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The Complete Guide to 18:6 Intermittent Fasting Schedule

February 16, 2023 6 Comments

The Complete Guide to 18:6 Intermittent Fasting Schedule

taylor picture
By: Taylor Ford
Executive Editor 



  • 18:6 intermittent fasting is when you abstain from eating for 18 hours and eat all your meals in a 6-hour window.
  • Benefits: increased energy, lower blood sugar, potential weight loss.
  • Our conclusion: Short term diets are not a long term solution, but the nutrition & lifestyle choices made while 18:6 intermittent fasting could be beneficial if added to your consistent routine.


Table of Contents


A recent study found that over the course of a year people can lose about 5% of their body weight by staying consistent with intermittent fasting. This article is a guide to the most popular form of fasting, 18:6.

During prehistoric times, before humans understood planting crops and farming, they would hunt and gather their food. This primitive eating pattern, rooted in the ebb and flow of resource availability, shaped the human body's response to periods of food scarcity.

Mark Mattson, a neuroscientist at Johns Hopkins with over 25 years of dedicated research on intermittent fasting, draws attention to the profound impact of this ancestral lifestyle on our metabolic processes. According to Mattson, the practice of intermittent fasting taps into an evolutionary adaptation known as the "metabolic switch." After hours without food, the body exhausts its sugar stores, prompting a shift to an alternative energy source—fat. This metabolic transition, called "ketosis," is a natural and evolutionary response that allowed our ancestors to endure times of food scarcity.

What our ancestors called a "bad hunt" due to the scarcity of food available while hunting and gathering, is now a deliberate and structured practice known as "intermittent fasting." This article is a guide to the most popular form of the intermittent fasting diet, the 18:6 diet.



Intermittent fasting (IF) is a diet in which you have a time-restricted window during the day when you can eat. The rest of the day, you fast, meaning you do not eat. This keeps your body in ketosis, burning fat for energy rather than carbohydrates.

There are different ways to participate in intermittent fasting. 18:6 intermittent fasting is the method of abstaining from eating for 18 hours and eating all your meals in a 6-hour window.

You should choose your time restricted eating window based on your lifestyle and what eating schedule works best for you. You could skip breakfast, start your first meal at 12:30 pm and end your time restricted eating window at 6:30 pm for dinner. Others may choose to start their first meal later in the day to have a later dinner. You may have to try out different schedules to see what works best for your lifestyle.

How does intermittent fasting work? I think Gin Stephens in her New York Times best selling book "Fast. Feast. Repeat." said it best:

"Insulin is the key to whether your body is in fat-storing mode or fat-burning mode, and fasting puts you solidly into the fat-burning side of the equation … which is just what we want!"


  • By fasting for 18 hours and consuming your calories within a 6 hour window, you can put your body into ketosis, allowing it to burn fat rather than carbs.



18:6 is known as one of the more difficult intermittent fasting schedules. Keeping your body in a fasting state for 18 hours isn't something you jump right into. If you have tried 12:12 or 16:8 and didn't see results, or if you want to kick your weight loss up a notch, 18:6 intermittent fasting might be for you.

Some people do alternate-day fasting (ADF) periods, which are a bit easier and potentially a starting point if you are interested in trying 18:6. Alternate-day fasting typically involves fasting every other day and restricting your daily caloric intake to 25% of your energy requirements. For example:

  • Day 1: Eat normally

  • Day 2: Fast, reducing calories (around 500 calories)

  • Day 3: Eat normally

As for the success of ADF, some studies have shown a potential weight loss between 3-8% within 12 weeks.


  • Other methods of fasting include changing out the fasting period or alternating your fasting days.





18:6 intermittent fasting benefits

18 hours without food can be challenging, but if you can stick to it, you could start to see some benefits in as little as a week!

