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How Do I Prepare For A 3-Day Modified Fast?

Robyn Openshaw - Apr 03, 2020 - This Post May Contain Affiliate Links

Photo of an open laptop with Green Smoothie Girl's flash fast facebook page on the screen from "How Do I Prepare For A 3-Day Modified Fast?" blog post by Green Smoothie Girl

How do I prepare for a 3-day modified fast?

First, bravo for asking this question! Modified fasting can give you a significant immunity boost, so it could be a fantastic practice to help you stay well. Not to mention the other exciting benefits, like experiencing more energy and dramatically lowering your disease risk.

While it’s totally possible to jump headfirst into modified fasting without an ounce of preparation (and still reap benefits!), a bit of planning will help you gain the maximum benefits from your fast, and you’ll sidestep some potentially uncomfortable side effects.

Let’s take a look at the ideal way to prepare for a modified fast, as well as some benefits you’ll gain from that preparation!

In this article:

How to Prepare for a 3-Day Modified Fast

Ideally, you’ll want to start preparing your body for a 3-day fast one or two weeks in advance. This will give you enough time for any withdrawal symptoms from caffeine or sugar to subside.

Do Your Homework

Make sure you understand the fundamentals of how modified fasting works, the potential health benefits, and the potential pitfalls to avoid before you begin. Not only will this help you sail through your modified fast, but it’ll help you avoid discouragement (for instance, if you realize halfway through that you’ve been missing an important element or doing something counterproductive!).

Cut Out the Caffeine

Cutting out caffeine at least one week before you fast can help you avoid unpleasant withdrawal symptoms like headache, nausea, and fatigue1 during your 3-day fast. If you experience those symptoms, you might blame the fast when it's really caffeine withdrawal. (By the way, if you need some motivation: going “off coffee” makes it work better as a stimulant when you start drinking it again.)

Studies have shown that caffeine use2 is linked to anxiety, agitation, restlessness, sleeping problems, and even tremors. It also taxes your adrenal system and almost immediately makes your heart pump harder,3 which can increase blood pressure.

Caffeine also forces your liver to dump large amounts of stored glycogen into the bloodstream4, making your body more vulnerable to sudden spikes and drops in blood sugar while you fast.

Nix Artificial Sweeteners

Artificial sweeteners are a group of dangerous chemical products that you should avoid at all times—but especially as you gear up for a 3-day fast! These sugar substitutes have been linked to weight gain, metabolic syndrome, type 2 diabetes, and cardiovascular disease.

As it does with other dangerous chemicals, your body attempts to run damage control by tucking these chemicals away in the adipose tissue6 (fat). The more you’ve been relying on artificial sweeteners (like aspartame, the worst one), the more your body may resist letting go of fat deposits.

And when these fat deposits are depleted for energy during a fast, the toxins that are simultaneously released may lead to more severe detox symptoms as these chemicals circulate the bloodstream.

Photo of small stack of pink artificial sweetener packets from "How Do I Prepare For a 3-Day Modified Fast?" blog post by Green Smoothie Girl
Artificial sweeteners stay in your body's fat tissues for a long time, and fasting can cause a detox reaction. Cutting them out before your fast can help lessen the reaction.

[Related Post: 19 Sugar Substitutes: The Good, The Bad, And The Ugly of Sugar Alternatives]

Stop Alcohol or Tobacco Use

Both alcohol and tobacco are toxins that tax your body’s resources in flushing them from your system and protecting your organs.

Use your three-day fast as an opportunity to break old habits and completely remove tobacco products from your life (the number of carcinogenic chemicals in any tobacco product7 is staggering) and limit your alcohol consumption to occasional use.

Cut Back on Salt, Sugar, and High Fructose Corn Syrup

As you prepare for a fast, eliminate as much salt, sugar, and high fructose corn syrup from your diet as you possibly can. These substances are taxing to your body’s cells, tissues and organs in a wide variety of ways — not to mention that, like caffeine, they are highly addictive8 and will lead to withdrawal symptoms as you fast (unless you eliminate them preemptively!).

