Liquid diets involve consuming most or all daily calories from liquids rather than solid foods, and they come in various forms. They are sometimes considered for weight loss. A clear liquid diet limits you to options such as water, broth and plain gelatin. These are easy to digest, and they don't leave food bits in your digestive tract. Your health care provider may prescribe a clear liquid diet before or after some medical procedures or if you have digestive problems such as vomiting or diarrhea. A clear liquid diet can't give you all the calories and nutrients you need. Clear liquids may have some color. Liquids with some color are allowed if you can see through them. Foods can be considered liquid if they partly or completely melt to clear fluid at room temperature.
Types of Liquid Diets
Several types of liquid diets exist, each with distinct characteristics and purposes.
Meal Replacement Diets
Some liquid diets involve meal replacement shakes, consumed instead of solid foods. Numerous companies sell these shakes for weight loss. These shakes are often lower in calories than typical meals and are designed to contain the necessary nutrients, including macronutrients (protein, carbs, and fat) and micronutrients (vitamins and minerals). Some weight loss programs use these shakes to account for your entire calorie intake for up to several months. Replacing just one or two meals per day with a low-calorie meal replacement shake may be a practical long-term strategy as a complement to eating healthy, solid foods.
Detox Diets and Cleanses
Other liquid diets include detox diets or cleanses, which involve consuming certain juices or drinks that supposedly remove toxic substances from your body. Unlike meal replacement shakes, these programs typically rely on a few natural ingredients like juices from certain fruits and vegetables and other botanical ingredients. Because of this, these diets may not contain all the nutrients your body needs.
Medically Prescribed Liquid Diets
Clear liquid and full liquid diets are examples of diets that are medically prescribed for specific health reasons. As the name implies, clear liquid diets only allow the consumption of clear liquids, such as water, apple juice, tea, certain sports drinks, and broths. These diets may be prescribed before or after certain surgeries or if you have digestive problems. A clear liquid diet is often used before tests or procedures that require an empty stomach or clear intestines. For example, you may need to have a clear liquid diet before a colon exam, also called a colonoscopy. Or you may need to be on a clear liquid diet before and after certain types of surgery. The clear liquid diet is not very exciting. But it's designed to keep your stomach and intestines clear. If your provider prescribes a clear liquid diet before a medical test, be sure to follow the diet instructions exactly. If you don't follow the diet exactly, you may not have correct test results.
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Full liquid diets are prescribed for similar reasons, but they are less restrictive than clear liquid diets. They allow most beverages and foods that become liquid at room temperature, such as popsicles, Jell-O, pudding, syrups, and some shakes. You cannot eat solid foods when you are on a full liquid diet. You may need to be on a full liquid diet right before a medical test or procedure, or before certain kinds of surgery. It is important to follow the diet exactly to avoid problems with your procedure or surgery or your test results.You also may need to be on a full liquid diet for a little while after you have had surgery on your stomach or intestine. You may also need to be on this diet if you are having trouble swallowing or chewing. If you are prescribed this diet for dysphagia (swallowing problems), your speech pathologist will give you more specific guidelines. Sometimes the full liquid diet is a step to advance from a clear liquid diet to your regular diet.A full liquid diet consists of consuming only liquids or foods that turn into liquid at room temperature, such as yogurt, strained soups, fruit juice, ice cream, and milkshakes. It helps with recovery from gastrointestinal procedures and management of difficulties with chewing and swallowing. The full liquid diet requires no chewing.
How Liquid Diets Work for Weight Loss
Liquid diets often contain fewer calories than diets consisting of solid foods. For a liquid meal replacement diet, the total number of daily calories may range from 500-1,500. Research has shown that both low-calorie (1,200-1,500 calories per day) and very low-calorie (500 calories per day) diets using liquid meal replacements can be effective for weight loss. While very low-calorie diets can lead to greater weight loss, they may also lead to greater risks, such as an increased risk of gallstones in some individuals. People participating in studies on low-calorie liquid diets are typically monitored closely by medical personnel, and many of these programs are not meant to be followed in the long term.
Replacing some or all meals with liquid meal replacements can promote weight loss. However, this is due to a reduced calorie intake. Research directly comparing low-calorie diets consisting of either food or liquids has found both diets to be equally effective when they contain the same number of calories.
