Is intermittent fasting right for you? DailyOM asked the experts to weigh in on everything you want to know about this trendier-than-ever eating style, including what you can and can’t eat, and when.
Like many people, Rumiez Hasseem put on a few extra pounds early in the pandemic, when COVID restrictions kept him from participating in triathlons and races he’d previously frequented. “I did a 10K at the end of 2019, and I was like, ‘Okay, I’m doing great. I’m going to train for a half marathon,” he says. “Then COVID hit and I continued to train outdoors, but it got a little more difficult because my kids were home all of the time, so there wasn’t as much time to train.” In 2021, he suffered a cycling injury, which caused him to pause his regular exercise routine for surgery, resulting in additional 30-pound weight gain.
Luckily, intermittent fasting helped Hasseem shed all of the extra weight and keep it off. “Before intermittent fasting, it was always hard to find something I could stick with,” says the Yorba Linda, California, resident. “I felt too restricted, but with this, if I want to go eat pizza, I can do that. If I want to go to [fast food] and eat a meal with my kids, I can do that.”
Hasseem isn’t alone. According to a poll conducted by YouGov.com, 24 percent of Americans say they’ve tried intermittent fasting (often referred to as IF) for weight loss, with half of them reporting that it was very effective.
So how do you know if intermittent fasting is right for you? DailyOM spoke to the experts to find out everything you need to know about this popular plan.
What Is Intermittent Fasting?
Intermittent fasting is a simple eating pattern where you refrain from eating and drinking during specific times of the day. “Intermittent fasting is really just any period of time where you don’t eat,” Jason Fung, MD, a Canadian nephrologist and New York Times bestselling author of The Obesity Code: Unlocking the Secrets of Weight Loss, tells DailyOM. “Your body stores calories that you eat, taking in more energy than you can use. It has the ability to store these calories either as sugar or as fat, which is why you have body fat. So, really, intermittent fasting is just letting your body use that stored energy to burn calories.”
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What Are the Main Intermittent Fasting Schedules?
There are three main intermittent fasting schedules:
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Time-restricted intermittent fasting
When practicing time-restricted fasting, a person limits food consumption during specific hours of the day. For example, you set an eating window of 8 hours, and then fast for the other 16 hours of the day. Or you can have an eating window of 12 hours, then fast for the other 12 hours. “The 16:8 schedule is probably the most popular fasting period because it is relatively short and easy to fit into a typical day,” says Fung.
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Complete fasting
This is a form of intermittent fasting when a practitioner does not eat at all on certain days of the week, while on other days, they eat whatever they choose without restrictions. It’s not as popular as 16:8 fasting, but can be an effective approach for people who don’t want to fast every single day.
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Modified fasting
This is when a practitioner eats a reduced-calorie diet for a few days of the week, then eats whatever they want for the remaining days, such as two days with modified fasting and five eating “regularly.” There’s no set calorie limit on your fasting days, since the whole concept behind IF is not having to count calories. There may be some trial and error as you find a comfortable routine that works for your body’s unique needs.
How Should You Choose an Intermittent Fasting Schedule?
Choosing a fasting schedule is a personal preference. In fact, Dr. Fung maintains that the “right” schedule is simply the one that is the most manageable for you. “The most popular schedule is the 16:8 schedule, where you fast for 16 hours and eat for eight hours,” he says. “But fasting can really be anything you want. Just choose whatever you prefer and think you can stick with from a lifestyle standpoint. There’s no magic. You can always switch to longer or shorter fasts later if you’re not getting the results that you want.”
That said, intermittent fasting definitely isn’t a one-size-fits-all solution. You should proceed cautiously in the beginning, especially if you have certain medical conditions like diabetes or heart disease. And most experts recommend avoiding fasting entirely if you’re pregnant or breastfeeding. “Should everyone be able to do a full day or a complete water fast? Probably not,” says Martica Heaner, PhD, adjunct associate professor of nutrition at Hunter College in New York City, whom DailyOM spoke with for this story. “And the more health issues that are involved, the more medical supervision is needed.”
What Can You Eat and Drink During Fasting Periods?