Focus on Organic, Whole, Raw Food

By eating a diverse mix of whole (unprocessed) food in the time leading up to your fast, you’ll be delivering the ideal variety of nutrients, fiber, and fuel to your organs and cells to encourage healthy function. Think primarily greens, vegetables, fruits, legumes, whole grains, nuts, and seeds.

Why the focus on raw foods? Because raw foods pack the biggest punch of nutrients and enzymes (which are damaged by the cooking process) that help facilitate important metabolic processes in your body.

Why organic? Part of the goal of fasting is to detox from chemicals! Introducing new chemicals from pesticide residue on non-organic produce is counterproductive.

[Related Post: Is Buying Organic Food Always Necessary? When To Save Your Money]          

Get Plenty of Prebiotic Fiber

Gut health is essential to digestive health, managing inflammation,9 and organ health. Help your microbiome get the most benefit from a fast by making sure it’s running smoothly in advance of your fast.

One of the best ways to do that is by getting plenty of prebiotic fiber in your diet. Prebiotic fiber is optimal fuel for your gut bacteria, and can be found in many different fruits and vegetables. 

Join a Support Group

There’s nothing like having personal support or advice while you’re trying something new or conquering a challenge.

Having a network of support can mean the difference between momentary discouragement and calling it quits.

Stop Eating Earlier in the Evenings

Eating late into the night can confuse your circadian rhythms, which are vital to a wide variety of biological processes in your body. At night, your body increases melatonin production and inhibits insulin production. By eating a snack right before bed, you set the stage for poor digestion and high blood sugar, in the absence of normal insulin production.

You’ll notice that a 3-day modified fast limits your “eating window” to 12 hours each day—which is a fantastic everyday habit as well! Stop eating about three hours before your bedtime for stronger circadian rhythms, better sleep quality, and improved blood sugar levels in preparation for your fast.

Don’t Eat a Huge “Last Supper”

On a similar note, don’t be tempted to eat a gigantic last meal before you start your fast. You’ll only stretch out your stomach and encourage additional hunger pangs! (Not to mention the possibility of an upset stomach, diarrhea, or sleeplessness from a sudden large amount of food!)

Eat a healthy-portioned meal, and remember: your modified fast is just three days. It’s a lot easier than you think! I played competitive tennis matches on Day 2 and Day 3 of “Flash Fasting” last summer! Recently, one of my former high school friends ran 5 miles on one day of her fast, and did yoga the other two days. She said she was clear-headed, and her knees didn’t hurt for once!

Get Lots of Rest and Water

Prepare your cells and organs for autophagy by paying special attention to quality rest and hydration. A well-rested, hydrated body is always the goal, but especially as you prepare to recycle mutated and damaged cells and flush chemicals from your body.

Photo of African American woman with long hair sitting on couch and drinking clear water from "How Do I Prepare For a 3-Day Modified Fast?" blog post by Green Smoothie Girl
Drinking clean water before and during your modified fast will help flush all the toxins your body releases quickly.

Rested, hydrated cells and organs can respond more quickly and efficiently to your body’s signals to “clean house” through autophagy.

Benefits of Preparing for a Modified Fast

Jazzed up about jumping into a modified fast? That’s understandable given all the health benefits it offers! So, why should you bide your time for a little longer to prepare your body? Let’s take a look!

Fewer Herxheimer Reactions

Herxheimer reactions, also known as detox symptoms, can happen as your body flushes chemical buildup and waste from your body (much which may have been tucked away in your adipose tissue). As these waste products and chemicals are released back into the bloodstream then flushed from the body, they can cause nausea, headaches, and fatigue.

The good news is that by preparing for a fast, you can lower your body’s toxic burden and reduce those symptoms before they even start!

Fewer Withdrawal Symptoms

Modified fasting is one of the easiest ways to access the benefits of fasting, but it’s certainly not easier than eating a full day’s worth of calories! Don’t increase the difficulty level of your fast by adding withdrawal symptoms from caffeine, sugar, and salt into the mix.

By eliminating sugar, caffeine, and overreliance on salt in advance of your fast, you can focus on and enjoy your fast instead of dwelling on your withdrawal symptoms!

