Liquid Diet
“Sometimes people can lose a few pounds,” says Isabel Smith, M.S., RD, CDN, dietitian nutritionist and founder of Isabel Smith Nutrition. But, “they can also gain them back quickly, too,” she says.
What Is a Liquid Diet and Is It Healthy?
Juices, soups, shakes—a liquid diet replaces all your meals with, well, liquids. It’s promoted as a fast way to shed pounds, reduce bloating and ease digestive woes, but are you better off sticking with solids?
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Lainey Younkin, M.S., RD, LDN Reviewed by Dietitian Jessica Ball, M.S., RD Updated October 13, 2022
Reviewed by Dietitian Jessica Ball, M.S., RD
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What Is a Liquid Diet and Is It Healthy?
Liquid diets promise weight loss, detoxing and cleansing. From protein shakes to cold-pressed juices, they claim to have a solution—albeit an expensive one—to your health worries and woes. But they may not actually be the answer. Should you try a liquid diet? Here we break down what a liquid diet include, any potential benefits and many of the downsides.
What Is a Liquid Diet?
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A liquid diet consists only of liquids instead of solid food. This includes homemade or store-bought juices and smoothies, homemade protein shakes, premade protein shakes and store-bought liquid meal replacements. You can replace all meals and snacks with liquids or do a partial liquid diet, eating some solid foods as well.
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Some companies have specific “juice cleanses” with different phases you can buy. Others offer a variety of liquid meal replacements to choose from based on your goals. These, however, can be expensive and usually must be purchased and mailed to you.
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Reasons for Going on a Liquid Diet
Liquid Diet for Medical Reasons
Some people go on a short-term liquid diet for medical reasons, such as difficulty swallowing or an intestinal issue.
“It’s difficult to make the case for a liquid diet in most cases,” says Ayla Barmmer, M.S., RDN, LDN, CLT, an integrative and functional dietitian in Boston. “However, the one exception would be when treating small intestinal bacterial overgrowth (SIBO), which is an increasingly common condition given widespread use of PPIs [proton-pump inhibitor medications for heartburn], chronic stress, antibiotic use and more.”
Not everyone with SIBO needs to follow a liquid diet, she notes, but if it is recommended, it should be done with the supervision of a health care professional such as a physician or dietitian.
Keep Reading: Cleanses & Detox Diets—Are They Safe?
Other Reasons to Try a Liquid Diet
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Featured Image: Carrot-Orange Juice
The more popular reasons for a liquid diet are weight loss and “detoxes.” Liquid meal replacements provide a convenience factor—grab your shake and go. Plus, calories and portion size are controlled, so it is easier to stay within calorie goals if you’re trying to lose weight.
Juice cleanses and detoxes have seen a surge in popularity in recent years but remain controversial in the nutrition world. Juices pressed from fruits and vegetables deliver a healthy dose of vitamins, minerals and antioxidants, but their claims to detox the body are not backed by science.
Liquid diets have pros and cons, regardless of your reason for doing them.
What Are the Benefits of a Liquid Diet?
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Liquid diets can help you lose weight-at least in the short term.
“Sometimes people can lose a few pounds,” says Isabel Smith, M.S., RD, CDN, dietitian nutritionist and founder of Isabel Smith Nutrition. But, “they can also gain them back quickly, too,” she says.
One study found that obese patients who replaced two meals a day with diet shakes lost more weight over a four-year maintenance period than those who ate calorie-controlled meals. This may have been due to the lack of variety in their diets. The greater the variety of food that is present, the more people tend to eat.
Liquid meal replacements also provide structure. Following a structured meal plan might lead to greater weight loss than a standard nutrition program.
The benefits of a juice cleanse are increased vitamin, mineral and antioxidant intake because of the amount of fruits and vegetables it takes to extract the juice.
“There are certainly studies that show benefits of juice on antioxidant concentration and anti-inflammatory mechanisms in the human body,” says Rachele Pojednic, Ph.D., M.Ed., assistant professor of nutrition at Simmons College, “but it’s generally in the presence of a healthy diet (or other solid foods). The biggest problem is that people think they are ‘detoxing’ their organs, which just isn’t how your liver, or kidneys, or any other organ works.”
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What Are the Risks of a Liquid Diet?
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- Feeling light-headed or dizzy
- Too few calories
- Lack of important nutrients
- Not sustainable long-term
- Lack of satiety
- Expensive
“There are very few rewards of going on a liquid diet,” Pojednic says. “You may lose a little weight in the short term due to water loss, and perhaps a couple of pounds in the longer term due to a massive calorie deficit. But achieving these results is not typical because the diet is so challenging and makes you feel pretty terrible.”
Most people can’t last more than a few days before giving in to everything they were restricting, which just leads to overeating, guilt and gaining back the weight you lost.
