How Much Weight Will I Lose on a Juice Fast?

Going on a juice diet for weight loss seems like the easiest way to shed stubborn fat and shrink your waistline. Compared to most diet plans, juice fasting requires no cooking and involves low costs. Proponents say that you can drop 10 pounds or more in as little as one week.

A juice fast can help you lose weight quickly. (Image: Johner Images/Johner Images Royalty-Free/GettyImages)

But, there's a big difference between weight loss and fat loss. While it's true that juicing can help you slim down, it doesn't mean it's safe.

Tip

Your activity level, calorie intake and metabolic rate will ultimately determine how much weight you can lose on a juice fast.

If you cut out 500 calories per day, you may lose up to one pound of fat a week. Regular exercise raises your energy expenditure and can lead to faster weight loss.

The Truth About Juice Fasting

Detox juice cleanses get a lot of praise from models, celebrities and alternative medicine practitioners. The internet abounds with homemade juice recipes for weight loss, from celery juice to fancy drinks with names like The Fat Killer or The Liver Scrubber. On top of that, it's common to see dieters who drink nothing but juice for weeks or months at a time. Some say that juice fasting increases your energy and stamina, skyrockets your metabolism and flushes toxins.

Fruit and vegetables juices are chock-full of antioxidants. These natural compounds help maintain liver function, scavenge free radicals and support cardiovascular health, according to a review published in the journal Antioxidants in October 2017. Furthermore, they may protect against neurodegenerative diseases and boost brainpower. Considering these facts, it's not surprising that juicing is considered a healthy practice.

However, it's one thing to drink a glass of fresh juice daily and another thing to go on a juice cleanse for weight loss. Detox plans and cleanses may pose serious health risks, as reported by the National Center for Complementary and Integrative Health (NCCIH). First of all, most detox programs severely restrict calories and food choices, which can result in nutrient deficiencies.

Grapefruit juice, for example, provides 48 calories, 11.3 grams of carbs and less than 1 gram of protein per serving. It also contains modest amounts of calcium, phosphorus, vitamin A and other micronutrients. One serving of grapefruit (5.4 oz), by contrast, has 65 calories, 1.1 grams of protein and 16.4 grams of carbs, including 2.5 grams of fiber.

See the difference? The whole fruit packs more fiber and protein. It also contains larger doses of calcium, potassium, phosphorus, vitamin C and other nutrients.

As the NCCIH points out, nutrient deficiencies are not the only side effect of fasting. This practice may also cause weakness, fatigue, headaches and increased hunger. Additionally, it may not be safe for people with kidney disease, diabetes and other conditions. Its role in toxin elimination is subject to debate.

Detox Juice and Weight Loss

Detox juice cleanses are typically low in calories. Most types of juice provide less than 100 calories per serving, so don't be surprised if you lose 10 pounds in a week or so. However, it's one thing to lose weight and another thing to lose fat.

Your body consists of water, fat-free mass (muscle, bone and organs) and fat mass. Depending on your diet and activity level, you can lose fat, lean mass or water weight. Low-carb and ketogenic diets, for example, cause rapid weight loss, especially in the first few days. The explanation is simple.

After ingestion, carbs are turned into glucose and used as fuel. Some of that glucose is stored as glycogen in your muscles and liver. Each gram of glycogen is stored along with 3 grams of water. That's why fasting, low-carb diets, ketogenic diets and other regimens that limit carbs help rid your body of excess water.

Furthermore, fruit and vegetable juices are extremely low in protein. Prolonged juice fasting can deprive your body of protein, causing muscle loss. You may also experience diminished exercise performance, reduced muscle strength, fatigue and slow recovery from training.

A November 2017 study published in Clinical Nutrition assessed the effects of low-protein diets on older adults. Study participants consumed less than 1 gram of protein per kilogram of body weight per day. By the end of the study, their physical performance and muscle strength decreased significantly. As the researchers point out, optimal protein intake is crucial for maintaining lean mass and staying healthy, regardless of age.

So if you're planning to go on a juice diet for weight loss, you can drop a few pounds within days. The problem is that you'll lose both muscle and fat. Once you break the fast and return to normal eating, the lost weight will bounce back. However, a two- or three-day juice fast is unlikely to cause muscle loss and other health problems (unless you have a pre-existing condition, such as kidney disease).

What to Expect

How much weight you'll lose on a juice fast depends on your activity level and calorie intake. According to Harvard Health Publishing and other health organizations, it's necessary to burn about 3,500 calories to lose one pound of fat. This number varies from one individual to another, though.

Before starting the fast, try to determine your daily calorie intake. For example, if you typically consume 2,000 calories daily, cut 500 calories per day to lose one pound a week. To achieve this goal, you must drink about 1,500 calories worth of juice daily while on a fast.

Exercise can help, too. Physical activity, whether it's running, jogging, strength training or swimming, burns calories. If you exercise while fasting, you can consume more than 1,500 calories per day and still lose weight.

The problem is that exercise breaks down muscle tissue. Protein and other nutrients facilitate muscle repair and help you build and preserve lean mass. When you're on a juice fast, you may not get enough protein in your diet. Strenuous exercise combined with strict dieting is a recipe for disaster.

Consider adding protein shakes to your diet to reduce muscle breakdown while fasting. Plant-based proteins, such as organic pea, hemp, soy and rice protein powder, are all great choices. Mix them with plain water to keep your calorie intake low. Choose an organic brand with no additives, artificial sweeteners or added sugars.

Also, experiment with homemade juice recipes for weight loss. Mix and match different fruits, try new veggies and add spices for extra flavor. This way, you'll keep your diet varied and boost your nutrient intake. Juice fasting doesn't have to be boring, so go ahead and put your blender to work.

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