Of course, the number one benefit of intermittent fasting for most people is weight loss. Here are some added benefits to 18:6 intermittent fasting:

Weight loss

One of the primary benefits of 18:6 intermittent fasting is weight loss. Your body goes into ketosis as your blood levels of insulin drop. Also, by limiting your calorie intake and the time frame in which you consume your calories, you may be able to create a calorie deficit without feeling deprived or hungry. Studies have shown that intermittent fasting can help you lose weight and reduce body fat, while maintaining muscle mass, leading to more muscle growth and a healthier overall body composition.

How much weight you could lose depends on a lot of factors, such as your lifestyle. Intermittent fasting works especially well if you combine fasting with a healthy, balanced diet, and exercise plan. One study found 3-8% weight loss over 3-24 weeks, and another found a reduction in waist circumference of 4-7% between 6-24 weeks.

May reduce bloating

Many people experience better digestion within their 6-hour eating window. With a goal of fasting for 18 hours, you may notice reduced bloating and indigestion that occurs when you eat too frequently.

May help reduce inflammation

Inflammation is the root cause of many chronic diseases, including heart disease, arthritis, and even cancer. By reducing inflammation in the body, 18:6 intermittent fasting can help lower the risk of developing these diseases. Studies have found that intermittent fasting can reduce inflammation markers in the body, leading to improved overall health.

May help balance blood sugar levels

By limiting the time frame in which you consume your calories, your body is better able to regulate blood sugar levels. This balance helps reduce the risk of diseases later in life.

Heightens energy levels

Many people who practice intermittent fasting report feeling more energized during the day. Fasting triggers a natural release of adrenaline and other hormones, leading to increased alertness and focus. Additionally, fasting can help regulate sleep-wake cycles, leading to better sleep quality and increased energy levels during the day.

May improve sleep.

Speaking of sleep, a 6 hour eating window may also improve your sleep. Most people doing 18:6 intermittent fasting end their meals between 6:30 and 7:30 pm, rather than eating right before bedtime. The structure of consciously timing your meals and not eating late helps regulate your sleep cycles, leading to better sleep quality and more restful nights.


  • Intermittent fasting can help you take control of your day and includes benefits like weight loss, reduced inflammation, better sleep, and more energy.



Numerous research studies on both animals and humans have shown a handful of benefits to practicing intermittent fasting. Studies have shown intermittent fasting to be effective at supporting healthy blood pressure, and optimal resting heart rates during the designated fasting window.

As for weight loss, intermittent fasting can effectively help lose around 0.8% to 13.0% of your body weight in multiple studies ranging from 2 weeks up to a full year. However, a recent study at John's Hopkins challenges the narrative, proposing that the conventional strategy of consuming fewer and smaller meals might be more effective for weight loss than an extended fasting regimen. 

The contrast in findings emphasizes the complexity of the human body's response to different dietary approaches. The 18:6 fasting schedule introduces a unique rhythm to metabolism with extended fasting periods, yet its effectiveness may vary based on individual factors like metabolism and lifestyle. Understanding the intricacies of the fasting hours and the optimal fasting window becomes crucial for personalized success.


  • Some studies show effective weight loss through intermittent fasting, while others show it isn't more effective than "fewer and smaller meals."




man eating meal at a table

You will likely be very hungry when it's finally time to start your eating window, but make sure you plan ahead for how you are going to break your fast. You can read the read the complete guide here, but to summarize:


Ease your system back into gear with something under 500 calories and easily digestible. 


Drink water during and after you break your fast. There are countless benefits to being hydrated.


Fruits, vegetables, and lean protein. Avoid eating heavy, high fat, high carb, and sugary foods. Here is a great lean protein that helps you burn fat. 


The rapid spike in blood glucose will definitely end up making you tired.


  • Don't ruin the hard work by binging eating heavy or highly-processed foods after your fast. Ease in, start small with easily digestible foods. Avoid high fat, high carb meals and especially avoid sugary foods.



Protein shakes can work well with intermittent fasting. Depending on your goals can determine how you how you incorporate them into your eating window.

