Not Sure Where To Start With Intermittent Fasting? The 16:8 Schedule Is A Great Entry Point
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Many weight loss plans involve tracking what you eat, but intermittent fasting (IF) tracks when you eat. IF consists of "eating windows"—when you can theoretically eat whatever you want—and fasting periods, when you're supposed to abstain from food, but you're allowed to have water, coffee, and tea. The duration of your eating and fasting windows depend on which intermittent fasting schedule you follow.
First: Can IF really help with weight loss? “Some research has shown IF may result in weight loss, but the reason is unclear,” says Cesar Sauza, RDN, a registered dietitian nutritionist at the National Coalition on Healthcare (NCHC). Limiting your "eating hours" may result in fewer calories consumed, but the benefits of intermittent fasting are still debatable since there's a lack of sufficient research on the topic, Sauza says. However, IF may help with focus and concentration. “By being in a fasted state, our bodies can focus on the tasks at hand instead of breaking down food,” he says.
That said, IF is not for everyone, and the last thing you want to do is stick to a plan that's unsustainable (or doesn't work for your schedule). It's definitely not a good idea for anyone with a history of disordered eating or diabetes and those who are pregnant or breastfeeding—even if weight loss is recommended, says Dana White, RD. Also, if your schedule is sporadic or you work out at various times of the day, you might want to reconsider IF.
So, who should try it? If you tend to overeat at night or are looking for a bit more discipline, intermittent fasting may help prevent mindless eating through the day. It might also be a good option if you've tried creating a calorie deficit in the past but it didn't work. “Practicing intermittent fasting may benefit those individuals who struggle to eat breakfast or prefer to eat later in the day,” adds Sauza. “Ultimately someone should choose to practice intermittent fasting if it works for them, but most importantly if it makes them feel good,” he says.
The 16:8 method (more on that below) is the most popular route, according to White. But there are plenty of other options to choose from. Here are six of the most popular IF approaches that people tend to follow for weight loss—and what research says about each one.
Meet the experts: Cesar Sauza, RDN, registered dietitian nutritionist at the National Coalition on Healthcare (NCHC). Dana White, RD, is a nutritionist based in Connecticut who specializes in culinary nutrition, recipe development, and sports nutrition. Amanda Baker Lemein, RD, LDN, is a Chicago-based nutritionist who works with clients to create meal plans and strategizes healthy eating approaches for those with busy schedules.
1. The 16:8 diet
The 16:8 method of intermittent fasting involves fasting every day for 16 hours and restricting your daily eating window to eight hours. For most people, this schedule means not eating anything after dinner and skipping breakfast. You might eat between, say, noon and 8 p.m.
If you like working out in the morning, White suggests opting for a schedule that's more accommodating than this one (see the 14:10 diet). But if you prefer to get in your workouts during the late afternoon or after 5 p.m., you'll still have time to eat after your workout to refuel with a meal.
How does the 16:8 method fare for weight loss? It could work, the (very limited) research shows. One example: Twenty-three obese men and women followed the 16:8 diet for 12 weeks in a small study published in the journal Nutrition and Healthy Aging. Compared to a group that had eaten normally and not within a set timeframe, those on the 16:8 diet took in 350 fewer calories per day, lost a modest amount of weight (about three percent of their body weight on average), and lowered their blood pressure. Still, it's important to note that this was a small study, and there isn't a ton of research on the 16:8 diet specifically, so it’s tough to say that following the 16:8 diet is a surefire way to lose weight.
Interestingly, following this kind of eating plan may help with appetite control. People who ate only during a six-hour window versus those following a normal eating schedule felt less hungry, even though both groups ate the same amount of calories, according to a recent study in the journal Obesity.
2. The 5:2 method
To follow the 5:2 diet, you eat normally five days a week and cut back to 20 percent of your normal daily calorie intake for the other two. Note: Women are supposed to have about 500 calories on fasting days, while men have about 600.
You burn calories every minute you're alive, including when you're sleeping. When you snooze, your body utilizes the glycogen stored in your liver to keep your blood sugar levels stable. So your body is already familiar with the mechanisms of fasting, explains White.
"Your body is designed to compensate when energy is not coming in from food," she adds. "The concept of something like fasting is to prolong that period where you're relying on your internal backup system in order to fuel you."
This IF method results in just as much weight and fat loss as those who followed traditional dieting methods, according to a recent study published in PLOS ONE.
3. Alternate-day fasting
As the name implies, this diet involves fasting every other day. There are several different versions of this plan, with some of them allowing about 500 calories on the fasting days, and some encouraging that you eat even fewer or close to zero calories on fasting days.
Much of the weight loss-focused research hasn't been conclusive. And this style of intermittent fasting was deemed not superior to a calorie-restricted diet in terms of weight loss or maintenance in a JAMA study.
IF schedules that require 24 hours of fasting are harder to stick to and people tend to experience more side effects, including mood swings and hunger, according to White. So, only try this if you have done IF before and are willing to track your calorie intake and cut down the intensity of your workouts on fasting days to avoid injury.