These diets can help by taking the guesswork out of portion control. They’re also beneficial if you have trouble chewing food.Liquid diets can work, like any diet that gives you fewer calories than you use.
When Liquid Diets Are Used
Although liquid diets are often associated with weight loss programs, there are other reasons why you may follow one. A clear liquid diet helps give you enough fluids to stay hydrated. It also provides electrolytes such as sodium and potassium. Depending on your medical condition, your health care provider may make changes to the list of allowed liquids. For certain tests, such as colon exams, your provider may ask you to stay away from liquids or gelatin with red coloring.
Read also: Explore the pros and cons of liquid diets
Clear liquids are typically easy to digest and do not leave much undigested material in your intestines. As a result, your physician may prescribe a clear liquid diet before certain surgeries, such as colonoscopies and bariatric surgery. They may also be prescribed after certain surgeries, such as gallbladder removal and bariatric surgery. Additionally, liquid diets are advised for those who have digestive problems, including diarrhea and vomiting.
Limitations and Potential Downsides
Solid foods contain many necessary nutrients. Therefore, it is not recommended to stay on a diet consisting of liquids alone in the long term. Medically prescribed liquid diets like the clear liquid diet or full liquid diet are not meant to be followed in the long term. Similarly, cleanse and detox programs may involve periods during which only certain juice mixtures are consumed for days or weeks.
Short-term, low-calorie diets can cause you to lose body weight quickly due to the loss of carbs and water, both of which are normally stored in your liver and muscles. What’s more, the Master Cleanse and similar programs recommend the use of laxatives, which could further contribute to the temporary weight loss. Thus, much of the weight you lose during these short-term liquid diets may not be due to fat loss. Once you resume a normal diet, you will likely regain much or all of the weight that you lost as your carbohydrate and water stores are replenished.
Short-term crash diets don’t typically lead to lasting weight loss because they don’t do anything to change your permanent eating habits. For these reasons, overly restrictive diets that don’t allow any solid foods are not generally recommended.
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.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.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.
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Who Should Avoid Liquid Diets?
While it is possible to find success with some liquid diets, such as those that use meal replacements, these programs aren’t ideal for everyone. Some people may find that replacing some solid foods with liquid meal replacements is a practical way to reduce their calorie intake. Nevertheless, others find this pattern of eating challenging. Several groups of people should not consider a liquid diet, such as pregnant or nursing women, children and adolescents, and those who are underweight. Not to mention, there are financial considerations. Commercial meal replacement shakes can often be more expensive than traditional solid foods.If you have diabetes, talk with the health care provider who helps manage your condition. Your provider can give you specific instructions to help manage your blood sugar, also called blood glucose, while on a clear liquid diet. Test your blood glucose levels often.
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.
Potential Side Effects and Safety Considerations
The safety of liquid diets depends on the type of diet and the duration of the program. Diets that replace one or several meals per day with meal replacement shakes are generally considered safe in the long term. Most meal replacement shakes are designed to contain the nutrients needed by the human body, including carbs, fats, protein, vitamins, and minerals. Yet, replacing only some meals with liquids ensures that you still get nutrients from solid foods as well.
One side effect of a liquid diet is constipation, which may be due to the low fiber content of most liquids. Additionally, very low-calorie diets (500 calories per day) may lead to a higher risk of gallstones than low-calorie diets (1,200-1,500 calories per day).
Following a liquid diet over the long term could increase your risk of nutrient deficiencies, particularly if you are only consuming juices or other beverages that do not contain all essential nutrients. Overall, it is probably a good idea to include some healthy solid foods in your diet, even if you are considering emphasizing liquids.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. Different liquid diets accomplish different things. Some studies suggest liquid diets may support your weight loss goals while others suggest the opposite.
Practical Tips for Following a Full Liquid Diet
Following the full liquid diet may present some challenges. You may need to do some extra planning to fit liquid-only meals into your daily life.
- Stock up your fridge and pantry: Stock up on as many items as you can before your diet starts, especially beverages and powder supplements you might need.
- Purée foods at home if you're on a budget: You may be able to save yourself some work by purchasing foods that have already been puréed, but these can be pricey and hard to find. You may find it more cost-effective to purée foods at home.
- Make food in advance: For convenience, you can also prepare many liquid meals ahead of time and freeze them.
