Popular Intermittent Fasting Schedules, Explained by Nutritionists
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Take a cruise through social media, and you’ll be quickly faced with a bunch of influencers claiming that intermittent fasting changed their body. While intermittent fasting has been buzzy for years, there is research to support this eating plan. That said, there are a bunch of ways to approach this, making it tough to choose an intermittent fasting schedule.
If you’re interested in embarking on an intermittent fasting eating plan, it’s important to know the basics first. That includes understanding the details of the different IF schedules, as well as what to consider for each. Here’s what dietitians want you to know before trying intermittent fasting.
Meet the experts: Jessica Cording, R.D., is author of The Little Book of Game-Changers; Keri Gans, M.S., R.D., is author of The Small Change Diet; Gabby Headrick, PhD, is an assistant professor in the Department of Exercise and Nutrition Sciences at the George Washington University Milken Institute School of Public Health
But there is some variety with intermittent fasting, including the length of time you choose to fast and what you can have during eating windows. Here’s what you need to know about the most common intermittent fasting schedules, plus things to keep in mind about each.
What is intermittent fasting?
You likely have some idea of what intermittent fasting involves, but it never hurts to start at the beginning, just in case. Intermittent fasting is a dietary plan that involves having set periods of time where you fast (i.e. don’t eat), followed by eating windows. There’s a lot of variety in how you can do this (more on that in a moment), allowing you to tailor this approach to your personal needs.
In general, intermittent fasting diets do not dictate what you should eat during the eating windows. Meaning, you can technically have whatever you want during those times. However, people tend to have optimal results and feel their best when they follow good nutrition during those eating windows, says Jessica Cording, R.D., author of The Little Book of Game-Changers.
During the fasting periods, you’re usually limited to having water, coffee, and tea, Cording says.
Benefits of intermittent fasting
There has been a pretty decent amount of research around intermittent fasting and its impact on health. One of the biggest reasons people choose to go on an intermittent fasting diet is weight loss. However, research has found that it’s pretty equivalent in results to going on a calorie-restricted diet.
One meta-analysis published in the journal JBI Database of Systematic Reviews and Implementation Reports found that intermittent fasting led to similar weight loss results to people who followed a calorie-restricted diet. Another randomized clinical trial published in JAMA Internal Medicine followed 100 adults with obesity and found that those who fasted every other day for a year only a little more weight than those who ate a calorie-restricted diet. (Worth noting: The difference in weight loss was so small, it was considered clinically insignificant.)
Yet another study, this one published in the Annals of Internal Medicine, followed 77 people with obesity and randomly assigned them to follow an intermittent fasting diet, eat whatever they wanted but reduced their total calorie count by 25%, or do nothing different. After six months, the researchers had the intermittent fasting group eat for a 10-hour window and the calorie counters eat until the felt satisfied. Ultimately, the IF and calorie restricted groups ended up losing similar amounts of weight.
Research has also linked intermittent fasting to lowered insulin levels, better insulin sensitivity, and lowered blood pressure. People on an intermittent fasting diet may also end up feeling less hungry than those who follow a normal eating pattern.
“The benefits really depend on the person,” Cording says. “A lot of the research has shown improvements in people with overweight or obesity, but we don’t have much data in people who have lower weights.”
While the data so far on intermittent fasting is promising, the research on the eating plan is still relatively new. “Further studies are needed for conclusive evidence,” says Keri Gans, M.S., R.D., author of The Small Change Diet.
Common intermittent fasting schedules
Technically, you can create any intermittent fasting schedule you want. However, these are the most common ones people choose.
The 16:8 diet
This IF schedule involves fasting for 16 hours a day and having an eight-hour eating window. People who follow the 16:8 diet can have their eating and fasting periods during any time of day, but many will choose to do something like start eating at 11 a.m. and begin fasting after 7 p.m., Cording says.
This type may be successful for weight loss, although that’s still being explored. A small study published in the journal Nutrition and Healthy Aging had 23 adults with obesity either do a 16:8 diet for 12 weeks or eat normally. The researchers found that those who followed the 16:8 diet ended up eating 350 less calories a day and lost about 3% of their body weight on average.
“If someone has a consistent schedule, this may be a good choice,” Cording says. The 16:8 diet is one of the most popular intermittent fasting schedules people follow, she says.
The 5:2 diet
This intermittent fasting schedule requires longer periods of fasting. “For five consecutive days, you eat as you wish,” Gans says. “Then, for two non-consecutive days, you consume only around 500 calories per day.”
A randomized controlled trial published in PLOS One had 300 adults with obesity either follow a 5:2 diet, or a more traditional diet and exercise plan for a year. The researchers found at the end that both groups achieved similar weight loss results. “Health professionals who provide brief weight management advice may consider including the 5:2 advice as an option,” the researchers concluded.