Raising the Bar for Autophagy

The more prepared you are for a fast (and the more you keep to a generally healthy diet), the more advanced work your body can do when it comes to autophagy and cleaning up damaged, mutated cells.

If your system is clogged with chemicals and damage caused by processed foods, your body is naturally going to focus its cleanup efforts on that red-alert damage first before it diverts resources to cells that are minimally damaged or mutated. However, if you maintain a healthier lifestyle when you're not fasting, autophagy can do more fine-tuning autophagy while you are fasting.

Creating Sustainable Healthy Habits

Read through the list above one more time. Notice a pattern? All of the ways that you should ideally prepare for a modified are pretty darn similar to the ways you should be taking care of your body on a daily basis!

By spending some time focusing on these practices, you can help yourself form new, healthier habits that you maintain year-round, not just while preparing to fast!

Kick Some Old Unhealthy Habits to the Curb

On that same note, that runway of prep time combined with your fasting period can be just enough time to break some bad habits. Use this opportunity to kick the bucket on sugar addictions, caffeine reliance, or alcohol consumption. Look at your fast as an opportunity to let go of daily habits that are holding you back!

Photo of white man standing in kitchen smiling and holding mug of tea from "How Do I Prepare For a 3-Day Modified Fast?" blog post by Green Smoothie Girl
Using your pre-modified fasting prep time to replace bad habits with good ones will make your post-fasting life happier and healthier.

TLDR: How to Prepare for a 3-Day Modified Fast

Think of modified fasting as giving a gift to your body. And just like a gift you might give another person, it’ll be most joyfully received if you have a healthy relationship!

Key points of preparation include eliminating caffeine, sugar, artificial sweeteners, and alcohol; eating whole, raw, nutrient-dense foods; getting enough rest and water; easing into an eating window; joining a support group; and getting enough prebiotic fiber.

By preparing for a fast through sound health and nutrition, you can make the most of your 3-day fast, maximize autophagy, create healthier habits, and eliminate some unhealthy habits.

More Resources on Fasting: Check out these other blogs, videos, podcasts, and freebies about fasting:

Photograph of Robyn Openshaw, founder of Green Smoothie GirlRobyn Openshaw, MSW, is the bestselling author of The Green Smoothies Diet, 12 Steps to Whole Foods, and 2017’s #1 Amazon Bestseller and USA Today Bestseller, Vibe. Learn more about how to make the journey painless, from the nutrient-scarce Standard American Diet, to a whole-foods diet, in her free video masterclass 12 Steps to Whole Foods.

Disclosure: This post may contain affiliate links that help support the GSG mission without costing you extra. I recommend only companies and products that I use myself.

Photo of an open laptop with Green Smoothie Girl's flash fast facebook page on the screen with post's title text overlaid from "How Do I Prepare For A 3-Day Modified Fast?" blog post by Green Smoothie Girl


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  2. Felman, Adam. “Is Caffeine Bad for You?”, November 7, 2019.
  3. Menci D, Righini FM, Cameli M, et al. Acute effects of an energy drink on myocardial function assessed by conventional echo-Doppler analysis and by speckle tracking echocardiography on young healthy subjects. J Amino Acids. 2013;2013:646703. doi:10.1155/2013/646703
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  7. Talhout R, Schulz T, Florek E, van Benthem J, Wester P, Opperhuizen A. Hazardous compounds in tobacco smoke. Int J Environ Res Public Health. 2011;8(2):613–628. doi:10.3390/ijerph8020613
  8. Avena NM, Rada P, Hoebel BG. Evidence for sugar addiction: behavioral and neurochemical effects of intermittent, excessive sugar intake. Neurosci Biobehav Rev. 2008;32(1):20–39. doi:10.1016/j.neubiorev.2007.04.019
  9. Telle-Hansen VH, Holven KB, Ulven SM. Impact of a Healthy Dietary Pattern on Gut Microbiota and Systemic Inflammation in Humans. Nutrients. 2018;10(11):1783. Published 2018 Nov 16. doi:10.3390/nu10111783

Posted in: Fasting, Healthy Weight, High-Vibe Living, Lifestyle, Tools & Products, Uncategorized

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