How much weight will I lose on a juice fast?


A juice fast, also known as a juice cleanse or juice detox, involves consuming only fresh fruit and vegetable juices for a set period of time. Some juice fasts last 24 hours while others can go on for 3, 5 or even 10 days. The goal is to flood your body with vitamins, minerals and enzymes while eliminating toxins and giving your digestive system a rest.

Many people choose to do a juice fast in order to lose weight quickly. Proponents claim you can lose up to 7 pounds in just 1 day of juice fasting. However, most of this initial weight loss is water weight, not fat. Over a 3-5 day juice fast, you may lose 3-7 pounds of actual body fat along with water weight.

So how much weight will you really lose during a juice fast? Let’s take a deeper look at what happens when you consume only liquids for multiple days.

Calorie deficit leads to fat loss

The reason you lose weight on a juice fast is that it creates a large daily calorie deficit.

To lose 1 pound of fat, you need to have a 3,500 calorie deficit. This means you need to burn 3,500 more calories than you consume. On a juice fast, your calorie intake is very low, so it’s easy to create a large deficit.

The average adult needs around 2,000 calories per day. On a juice fast, you may only consume 600-1,200 calories from the juices. This would create a daily deficit of 800-1,400 calories.

Daily calorie needs 2,000 calories
Juice fast calorie intake 600-1,200 calories
Calorie deficit 800-1,400 calories

Over a 3 day juice fast consuming just 600 calories per day, this would amount to a 6,600 calorie deficit which equals about 2 pounds of fat loss.

So in terms of pure fat loss, you can expect to lose approximately 1 pound for every 2-3 days on a juice fast. The longer you juice fast, the more fat you’ll lose. However, much of the initial weight loss will come from water and waste reduction.

Water weight reduction

In the first 1-2 days of a juice fast, you’ll notice rapid weight loss on the scale. But again, this is primarily from losing water weight, not fat.

When you stop eating solid foods, your body’s glycogen stores become depleted. Glycogen binds to water in the muscles and liver, so when glycogen is reduced, you lose the water weight associated with it.

Each gram of glycogen is bound to 3-4 grams of water in the body. On a normal diet, our glycogen stores are topped up, leading to water retention. When you cut out carbs and protein from solid food, glycogen drops rapidly along with the bound water.

According to some estimates, glycogen reduction in the first 1-2 days of a juice fast can free up around 2 pounds of water weight. So if you lose 5-6 pounds in the first couple days, at least 2 pounds is just from water excretion as glycogen stores decline.

Loss of food waste

In addition to fat loss and water weight reduction, the other main way a juice fast leads to weight loss is the elimination of food waste from your digestive system.

At any given time, most people have between 4-8 pounds of undigested food waste and fecal matter in their colon, small intestine and stomach. When you stop eating solid foods for several days, these waste products clear out of your system very quickly.

So some of the initial weight lost during a juice fast, especially if you are constipated or irregular, will be in the form of cleansing this built-up food waste from your digestive tract. Like water weight, it will come back once you start eating again.

Muscle loss risk

The main risk with long juice fasts is losing muscle mass in addition to fat due to inadequate protein intake. The juices are high in carbohydrates from the fruit but low in protein.

According to research, the minimum protein intake to prevent muscle wasting is around 0.5 grams per pound of body weight (or 1 gram per kg). For a 150 pound person, this would equal 75 grams of protein per day.

Most juices contain only 1-2 grams of protein per serving. To get 75 grams of protein from juices alone you would need to drink 12-15 juices per day!

This is why bodybuilders and athletes rarely do long juice fasts – it results in catabolism and breakdown of muscle tissue once the body has used up its glycogen reserves for energy.

So if you wish to keep your muscle mass intact, limit your juice fasts to 24-48 hours. Or consider doing alternate day fasting rather than a prolonged juice fast.

Benefits beyond weight loss

While quick weight loss is the main draw, there are some other potential benefits of a juice fast when done for just 1-3 days:

  • Gives the digestive system a rest
  • Hydrates the body and provides electrolytes
  • Floods the body with antioxidants
  • Eliminates processed foods and empty calories
  • Breaks sugar and fast food cravings
  • More energy and clearer thinking
  • Improves complexion and skin

However, long term juice fasts of 5+ days can deprive the body of important nutrients like protein, fiber and healthy fats. Most nutritionists recommend getting back to eating solid whole foods after 3-5 days max.

Tips to maximize fat loss

Follow these tips if your main goal from a juice fast is losing body fat:

  • Stick to vegetables like spinach, kale and celery which are low in sugar instead of high glycemic fruits. The less blood sugar spikes, the more fat burning.
  • Drink at least 64oz of juice daily to prevent metabolic slowdown.
  • Include a green juice with every fruit juice for nutrients and minerals.
  • Do 60 minutes of cardio exercise on an empty stomach after 24 hours of fasting to really burn fat.
  • Drink mainly green juices in the 2nd half of your cleanse for more effective detoxing.
  • Add lemon juice to your drinks as it stimulates the liver to flush out more toxins.

Expectations and reality

While juice fasts can provide quick weight loss, it’s important to have realistic expectations. A 3-5 day juice fast may help you lose 3-7 pounds. However, 2/3rds of this is likely to be water weight and intestinal waste that will return once you start eating again.

The actual fat loss from a juice fast is 1-2 pounds typically. This can be a great kick start to a weight loss plan but not a long term solution. Any longer than 3-5 days and you risk nutrient deficiencies, muscle loss and a lowered metabolism.

For lasting weight loss results, transition back to eating whole fruits, vegetables and proteins after finishing your juice fast. Keep total calories in a deficit by monitoring portions and staying active.


In summary, a short 24-72 hour juice fast can help you lose 3-7 pounds very quickly. However, the majority of this rapid weight loss will be water and waste reduction. Actual body fat lost will be 1-2 pounds on average. While juice fasting is not a sustainable long term solution, it can provide a motivating jump start to a more holistic weight loss program focused on healthy whole foods and an active lifestyle.

Type of Weight Loss Amount Lost During 3-5 Day Juice Fast
Water weight from glycogen reduction 2-3 pounds
Undigested food waste 1-2 pounds
Body fat 1-2 pounds

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *