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What is a liquid diet? And can it help me lose weight?

They may sometimes be necessary due to medical reasons, but dietitians advise against liquid diets and juice cleanses for weight loss.
Liquid diets lack the vitamins, nutrients and antioxidants you should be getting from food for optimal health.
Liquid diets lack the vitamins, nutrients and antioxidants you should be getting from food for optimal health.TODAY Illustration / Getty Images

You’ve probably heard the hype about the energy-boosting and weight-loss benefits of juice cleanses and bone broth diets. But do they have any merit?

In some cases, a liquid diet can be medically necessary (usually for a short period of time, but sometimes for longer), Katherine Zeratsky, a registered dietitian at the Mayo Clinic in Rochester, Minnesota, told TODAY. “But it wouldn’t be anything I would recommend people do without medical supervision. Generally speaking, the diets are not nutritionally complete.”

If a New Year's resolution has you considering a liquid diet for weight-loss purposes, here's what experts want you to know.

What is a liquid diet?

A liquid diet, as the name implies, usually refers to a diet where all the calories you consume are coming from foods in liquid form at room temperature. Zeratsky categorizes these liquid diets in two groups: diets that are medically necessary (for various health conditions, in preparation for a surgery or procedure or as post-operative care) and ones that fall more into the realm of fad diets.

Here are a few examples of diets that may be required for health reasons:

  • Clear liquid diet: Allows liquid foods at room temperature that are transparent, like bone broth, coffee or tea without milk, gelatin, strained juices without pulp, soft drinks and sports drinks — though red and purple dyes should be avoided in some cases.
  • Full liquid diet: Allows everything allowed on a clear liquid diet as well as non-transparent liquids, like dairy, ice cream, pudding, milk shakes and strained creamy soups.

In the latter group, there are juice cleanses, liquid diets that have you eating packaged juices and nutritional supplements, detox tea cleanses and the Master Cleanse — all diets where most calories come from things like meal replacement shakes or teas/lemonades.

Who should go on a liquid diet?

The clear liquid diet is one that leaves little residue in the bowel and digestive tract. Someone might need to do it in preparation for a surgery or procedure (like a colonoscopy), which require these organs to be clear. Eating this type of diet also allows the bowel to rest, so it may be prescribed after a surgery or procedure involving the stomach or intestines or weight-loss surgery if you want to gradually reintroduce food, Dr. Neal D. Barnard, adjunct associate professor of medicine at the George Washington University School of Medicine in Washington, D.C., told TODAY.

“It’s generally used for less than 24 hours, as it isn’t nutritionally complete ... (A liquid diet) can also be helpful if swallowing food causes pain, such as if someone has mouth sores during chemotherapy,” added Barnard, who researches the effects of diet on diabetes, body weight and chronic pain.

As for juice cleanses and other liquid detoxes that are not medically necessary, Zeratsky doesn’t recommend them because they tend to be incomplete when it comes to the vitamins, nutrients and antioxidants you should be getting from food for optimal health.

Can a liquid diet help with weight loss?

In rare cases a version of a liquid diet may be prescribed to someone for weight loss or before weight-loss surgery, Zeratsky said, but she cautions people against trying it on their own without medical supervision. They’re usually always nutritionally inferior to a well-balanced diet of solid and liquid whole foods, no matter what supplements and meal replacement products you’re consuming, she said.

You can lose weight on a liquid diet, but usually people end up gaining back the weight once they stop the diet and may even regain excess weight, Zeratsky stressed.

Liquid diets also tend to be difficult to follow, Robin Danowski, a registered dietician and assistant professor at La Salle University in Philadelphia, told TODAY. “Liquids move through the gastrointestinal system fairly quickly. Solid food fills us up and take longer to digest,” she explained. “So after a liquid meal you may not have that same feeling of satiety (that feeling of fullness).”

Liquid diets lack the disease-fighting phytochemicals and nutrients found in a diet that includes whole foods and a lot of plants, Barnard said. “They don’t teach people how to choose healthy foods,” he added. “And they don’t help people develop a healthy relationship with food.”

Is a liquid diet safe for the long-term?

In some cases (if someone has a chronic medical condition that limits chewing or swallowing) a full liquid diet may be necessary for the long term. And there are ways (using nutritional supplements and meal replacement shakes) for people to get the nutritional components they need, Zeratsky explained.

Someone may need to go on this type of diet if they have permanent difficulty swallowing and require tube feeding, such as after a stroke or because of other injury to the throat, Barnard explained.

But outside of cases where it’s medically necessary, liquid diets should not be used long term, Zeratsky stressed.

What will a day of eating on a liquid diet look like?

It depends on which version of a liquid diet you’re following. Some juice cleanses recommend you only eat pre-packaged juices made by the diet company. If you’re following the Master Cleanse, during the lemonade diet portion of the plan, you’ll only be consuming a juice made from lemon, maple syrup and cayenne pepper.

If you’re on a full liquid diet for a medical reason, here’s what a day of eating might look like, Zeratsky said:

  • Breakfast: Fruit juice, hot cereal (such as Cream of Wheat or another one that is very thin in consistency) made with milk, yogurt drink, hot tea with sugar and lemon
  • Lunch: Strained squash cream soup, fruit juice, milk, hot tea with sugar and lemon
  • Dinner: Strained cream of broccoli soup, vegetable juice, milk, pudding
  • Snacks: Fruit or vegetable juice, custard

Zeratsky noted that serving sizes may vary depending on someone’s condition and calorie needs.

The bottom line:

Liquid diets may sometimes be medically necessary for the short or long term, but only with the guidance of a health care professional. They are nearly always less nutritious than a diet with whole foods that include fruits, vegetables, whole grains and healthy fats and not recommended for otherwise healthy people.

If weight loss is your goal, focusing on whole foods, including lots of fruits and veggies, is your best bet for sustainable changes.