Will a protein shake break your fast?

One common question that arises during intermittent fasting, especially in the context of the 18:6 schedule, is whether consuming a protein shake breaks the fast. The answer depends on your fasting goals and the specific ingredients in your protein shake.

Protein shakes contain calories, and consuming calories during the fasting period will technically break the fast. However, some argue that the insulin response to protein is minimal compared to carbohydrates, and therefore, a moderate protein shake might not significantly impact the metabolic state achieved through fasting.

If your primary goal is weight loss, a small protein shake within your fasting window might be acceptable for some individuals. However, for those strictly aiming for the metabolic benefits of fasting, such as ketosis and enhanced fat burning, sticking to water, herbal tea, or black coffee is recommended.

Should you start your eating window with a protein shake?

Initiating your eating window with a protein shake can be beneficial for several reasons:

  1. Appetite Control: Protein is known for its satiating effect, helping control hunger and reducing overall calorie intake during your eating window. This can be particularly advantageous for individuals aiming to manage their weight.

  2. Muscle Preservation: If you engage in physical activity, starting with a protein shake provides essential amino acids that support muscle preservation and recovery. This is crucial, especially if you've been in a fasting state where your body may benefit from a quick protein source.

  3. Nutrient Density: Depending on the ingredients, a well-balanced protein shake can provide essential nutrients, including vitamins and minerals, contributing to your overall nutritional intake.

  4. Metabolic Boost: Protein has a higher thermic effect compared to fats and carbohydrates, meaning it requires more energy for digestion and metabolism. Starting with protein may contribute to a slight metabolic boost.

 Considerations for an Ideal Protein Shake:

  • Low Sugar and Carbohydrates: Opt for a protein shake with minimal added sugars and carbohydrates to mitigate insulin response.

  • Moderate Caloric Content: Keep the caloric content moderate to avoid disrupting the metabolic state achieved through fasting.

  • Branched-Chain Amino Acids (BCAAs): Can support muscle preservation during weight loss.

Our recommendation: Mdrive Lean. It's a high quality protein powder with only 100 calories, 5g carbs and less than 1g of sugar.


  • Protein shakes can complement intermittent fasting, but whether they break a fast depends on specific goals. Starting your eating window with a protein shake aids appetite control, muscle preservation, and nutrient intake.



Incorporating vitamins and supplements during intermittent fasting can be a strategic choice, especially when aiming for weight loss. Certain supplements may assist in enhancing the effectiveness of your fasting period.

When to Take Vitamins & Supplements:

  • It's generally advisable to take vitamins and supplements with meals to enhance absorption, as many nutrients are fat-soluble and benefit from food intake.

  • If your eating window falls within the evening, consider taking your vitamins and supplements with your first meal to ensure proper absorption.

Can You Take Them While Fasting?

  • Most vitamins and minerals do not contain calories, so taking them during the fasting period might not technically break your fast.

  • However, some supplements, especially those in oil or gel capsules, may have a small caloric content. Be mindful of these if your fasting goal is strictly calorie restriction.

Does It Break Your Fast?

  • In most cases, taking vitamins and supplements with little to no caloric content is unlikely to disrupt the metabolic state achieved through fasting.

  • Still, if your primary fasting goal is the metabolic benefits, consider taking them strategically within your eating window.

Recommended Supplements for Weight Loss:

  1. Multivitamins: Ensure you get essential nutrients that may be lacking during calorie restriction. This multivitamin is formulated specifically for active men.

  2. Omega-3 Fatty Acids: Support overall health and may contribute to weight loss efforts.

  3. Vitamin D: Linked to metabolism and weight regulation; consult with a healthcare professional for appropriate dosages.

  4. Thermogenic Supplements: These supplements, often containing ingredients like caffeine, green tea extract, and capsaicin, and Advantra Z may boost metabolism and aid in fat burning.

