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Home arrow Nutrition arrow Intermittent Fasting arrow Juice Fast: What Is It, and How Does It Work?

Juice Fast: What Is It, and How Does It Work?

Written by Isabel Mayfield
Dr. Donika Vata
Fact checked by Donika Vata, MD
Last update: October 17, 2023
7 min read 844 Views 0 Comments
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Juice fasting is a popular option for people looking to detox and find new ways to maximize their weight loss potential, but does it really work?

juice fast

Whether you’ve seen juice fasts mentioned on social media or seen them advertised at your favorite smoothie shop, this type of fasting is undoubtedly growing in popularity.

And while many people only see it as a way to promote weight loss, the truth is that its benefits go far beyond shedding pounds.

If you’re considering juice fasting for yourself, here’s everything you need to know to get started.

What Is a Juice Fast?

A juice fast, also known as a juice cleanse, is a kind of diet where you abstain from eating solid foods and instead drink only fresh pressed juice, water, and herbal tea for a specific amount of time – usually anywhere from 3 days to 3 weeks.

For anyone following a juice cleanse, it’s recommended to drink a variety of both fruit and vegetable juices to provide the body with a wide range of vitamins and minerals. Drinking only store-bought orange juice for a week likely won’t do the trick.

Some people may choose to juice fast in an effort to cleanse their bodies and increase their energy levels. Others use it for their weight loss benefits, as it’s estimated that you can lose between 1–2 pounds a day while only drinking juice.

Benefits of a Juice Fast

As mentioned above, there are many benefits that have been attributed to juice cleanses. This study helps prove the efficacy of juice cleanses in regard to weight loss and also demonstrates the benefits of juice cleanses in relation to gut health.

However, many of the perks that are attributed to juice cleanses aren’t totally substantiated and may instead be more anecdotal. 

#1 May help with weight loss

Cucumber juice has long been a drink that people consume in an effort to keep their calorie count low and provide their bodies with a healthy dose of vitamins and minerals. As it happens, juices made from a variety of fruits and vegetables can be used to help you lose weight for a number of reasons.

Namely that, when on a juice cleanse, you naturally consume fewer calories. In one study, which had participants consume 6 bottles of fruit and vegetable juice per day, their daily caloric intake was approximately 1,310 calories. Between 700–1,200 calories less than the daily recommendation.

Eating in a caloric deficit has long been considered one of the best ways to lose weight, as your body naturally turns to its reserves for fuel. For this reason, juice fasting remains an attractive option for people who want to shed pounds quickly.

#2 Abundance of vitamins and minerals

In a world that is full of processed foods, it can be hard to get all the nutrition we need from our diets. Taking vitamin supplements can help us avoid deficiencies, but experts agree that vitamins will never replace nutrient-rich foods.

Whole fruits and vegetables remain one of the best sources of vitamins and minerals in our diets. These essential nutrients are necessary for some of our most important bodily functions, including immune system support, bone and blood health, and nervous system function.

Not only that, but many fruits are high in antioxidants, a natural substance that helps protect us from cell damage. Diets high in antioxidants can keep us looking young and even protect us from chronic diseases.

Doing a juice cleanse is an easy way to provide your body with all the nutrients it may be lacking, especially if you don’t normally eat a diet rich in fruits and vegetables.

#3 Improves healthy gut bacteria

The health of your gut is an often overlooked aspect of overall longevity. Having an imbalanced gut microbiome can leave a person more vulnerable to pathogens and has even been linked to anxiety disorders and depression

This is because of something called the vagus nerve, a pair of nerves that directly connect the brain and the gut. The two are always in communication with each other, and when your belly is in distress due to bacterial overgrowth, your brain feels it.

Juice fasting has been shown to increase levels of good bacteria while reducing the growth of bad bacteria. The bacteria Bacteroides, which has been shown to decrease blood pressure and cholesterol, were reportedly higher on day 4 of a 6-day fasting study.

Risks and Side Effects of a Juice Fast

There are also potential downsides to doing a juice cleanse that you should be aware of before getting started.

#1 Too much sugar

Another reason why it’s important to drink juices made from both fruits and vegetables instead of just fruit is due to the high sugar content of fruit.

For women, it’s recommended not to exceed 24 grams of sugar per day and 36 grams for men. Since a single 8oz glass of fresh apple juice contains close to 30 grams of sugar, it’s important to limit the amount of fresh juice you drink made from high-sugar fruits.

