A liquid diet is a blanket term to describe a diet that consists only of liquids.
There are various types of liquid diets, each with its own rules, uses, and downsides.
This article explains everything you need to know about a liquid diet, including the various types, their benefits and uses, and more.
Types of liquid diets
A liquid diet is any diet that consists only of liquids.
Many types of liquid diets exist, differing in the types of liquids they allow and their uses.
Common types of liquid diets include:
- Clear liquid diet: A diet that consists only of clear or transparent liquids, such as flavored gelatin, broths, strained soups, popsicles, and tea or coffee with no added milk or cream.
- Full liquid diet: This diet allows the same foods allowed on a clear liquid diet plus all other forms of liquids, including ice cream, milk, and shakes or smoothies
- Elemental diet: A diet that consists of nutritionally-complete formulas that contain predigested nutrients, such as the Physicians’ Elemental Diet.
- Exclusive enteral nutrition diet: A diet that provides nutritionally-complete formulas by mouth or a feeding tube.
These types of liquid diets are commonly prescribed by a physician or registered dietitian — either in a clinical or non-clinical setting.
The clear liquid diet is designed to maintain hydration, but it is nutritionally inadequate because of its strict limitations.
As such, the clear liquid diet should only be followed for a few days.
The other types of liquid diets are more nutritionally adequate and can be followed for several weeks.
Juice cleanse or liver detox diets are other types of liquid diets but there is a lack of evidence to support the effectiveness of these diets for their purported health benefits (1).
These types of diets can also lead to an unhealthy relationship with food and increase the risk of developing an eating disorder (2).
Uses and benefits of a liquid diet
Liquid diets are commonly prescribed before and after certain surgeries or to manage certain digestive conditions.
And while not always their intended purpose, they can also help with weight loss.
Surgeons commonly prescribed liquid diets around surgeries that involve the stomach or intestines, especially gastric bypass or other weight-loss surgeries.
For example, a surgeon may prescribe a liquid diet after weight loss surgery for a short period before advancing their diet to solid foods.
Other times, a liquid diet may be recommended as part of the colonoscopy preparation diet process to clear the bowels and allow the doctor to have a clear view of the colon lining.
Still, many surgeons choose to prescribe a liquid diet before the procedure.
Liquid diets are commonly prescribed for managing various digestive conditions.
The type of liquid diet and duration in which to follow it depends on the digestive condition and various other factors.
Digestive conditions for which a liquid diet may be helpful include:
- Diverticulitis: A clear liquid diet may be needed during flare-ups or attacks to help the digestive tract heal.
- Pancreatitis: A clear liquid diet may be needed during acute episodes to help manage symptoms.
- Crohn’s disease: The exclusive enteral nutrition (EEN) diet is the first-line treatment for inducing remission during active Crohn’s disease (6).
- Eosinophilic esophagitis (EoE): Although an elimination diet is generally the first-line treatment for EoE, an elemental diet may be more effective for reducing inflammation and relieving symptoms (7).
- Small intestinal bacterial overgrowth (SIBO): An elemental diet may help promote a healthy balance of bacteria in the gut and alleviate digestive symptoms associated with SIBO (8).
Except for liver cleanses and the like, liquid diets are generally not prescribed for weight loss.
However, weight loss may occur as a result of following a liquid diet since many tend to be low-calorie.
For example, a clear liquid diet generally contains fewer than 1,000 calories, while a full liquid diet may have around 1,500 (9).
These calorie levels can help most people — if not everyone — lose weight, but any weight loss tends to be quickly erased after resuming a normal diet.
Moreover, many liquid diets tend to be low in protein, which can result in more weight loss from muscle rather than fat.
The less muscle mass you have, the lower your metabolism and the more difficult it is to lose weight and keep it off (10).
So while liquid diets can promote rapid weight loss, they are not a sustainable solution.
However, if weight loss is your goal, replacing one or two whole-food meals with liquid meal replacements can be an effective strategy for sustainable weight loss (11).
Downsides of a liquid diet
Despite their benefits, liquid diets have many downsides.
Difficult to follow
Most liquid diets are designed to be followed short-term, in part because they are difficult to follow long-term.
Liquid diets take away the joy and comfort of eating solid foods and they make socializing with friends or attending special events that are generally centered around food difficult.
Some liquid diet formulas — especially elemental formulas — don’t taste the best, creating additional challenges.
Still, some types of liquid diets don’t pose these challenges since they may only be prescribed for a few days.
In other instances, however, a liquid diet such as an EEN or elemental diet may be prescribed for several months, making them more difficult to follow.
However, if a liquid diet offers symptom relief from digestive issues that have a more significant impact on one’s quality of life, the factors that make a liquid diet difficult to follow long-term may not mean as much.
Some types of liquid diets can be costly.
Specifically, following an EEN or elemental diet can be expensive since the formulas are highly specialized.
For example, one carton of an elemental formula called Vivonex costs about $7.00 on Amazon.com.
An average person would have to consume six of these cartons — costing around $42 per day — to meet 100% of the dietary reference intake (DRI) for vitamins and minerals.
Other types of formulas including semi-elemental or polymeric formulas are less expensive and more available than elemental formulas, but relying on them as your sole source of nutrition can still become costly.
Liquid diets — except those that consist of nutritional-complete formulas, such as the EEN or elemental diet — tend to be nutritionally inadequate.
The inclusion of approved protein supplements may help you get more of the protein, vitamins, and minerals that liquid diets tend to lack but your diet may still fall short in several key nutrients, including fiber.
Short-term nutrient shortfalls are unlikely to pose any immediate health concerns, but following a liquid diet for longer than prescribed or recommended could lead to health problems, especially without guidance from a registered dietitian.
Low-calorie liquid diets can cause various side effects, including:
- hair thinning
- cold intolerance
- poor sleep quality
- low sex drive
- constant hunger
- low energy
Although relevantly minor, these side effects can interfere with your everyday responsibilities and relationships with family, friends, and coworkers.
The bottom line
A liquid diet is any diet that allows only liquids.
Common types of liquid diets include the clear liquid diet, full liquid diet, elemental diet, and EEN diet.
These diets are usually prescribed by a physician or registered dietitian and vary in their uses, benefits, and downsides.
It’s best to consult one of these healthcare providers if you’re thinking about trying a liquid diet that you were not prescribed to discuss its benefits and risks.