4. Eat-stop-eat diet
This method of intermittent fasting involves a full fast for 24 hours once or twice a week. For example, you may eat dinner at 6 p.m. and then fast until 6 p.m. the next day, and you would do this one or two times per week—but not in a row.
Keep in mind that not eating for an entire day can be dangerous under certain circumstances and should not be taken lightly. While the weight-loss potential might be appealing, skipping full days of eating is not sustainable long-term.
"If you are knocking out two full days of eating, I would worry that the longer you do that, the greater at risk you would be for certain micronutrient deficiencies," says White.
5. The 14:10 diet
This one is similar to the 16:8 method, but involves fasting for a 14-hour window and eating for 10. It's a little easier to stick to than 16:8 because you have a longer eating window. But that doesn't mean it's not effective.
In fact, those who followed the 14:10 diet while incorporating nutritious foods and consistent exercise lost more weight than those who did the 12:12 diet, a recent study in Nutrition & Diabetes found. They also showed a more significant improvement in blood glucose levels after eight weeks.
Given that the fasting period is short and pretty much follows the way people already eat, it may be hard for some people to achieve a calorie deficit with this diet. Still, it could be a good way to ease into IF if you're new to it and want to see how you do when you have a specific timeframe for eating. It's also a great option if you like to get your workouts in between 8 a.m. and 10 a.m.
6. The Warrior Diet
This diet is way different from the rest, with the majority of eating happening at night. The Warrior Diet was coined by fitness author Ori Hofmekler. It involves eating only small portions of raw fruits and vegetables during the day, then feasting on one huge meal at night within a 4-hour eating window.
There's no specific research on the Warrior Diet. While the fasting periods still allow for some food, the period when you can have heavier foods is very short, and the diet also involves focusing on paleo foods, so it's stricter than other forms of IF.
And like the eat-stop-eat diet, this option is not sustainable long-term. "There's no way you're going to meet your nutrient needs eating this little food," explains White. "Your energy levels would suffer and you're basically asking to overeat. You're just going to hurt yourself if you go this route."
What are the benefits of intermittent fasting?
Although there is limited research, the initial findings are promising. Here are the potential benefits of IF based on recent studies.
IF may reduce insulin levels, fat mass, and the risk of developing age-related diseases in those that are overweight, according to a review in the Journal of Physiology and Biochemistry that investigated intermittent fasting in metabolic syndrome and type 2 diabetes.
IF may help prevent short-term and long-term memory loss, per an animal study in the journal Experimental Biology and Medicine.
IF could aid in the treatment and prevention of obesity, per Wageningen Academic.
Which intermittent fasting schedule is best for weight loss?
In short, the one that's easiest for you to follow. "It is all about sustainability for the individual," says Amanda Baker Lemein, RD, a Women's Health advisor. "If one of these diets work well for you and your lifestyle and preferences, then you will likely see some success. If not, then you'll likely not see the results you're looking for, as the sustainability piece will not be there." That means picking a diet that works best with all the lifestyle factors you need to consider, like your work schedule, family dynamic, living situation, commute time, and travel commitments, Lemein says.
It's worth pointing out, though, that the 16:8 diet seems to be the most doable for a lot of people who are into IF. The 16:8 method also scores points for preventing overeating at night, which can often be a big obstacle for weight loss. And sticking to an eight-hour eating window during daylight hours allows your metabolism to run as it’s supposed to—you fuel up for energy during the day (when you’re most active), and stop eating for rest and recovery at night, per a recent article in the journal Nutrition Reviews.
Now, any weight loss that you experience from IF is most likely due to the basic fact that you're consuming less calories, not necessarily the timing of your eating, says Lemein. And you can totally eat less, and lose weight, without taking on fasting. Case in point: Intermittent fasting had similar weight loss results to a traditional calorie-restricted diet, a meta-analysis published in the JBI Database of Systematic Reviews and Implementation Reports found. So, unless fasting makes dieting easier for you, there's really no reason to choose IF over other diets.
Tips For Sticking To Intermittent Fasting
Pick a feeding window that works for your schedule. “Following an intermittent fasting schedule is not sustainable unless it fits with someone’s daily schedule,” Sauza says.
Gradually ease into an intermittent fasting schedule instead of immediately beginning. “A standard approach is to begin narrowing your feeding window by one hour per week until you reach your desired meal schedule,” says Sauza.
Customize your timing. “Someone who skips breakfast should have a feeding window that begins around lunchtime," says Sauza. On the other hand, someone who eats and exercises earlier may benefit from a feeding window that begins early and ends before dinner time.
Set an alarm. “Set a phone alarm at first for the feeding window to maintain consistency, eventually, it should become second nature,” says Sauza.
Switch it up at least once per week and break your fast a little earlier. “Having this one-day outlier makes it easier to maintain the fasting schedule all other days in the week,” says Sauza.
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