daily fasting.

The 5:2 Diet

The 5:2 Diet involves fasting for two days of the week. Like modified alternate day fasting, you can consume about 500--600 calories on fasting days. While you do not want to fast two days in a row, this schedule works nicely for those with a busy social life because you can choose which days of the week to reduce your calorie intake. 

Extended Fasting

Extended fasting is defined as any fast that lasts longer than a day. There is no standard length of time, but 3-to-7-day fasts are typical. This extreme fasting form may prove beneficial for those with special health or weight loss needs. However, there are risks involved when multiple days of fasting are strung together. The risks include, but are not limited to, muscle loss and a drop in metabolism. Therefore, prolonged fasts should be performed under your doctor's supervision. 

Do you have any words of advice for those looking to get started with intermittent fasting?

​​​​​​​It is common to have questions about fasting or be concerned that you won’t feel good without food. We tend to overlook the fact that we all fast on a daily basis. We just call it sleep. Your body is wonderfully adaptive and fully prepared for these periods without food. Fasting is easiest to do if you include the hours you sleep, and starting with a 12:12 fast will calm your fears and build your confidence. If you can stop eating a few hours before bed and delay breakfast until 12 hours have passed, you can do intermittent fasting.