How does juice fasting work?

Juice fasting has become an increasingly popular way to detox, lose weight, and “reset” the body. But what exactly is juice fasting, and how does it work? Here’s a comprehensive look at the juice fasting process and its purported health benefits.

What is Juice Fasting?

Juice fasting, also known as juice cleansing, is a type of fasting that involves consuming only fresh fruit and vegetable juices for a set period of time. This liquid diet provides nutrients while eliminating solid food consumption. The duration of a juice fast can range from a few days to several weeks. Most people start with a 1-3 day juice fast and work their way up to longer fasts.

During a juice fast, only fresh, raw juices extracted from fruits and vegetables are consumed. Some people also allow nut milks like almond milk or coconut water. But no solid foods or animal products are eaten during the fasting period.

The goal of juice fasting is to:

  • Flood the body with nutrients from fruits and vegetables
  • Give the digestive system a rest by eliminating solid foods
  • Detoxify the body and remove toxins
  • Rebalance and restore the body
  • Promote weight loss

Most fresh juices are made using a juicer or blender. Produce is juiced or blended and then strained to remove fiber, resulting in only the liquid essence of fruits and veggies.

How Does Juice Fasting Work?

During a juice fast, you abstain from solid foods and only drink fresh vegetable and fruit juices. By temporarily eliminating solid foods, juice fasting allows the body’s natural detox and healing systems to kick in.

Here’s a look at some of the purported ways juice fasting works:

Gives the Digestive System a Rest

By avoiding solid foods that require digestion, the digestive system is able to take a break during a juice fast. The nutrients from the vegetable and fruit juices are absorbed by the body without requiring the usual digestion process. According to advocates, giving digestion a rest allows the body’s energy to be used for cleansing and healing instead.

Floods the Body with Nutrients

Fresh fruit and vegetable juices provide concentrated amounts of vitamins, minerals, phytonutrients, enzymes, and antioxidants. Juicing provides these nutrients in an easy-to-absorb liquid form that goes straight into the cells to nourish the body during the fast.

Promotes Detoxification

Not having to digest solid foods during the juice fast allows the body’s natural detoxification systems to kick into higher gear. The liver is able to focus its efforts on clearing toxins and waste from the body instead of on digesting food. According to advocates, juice fasting helps expel stored toxins and waste material.

Resets and Balances

Abstaining from solid foods provides a chance to reset and rebalance. According to some health practitioners, juice fasting creates an environment in the body that allows it to heal and restore itself on a deep cellular level.

Encourages Weight Loss

Since juice fasting involves consuming minimal calories from only fruits and vegetables, it can lead to quick weight loss, especially in the short-term. However, most of the weight lost during a juice fast is water weight that will likely be regained once you start eating again.

Typical Juice Fast Protocol

There is no one standard protocol for juice fasting, but here are some general guidelines people often follow for a successful juice fast:

Pre-Fast Preparation

  • Gradually cut back on caffeine, alcohol, meat, dairy, and processed foods in the days leading up to the fast.
  • Increase consumption of fresh fruits, vegetables, nuts and seeds.
  • Drink more water to stay hydrated.
  • Plan ahead and shop for all the produce, nuts, and supplements you will need for the duration of the fast.
  • Make a schedule of the juices you will make each day.

During the Fast

  • Drink 6-8 glasses of fresh juice per day. Drink water, herbal tea, or broth if hungry between juices.
  • Get adequate rest and sleep.
  • Exercise lightly like yoga, walking, or light resistance training. Avoid strenuous exercise.
  • Listen to your body and rest as needed.
  • Avoid smoking, alcohol, and caffeine.
  • Supplement with psyllium husks, probiotics or electrolytes if needed.
  • Use dry brushing or massage for lymphatic drainage.

Breaking the Fast

  • Break the fast gradually. Do not eat a large meal immediately after fasting.
  • Introduce solid foods slowly, starting with fresh fruits, salads, broths, etc.
  • Chew food thoroughly and eat slowly.
  • Continue to avoid processed foods, caffeine, alcohol.
  • Drink plenty of water.

Benefits of Juice Fasting

There are many purported benefits of juice fasting. However, more research is still needed on most of these potential benefits.

Weight Loss

Juice fasting can lead to quick weight loss, especially in the short-term. Since you are consuming very few calories, your body will start burning glycogen and fat stores for energy. However, most of the weight lost is water weight that will likely return once you start eating again.


Proponents say juice fasting helps the body get rid of stored toxins and waste material. By abstaining from solid food, your digestive system can take a break and your body’s detoxification systems can work more efficiently.

Boosts Immunity

The flood of vitamins, minerals, and nutrients from juicing may help boost immunity by providing antioxidant protection. However, more research is needed to support this benefit.

Improved Energy

Some juice fasters report feeling increased energy and vitality during and after the fast. However, others report fatigue, headaches, and weakness while juice fasting.

Improves Skin

Anecdotal reports indicate juice fasting can improve skin conditions like acne, eczema, and psoriasis. The nutrients and antioxidants may help skin heal and rejuvenate.

Lowers Blood Pressure and Cholesterol

The nutrients in juices may help reduce blood pressure and cholesterol levels. But more studies are needed to substantiate these benefits.

Reduces Inflammation

The antioxidants in fresh juices may help reduce inflammation throughout the body. But additional research is required to confirm anti-inflammatory effects.