  5. Adaptogens: Incorporating adaptogens during intermittent fasting can strategically aid weight loss. These herbs help the body manage stress, potentially supporting weight management by reducing stress-related eating. Known for their energizing properties, adaptogens can also enhance exercise performance and increase energy levels. Some adaptogens to consider are ashwagandha, maca, ginseng, cordyceps and tongkat ali.

Looking for a supplement to help check off these boxes? Mdrive Boost & Burn is a well-balanced formula that includes several of these recommended supplements for weight loss.


  • Taking vitamins and supplements during intermittent fasting can be strategic for weight loss. While it's best to take them with meals for absorption, most supplements won't break a fast.



Short term diets are not a long term solution, but the nutrition & lifestyle choices made during 18:6 intermittent fasting could be beneficial if added to your consistent routine. Once your body adjusts, it should become easier. It takes 66 days to make a habit automatic, but you can do this!


How often should you do intermittent fasting?

How often you fast is completely up to your personal preference and depending on your health conditions as well as what goals you are looking to achieve

Is intermittent fasting safe?

If you have concerns you should consult your doctor before making any dietary changes. A fast should always be planned ahead including timing, hydration, and breaking the fast. Pay very close attention to how your body feels and what it is signaling.

What are the rules for 18:6 fasting?

18:6 intermittent fasting is when you abstain from eating for 18 hours and eat all your meals in a 6-hour window. You should choose whichever window suits you the most. You might start eating at 1:30pm and then finish with dinner at 7:30pm.

You can drink liquids that don't contain calories like water, herbal tea, or black coffee.

Anything over 50 calories would be considered breaking the fast and disrupting the metabolic state otherwise achieved through fasting.



This article offers general information and is not a substitute for professional medical advice. Consult with a healthcare professional or dietitian before making any changes, especially if you have medical conditions or are on medications. Individual responses to intermittent fasting vary. This article does not endorse specific protocols. Decisions about dietary changes should involve healthcare professionals who can provide personalized guidance based on individual health needs. The author and publisher are not responsible for consequences resulting from applying the information.

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6 Responses

The Driven Team
The Driven Team

May 15, 2024

Josh – While there’s no strict “cheat day” with the 18/6 method, it’s flexible. If you feel like you need a break or want to enjoy a meal outside of your usual eating window, you can certainly do so occasionally. The key is to maintain balance and moderation so you can create long-term sustainable eating patterns. If you have any questions, feel free to ask. Best wishes on your journey to better health!

Josh G
Josh G

May 15, 2024

Is there a cheat day with 18/6? First timer to i-diet. Thank you.

Mike W
Mike W

September 06, 2023

Hi; I am very interested in doing the 16/8 fasting diet program, but my question is, as I read up on what foods are good to eat during my 8hr fasting window, Im wondering how MUCH of each food type can I eat? Like for instance, one suggestion was eating a salad, but how much of a salad? What should the salad include? Should I eat a small salad, a big salad? Is a small salad at like Salata sufficient?

Robert w
Robert w

June 15, 2023

Thank you for your. Write-up. Going to get my self better versed up on this ketosis. Have been doing the 18/6 first for past 3 weeks, Only had 1 major previous diet, low carb diet which was effective, until I fell off wagon, I hope to combine, low carb diet with the fasting along with a set of rules or principle . Last few weeks have had a bit of success on my journey to lose 32 kilos, loosing 7 kilos . Your comment on Ketosis grabbed my attention , I feel like I shredding weight particularly last couple hour of fast? Is that something u can feel? Particularly when I’m walking or exerting last couple hours of fast. Or is that just the hunger pains. Thank for your insights
Cheers rob

Taylor Ford - The Driven
Taylor Ford - The Driven

April 28, 2023

Martha, that is incredible! Has it helped and how do you feel?

Martha Rampton
Martha Rampton

November 09, 2022

I can only fast 14-15 hours. Does that do any good?

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