By Hilary Sheinbaum
Intermittent fasting sounds pretty self-explanatory — right? You eat, and then fast, and then eat again, and, then… unsurprisingly, you fast. But it’s not quite that straightforward. The science behind intermittent fasting is a bit more complex — with time frames to observe in order to reap the benefits of this diet tool. And of course, there are parameters and important details to note so you can participate in a safe and healthy manner. Instead of oversimplifying the process, we tapped the experts to uncover what intermittent fasting is all about. We wanted to know how to do it, why people do it, and if it’s a lifestyle that is suitable for everyone (spoiler alert: it’s not).
Read on to find out what three experts in nutrition and fitness have to say about this buzzy way to eat and drink, and if intermittent fasting is right for you.
First things first: what is intermittent fasting and how does it work?
Intermittent fasting is an eating pattern that is based on limiting the time of eating to a certain window during the day. It can also involve eating a number of calories on certain days during the week while reducing food intake for the other days, says Ariel Rasabi Cohn, RD, at Nutrition in Motion in Fort Lauderdale, Fla. (More on that soon.)
“The most common and safest form of intermittent fasting is daily time-restricted fasting. It works by putting the body into ‘starvation mode’ during the fasting windows,” she said. “Some studies suggest that during this time, the body will use up all of its readily available glucose stores for energy and begin using ketones for energy.” In short: the body will burn fat.
How do you do it?
Depending on your lifestyle (and in order to set yourself up for success), there are different options and windows for intermittent fasting. One popular option is the 16:8, where intermittent fasting participants eat within an 8-hour window (i.e. 11 a.m. to 7 p.m.) and fast for the other 16 hours, says Rasabi.
The other popular option is the 5:2 intermittent fasting in which someone eats normally for five days and restricts themselves to only 500-600 calories the other two days of the week, according to Mason Pope, a certified personal trainer at Performix House West Hollywood.
While eating “normal” for five days sounds like a cinch, Pope wants to be clear about the fine print. “Intermittent fasting will only be successful with weight loss if you adhere to a calorie deficit,” says Pope. “To put it simply: that means consuming fewer calories than what you expend daily. Intermittent Fasting doesn’t mean you can binge in your designated eating window.”
What are the benefits of intermittent fasting?
While taking on any new regimen, the key reason for starting something new is to better ourselves one way or another — right? On that note, intermittent fasting can yield a number of helpful changes. Intermittent fasting benefits include weight loss, improved insulin resistance, and some studies suggest that it can improve your metabolic rate, which helps burn more calories during the fasting windows, says Rasabi.
How soon can you see the benefits of intermittent fasting?
Annie Mulgrew, VP Founding Instructor at CITYROW in New York City, says intermittent fasting changed her life. It did, however, take a commitment to making a schedule and having patience.
“While I felt results within the first week or two of the routine, it tooks months before I saw and felt considerable changes,” she said. “As with anything, it takes little adjustments, and a desire to get the ultimate benefits overtime.”
So, is intermittent fasting for everyone?
Not exactly. It really depends on the individual.
Intermittent fasting can be beneficial for those who are pre-diabetic or diabetic, as it can improve insulin sensitivity in the body, and it can also benefit those who are looking to lose weight due to reduced overall calorie consumption throughout the day, says Rasabi. On the other hand, she notes, children or pregnant women should not participate in intermittent fasting, nor should anyone with a history of eating disorders. Mulgrew, also adds: those who are breastfeeding should consult their doctor before starting intermittent fasting. And, while research shows that men are able to fast for longer periods and receive benefits, women should not fast for longer than 16 hours at a time — so, be mindful of your body!
What are the potential drawbacks to intermittent fasting?
As you may have guessed already: not eating for a long period of time can be tricky.
“Intermittent fasting is easier said than done,” says Pope. “If you currently struggle with overeating or haven’t ever been strict with your diet then you need to account for a transitional period to intermittent fasting. Going from 0 to 100mph, and fasting 16 hours per day could lead to you being voraciously hungry.”
His advice for people who are novice to food restriction is to start with a 10 hour fasting period and gradually add an hour each week of successful fasting. “That way you don’t jump the gun and end up falling off the wagon.” Pope also brings up a very good point about intermittent fasting as a whole. Frankly, it doesn’t fit everyone’s goals.
“Restricting your calories may improve your body composition, but most likely at the cost of your [fitness] performance. Let’s not forget the food that we eat is fuel to power us through our intense weight training, long bouts of running, or explosive boxing sessions,” he said. “Ultimately, if reaching your athletic potential is your goal then intermittent fasting doesn’t seem like the most optimal way to achieve that.”