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Is 18/6 Intermittent Fasting For You? Health Impact & Weight Loss

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Fast 18 hours everyday
Melissa Mitri post Reviewer Melissa Mitri post Reviewer
Verified by Melissa Mitri
MS, Registered Dietitian, Former President of CT Academy of Nutrition & Dietetics

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Intermittent fasting (IF) is an approach where you restrict the number of hours per day you’re eating rather than the number of calories or the type of food you eat. 

Numerous research studies suggest that IF produces various health benefits, including weight loss [1], reduced risk of diabetes [2], and improved brain health [3]. There are several versions of IF according to the duration of the eating and fasting windows. 

The most common ones are the 16/8 method, alternate-day fasting, and the 5:2 method. 

Another popular routine is 18/6 intermittent fasting which is thought to produce faster and better results. In this post, we aim to discover the pros and cons of 18/6 fasting and its weight loss potential.

What is 18/6 Intermittent Fasting, and How Does it Work?

An 18/6 intermittent fasting schedule means that you eat within a window of 6 hours and fast for 18 hours. 

During the hours you’re fasting, your body begins to use up much of its glucose and may begin to break down fat, producing compounds called ketones [4]

If you don’t have a lot of glycogen (stored glucose) stored up, you may produce ketones faster. However, if you have a lot of glycogen stored, it could take 2-4 days of fasting to fully enter this fat-burning phase [5].

This phase is known as ketosis, and it is proven to have many benefits, such as improved insulin resistance, reduced risk of heart disease, and weight loss [6]

Compared to other IF methods, such as 14/10 and 16/8, an 18-hour fast is more restrictive and can be challenging for a beginner. 

However, there are more extreme fasting plans, such as 24-hour fasting, in which you fast for an entire day, or 5:2, in which you consume only around 500-600 calories two days per week. 

Check out our intermittent fasting guide for beginners to learn more about the various fasting schedules. 

18/6 Intermittent Fasting Eating Window

While following the 18/6 method, you can arrange your eating and fasting schedules in a way that effortlessly aligns with your day. 

For instance, you can choose to skip breakfast and have lunch as your first meal around 12 PM and have an early dinner at 6 PM. This suits you well if you don’t feel hungry in the mornings and prefer to enjoy dinner with your family.

If, on the other hand, you find your energy levels are low during the mornings, you can have breakfast around 9 AM, eat lunch at 3 PM, and skip dinner. 

Depending on your timing, you can have two large meals per day: breakfast and lunch or lunch and dinner. You can also have a snack in between if you prefer. 

You can easily track your meals using an all-in-one weight loss app to make things easier and to help you stick to your desired schedule.

As you can see, it doesn’t matter when you eat or how many meals you eat, as long as you keep it within the 6-hour window. 

What to Eat During18/6 Intermittent Fasting

Intermittent fasting guidelines don’t dictate what you eat as long as you stick to your eating and fasting windows.

However, filling your plate with nutrient-dense foods rather than junk will yield better results.

Since you’re only eating two meals, you need to make sure you get enough nutrients that your body needs to function effectively. Eating wholesome portions of proteins, fiber, and healthy fats will make sure that you will stay full during your extended fasting window. 

We have a guide on what to eat during intermittent fasting if you want to read more. 

This doesn’t mean there isn’t room for an occasional cheat meal or two. You can incorporate a cheat meal—or a cheat day—safely with intermittent fasting without sabotaging your weight loss progress—if you do it wisely. 

Pros and Cons of 18/6 Intermittent Fasting

As we briefly explained earlier, research has proven that time-restricted eating strategies such as intermittent fasting promote significant weight loss [1]. Apart from that, intermittent fasting has been found to impart various health benefits, and those advantages apply to 18/6 fasting as well. 

list of benefits and drawbacks of 18:6 Intermittent Fasting

Health Benefits of an 18-hour Fast

You will have better weight loss progress

You already know that intermittent fasting produces weight loss. However, research has shown that 18-hour intermittent fasting reduces BMI (Body Mass Index) more effectively than 12-17 hour fasts [7]

You will experience enhanced insulin sensitivity

Intermittent fasting has been proven to significantly improve insulin resistance in patients who are suffering from weakened glucose metabolism [8]. During lengthier fasts, blood insulin levels stay low for longer, thus increasing the effect on insulin sensitivity. 

Your heart health will improve

When your body goes into ketosis during the fasting window, it starts to burn fat. It also stabilizes blood sugar levels as we explained in the previous section. 

Studies have also discovered intermittent fasting produces a certain protein that controls inflammation [9]. These factors work together to support a healthy heart. 

You can eat larger meals

Since you will only be eating 2 main meals per day, you can afford to eat larger portions (if you want them). This will help you to stay more satisfied in between meals mentally as well as physically. 

You can eat the food you love

Since IF regimens don’t restrict what you eat, you can add foods you love to your meals—within reason, of course. While this doesn’t mean you can eat fast food every day, you can definitely indulge in a food you love once in a while without disrupting your diet. 

Drawbacks and Risks

It can feel too restrictive

As we said, fasting for 18 hours is no easy task. You may feel your eating window is too short, especially in the first few weeks. You might even feel like giving up altogether. Our suggestion is to give it some time and start slow. 

