Your Definitive Guide To Intermittent Fasting

mbg Health Contributor By Gretchen Lidicker, M.S.
mbg Health Contributor
Gretchen Lidicker earned her master’s degree in physiology with a focus on alternative medicine from Georgetown University. She is the author of “CBD Oil Everyday Secrets” and “Magnesium Everyday Secrets.”
Expert review by Abby Cannon, J.D., R.D., CDN
Registered Dietitian
Abby K. Cannon, JD, RD is an attorney turned dietitian who lives a very low waste lifestyle. She graduated from the University of Pennsylvania with a degree in psychology and received her law degree from Brooklyn Law School cum laude. She graduated from Queens College and became a registered dietitian in 2016.

Photo by Holly Clark

Our editors have independently chosen the products listed on this page. If you purchase something mentioned in this article, we may earn a small commission.

There are a lot of people talking about the health benefits of intermittent fasting, and that means your internet search is going to yield a LOT of results. This can be overwhelming, especially if you consider yourself a newbie and fasting is outside (or way outside) of your comfort zone. If you're interested in Intermittent Fasting (IF), you may not know where to start or even if it's the right choice for you, and since it's a blossoming area of study, it's likely that you'll encounter some conflicting advice.

At mbg, we work with leading experts in the field of integrative and functional medicine, and many of them are big fans of fasting. Some do it themselves or suggest it to their patients and others have have written books on the topic or developed their own fasting protocols. In other words: We have access to a lot of fasting knowledge. Here, we put all that hard-earned knowledge in one place so that whether you’re new to fasting or a frequent 16:4-er, you can get answers to your most burning fasting questions.

What does it really mean to fast?

Quite literally, fasting means going a period of time without food. According to Jason Fung, M.D., fasting expert and author of the book The Complete Guide to Fasting, when it comes to fasting "there's actually infinite variability. It can be any time. Any time that you don't eat—that's fasting. It's the flip side, the B side of eating. It's really that simple." But it can start to feel complicated the more you think about the logistics: Is fasting the same thing as intermittent fasting? Am I allowed to drink water or other zero-calorie beverages? Is fasting actually safe for humans? If you've asked some of these questions and had a hard time finding answers, don't worry—and read on!

Article continues below

Is intermittent fasting just a wellness fad?

At mbg revitalize, Dr. Steven Gundry, a renowned cardiologist and author of The Plant Paradox, explained that "Our ancestors didn’t crawl out of their cave and say 'What’s for breakfast?' There wasn’t any refrigerator or even any storage system." In many ways, following an intermittent fasting protocol re-connects us with the way our ancestors lived before there was food at every single checkout counter.

Have you ever noticed that the first thing you do when you get sick is stop eating? According to Dr. Fung, this is a totally normal response from the body. "You have a surge in hormones and you lower blood glucose to fight infection. This [fasting] isn't a passing fad: It's a 5,000-year-old fad. All of the mechanisms of fasting are deeply, intrinsically human." If you think fasting is a totally alternative practice, Dr. Carrie Diulus—a surgeon and expert in all things health and nutrition—fasting is something she's used to talking about. "As a surgeon, we fast every single patient before surgery. For people with type 2 diabetes or any kind of insulin resistance, different types of fasting can be helpful in reversing those." In other words: Intermittent fasting isn't very "woo-woo" at all.

Is intermittent fasting all about weight loss?

When we think about going periods of time without food, it's easy to assume that it’s all about calorie restriction and that weight loss is the primary goal. And it's true: One of the most common goals of fasting is to make your metabolism more flexible so that you can burn more fat. This means that your body gets used to switching from burning glucose (sugar) for fuel to burning fat to provide your body with energy, something it loses practice at when we're eating every three or four hours—as we’re constantly bombarded by tasty snacks and treats as we go through our day.

We're finding more and more evidence that we can actually train our bodies to burn more fat, which helps many people break through stubborn weight loss plateaus. Fasting before a workout can even help you improve athletic performance, and many experts suggest ending your fast with a workout and then a balanced meal. It might surprise you, but it’s possible you’ll find you actually have more energy for your workout when you've been fasting beforehand. All that said, weight loss and weight management are just the beginning when it comes to the health benefits of intermittent fasting.

It's worth noting, however, that there is definitely a transition period when it comes to fasting. There's a certain window where doing less intense workouts recommended during fasting. If you’re not used to a fasted workout, your blood sugar can dip so low you might feel side effects of hypoglycemia (feeling faint, dizzy, sweaty, etc.).

Article continues below

Related Class

How To Balance Your Hormones
How To Balance Your Hormones

What are (all) the health benefits of intermittent fasting?

If you've read up on fasting, you've likely encountered health benefits that range from killing sugar cravings to improving symptoms of Alzheimer's to helping with autoimmune disease. Here is a list of just some of the suggested benefits:

Fasting is thought to help with the following conditions and many more:

The list goes on and on. But how can one simple practice possibly do all this? Well, according to leading researchers, this all comes down to a cellular process called autophagy. Autophagy is what happens in the body when cells clean house and the weak ones die off. This makes room for the regeneration of new, healthier cells and tissues, which affects longevity and helps reverse diseases of all kinds. It’s even been shown to play a role in decreasing inflammation and improving immunity. In other words: Fasting gives your body a break from digesting and allows it to focus on other things. According to Dr. Gundry, this is especially important when it comes to the brain. "The brain needs huge amounts of blood flow. Digestion is incredibly energy-expensive and we divert all of our blood flow to our digestive system" he explained at revitalize 2017.

