What is Intermittent Fasting & Is It Actually Healthy?

You’ve probably heard about intermittent fasting (also known as IF), a wellness trend that has gained major momentum in the last few years.

From Kourtney Kardashian and Chris Pratt to Twitter’s CEO Jack Dorsey and ex-NFL player Terry Crews, some of the biggest names in Hollywood, sports, and business say fasting has given them a leg up on the field, at the office, and in the gym. In less than a decade, fasting went from something we only thought about in the context of surgery or religion to a word we’re seeing in the headlines almost daily.

Intermittent fasting can be divisive; it’s both praised as the best thing to happen to health and medicine and criticized for being a “woo-woo” trend created by a wellness culture obsessed with dieting, restriction, and calorie counting; some even call it dangerous.

This leaves many of us wondering: What is intermittent fasting — and is it actually healthy?

Read on to have all your IF questions, answered.

What is intermittent fasting?

Intermittent fasting means going specific periods of time without eating or drinking, with the exception of water, black coffee, or tea. We all fast naturally at night while we’re sleeping, but IF takes it a step further, asking us to extend our “fasting” window for longer than just 7 or 8 hours.

With a typical IF plan, you would skip your first meal of the day and fast for 12 to 16 hours. So for example, you might eat dinner at 8 p.m. and then break your fast with lunch at noon the next day. That said, there are many different fasting methods, including:

• The 16:8 method — where you fast for 16 hours and have an 8-hour “eating window”
• The 5:2 method — where you cap our calories at 500 two days a week
• Alternate day fasting — where you cap your calories at 500 every other day
• The 24-hour fast — where you fast for a full 24 hours and then follow that with a normal day of eating

The style of fasting that’s best for you depends on your unique goals and your current health status. L.J. Amaral, a registered dietician who specializes in oncology and the ketogenic diet, recommends a gradual approach to fasting. “For instance, going for 12 hours in between dinner and breakfast for a while to get used to time restricted eating, because it is a lifestyle change,” she says. Once you’ve mastered the 12-hour fast, you can increase your fasting window or experiment with other types of fasting. “Depending on one’s goals, I would start to gradually increase the amount of time in between dinner and the next meal,” says Amaral.

What are the benefits of intermittent fasting?

Going 12 to 16 hours without food can be a challenge, so let’s talk about what you’re getting out of it. According to Dr. Marvin Singh, an integrative gastroenterologist in San Diego, “fasting can have many great benefits such as weight loss, boosting your metabolism, and balancing your blood sugar.”

Science agrees with him. In fact, an in-depth review paper, published in the New England Journal of Medicine, showed that it lowers blood sugar, lessens inflammation — which has the potential to impact inflammation-related conditions like arthritis and asthma), improves metabolism, and clears out toxins and damaged cells.

Studies have also shown that IF may improve longevity and can help you lose visceral fat, which accumulates around the midsection and can be particularly challenging to lose. And finally, “As an integrative gastroenterologist, I also suggest it to help people with their bloating symptoms, as it seems to help in this setting as well!” says Dr. Singh.

Looking at the benefits of fasting, you may wonder what if there’s anything it can’t help with.

Well, as it turns out, there are some risks and drawbacks we should all be aware of.

What are the risks of intermittent fasting?

“Fasting isn’t for everyone,” says Dr. Singh. “If you’re a child, elderly, or have another health issue that would make fasting potentially dangerous, it might not be for you and you should definitely talk to your doctor,” he continues.

“I don’t recommend it for my adrenal fatigue patients,” says Dr. Bindiya Gandhi, integrative medicine doctor and founder of Revive ATL MD. “If you’re in adrenal exhaustion, when you eat food, you’ll experience a big blood sugar spike,” she says. Not to mention, going without food for long periods of time puts your body in starvation mode, so if you’re stressed or not sleeping well it can trigger your nervous system and end up doing more harm than good. If you’re struggling with sleep, anxiety, adrenal fatigue, a thyroid issue, or chronic stress, Dr. Gandhi doesn’t recommend fasting for more than 12 hours. “Another group of people that shouldn’t fast are women trying to get pregnant,” she adds.

As registered dietitian Anna Taylor, MS, RD, LD, CDE also told the Cleveland Clinic: “If you’re at risk for an eating disorder, you shouldn’t attempt any sort of fasting diet.” Studies have shown that fasting increases the risk for binge eating and bulimic pathology.

If you have any chronic health condition or any concerns about whether fasting is right for you, definitely check with your doctor beforehand.

And even if you don’t have a health issue, fasting can increase your risk for dehydration or an electrolyte imbalance. “While the window of time for eating becomes more restricted, I highly recommend people to be more mindful of their hydration,” says Amaral. And it’s not just water that you need to be mindful of, either. “Electrolytes are imperative during this time; this will help with energy, preventing dehydration, and keeping you from losing too much water weight initially,” she explains. Amaral recommends broths, electrolyte replacement powders, and just plain salt water daily to offset any potential side effects from fasting.

Finally, those prone to hypoglycemia, or low blood sugars, should proceed with some caution. “Signs that you have low blood sugars include shakiness, nausea, headache, irritability, lightheadedness, excessive sweating, and anxiety,” says Amaral. If you’re experiencing any of these symptoms, it’s time to eat something. Your immediate health is always more important than completing your fast.

Intermittent fasting is proving to be an extremely effective tool for fending off disease, losing weight, balancing blood sugar, and generally living a healthier life. That said, it’s not without risks — and it’s not for everyone. The ultimate take home? Always start slow and listen to your body.

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