Stabilizes Blood Sugar

Fresh juices provide nutrients without spiking blood sugar like processed foods. But juice fasts are not typically recommended for diabetics without medical supervision.

Improves Digestion

Taking a break from solid foods can allow the digestive system to rest and rejuvenate. Juice fasts may help resolve some digestive issues, but can cause others.

Promotes Healing

Advocates state that juice fasting creates an optimal environment for the body to heal itself on a deep cellular level. But more research is needed.

Potential Dangers and Side Effects

Despite the benefits, juice fasting also has some potential dangers and side effects to be aware of. These include:

Nutrient Deficiencies

Although juices provide vitamins and minerals, they lack protein and healthy fats. An extended juice fast may result in nutrient deficiencies over time.

Blood Sugar Issues

The high sugar content of fruit juices can cause blood sugar spikes and crashes, especially for diabetics. Vegetables are generally lower in sugar.

Tooth Decay

Some acidic fruit juices may erode tooth enamel over time. Brush teeth after drinking juice.

Fatigue and Weakness

As the body enters ketosis, feelings of fatigue, nausea, and weakness are common. Light exercise helps manage these symptoms.


Headaches are a common side effect at the start of a juice fast due to sugar and caffeine withdrawal.

Hunger and Irritability

Big changes in diet can impact mood and cause crankiness. Be prepared for some adjustment period.

Reduced Ability to Focus

With the brain no longer fueled by food, you may experience concentration challenges. Work productivity may suffer.

Dangerously Low Calorie Intake

If juicing recipes are not planned well, juice fasts may provide far fewer calories than your body requires. Most adults need at least 1200 calories daily.

Severe Fasting Dangers

Longer fasts of over 5 days can result in more severe side effects and should only be done under medical supervision. Extended fasting risks include fainting, heart arrhythmias, heart attack, electrolyte imbalances, and more.

Who Should Not Juice Fast?

Juice fasting is not suitable for everyone. The following groups should avoid juice fasting:

  • Children or teens
  • Pregnant or nursing women
  • Those with diabetes or blood sugar issues
  • Anyone with eating disorders
  • People who take medications that require food
  • Those with chronic health conditions
  • Anyone underweight or malnourished
  • People who physically demanding jobs

Those with health conditions should only fast under medical provider supervision. Only undertake a juice fast if you are generally healthy.

How Long Should You Juice Fast?

There is no standard juice fasting duration since people’s bodies and goals vary. Here are some general juice fasting duration guidelines:

Fast Duration Purpose
24-72 hours Quick reboot and detox
3-5 days Detox and weight loss boost
5-10 days Dedicated detox and weight loss
10-30 days Extreme detox and weight loss under medical supervision

It’s best to start with shorter fasts of 1-3 days and work up to longer ones. Extreme fasts over 5 days should only be done under medical supervision due to severe health risks.

Tips for a Successful Juice Fast

Here are some tips to help you get the most out of a juice fasting experience and make it as pleasant as possible:

Ease Into It

Cut out processed foods, meats, dairy, alcohol, and caffeine in advance before going “cold turkey.”

Keep Variety in Your Juices

Mix up vegetable and fruit juices to prevent taste fatigue. Include green juices as well as fruit juices.

Balance Fats in Juices

Add healthy fats like avocado or coconut oil to your juices to slow sugar absorption.

Avoid Extreme Calorie Restriction

Monitor calories to make sure you are consuming enough for your body’s needs. Most adults need at least 1200 calories daily.

Supplement If Needed

Use psyllium husk to stay regular or electrolytes if experiencing symptoms like fatigue, headaches, or cramps.

Plan an Exit Strategy

Gradually reintroduce solid foods starting with fruits and veggies. Avoid diving back into large meals, processed foods, caffeine or alcohol.

Listen to Your Body

Be prepared to cut a fast short if experiencing adverse side effects like dizziness, weakness, heart palpitations, etc.

Sample Juice Fast Schedule

Not sure how to schedule out your juice fasting days? Here is an example 3-day juice fast plan:

Day 1

  • 8 am – Green juice
  • 10 am – Citrus juice
  • 12 pm – Carrot juice
  • 2 pm – Green juice
  • 4 pm – Berry juice
  • 6 pm – Cucumber juice

Day 2

  • 8 am – Cucumber juice
  • 10 am – Carrot-apple juice
  • 12 pm – Spinach-kale juice
  • 2 pm – Beet juice
  • 4 pm – Celery juice
  • 6 pm – Tomato juice

Day 3

  • 8 am – Lemon juice
  • 10 am – Carrot juice
  • 12 pm – Berry juice
  • 2 pm – Cucumber juice
  • 4 pm – Orange juice
  • 6 pm – Herbal tea


Juice fasting involves consuming only fruit and vegetable juices for a period of time to detox, lose weight, and support healing. Benefits may include detoxification, weight loss, improved immunity and skin health. However, juice fasting also carries some risks like nutrient deficiencies, blood sugar spikes, fatigue, and headaches if not done properly.

It’s important to ease into a juice fast, balance nutrients in juices, supplement if needed, and break the fast gradually. Extreme fasts over 5 days should be supervised by a doctor. Overall, juice fasting seems to provide some benefits when done safely for a short duration, but more research is needed on optimal protocols.

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