- Try different ways to thin soft foods: The easiest way to thin soft foods is to add water or milk. If a food doesn’t fully liquefy, apply a little heat or microwave it. Pasta, rice, and potatoes can be cooked until very soft and then thinned with water, butter, or gravy.
- Invest in kitchen appliances: Kitchen tools like food processors can be a big help if you’ll be making liquid meals for yourself at home. A blender is useful as you purée fruits and veggies. You can also use it on a lower setting to pulse thicker foods like oatmeal into a safe consistency.
- Utilize puréed baby food: This can be a convenient option, but keep in mind that baby food doesn’t come in big enough portions for adults (and, at a dollar or so a jar, can end up being costly). Even so, you can use them as the base for a liquid meal.
- Supplement your diet with nutritional shakes: While nutritional shakes like Ensure and Glucerna are costly, they can add a good boost of protein and nutrition to better meet your daily needs. While the added cost of nutritional shakes may be well worth the investment, they should not be used as the sole source of nutrition.
- Let others know about your diet: Friends and family may be willing to help with grocery shopping and/or preparing meals.
Foods Allowed and Excluded on a Full Liquid Diet
The following table outlines foods that are allowed and foods that are excluded on a full liquid diet.
- Fruits and vegetables: Apple, grape, pear, tomato, and strained orange juice are good options. Avoid high-fiber juices such as prune juice, nectars, and orange juice with pulp.
- Grains: Grains are not usually recommended on a full liquid diet. In some cases, cooked cereals (like farina or rice) can be thinned with water or milk and then strained, but check with your healthcare provider first.
- Dairy: Milk or lactose-free alternatives are approved for a full liquid diet. You can drink it by the glass or add it to smoothies and shakes. Yogurt is also allowed.
- Protein: Protein shakes and powders, nonfat dry milk, instant breakfast powders, and powdered egg whites are recommended for adding protein to the full liquid diet. Check with your healthcare provider if you can include cooked eggs or meat pureed to a liquid or baby food consistency.
- Desserts: Ice cream, frozen yogurt, and ice pops are approved on a full liquid diet as long as they do not contain nuts, candy, pulp, or other hard pieces.
- Beverages: Any clear broths, pulp-free juices, or other drinks are approved on a full liquid diet. You can use milk, half-and-half, and non-dairy creamer to add calories to coffee or tea.
Full Liquid Diet: Additional Considerations
A clear liquid diet has limitations in that it delivers low calories and low levels of carbohydrates, possibly starting as low as 50 grams a day after bariatric (weight loss) surgery. Compared to a clear liquid diet, a full liquid diet includes foods that are nutritionally dense with higher levels of protein and carbs. The average adult in the United States requires between 1,600 and 3,000 calories per day (and between 225 and 325 grams of carbs per day) to function normally. A full liquid diet may be inadequate in fiber and certain vitamins.
Goals of a Full Liquid Diet
The aim of a full liquid diet is to consume enough nutrition without placing stress on the digestive tract.
- How much you eat: As a general rule, eat enough to feel satisfied.
- What you eat: The diet should also include a variety of six or seven different foods that are nutritionally dense.
A full liquid diet is generally prescribed for only a few days to help you transition back to your normal diet.
Potential Side Effects of a Full Liquid Diet
If you need to be on a full liquid diet for more than a few days, you may become constipated from the lack of fiber. You might also have frequent, loose stools on a full liquid diet simply because you are not consuming solids.
Because you are consuming fewer calories, vitamins, and minerals, you may feel fatigued, irritable, depressed, or generally unwell. Diabetes: You may need to take extra steps to manage your blood sugar. Some adjustments may be needed to make the full liquid diet safe for babies, toddlers, and children. When creating purées or liquid meals, avoid adding new foods to your child’s diet. Speak with their healthcare provider about how much milk a child should drink, as it can be very filling.
You can lose weight on a full liquid diet if you do not consume enough calories. To overcome this, ask your healthcare provider about high-calorie protein shakes like Ensure.
Tips to Increase Calorie Intake on a Full Liquid Diet
Ask your provider if you can eat these foods together to add calories:
- Nonfat dry milk added to your drinks
- Protein powders or liquid or powdered egg whites added to drinks
- Instant breakfast powder added to milk, puddings, custards, and milkshakes
- Strained meats (like the ones in baby food) added to broths
- Butter or margarine added to hot cereal and soups
- Sugar or syrup added to beverages