#2 Fatigue

There are a number of factors that can contribute to you feeling tired while doing a juice cleanse. Some of these include:

  • Being in a calorie deficit
  • Limited protein intake
  • Blood sugar swings
  • Detoxification effects

Since you can expect to have lower energy levels while on a juice fast, it’s a good idea to lay low and keep physical activity to a minimum while fasting.

#3 Protein deficiency

Protein is an essential nutrient that the body uses to balance hormones, repair tissue, and muscle, and maintain optimal immune system function. Since juice has almost no protein, you may find that you lose some of your muscles while juice fasting.

This is another reason why it’s important not to over-exercise while fasting, as your muscles don’t have enough protein for post-workout reparation.

How to Do a Juice Fast Safely?

Still, want to try a juice fast? Here are some tips that will help you maximize results and ensure that you complete your fast safely.

Prepare for the fast

Instead of going cold turkey when you start juice fasting, prepare to wean off of things like caffeine, alcohol, and high-sugar and processed foods at least 3 days before your cleanse.

You’ll also want to up your daily intake of water to at least half a gallon (ideally 1 gallon) a day, and of course, pick up a high-quality juicer.

Select fruits and veggies carefully

Undershopping or not planning your juices is a good way to ensure that you will have to make several trips to the grocery store each day. Instead, decide on a well-balanced combination of juices that you can drink each day and pick up all the supplies you need for a 3-day period in one trip.

Keep in mind that you should aim to drink about 64 ounces of juice per day while on a juice cleanse, though this number will vary depending on your size and individual goals for cleansing. Ideally, you’ll want to spread these juices out throughout the day to avoid getting too hungry.

You may also want to sneak a nut milk, like almond milk or cashew milk, into your liquid diet once per day as a way to increase the amount of fat and protein you consume.

Avoid strenuous physical activity

As mentioned above, it’s a good idea to limit the amount of physical activity you do each day while juice cleansing. 

Not only can you expect to be more tired than usual, but your body won’t have the nutrients it needs to fuel your body during your workout and repair your muscles afterward.

Break the fast slowly

As tempting as it might be to break your juice cleanse with a hamburger, how you break your cleanse is as important as the cleanse itself. Your digestive system will need time to readjust to digesting solid foods again, including producing the enzymes necessary for breaking them down.

The best foods to break a fast with are things like bone broth, yogurt, organic produce like fruits and avocados, and eggs.

A Word From an RD

Juice fasting is a method that many people turn to in an effort to maximize weight loss. And while swapping solid food for fruit juice may help you shed a few pounds, it’s not a long-term solution.

This style of fasting has many benefits, but like many other unsustainable diets, relying on it for weight loss can lead to yo-yo dieting, where you lose weight only to regain it shortly thereafter.

Instead, it’s best to focus on a more holistic approach that includes regular exercise, a balanced daily diet, and the occasional 1–3 day juice cleanse when your body needs it.


How long can you do the juice fast for?

The length of a juice fast can vary, with the ideal length depending on the specific results you are seeking. A short juice fast of 1–3 days is a great option for a quick cleanse, while a 1–3 week juice cleanse offers the opportunity for a full body detox.

How much weight can you lose on a juice fast?

The amount of weight you can lose on a juice cleanse will depend on the length of your cleanse and your starting weight. Generally, most people can expect to lose 1–2 pounds a day.

Is juice fasting healthy?

Overall, yes. Juice fasting can be a great reset for your body when done correctly. The many vitamins and minerals found in fruit and vegetable juices help sustain your body despite the protein deficiency for the duration of the cleanse.

Can you eat solid food during a juice fast?

Traditional juice cleanses are done sans food to give the digestive system a break. However, some people choose to do modified juice cleanses where they continue to eat fruits and vegetables throughout the fast.


Juice fasting is a safe and effective way to lose weight, balance your gut microbiome, and load your body with tons of essential micronutrients-but only if it’s done right. 

Things like drinking a lot of high-sugar fruit juice or exercising too much while fasting can negatively impact your experience and result in your fast having more positives than negatives. It’s also important to remember that juice fasting should not be overused in an effort to lose weight.

However, following the tips outlined in this article can help ensure that you come out of your juice fast feeling better than ever.

Written by Isabel Mayfield
Isabel Mayfield is a certified yoga instructor with over 10 years of experience in the fitness industry. She is passionate about self-improvement and loves to help people improve their sense of self-worth through education and support in meeting their fitness goals.
The article was fact checked by Donika Vata, MD
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Written by Isabel Mayfield
Dr. Donika Vata
Fact checked by Donika Vata, MD
Last update: October 17, 2023
7 min read 844 Views 0 Comments

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