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The Easy Guide To 18:6 Intermittent Fasting

Fasting for 18 hours a day has been touted for weight loss, better focus, and improved health.

Fast Facts

  • 18:6 is a form of intermittent fasting that may yield more pronounced weight loss than other forms of IF.
  • Some studies also suggest 18:6 intermittent fasting may lower your risk for some diseases, improve memory, and reduce inflammation.
  • You should ease into 18:6 with less intense forms of IF, then extend your fasting window.

Far from a fad, intermittent fasting (IF) was popularized about a decade ago and continues to be many health-seekers’ go-to eating plan, thanks to research suggesting its potential to melt away excess body fat (1), reset digestion, boost brain power, quell inflammation (2), crush cravings (3) and help better protect us against a variety of conditions and diseases (4). One of the most popular types of fasting is a form of IF called 18:6.

Why would you choose 18:6 over the more common 16:8 fasting timing? The longer fast time may yield greater results, especially as it relates to weight loss.

Here’s everything you need to know about the 18:6 fast, its many possible benefits and how to do it safely.

What Is 18:6 Intermittent Fasting?

18:6 is a method of time-restricted eating where you fast for 18 hours and then limit all of your calories to the remaining 6 hours of the day. If your first meal of the day is at 11AM, you’d limit all your daily calories to the 6-hour window between 11AM and 5PM, with the exception of water and fast-approved beverages like tea and black coffee. As long as your drink of choice remains under 50 calories, it won’t break your fast (5).

Not eating for 18 hours may sound difficult. But consider that you’re asleep for approximately eight of those hours. You may find it surprisingly easy to go without food for this length of time, says Jonny Bowden Ph.D., CN., especially if you ease your body into longer fasts.

Before diving into the 18:6 plan, you’ll want to build up to that timing in increments (we’ll talk about that shortly) but first, let’s go over some of the basics of intermittent fasting.

What Is Intermittent Fasting (IF) and Why Do People Use It?

IF has had a cult following in health and wellness circles for a decade and there are more than a half dozen ways to do it from alternate-day fasting, 5:2, and the OMAD diet.

Where most diets focus on what to eat, IF is mostly about when to eat, giving your body a prolonged break from the intensive task of breaking down and digesting food. Studies suggest that when your body gets a break from the consuming job of digestion, all kinds of reparative functions may take place throughout the body: inflammation may cool (6), brain fog may clear, and mental focus may sharpen (7, 8). Some studies suggest that your risk for metabolic diseases, obesity, and cancer may drop, and weight loss may become a heck of a lot easier.

  • 18:6 is a method of time-restricted eating where you fast for 18 hours and then limit all of your calories to the remaining 6 hours of the day.
  • Before diving into the 18:6 plan, you’ll want to build up to that timing in increments.
  • Some studies suggest that when your body gets a break from digestion, inflammation may be reduced, brain fog may clear, and mental focus may sharpen.

As long as your drink of choice remains under 50 calories, it won’t break your fast.

The Benefits of 18:6 Intermittent Fasting

Over time, the benefits of intermittent fasting—whether you’re doing 18:6, 16:8, or another plan—may be far-reaching and varied, including, potentially:

  • Weight loss
  • Improved gut health and digestion
  • Mental health: memory, focus, mood & wellbeing
  • Reduced inflammation
  • Reduced cravings
  • Lower risk of disease (cancer, Alzheimer’s disease, heart disease, diabetes)

“The idea is simply to give more time in the fasting state,” says nephrologist Jason Fung, M.D., a world-leading expert on intermittent fasting and low-carb diets and author of The Obesity Code. Just like 18:6 is more advanced than a 16:8 or a 14:10 fast, “It’s easier to implement into a regular day and gives structure to the eating schedule.”

18:6 intermittent fasting can prevent, treat, or reverse [insulin resistance], says Bowden, who is a weight-loss expert and creator of “In my opinion, insulin resistance is the biggest metabolic pandemic of our time. 88 percent of Americans have some degree of it and it underlies every major chronic disease, including all the co-morbidities for covid-19,” says Bowden.

How Much Weight Can You Lose Intermittent Fasting 18:6?

There have been many studies on the weight-loss results associated with different forms of fasting for various lengths of time.

In one study (9), weight loss participants lost an average of about 8.8 pounds after following a time-restricted fasting protocol for 12 weeks. In the study, participants fasted for 16 hours and ate for 8, so weight loss could potentially be even greater when employing an 18:6 method.

Who Shouldn’t Follow an 18:6 Plan?

While IF is generally considered safe for most, there are some people that should avoid fasting:

  • Anyone with diabetes or blood sugar problems
  • People on blood pressure or heart-health medication
  • Anyone with a history of an eating disorder
  • Individuals who are underweight or struggling with weight gain

Always check with your doctor before starting any type of fasting regimen.

How Long Does It Takes 18:6 Intermittent Fasting to Work?

As with all nutritional advice, there is no one-size-fits-all answer to this, as every person’s body and lifestyle are different from one another. More to the point, what “working” looks like may be different for each new faster. Intermittent fasting may be used for weight loss, but, as we discussed, it isn’t the sole benefit of embracing a timing-based diet plan.  

That said, the benefits of an 18:6 fast are attained a little faster than some of the other types of fasting, says Fung, and the reason why is rather simple: because 18:6 fasting is a more intense fast, it can produce longer and greater results.

  • 18:6 fasting is a more intense fast than other forms of IF, so it can produce longer and greater results.
  • The amount of weight you can lose on 18:6 varies but in one study, people lost almost 9 pounds in 12 weeks.
  • Always check with your doctor before starting any diet plan, including 18:6 IF. 

How to Start Intermittent Fasting

While 18:6 is a fantastic fasting window to progress to, “I wouldn’t start with it,” says Bowden. Instead, he suggests this approach:

Step 1: Ease in

Start with a 12:12 fast—12 hours fasting, 12-hour eating (e.g.: Fast from 8PM to 8AM and eat between 8AM and 8PM). During this time eat three meals (let at least 4 hours pass between meals) and no snacks.

Step 2: Extend your fasting window

After several days or a week, move to a “brunch fast” of 14:10, then 16:8 intermittent fasting, and then to 18:6 intermittent fasting.

“And remember what you eat during the window matters,” says Bowden. “Eat real food, always.”

To fill up on quality food and a variety of nutrients that means avoiding highly processed food, fast-food, simple carbs and sugary treats and opt for nutrient-dense whole foods that include plenty of vegetables and fruits, high-quality protein, healthy fats and nuts and seeds.

Step 3: Listen to your body

Not every day has to be the same when it comes to fasting. In fact, Bowden and Fung both agree it’s best to occasionally modify your fast-to-feeding windows. Some days, you’ll be hungrier and will need a longer eating window, while other days, you’ll be able to sustain super-long fasts and may only need a single meal, OMAD-style.

Above all, listen to your body and monitor your progress. If you feel your progress slipping, dial it in for a period of time with a stricter schedule. The beauty of IF is how fluid and flexible you can be from one day to the next, while still reaping the many benefits of fasting.

The Bottom Line

18:6 is one of the most popular forms of intermittent fasting. In this type of fasting, you abstain from eating for 18 hours, then eat during the following 6. 18:6 intermittent fasting has been associated with weight loss, gut health, cognitive benefits, lower inflammation and reduced insulin resistance. 18:6 intermittent fasting can be intense, so start with a less-intense form of IF, and work your way up.