In addition to feeling hangry, you might be missing important nutrients, too. Juices have vitamins and minerals, but they don’t have fiber, fat or protein. Drinking juice alone can lead to “debilitating headaches, overwhelming hunger and diarrhea,” Pojednic says. “Despite the hype that you feel this way because your body is ‘detoxing,’ these symptoms are actually because your calorie intake is so low, your blood sugar in between ‘meals’ is tanking, your body is responding to never feeling satiated, and there’s nothing in your gut to bulk up your stool.”
Rest assured that your body takes care of the cleansing for you.
“Your body operates on very tightly regulated signaling mechanisms to keep you upright, functioning and clearing out molecules that it doesn’t need,” Pojednic says. This is why you don’t overdose on aspirin. “Your liver has very specific enzymes to ‘detoxify’ your body. Some foods can influence these enzymes, but flooding your body with liquid isn’t going to dramatically change those mechanisms or ‘flush out your system,'” she says.
One final downside? Cost. Subsisting on liquids alone gets expensive.
Differences in Nutrient Absorption
There is a difference in how your body absorbs liquids and solids. Solids come with an extra step in the digestion process: chewing. Chewing your food increases your fullness factor. Fiber also slows down digestion, helping you stay full longer, but juices lack this key ingredient.
“The sugars (glucose and fructose) in the juice will cross the intestinal wall much more quickly without the soluble fiber present in whole fruit, because that fiber barrier will be missing,” Pojednic says. And while you are getting a concentrated dose of vitamins and minerals (and sugar) from juice, you might not absorb them all. Vitamins A, D, E and K require fat for absorption.
Can You Do a Liquid Diet Yourself?
You can follow a liquid diet on your own, but check with your doctor or dietitian before doing it. You want to ensure you are getting proper nutrients.
Liquid diets could also be dangerous if you are pregnant, on certain medications, have had a recent procedure, or have intestinal or digestive issues.
Not sure if a liquid diet is right for you? Talk to a dietitian, who can guide you through the pros and cons based on your goals. If you choose to go for it, choose beverages that have protein, carbohydrates and fat to help you stay full. Swapping juices for smoothies can help. Consider having one liquid meal per day instead of all three. And don’t stay on the liquid diet for long.
“You probably won’t do much damage if you keep it to less than three to seven days,” Pojednic says. “In the meantime, though, prepare to feel like crap.”
Liquid Diet
As the name suggests, a liquid diet means you’re getting all, or at least most, of your calories from drinks. There are different kinds.
A clear liquid diet is something a doctor may put you on for a short while. You’re often asked to follow one before a medical procedure or if you’re having some digestive issues. You won’t get the calories and nutrients you need with one of these diets, so you can’t be on them for long and shouldn’t do them without medical supervision.
People choose to go on other types of liquid diets for weight loss. Typically, they’re limited to fruit or vegetable juices, or shakes. These drinks may replace all of your meals or just one or two meals (usually breakfast and lunch). You also get snacks on some of these plans.
These diets can cut the calories you take in and can help you lose weight, but you shouldn’t stay on them for very long. Talk to your doctor before you go on a liquid diet. You’ll need to make sure you get enough important nutrients, like fiber and protein.
Do liquid diets work for weight loss?
Liquid diets can work, like any diet that gives you fewer calories than you use. These diets can help by taking the guesswork out of portion control. They’re also beneficial if you have trouble chewing food.
But the results may not last. When you drastically cut calories, your metabolism slows to save energy. Unless you change your eating habits, you’re likely to regain the weight you lost after you go off the liquid diet.
Some liquid diets work better over the long term than others. Diets that include both solid food and liquids can be an effective and convenient way foroverweight people to control the number of calories they eat.
Liquid Diet Risks
Ideally, liquid diet drinks should give you a balance of nutrients you need throughout the day, but that isn’t always the case.
Very low-calorie diets (400-800 calories per day) in particular can be lacking in a balance of protein, carbohydrates, fats, vitamins, and minerals you need and should only be used under medical supervision.
Missing out on essential nutrients can lead to side effects such as fatigue, dizziness, hair loss, gallstones, and heart damage.
Also, if you don’t get enough fiber, because you’re not eating whole grains, fruits and vegetables, you can get constipated.
You also can lose muscle if you don’t get enough protein calories in your diet.
Talk to Your Doctor Before Starting A Liquid Diet
If your doctor prescribes you a liquid diet, they’ll go over what liquids you can have, and how long you should be on it. Make sure you follow their instructions carefully.
If you want to go on one for weight loss, talk to your doctor first about whether a liquid diet is appropriate for you. Pregnant or nursing women, and people who take insulin for diabetes, or anyone with a chronic illness shouldn’t go on a liquid diet.
If your doctor gives you the OK to go on one, you should also see a registered dietitian, who can go over it with you and make sure you’re getting enough calories and nutrition. Your dietitian might recommend that you take a vitamin or nutritional supplement while you’re on the liquid diet.
