What Is Intermittent Fasting?

What if a key part of staying healthy and losing weight was simply skipping a meal? That’s the idea behind intermittent fasting, maintaining a daily window of time when you don’t consume anything other than water.

Benefits of Intermittent Fasting

“There’s a cycle of eating and fasting you’re supposed to go through every day,” says Jason Fung, M.D., author of The Complete Guide to Fasting (Victory Belt, 2016). “During the period you’re eating, you’re going to be adding body fat, and during the period you’re not eating, you’re going to be burning fat.” When a person starts eating as soon as they get up and doesn’t stop until they go to bed, there’s little time to burn calories. 

That’s the reason intermittent fasting can help with weight loss. But shedding a few pounds isn’t the only benefit. When Naomi Whittel, author of Glow15: A Science-Based Plan to Lose Weight, Revitalize Your Skin, and Invigorate Your Life (Houghton Mifflin Harcourt, 2018) started a fasting regimen, she noticed that her skin looked younger, her energy level was higher and her chronic inflammation eased. 

Numerous health benefits from fasting appear to be the result of autophagy, which literally means “self-eating.” Studies have found autophagy to help fight infectious disease, regulate inflammation and bolster the immune system. So, what is it? When cells are placed under an appropriate level of stress—such as a reduced amount of food during a fast—they consume and dispose of toxins and unneeded proteins, aka “bad cells.” Whittel likens autophagy to a Pac-Man traveling through each cell and gobbling up waste materials. 

How to Start an Intermittent Fast

It’s a good idea to check with your doctor before beginning any fasting routine. After that, educate yourself and develop a plan (see “Intermittent-Fasting Plans” for ideas). 

Whittel recommends identifying the meal you’re the least attached to and skipping it. Although some research indicates it’s better to concentrate eating earlier in the day, many people, including Whittel, find it’s easier to skip breakfast and maintain their fast until lunch. When she is fasting, Whittel concentrates on hydrating after waking. “We lose significant water while we sleep at night, so make sure you’re drinking at least 16 ounces of water first thing in the morning,” she says. Adding a pinch of sea salt or Himalayan salt can add back some of the minerals lost during slumber. 

Your body may need time to adjust to fasting, so don’t take the plunge too quickly. “If you try 16 hours of intermittent fasting and you’re getting headaches or don’t feel good, then you can pull back and go to 12 hours and start to become good at that,” Whittel says. 

When it’s time to break the fast, Whittel advises doing it fat first, carbohydrates last. Why? Foods with healthy fats will help you feel more satisfied and extend the time your body relies on ketones, which your body produces when it burns fat for energy. Some of Whittel’s favorite post-fast foods: an avocado drizzled with olive oil and lemon juice and seasoned with salt, or cooked pasture-raised eggs and nitrate-free bacon. 

Intermittent-Fasting Plans

An intermittent-fasting window should last at least 12 hours but can be as long as 36 hours. According to Fung, the following are some of the most popular plans:

16-hour

Also called time-restricted eating, where a person fasts for 16 hours and eats in the eight-hour window. This can be done daily. 

24-hour

A person eats dinner one day and doesn’t eat again until dinnertime the next day. Fung recommends starting with one to three times per week. This plan is often called One Meal a Day. 

36-hour

Involves eating dinner one day, skipping all meals the following day and eating breakfast on the third day. This can also be done one to three times per week.

Questions or concerns about fasting? It’s always wise to check with your doctor.