5 Week Intermittent Fasting Challenge – From 0 to Expert in 35 Days

5 Week Intermittent Fasting Challenge – From 0 to Expert in 35 Days

Video | Week 1: 12:12 Fasting | Week 2: 16:8 Fasting | Week 3: 20:4 Fasting | Week 4: eTRE | Week 5: Modified ADF | Alternate Week 5: Full ADF | IF Challenge Overview

Intermittent fasting is the simple practice of introducing periods of not eating, (or fasting), into your daily routine. It can be used to improve health and weight loss. By following this blog post, you’ll have the opportunity to test drive five popular fasting methods. At the end of five weeks, you’ll not only have reaped the health and weight loss benefits but also discovered which fasting method fits your lifestyle the best, so you can continue to bring those rewards into your life. 

5-Week Intermittent Fasting Challenge – At-A-Glance

5-Week Intermittent Fasting Challenge – At-A-Glance

5 Week Intermittent Fasting Challenge – From 0 to Expert in 35 Days [Video]

In this video, you’ll learn…

  • The difference between intermittent fasting and time-restricted eating.
  • The five fasting challenges you can complete in five weeks.
  • An alternate, advanced schedule for those with prior fasting experience.

Intermittent Fasting vs. Time-Restricted Eating

What you’ll be performing are technically time-restricted eating methods because, with each one, you will be eating every day. Intermittent fasting is more of an umbrella term that includes fasts lasting longer than a day, which we won’t be doing for this challenge.

Week 1: 12:12 Fasting

Week One is all about easing into fasting. For the first full week, you’ll perform a 12:12 fasting routine, which is simply splitting the 24 hours of the day in half. You’ll fast for 12 hours and consume all your calories for the day within the remaining 12-hour eating window. 

Note: If you already have fasting experience, this easy method may feel too easy. If that is you, you can skip ahead to the next method. I will have a bonus routine for you at the end so you can complete all five weeks. 

If you have never tried fasting or struggle to feel comfortable with the strategy, 12:12 is the ideal starting point. Use the hours that you sleep to make it even easier. For instance, stop eating three hours before bed and resume eating after 12 hours. This might look like finishing dinner by 7 pm and eating breakfast at 7 am. Do this for one full week before moving to the next level.

Week 1

Week 2: 16:8 Fasting

For Week Two of your intermittent fasting challenge, you’ll increase your fast to 16 hours and consume your daily calories within 8 hours. This 16:8 method is the one most often used in research. It is a great option for anyone from those looking to head off blood sugar disorders like diabetes to those wanting to improve their body composition by building muscle as they lose fat.

If you think about achieving a body composition change, what you are asking your body to do is build one structure (muscle) and tear down another being body fat. Fortunately, 16:8 fasting stimulates both of these actions.

It encourages fat loss by reducing the calories you consume and the level of insulin in your blood. Fasting also stimulates the production of growth hormone (GH), which promotes muscle growth. If you are interested in learning more about building muscle with fasting, it is a topic I cover in my book on intermittent fasting. You can get it on Amazon or from other book retailers.

Beyond the health benefits, 16:8 fasting is also the most popular form of fasting because it fits so many lifestyles. To perform it, you can skip breakfast and open your eating window with lunch. For instance, if lunch for you is at 11 am, finish eating for the day at 7 pm. That is just an example: you can shift that eating period depending on what is happening in your life. 

Week 2

Week 3: 20:4 Fasting

After One Week of 16:8 fasting, you’ll be ready to extend your fast to 20:4, meaning you’ll fast for 20 hours and eat within 4 hours of the day. This is a good level for those looking to get a weight-loss edge because you can still fit two healthy meals into a 4-hour window while getting a full 20 hours of blood sugar and insulin stability. 

Surprisingly, many research studies on OMAD or one meal a day fasting actually utilize a 4-hour eating period. There is little research on the one-hour eating period that most people who practice OMAD consider to be the proper time frame.

The reality is that it is challenging to get all of the nutrients and calories needed to support your metabolism in a single meal, so OMAD will not be one of our five challenge routines. If you’d like to try OMAD, I recommend using it as an occasional tool rather than a daily practice. 

To clarify, for Week Three of our intermittent fasting challenge, you’ll be eating within four hours. For instance, you can postpone lunch till 2 in the afternoon and finish dinner by 6 pm.  

Week 3

Week 4: Early Time Restricted Eating (eTRE) 

Once you’ve spent a week with 20:4 fasting, you’ll give your body an even better weight-loss advantage by shifting your eating window to earlier in the day. This is a practice known as early time-restricted eating (eTRE). It is a good strategy for any adult but really valuable for those of us over the age of 50 or with a history of poor eating. 