Fasting 18 hours a day is not for you if you’re a beginner. It’s best to start with a longer eating window, such as 12/12 or 14/10, and then gradually lengthen the fasting duration.

It can make you feel too full

Eating two to three meals within 8 hours can leave you feeling too full, as food typically stays in the stomach and the small intestine for 6-8 hours after consumption. 

The trick is to start eating moderate portions during each meal and find out the right portion size per meal.

You might feel hungry during the fasting window

Since the fasting window is long, you may feel hungry during the first few days. You might have mood swings, low energy levels, and trouble focusing. However, it may get better as your body gets used to your new eating pattern.

It might be difficult to fit in your workouts

Because this IF method involves extended fasting periods, you might have trouble fitting a workout schedule into your day. Working out in a fasted state is not a good idea; you might feel your energy levels dropping during the first couple of days or weeks. 

In such a situation, you can start with less-intense workouts and progressively increase the intensity. However, it would be best if you work out during your eating hours to keep it safe.

18/6 IF as a Weight Loss Strategy

Numerous reviews have confirmed the effectiveness of intermittent fasting as a weight-loss strategy [10][11]. One review concluded that intermittent fasting can produce 7-11 pounds of weight loss within 10 weeks [10]

As we explained earlier in the article, during fasting hours, your body may transition into ketosis, flipping a metabolic switch in the process [12].

In simple terms, it means your body exhausts the glucose reserves and switches over to fat reserves, thus burning fat to produce energy. Your body needs at least 12 hours to make this switch [13], which means you need to stay in the fasting state for more than 12 hours.

One study reported that energy intake was reduced by around 550 calories per day during a 4 and 6-hour feeding window, and the subjects lost around 3% of their body weight over 8 weeks [14]. 

How Long Does it Take to See Results from 18/6 Fasting?

Based on the studies, you can expect to see noticeable results after 8 to 10 weeks of 18/6 fasting.

During the first couple of weeks (2 to 4 exactly) of IF your body is getting used to a new regimen, so it’s unlikely to see results during this period [15].

So, Is 18/6 Intermittent Fasting Good for You?

Considering all these facts, we can agree that 18/6 intermittent fasting can be good for you in terms of weight loss and general health.

However, you should keep in mind that this is not the best-suited fasting schedule if you’re just starting off. 

If you’re a beginner, it would be best to start with a longer eating window, such as 12 hours or 10 hours, and gradually work your way up to shorter eating periods. 

Also, there are a few categories of people who should bypass IF [15]:

  • Children and teens
  • Pregnant or breastfeeding women
  • People with type 1 diabetes who take insulin
  • People with a history of eating disorders

With that said, you should speak to your doctor before starting any diet plan, including an intermittent fasting protocol, especially if you have conditions such as diabetes and thyroid issues. 

How to Start 18/6 Intermittent Fasting

Start With a Less Restrictive Type of Intermittent Fasting

If you’ve never tried IF, it might not be the best idea to start with 18-hour fasts. Begin with the 14/10 or even 12/12 regimen to let your body get used to a new schedule. Then, gradually shorten the eating window to 8 and then to 6 hours.

Choose Your Timing

During 18/6 intermittent fasting, you need to skip one meal, either breakfast or dinner. Use our intermittent fasting calculator to calculate when you should start and stop eating and determine which meal will be easier for you to skip.

Here is an example of such a calculation. If you choose to skip breakfast, you can start your eating window at 12 pm, and during the next 6 hours—till 6 pm—you can have a couple of meals and a snack. The next 18 hours, from 6 pm to midday the next day, you’ll be fasting.

Stay Hydrated

All the time! Clean water should be your good companion throughout fasting, but you can definitely add some variety by drinking other zero-calorie drinks permitted during fasting, like green tea, coffee, or even coffee with creamer!

Sustain a Balanced Diet

This is not one of the rules of intermittent fasting, but it’s still important to be mindful of your food choices. You still need to get your nutrients out of a limited number of meals (you have only 2 now).

You can adopt the 80/20 approach where your diet mostly consists of nutritious and balanced meals but you are left with 20% that you can fill with any junk food you want. Another approach is to have occasional cheat days during fasting.

Avoid Common Mistakes

Here are a couple of mistakes you should avoid while fasting:

  • Not achieving calorie deficit if you fast to lose weight.
  • Undereating can make you feel extremely hungry during the fasting window and lead to nutritional deficiencies.
  • Choosing the IF type that is too restrictive for you. As mentioned, start slow and let yourself adapt to a new schedule.
  • Not being consistent with your schedule. Aim to start your eating window at the same time every day.

Bottom Line

  • An 18-hour fast can produce faster and more effective weight loss results than less restrictive fasts if done right.
  • However, this approach is best suited for experienced fasters, and it’s wise to slowly work your way up from shorter fasting durations.
  • You better avoid doing high-intensity workouts during the first couple of weeks and it’s best if you can work out during the eating window.
  • Talk to your doctor before starting a new eating pattern or increasing your fasting period.
Disclaimer This article is intended for general informational purposes only and does not address individual circumstances. It is not a substitute for professional advice or help and should not be relied on to make decisions of any kind. Any action you take upon the information presented in this article is strictly at your own risk and responsibility!

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