What Really Happens to Your Body When You Do a Juice Cleanse

BluePrint. Juice Press. Organic Avenue. You're probably familiar with the slick marketing campaigns for these brand-name juice cleanses, often touted as liquid miracles that promise to eliminate toxins, bloat and guilt.

But are juice cleanses actually effective? And are they even safe? The short answer: Juice cleanses are not (and should never be) a long-term strategy for weight management. Any changes you experience are temporary at best. Here's how a juice cleanse really affects you.

Juice can be made from any fruit, vegetable or nut by squeezing or pressing food into liquid form. But a juice ‌cleanse‌ involves spending several days consuming nothing but juice.

Most people try a juice cleanse with the intention of losing a few pounds — fast — or eliminating toxins from the body. Still others are looking for cosmetic benefits, such as clearer skin. But the perks are at worst, misguided, and at best, short-lived.

The number of pounds you can lose on a juice cleanse depends on the number of days you commit to one.

Juice cleanses are typically designed to last anywhere from three to 10 days, according to a September 2013 ‌American Journal of Medicine‌ editorial, and often require participants to drink up to six bottles a day of a combination of fruit, vegetable and nut juices or milks — and eat no solid food.

If you're still willing to deprive yourself in the name of fitting into your jeans, let's talk about the part that probably matters to you: How much weight can you realistically drop — and how quickly — on a juice cleanse?

You'll probably start to notice you've lost a few pounds by day three. But that doesn't mean those pounds are gone for good. "It's likely that much of the initial weight loss you'd experience from a juice fast would be from water weight rather than fat loss," says Samantha Cassetty, RD, nutrition and wellness expert and co-author of ‌Sugar Shock‌.

When you limit your calories on a juice cleanse (or any other restrictive diet), your body starts to use up carbohydrates stored away in the form of glycogen. Glycogen holds a fair amount of water, according to the American Council on Exercise, so burning through it can lead to losing water weight that shows up on the scale.

You're also likely cutting back on sodium, Cassetty says. "The majority of sodium in our diets comes from packaged foods, so if you're eliminating those on your juice fast, you'd be slashing your sodium intake. Since sodium retains water, you'd also be releasing that water."

The fast results obtained after days of forgoing food simply don't last. "Unfortunately, you're likely to gain weight back just 72 hours after consuming your first solid meal," explains Natalie Stephens, RD, lead dietitian in nutrition services at the Ohio State Medical Center, as your body works to restore a balance of fluids and energy.

"Maintaining a diet lower in calories is the best way to sustain the weight loss obtained in a juice cleanse diet," says Jane S. Sadler, MD — not giving up food altogether.

Some juice cleanses contain cayenne pepper, a spice known to have metabolism-boosting properties — although the effects are small and temporary.

For example, a March 2011 study of 25 men and women published in ‌Physiology and Behavior‌ found that eating one gram of red cayenne pepper (about a quarter of a teaspoon) during a meal led to a temporary reduction in appetite, but this reaction lost its effect over time and was less pronounced in those who already had a tolerance for spicy food.

That said, some people who go the juice cleanse route may experience the exact opposite effect: When you go without food for several days and consume less than 1,000 calories in juice instead, your body works to protect itself. Thinking food is scarce, you may actually burn fewer calories to conserve energy.

When you only drink juice for three days, you miss out on the pleasure that comes from eating food in its natural form.

"When you're on a juice cleanse, you're not getting sufficient protein, fiber or fat, nutrients which help you feel full," Cassetty says. "That means you'll likely be really hungry, irritable and potentially even anxious."

You're also setting yourself up to overdo it once you start eating whole foods again. "Juices contain way more fruit than you'd ever sit down to eat," Cassetty says. "For example, would you eat three or four apples? Your body doesn't get as full off of liquid calories as it does from calories you chew." That can lead to overindulging once you return to eating, she says.

Thinking about your own relationship to food can help you identify ways to maintain your weight once you're done with the cleanse in a healthy, sustainable way, which will go much further in helping you feel present and comfortable in your body.

"It's better to focus on fruits and veggies in other forms, whether fresh, frozen, dried or canned," Cassetty says. "These foods provide vitamins, antioxidants and fiber."

Your plan to slim down quick before a big night could backfire if you're left with gas, heartburn or constipation that can accompany a low-fiber, high-acid "diet" like a juice cleanse, Dr. Sadler says.

As if those digestive complaints weren't uncomfortable enough, they could also make it harder to sleep — as could frequent bathroom trips from drinking so much fluid throughout the day, she adds. "'No one should go to bed hungry' speaks many truths."

The claims that cleanses supposedly enhance liver detoxification by eliminating pollutants from your body simply aren't supported by scientific evidence, Cassetty says. "Though the sugar from fruit is natural, it's not natural to have it in such a concentrated form. Consuming foods closest to their natural state has the best health payoffs."

While you're not doing yourself any harm by having a glass of juice regularly, the human body is already designed to do a great job of eliminating toxins via waste, sweat and breathing. Your liver works with the kidneys, lungs, respiratory system and your digestive tract to keep your body functioning at its peak by processing and filtering blood to get rid of any harmful byproducts, according to the University of Michigan.

Juice cleanses aren't a great fix if you're looking to lose weight and keep it off, and they don't live up to the detox hype. They can also create an unhealthy relationship with food, causing you to eat more when you're done with the cleanse.

"Whether you want to manage bloat or drop a few pounds quickly, a juice cleanse doesn't offer any tools to help you navigate the complex eating environment that we're faced with," Cassetty says. "Most people can live with a few days of intense hunger — though I don't think it's necessary, and would discourage you from trying it — but once you eat routinely again, you haven't learned any sustainable skills to help you feel better, nourish yourself properly and reach a comfortable weight."

Instead of an extreme and unscientific cleanse, consider making small, sustainable diet tweaks that can help support weight loss, such as drinking more water and avoiding eating after dinner, or an eating plan like intermittent fasting, which has been linked to weight loss, reduced inflammation and more in early research.

If you are going to try any new diet — including a juice cleanse — it's always smart to run it by a health care professional first. "Review detox plans with your medical provider before initiating diet changes," Dr. Sadler says.