Before you choose a liquid diet plan, know what you’re drinking. If you’re considering one of the commercial diets, look at the daily values on the nutrition facts label. Be sure you’re getting 100% of all the recommended vitamins and minerals.
Look for a diet that is not too low in calories and contains plenty of protein and fiber to keep you feeling full while you lose the weight gradually. Liquid diets that include a solid meal or two per day, or that teach you healthier eating habits, will be more likely to help you keep the weight off in the long run.
Show Sources
Andrea Giancoli, MPH, RD, spokeswoman, Academy of Nutrition and Dietetics.
Flechtner-Mors, M. Obesity Research, August 2000.
National Digestive Diseases Information Clearinghouse: “Crohn’s Disease.”
Yamamoto, T. Inflammatory Bowel Diseases, December 2007.
Southwest College of Naturopathic Medicine and Health Sciences: “The Benefits and Downsides of Liquid Diets.”
Mayo Clinic: “Clear liquid diet.”
How to Lose Weight Fast With the Liquid Diet
One specific liquid diet for weight loss doesn’t exist. Many variations of a very-low-calorie diet that has you subsist on juice, clinically prepared nutritional drinks, smoothies, or concoctions of cayenne pepper and lemon juice for days, weeks or even months persist, however. Some of these diets are used by medical professionals to intervene in cases of morbid obesity; others are followed by Hollywood starlets seeking to slim down for a role; some are followed by people hoping for miracle weight loss.
If you want to lose weight quickly using a liquid diet, educate yourself on the implications and risks before choosing one. Also, check with your physician — some are simply not a good idea to follow unless you’re under medical care. You can lose weight fast if you do follow one, but it may not be worth the long-term consequences.
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About Liquid Diets
A liquid diet involves replacing all whole, solid food with juice, smoothies, soups, frozen bars or a combination of any or all of these products. A liquid diet usually results in quick weight loss, because you restrict calories severely when you cut out whole foods. Weight loss occurs when you eat fewer calories than you burn; you lose a pound when that deficit reaches 3,500 calories. The average person needs about 2,000 calories to maintain body weight. Most liquid diets contain 600 to 1,000 calories per day, meaning you are creating a large deficit — essentially starving yourself — and will inevitably lose weight.
Don’t confuse a liquid weight-loss diet with an all-liquid diet that is prescribed before or after certain surgeries or medical procedures. These diets aren’t designed to be low in calories, but to be gentler on the gut and easier to digest.
Losing Weight on Liquid Diets
In cases of extreme obesity, a physician may place a patient on a very-low-calorie liquid diet to help shed pounds quickly. This can avert an immediate medical consequence resulting from excess weight or prepare a patient for bariatric surgery. A patient typically loses 3 or more pounds per week but is followed closely by the doctor to make sure no complications arise.
Many non-medical versions of liquid diets exist too. To lose weight quickly, proponents of liquid diets require you to stick primarily to vegetable juices or low-sugar liquids and avoid solid food. You may choose to drink home-pressed or purchased juice for all meals. Other liquid diets may have you sip broth or smoothies instead of eating vegetables, fruits, lean protein and whole grains. These diets aren’t usually developed by a dietitian or doctor, but simply reduce your calorie intake so you lose weight. You see faster results if you stick to the liquids only and don’t snack to supplement.
Side Effects of Liquid Diets
Whether you’re following a juice fast that’s promoted as “cleansing” or a liquid diet that promises to help you drop 10 pounds quickly, you’re essentially starving your body and denying it the whole foods it needs to survive. A juice fast risks overloading your body with carbohydrates and sugar while forcing it to burn your muscle mass for energy. You may lose weight quickly if you subsist on juice alone, but you risk nutritional deficiencies, loss of energy, quick muscle loss and nausea.
Even medically supervised very-low-calorie liquid diets can have serious consequences. Followers may develop liver inflammation, abdominal discomfort, diminished immunity, muscle loss, nutrient deficiencies, bad breath, headaches, dehydration, severe fatigue, gallstones and kidney stones.
Liquid Diet Deficiencies
A juice fast can provide you with generous phytonutrients, carbohydrates and vitamins — but is missing essential fatty acids, which support a healthy brain, and protein, to support muscle. Medically supervised liquid diets require hospitalization or regular checkups to ensure complications are not developing; a very-low-calorie liquid diet should not be followed for more than 12 weeks, even in a medical setting. Most people do not need to follow a very low-calorie diet and should follow a whole foods low-calorie diet to lose weight.
Liquid diets also fail to teach you how to craft meals that will support any weight loss in the long term. At some point, you’ll start to eat whole foods again; if you don’t have good, healthy habits in place, you could end up regaining any lost weight and possibly more when you return to old ways of eating.
