Is Intermittent Fasting Good For You?

Food: Nutrition

By: // December 14, 2018

Here at GHU, it’s no surprise we aren’t into fad diets or crazy concoctions that claim they’ll help you lose weight. We’re more into the 80/20 philosophy—aim to eat right and make good choices about 80% of the time, but leave 20% room for indulgences and your favorite treats. (In other words: life is short, eat the cake every now and then.) So when we heard that people have been trying intermittent fasting as a way to lose weight, we were curious. Does this actually work? Is it safe? We researched whether or not intermittent fasting is good for you so we can tell you our honest opinion.

What Is Intermittent Fasting?

The concept of fasting is nothing new—people have been fasting for religious reasons for centuries. Fasting itself simply means to go a stretch of time without eating. We all naturally fast when we sleep every night. Intermittent fasting does not require you to go more than 24 hours without eating. Instead, you have a few options:

  • Fasting Window. You can choose a fasting window of which to not eat during the day, typically around 16 hours. Because you spend roughly 8 hours per night asleep (naturally fasting,) you’re then only required to tack on an additional 8 hours of fasting during the day. Many people choose to fast 4 hours before they go to bed, and 4 hours after they wake up—skipping breakfast. You can still drink water, coffee, and tea during your fasting hours.
  • Full 24-Hour Fast. You can do a full 24 hour fast once or twice a week, so from 7 pm Friday to 7pm Saturday, for example. You can once again still drink water, tea, or coffee during your fasting period. You return to normal eating after the fast is over, meaning you aim to consume the same amount of calories you normally would, not more, after you’re done fasting.

Related: The Science of Skipping Breakfast

Why Do People Do Intermittent Fasting?

From our research, we read many accounts of people who have tried intermittent fasting for different reasons, both relating to physical and mental well-being. But here are the three biggest reasons for intermittent fasting that we’ve come across.

Should you try intermittent fasting?

1) A Belief That It Burns More Fat

Some people believe that by fasting intermittently, you are able to reset your digestion, helping your body burn fat more effectively and ultimately lose weight. It takes about 6-8 hours to digest a meal. Some people think that by fasting for that amount of time, you then force your body to use stored fat—and not your food—as energy. The belief is that this burns up the fat instead of the food.

2) To Create a Calorie Deficit

By eliminating one meal out of your day, it’s suggested that you’ll create a calorie deficit. While it’s true that you need a calorie deficit (fewer calories going in than the amount of calories burned) in order to lose weight, if you are too hungry from fasting you can overeat at your next meals and end up eating just as many calories—if not more—than you would if you ate throughout the day.

3) A Desire To Retrain Your Appetite

Proponents of intermittent fasting will tell you that by doing this, you train your brain to only eat when you’re truly hungry, not by arbitrary times of the day (breakfast, lunch, and dinner). Some people claim that this can help people who tend to over-eat or binge-eat better identify when they are actually hungry. However, as noted above and as we’ll discuss in further detail below, fasting can actually cause “rebound overeating” in some cases.

Negative Side Effects of Intermittent Fasting 

  • Rebound Overeating

    This is perhaps one of the biggest drawbacks to intermittent fasting: it makes you overly hungry so you end up overeating and consuming more calories than you normally would at your next meal.

  • Mood swings

    Some people are particularly sensitive to drops in blood sugar. (Have you ever heard the term “hangry?”) Intermittent fasting can cause anxiety, irritability, and mood swings.

  • Poor sleep

    Going to bed when your stomach’s growling is never a good idea. Being hungry can wake you up in the middle of the night and keep you from getting a solid night’s sleep.

  • Weakness or fatigue

    It can be harder to work out when you feel hungry or unsatiated, and you can experience muscle weakness, headaches, or just overall fatigue.

  • Adrenal stress

    You can place undue stress on your adrenals by making your blood sugar spike and drop so significantly.

  • Lack of nutritional guidance

    Fasting doesn’t require that you eat certain foods during the time you’re actually eating. Because of this, you can technically eat whatever you please when you’re not fasting…and that lack of direction won’t help someone lose weight who consumes unhealthy foods for the rest of their day.

What We Think About Intermittent Fasting

There is no one-size fits all approach to nutrition. Our bodies have different needs. Some of us are sensitive to dairy or gluten, while others may be deficient in things like iron or magnesium. Some people are comfortable going long stretches without eating, while others feel the effects of low blood sugar a few hours after a meal. Finding the nutritional strategy that works for you is all about identifying what makes your body feel good and operate most efficiently.

As a trainer and health coach, however, the concept of fasting does not make me think “fat loss.” What proponents of intermittent fasting might not realize is that fasting doesn’t cause your body to break down only fat. When you don’t consume carbohydrates after about six hours, your body will begin to convert some lean tissue (meaning muscle) into carbohydrate as well. Your metabolism needs fuel in order to work efficiently. When you starve your body, your metabolism shuts down to conserve energy. In some fasting cases, you’ll burn less fat than if you actually fueled your body with healthy food regularly, because glucose must be present for body fat to burn.

