What Is the 18:6 Intermittent Fasting Method? Experts Explain

The benefits of intermittent fasting (IF) some people experience include weight loss, more energy, improved digestion, decreased sugar cravings, and better sleep. There are so many ways to fit intermittent fasting into your life, so if you've been thinking about it, there's bound to be one that's right for you.

Of course, before starting any new diet plan, including intermittent fasting, be sure to check in with your doctor first. Once you get the OK, doing 14:10 fasting is a great place to start, where you fast daily for 14 hours and have a 10-hour eating window. If you're ready to do longer fasts, the 16:8 protocol is the perfect next step. It extends your fasting window by two hours; for example: eating from noon until 8 p.m. If you find that you eat dinner earlier, though, you might be interested in trying 18:6.

What Is 18:6 Intermittent Fasting?

18:6 involves fasting for 18 hours out of the day, leaving you with a six-hour eating window. This could mean eating lunch at 12:30 p.m., a snack at 3 p.m., then finishing dinner by 6:30 p.m. This is a much more rigid form of intermittent fasting and definitely best saved for experienced fasters who've tried other methods. This method of an 18-hour fast might be right for you if your weight loss has stalled doing 16:8 or if you tend to overeat with a longer eating window.

How Does 18:6 Intermittent Fasting Help With Weight Loss?

Jason Fung, MD, a nephrologist (kidney specialist) and author of The Complete Guide to Fasting, explained that intermittent fasting can help you burn fat by lowering insulin levels.

This is different than the typical method of weight loss suggested by most experts, which is to restrict calories. Dr. Fung said if you reduce your calories from 2,000 to 1,500 a day (to create a 500-calorie deficit), the body is forced to reduce its metabolic rate to match. The slower metabolism makes you feel cold, tired, and hungry. Weight loss eventually plateaus, which means you'll need to eat even less to lose weight, which is not sustainable. This is why Dr. Fung said calorie-restriction diets fail, which was also proven in contestants from weight-loss TV show The Biggest Loser. A major study that looked at former The Biggest Loser contestants found that a period of intense calorie restriction and weight loss had wrecked their metabolisms, leaving them needing much fewer calories to maintain their new weight than before they went on the show. Most of the contestants ended up regaining most, if not all, the weight they had lost on the show.

Dr. Fung works with patients with diabetes, and he said fasting has helped them lose weight, reverse their diabetes, and get off medication. "If insulin is low, then the body can get its energy from fat stores," he said. Many people who fast actually find that hunger decreases, which is why IF can help people who tend to overeat. When doing any form of daily intermittent fasting, you aim to eat your daily calories, just in a shorter eating window.

To find out your target calories, you need to calculate your basal metabolic rate (BMR) and total energy expenditure (TDEE). Use this formula to estimate how many calories you should eat a day for weight loss.

Pros of 18:6 Intermittent Fasting

  • It's easy to maintain every day: Without much disruption to your daily schedule, you basically skip breakfast and then have your dinner on the earlier side.
  • It's flexible: If you prefer eating a later lunch, you can shift your eating window (2 p.m. to 8 p.m.) or shift it earlier (10 a.m. until 4 p.m.).
  • Improved digestion: Eating less time during the day can help reduce or prevent bloating and improve digestion.
  • Clear mind and increased energy: After your body adjusts, you'll experience a heighten sense of mental clarity and focus, which means no more brain fog, and more energy.
  • Improved sleep: If you tend to go to bed earlier, eating dinner by 6 p.m. means you're not snacking after dinner, so you're hitting the sheets with a full stomach. You can just start a new habit where you curl up on the couch with a hot cup of herbal tea.
  • You can eat larger meals: Since you're consuming all your daily calories within a shorter window, another pro is that you can sit down and eat larger meals and feel more satiated than if you were eating three to six small meals throughout the day.
  • You can eat the foods you love: You have more leniency with the foods you eat as well, so you can choose higher-calorie or higher-carb foods you may have denied yourself before. And even if you skip breakfast, you can still eat the breakfast foods you love; you'll just be delaying your meal until later in the day.

Cons of 18:6 Intermittent Fasting

  • It can feel restrictive: For those who are used to eating all day long, limiting your meals and snacks to a six-hour window may seem impossible.
  • It can cause digestive issues: While some people may experience improvement in their digestion from eating fewer hours during the day, since it can be tough fitting all your daily calories into a six-hour window, you might find it hard to eat as many as you need without feeling stuffed.
  • You may feel hungry: If you don't make a point to eat enough calories or eat enough protein and healthy fats, 18:6 may cause you to feel hungry or tired.
  • Can trigger binge eating: Any form of intermittent fasting, especially 18:6 since it's stricter, could potentially be a trigger for unhealthy behaviors for those with a history of eating disorders. Lisa Eberly Mastela, MPH, RD, told POPSUGAR that any form of IF should be done under the supervision of a registered dietitian, and any diet that encourages a restrictive eating schedule really should be approached with caution from the start. You might be fine doing a less rigid form of intermittent fasting, such as 16:8, but if you have any doubts, it's best to talk to a doctor or dietitian, and, if you have a history of disordered eating, a therapist. Intermittent fasting shouldn't negatively affect your life.

Tips For Success With 18:6 Intermittent Fasting

Like any new way of eating, there is an adjustment period. The best advice is to not dive right into 18:6 if you've never fasted before. Start with a 12-hour fasting window, then gradually work your way up to 14 hours, then 16 hours. While fasting, make sure you are only drinking black coffee, tea, carbonated water, and plain water. Consuming a little bit of cream or stevia in your coffee can actually induce hunger, which will make fasting harder. And be sure to get at least seven hours of sleep a night to prevent cravings caused by fatigue. Choose nutrient-dense foods, and eat until you're satiated but not stuffed, and focus on getting protein, healthy fats, complex carbs, and plenty of fiber.

Using an intermittent fasting app might be helpful to track your daily progress and inspire you to stick with it. But always remember the cardinal rule about fasting: if you don't feel well, end the fast and try again the next day.