The 14:10 diet
This schedule involves fasting for 14 hours and eating for 10. Cording says it’s more approachable than the 16:8 and can be an easier way for people to see if an intermittent fasting diet is for them.
Research has supported this eating plan for weight loss. One randomized controlled trial of 78 people with obesity found that those who paired a 14:10 diet with a healthy eating plan and workout routine lost more weight than people who followed a 12:12 diet (which involves having a 12-hour eating window and fasting for the other 12).
Eat stop eat diet
This is essentially a variation of the 5:2 diet. “You eat whatever you want and then for one to two days, you completely fast with consumption of only zero-calorie beverages,” Gans explains.
Cording is not a fan of this approach. “I don’t like getting rid of calories in an entire day,” she says.
Alternate day fasting
This plan involves eating normally for one day and restricting your calories the next, Cording says. You can choose to either completely fast during those days or limit yourself to 500 calories, Cording says.
This is a tricky one to follow, Cording says. “It tends to create a feast or famine mindset,” she says. “People tend to go above and beyond on the non-fasting days.” Research also doesn’t suggest that you’ll lose more weight on this diet compared to more traditional calorie cutting.
The Warrior Diet
This is a unique approach to intermittent fasting. “You can eat small amounts of raw fruits and veggies throughout the day, and enjoy one four-hour window in the evening of eating whatever you want,” Gans explains. It was created by fitness and health writer Ori Hofmekler and focuses on eating unprocessed, organic foods.
Cording is also not a fan of this eating plan. “When someone doesn’t get enough protein during the daytime, that sets them up for cravings,” she says. “When they do finally eat a meal, they eat a really large quantity—probably much more than they would otherwise. That’s not helpful for metabolic health.”
How to choose an intermittent fasting schedule
If you’re interested in intermittent fasting, Cording suggests trying a 16:8, 14:10, or 12:12 plan. “Look at your schedule and pay attention to when you tend to naturally the hungriest,” she says. “That will give you clues as to what the ideal eating windows would be for you.”
She also recommends thinking about your exercise habits, too, and making sure you can properly be fueled after workouts.
Finally, take your lifestyle into account. “The more flexible the intermittent fasting plan is, the more likely you are to stick with it,” Gans says. “One must choose one that can fit into their lifestyle—otherwise they most likely will fail.”
Will intermittent fasting cause weight loss?
Intermittent fasting can cause weight loss, but it’s not a guarantee, says Gabby Headrick, PhD, an assistant professor in the Department of Exercise and Nutrition Sciences at the George Washington University Milken Institute School of Public Health. However, she points this out: Research suggests that intermittent fasting is no more effective for weight loss than traditional calorie restriction.
“Intermittent fasting could be particularly helpful for those who benefit from regimented schedules,” Headrick says. “There are different methods to intermittent fasting, but all require strict periods of eating and periods of fasting.”
Ultimately, you’ll lose weight if you’re in a calorie deficit. “Intermittent fasting can help people achieve just that,” Headrick says. However, she stresses the importance of following good nutrition during your eating windows. “It is important to consume nutrient-dense foods during the times of eating—fruits, vegetables, whole grains, beans, and lean proteins—and to limit added sugars, sodium, and saturated fats,” Headrick says. “These principles of healthy eating don’t disappear with the method of intermittent fasting.”
Is intermittent fasting safe?
It depends. Research into the safety of intermittent fasting is not robust at this point. There is one data analysis that was published in the journal Nutrients in 2022 that suggested that fasting may interfere with fertility in women. The reason, per researchers: Fasting lowers the levels of sex hormones like testosterone and lowers your libido as a result.
People who are pregnant, breastfeeding, or who have a history of disordered eating should not do intermittent fasting, Cording says. She also recommends talking to your doctor about going on an intermittent fasting diet if you have diabetes.
How to start intermittent fasting
If you’re interested in following an intermittent fasting diet, Headrick suggests talking to a healthcare provider, like a registered dietitian or your general doctor, to make sure you don’t have an underlying condition that will make this risky for you.
“People who are pregnant, have diabetes, and people using certain medications should not follow intermittent fasting,” Headrick points out.
From there, Cording suggests starting slowly. That can mean deciding you won’t eat after 8 p.m. and then before 8 a.m. and seeing how you feel before ramping things up, if you decide to go that route. Headrick agrees.
“If it is going well, you can decrease the eating window to eight hours and increase the fasting window to 16 hours,” she says. That might mean eating from 10 a.m. – 6 p.m. and fasting from 6 p.m. – 10 a.m.
“If choosing to intermittent fast, it is helpful to align your fasting period with your sleeping hours,” Headrick says.
Cording says that the good news about intermittent fasting is that it’s easy to adjust. So, if you find that a particular schedule isn’t working for you, you can simply change it and see how you feel. And, of course, if you ultimately decide that intermittent fasting isn’t your thing, that’s just fine, too.
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