Here’s what I suggest for people to stay healthy and burn fat:

  • Eat a healthy diet of sensibly portioned meals comprised of as many plant based foods as possible. Fill up on veggies, fruits, nuts, seeds and healthy fats. Add in lean protein, whole grains and dairy in moderation if you like it.
  • Incorporate both cardio and strength training into your workout routine. Strength training builds muscle, and muscle is a more metabolic tissue than body fat. This means that the more muscle you have, the more calories you’ll burn daily, even at rest.

This is what we want for both fat burn and long-term health: a metabolism that runs efficiently—not one that’s constantly going into starvation mode. Have you tried intermittent fasting? What works best for you? Let us know in the comments below!

READ THIS NEXT: The One Diet I Actually Suggest

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on April 9, 2019 at 12:03 PM Reply

There are so many options like fasting, specific diets etc. Most have some scientific claims and proponents who swear by the science. But for me, many feel like there is always a deprivation component. At the ripe old age of 60, I gave up chasing the latest claims to stay in shape as I find the approach that Chris mentions, the easiest to follow without any deprivation.

    on April 17, 2019 at 4:50 PM Reply

    Yes Kathy!! You hit it right on the spot. There are so many different health and diet "fads" that come and go but what I always encourage people is to do what is right for your body. What works for one person may not work for another. You have to do what is right for your own health and your own gut. Keep doing you!!

on January 12, 2019 at 6:58 AM Reply

There are many more benefits to intermittent fasting besides weight loss. After 16 hours of fasting your human growth hormone increases significantly. If you look at the benefits of what your human growth hormone does, you’ll want to increase it. It helps with cell turnover, brain function, and metabolism to name a few. I eat relatively healthy (clean foods) and I exercise (love Chris’s videos) I don’t need to lose weight, but I intermittently fast 16 hours a few days a week just to get the other benefits.

on May 17, 2018 at 2:14 PM Reply

This is not complete. Hunger doesn't go up with time. Hunger appears when you're used to eating. I've been skipping breakfast for about a month and now I start feeling hungry at twelve o clock. There's studies on this and I think there should be included in this article.On the other hand, the research on fasting on humans is limited and seems to produce more questions than does answers. It has been working for me and those symptoms dissapeared after the first week. Once again I think this article is incomplete.Anyway, it has always been about finding what it works for you... so yeah: no one size fits all.

on July 16, 2017 at 1:30 PM Reply

I've tried intermittent fasting. I felt great that first time that I did. Each time it got harder to do. I ended up becoming anemic because I became reliant on it for weight loss and I was running for 7 miles one day a week and weight lifting my other days. After becoming so weak from anemia, I decided that it wasn't for me. A healthy diet and exercise are the best way to lose weight and keep it off.

on January 26, 2017 at 12:39 PM Reply

Hi Chris!I agree with you. Intermittent fasting does not work for me. If I starve myself during the day I would be starving late at night, not be able to sleep so I would scrounge around the fridge and overeat. I would much rather be in control and eat properly during the day.Great article!

on January 26, 2017 at 12:01 PM Reply

Thank you for this! I was actually going to be submitting this as a question for the Q&A session next week. There has been all kinds of buzz around the internet lately about this and it peeked my interest. I am right there along with you in regards to eating healthy. The lifestyle that you choose has to be sustainable for the long haul. There is no way that I can do without breakfast for the rest of my life! I am slowly (but surely) realizing that I don't need to have 10% body fat, workout for an hour a day, and only eat fish, chicken, and veggies. I want to enjoy life, have my wine, and be functional and active when I am 80 years old. I can achieve this by eating relatively healthy and working out smarter, not longer.

on January 26, 2017 at 11:23 AM Reply

I used to incorporate fasting seasonally. Fall and Spring seemed like a good time to reset my system by going on a 24 hour fast, or as long as a 3 day fast. I'm hypoglycemic, so just drinking water or tea doesn't cut it since my blood sugar is already very low (about 55 normally). So, I drink liquids throughout the day: kombucha or organic lemon water with a touch of maple syrup, as long as it's pure, organic and keeps my blood sugar levels where I need them to be. I also added a fiber supplement on my last day of fasting. What I discovered: it really resets your appetite and your relationship with food. When I did go back to eating, I found I could only eat a small amount, as if my stomach had shrunk a bit. I also noticed that my joints weren't as 'creaky' in the morning. Setting off on my morning walk seemed somehow easier and I felt lighter. Also all that water consumption helped to reduce water weight, so my tummy flattened right out. It may not be for everyone, but it certainly worked for me. Now that I'm weight training I haven't resumed fasting, since fasting requires not much energy output, as it can leave you feeling a little listless and I want to keep training as much as I can.

on January 5, 2017 at 9:30 PM Reply

This is so timely for me to read. I just read an article in AARP regarding mini fasting and was a bit intrigued. It entailed different strategies, but one was to limit yourself to 500 calories a day a couple days a week and the other 5 days eat normal. I guess if your normal is healthy eating, well of course you'll lose weight, but I think I'd tend to say to myself "well, I just saved all those calories so I can go a little crazy". I envision the same up and down in weight I've had all my life. I think I'll continue to read the great tips and advice I get here on Get Healthy U and even if I don't commit 100% or even the 80/20 all the time, I know I'm incorporating small changes in my life from those tips and the sound advice I am reading.

    on January 6, 2017 at 8:24 AM Reply

    So glad you found it useful, Tammy! And we're thrilled that we've found a returning reader in you :)

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