Contrary to popular belief, you don’t have to avoid all food and drink during intermittent fasting periods. Despite the fact that you do need to stick to a restricted eating schedule, you can still drink water, coffee, tea, and other zero-calorie beverages. Just try not to add milk, sugar, or artificial sweeteners to your drinks to avoid breaking your fast.
“The main thing is just to avoid anything that’s excessively sweet,” says Fung. “That’s why artificial sweeteners are not good. Of course, anything with calories is going to bring you out of your fast. If it’s a very little bit, then no problem, you’ll go right back into your fasting state. It’s probably okay as long as you keep it small.”
If you’re following a modified fasting schedule, Fung recommends reducing sugar and refined starches and sticking mostly to low-carb options for the best results. Some of his favorite go-to meals include grilled salmon served with Brussels sprouts; grilled skirt steak with chimichurri sauce and a side of eggplant; or braised chicken thighs with a side salad.
You should still be mindful about choosing a wide variety of nutritious foods on your non-fasting days. “There are people who are not eating for 20-plus hours a day and then, when they do, they indulge in bacon, eggs, and cheese,” says Dr. Heaner. “People do this for a year and lose [weight], except they put themselves at severe nutritional risk. Even if you get benefits from weight loss, pumping your body full of inflammatory foods [that are] high in saturated and trans fat is not a good recipe for health. It can worsen insulin resistance, and your triglycerides and cholesterol can often shoot up, both risks for heart disease.”
Is Fasting Tea Safe?
Drinking unsweetened tea is a great way to stave off hunger during your restricted eating and drinking periods. And you don’t need to spend a lot of money to purchase specific brands or pricey diet products. “Get something like green tea, which is relatively inexpensive,” says Fung. “There are also flavors like ginger and matcha, which are high in antioxidants. Tea is good for digestion and helps suppress hunger a little bit,” and he says that unsweetened tea won’t break your fast.
What Are the Goals of Intermittent Fasting?
People fast for a wide variety of reasons, but these days the primary incentive is weight loss. According to a recent study conducted by the University of Illinois, intermittent fasting has been scientifically proven to produce significant weight loss results. Study participants who were obese lost an average of 3 percent of their total body weight, regardless of the timing of their eating window. And everyone in the study experienced a 3 to 8 percent weight loss in the first three to eight weeks.
But dropping pounds isn’t the only reason intermittent fasting has gained such a devoted following. “Everyone is going to have a different goal,” says Fung. For example, he says, some people practice IF because they desire a healthier lifestyle, while some people with certain health conditions, like type 2 diabetes, are looking to control their blood sugar.
If you’re diabetic, experts recommend discussing IF with your doctor first, as well as fasting under their supervision to avoid potential pitfalls. “Someone with diabetes or other low blood sugar conditions should always consult with their doctor first,” says Heaner. “Medication doses may need to be reduced or even omitted during periods of fasting, depending on how long. A board-certified physician will always have a protocol for monitoring and medications as needed.”
Who Should Avoid Intermittent Fasting?
Despite its increasing popularity, intermittent fasting definitely isn’t for everyone. If you’re elderly or an adolescent, underweight, pregnant, or breastfeeding, or you have a history of disordered eating, it’s probably best to steer clear of fasting. “Someone with a history of eating disorders should not practice intermittent fasting because it can be triggering,” says Heaner.
The Bottom Line
Intermittent fasting is a great way for some people to lose weight and reduce their risk of illnesses like diabetes and heart disease without worrying about counting calories or ruling out any food groups. But it isn’t the only option out there if you want to shed pounds. Other plans like intuitive eating and whole food diets offer healthy alternatives for people who might be at risk from restricted eating cycles.
“Intermittent fasting has been proven to be an easy way to reduce calories without counting them, but so can a whole-foods, plant-based, high-fiber diet,” says Heaner, who advocates choosing foods like fruits, vegetables, plants, seeds, beans, whole grains, and nuts. “For some people, it might be easier to have strict time limits because it takes the decision out of the equation. But it might make other people more obsessive and crave food more.”
For those who appreciate the flexibility of IF and find the eating style fits their lifestyle, it can be extremely rewarding — and doable. As Rumiez Hasseem says, “Once you start to see the results, you realize it’s just a total lifestyle change and it really works.”