The migrating motor complex (MMC), a pattern of electromechanical activity in the digestive system, works in between meals and during fasts. It sweeps residual, undigested material through the digestive system. That’s another reason why giving your body a break from food is super important and can have significant benefits.

Article continues below

What are the different types of intermittent fasting?

There are a lot of different types of fasting, so it’s a good idea to get specific about the terminology we use. Let’s break it down:

Intermittent fasting is a term used to describe a lot of different protocols. One of them is something called time-restricted feeding, which means you restrict the time you spend eating each day to a specific number of hours. This could simply mean maintaining a 12-hour window between dinner and breakfast, which, according to experts, is something we should all be doing. There's also the 16-hour fast, which means you might eat dinner at 8 p.m. and not eat again until noon. A more advanced plan would be to restrict your daily "eating window" even more. In an extreme example, Dr. Steven Gundry only eats between 6 and 8 p.m. from January until June. (This definitely shouldn't be done if you're a beginner, and you should always talk to your doctor before making any drastic changes to your diet or lifestyle.)

Also under the umbrella of intermittent fasting is alternate-day fasting and the 5:2 plan. Alternate-day fasting is just how it sounds: You only eat every other day. And the 5:2 plan means you keep your daily calorie intake low (under 600) two days a week, then the other days of the week you eat a normal diet full of healthy fats, protein, healthy carbohydrates, and vegetables.

A word on prolonged fasting.

Prolonged fasting and fasting mimicking diets are pretty different from intermittent fasting. According to Dr. Valter Longo, "Prolonged fasting and fasting-mimicking diets are very different since they last two or more days (usually four or more) and they are not intermittent—meaning that they can be done when needed and not at particular intervals." This includes the ProLon 5-Day Fasting Mimicking Diet, which was developed by Dr. Longo at the USC Longevity Institute. The point of this program is to "allow the body to enter a full ketogenic mode, meaning it will break down and kill damaged cells and cellular components, activate stem cells, and preferentially decrease visceral and abdominal fat." Essentially, their fasts are about longevity and cellular repair.

Article continues below

I want to start intermittent fasting, so where do I begin?

If you want to start an IF protocol but aren't sure where to start, first ask yourself what your goals are. If you're looking to kick sugar cravings and have more energy, you might start with one of the simpler intermittent fasting plans (like a 16-hour fast a few days a week). If you're looking for something a little more extreme and your goal is to promote longevity, then you might sign up for the fasting mimicking diet or talk to your doctor about experimenting with a prolonged fast. Keep in mind that prolonged fasts will require your full attention and are more difficult to incorporate into a normal daily routine, so you'll need to plan ahead. Intermittent fasting is easier to accomplish while sticking to your normal schedule. It’s almost always recommended that you do some intermittent fasting before moving onto an extended fast.

Are there any risks associated with intermittent fasting?

According to fasting experts, there are some people who should avoid fasting altogether. First on that list? Pregnant and breastfeeding women. Second is anyone with a history of an eating disorder. The goal of fasting is improved well-being, but it can be triggering for anyone with a history of eating disorders, so it's best to steer clear if that’s part of your health history. According to Vincent Pedre, a functional medicine physician and author of the book Happy Gut, you should also exercise some caution if you have gut issues, food sensitivities, a sleep problem, and anxiety or chronic stress. Going without food can sometimes trigger your fight-or-flight response, and it's important to stay in tune with your body at all times. And as mentioned before, always talk to your doctor about starting a fasting plan, especially if you have any kind of chronic health condition.

Article continues below

How do I take my intermittent fasting to the next level?

According to our experts, water and black coffee or tea are fine to consume during a fast, and you'll still receive the health benefits. Just don't start throwing back espresso shots to suppress your appetite; this will not do good things for your nervous system, and it can negatively affect your hormones. Some experts suggest taking l-glutamine during a fast to stave off sugar cravings and help heal the gut. Another option is to add some MCT oil to your coffee or tea—or sip on some full-blown Bulletproof coffee—during your fast, this will help your body switch more easily into ketosis.

And one last thing: While fasting is great, keep in mind that the way you break your fast is just as important. It's completely counterproductive—and even dangerous for insulin and blood sugar balance—to fast and then immediately binge on unhealthy foods. That being said, it's really important to emphasize that what you eat during your eating window is just as important as the fasting period itself. In other words, don't break your fast by going through the drive-thru or eating a bunch of white bread or sugar. Try instead a meal with plenty of protein, fiber, vegetables, and healthy fats. Your body will thank you!

Ready to learn more about how to unlock the power of food to heal your body, prevent disease & achieve optimal health? Register now for our FREE web class with nutrition expert Kelly LeVeque.

More On This Topic

How To Balance Your Hormones
More Health

Popular Stories

Latest Articles

Latest Articles

Sites We Love

Your article and new folder have been saved!