Advanced age and years of eating refined carbohydrates are risk factors for a common weight loss barrier called insulin resistance. Early time-restricted eating has been shown to improve insulin sensitivity, helping to keep your body in a fat-burning state longer (1).

For Week Four, you’ll continue your 4-hour eating window but eat early. For instance, you can eat lunch at 10 am and dinner at 2 pm. That, of course, is just an example. You can opt for breakfast and lunch, skipping dinner altogether, but aim to finish eating for the day by no later than 3 pm. 

Don’t put limits on yourself by getting hung up on norms. There is nothing wrong with eating a salad as your first meal of the day, even if that happens at breakfast time. Likewise, an omelet can work for dinner. It’s quick to get on the table, can be packed with veggies, and provides a high amount of healthy fats and protein to keep hunger under control for hours. 

Week 4

Week 5: Modified ADF

We are now ready to move into the 5th and final week of our challenge. This week, you’ll try a variation of fasting known as alternate day fasting (ADF). This method is what it sounds like; you will alternate between days of fasting and eating. However, for this final week of the challenge, you’ll perform modified alternate day fasting. That means you get to eat 500 calories on your fasting days. 

I realize that this sounds like cheating, but Dr. Krista Varady, who is one of the leading researchers on alternate-day fasting, found that modifying the fasting days to allow for some food intake made participants more apt to stick with the routine and it did not sacrifice the health and weight-loss benefits. 

In the research, the eating days had few calorie or food choice restrictions, basically allowing participants to eat freely every other day. I purposely made modified alternate day fasting the final week of our challenge because, by this point, you’ve likely found that making whole food choices has made fasting easier to perform.

In other words, while you can look at your alternate eating days as free days, you’ll be happiest with your results if you stick with healthy foods and skip the processed and refined foods that put your blood sugar on a rollercoaster ride, intensifying hunger and cravings. 

To be clear, let’s look at what a week of modified alternate day fasting may look like for you. 

Since you will be coming off a week of early time-restricted eating, you can eat freely on day one of this fifth and final challenge week. On day two, you’ll consume 500 calories for the day. Those calories can be split any way you’d like, but you’ll likely find that consuming them in two small meals timed within a few hours of each other or one large meal will be the most satisfying. You’ll finish out the remaining five days of the week with this back-and-forth routine. 

Alternate Week 5: Full ADF (Advanced)

I promised earlier that I would include a bonus week for those who wanted to skip the 12:12 fasting routine. If that is you, your fifth week of fasting will be full alternate day fasting, meaning that you will consume nothing but non-caloric drinks on your fasting days and eat freely every other day. If we use the pattern from earlier, your complete fasting week will look like this. On Days 1, 3, 5, and 7, you eat freely. on Days 2, 4, and 6, you consume nothing but water, coffee, or tea. 

Week 5

5-Week Intermittent Fasting Overview

Here is a look at the entire 5-week intermittent fasting challenge. 

  • Week 1, you’ll fast for 12 hours (using the overnight hours to your advantage) and consume all your daily calories within the remaining 12 hours. 
  • During Week 2, you’ll immediately up your game, fasting for 16 hours and eating within an 8-hour eating window. 
  • Week 3, you’ll up your game another notch, extending your fast to 20 hours, with a 4-hour eating period. 
  • Week 4, you’ll breakthrough insulin resistance by shifting the 20:4 fast that you mastered the week prior to earlier in the day. For this early time-restricted eating week, you’ll finish eating by no later than 3 o’clock in the afternoon. 
  • Week 5: For the fifth and final week, you’ll shift gears to test drive alternate day fasting. You’ll do a modified alternate day fast for your final week. This means that you eat 500 calories a day every other day, with the alternate days being free eating days. 

If you are following the advanced schedule that skipped 12:12 fasting, your final week will be full alternate day fasting. You’ll alternate between no-food fasting days and free eating days. 

Go For It!

Now, all that’s left is for you to go for it! Follow this plan, and you’ll go from zero to expert in just 5 weeks. Bookmark this blog post and come back to refresh your memory. Share the post with a friend and ask them to take this challenge with you. 

Thank you for reading and have a wonderful week!


(1) Sutton, Elizabeth F., et al. “Early time-restricted feeding improves insulin sensitivity, blood pressure, and oxidative stress even without weight loss in men with prediabetes.” Cell metabolism 27.6 (2018): 1212-1221.

About the Author

Becky Gillaspy, DC, is the author of The Intermittent Fasting Guide and Cookbook. She graduated Summa Cum Laude with research honors from Palmer College of Chiropractic in 1991. 

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