Liquid diets have become a popular approach for individuals seeking weight loss. These diets involve consuming a significant portion, or all, of daily calories through liquids rather than solid foods. While some liquid diets are medically prescribed, others are chosen by individuals for weight loss purposes. Understanding the different types of liquid diets, their potential benefits, risks, and guidelines is crucial before embarking on such a dietary plan.
Understanding Liquid Diets
Liquid diets are nutrition programs that require you to get either some, most, or all of your daily calories from liquids, rather than solid foods. There are various types of liquid diets, each with its own characteristics and purposes.
Meal Replacement Diets
Some liquid diets involve meal replacement shakes, consumed in place of solid foods. Numerous companies sell these shakes for weight loss purposes. Meal replacement shakes are often lower in calories than typical meals and can replace one or multiple meals each day. They are designed to contain all the nutrients your body needs to function, 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.
Detox Diets and Cleanses
Other liquid diets include detox diets or cleanses, which require the consumption of 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. For example, the Master Cleanse consists of 3-10 days of only consuming a special beverage made of lemon juice, maple syrup, cayenne pepper, and water.
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. Full liquid diets are prescribed for similar reasons, but they are less restrictive than clear liquid diets. They allow most beverages, as well as foods that become liquid at room temperature, such as popsicles, Jell-O, pudding, syrups, and some shakes.
Read also: Troubleshooting Carnivore Diet Diarrhea
How Liquid Diets Work for Weight Loss
Liquid diets often contain fewer calories than diets consisting of solid foods. Replacing some or all meals with liquid meal replacements can promote weight loss. 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.
For instance, one weight loss study in 24 obese people involved a 30-day period in which participants consumed 700 calories per day from meal replacements but no solid foods. Over the next 150 days, solid foods were gradually reintroduced. Daily calorie intake increased gradually from 700 to 1,200 calories. This program was effective for weight loss and reduced body fat from 33% to 26%.
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.
Medical Uses of Liquid Diets
Although liquid diets are often associated with weight loss programs, there are other reasons why you may follow one. For example, 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.
A clear liquid diet is medically prescribed for short periods to rest and clean out your digestive tract while providing adequate short-term hydration and some energy. The diet is usually prescribed for one of three reasons:
Read also: Weight Loss with Ozempic and Cigna
- To clear out your digestive tract and/or prevent nausea before a procedure, such as an imaging test or surgery.
- To give your digestive system a rest from severe gastrointestinal symptoms, such as inflammation, vomiting, and diarrhea.
- To offer nutrition without eating after a fast or surgery.
Guidelines for Clear Liquid Diets
If your healthcare provider prescribes a clear liquid diet, they will give you more specific directions on the amounts of each type of liquid you should consume. The clear liquid diet includes:
- Coffee and tea without milk or non-dairy creamer (sugar or honey is OK).
- Clear, nonfat broths.
- Strained, pulp-free fruit and vegetable juices.
- Sodas and sports drinks.
- Clear nutritional drinks.
- Pulp-free popsicles.
- Jell-o®.
If the diet is prescribed before an imaging test, you might be asked to exclude the color red because red liquid can resemble blood on an imaging test. The diet is usually only prescribed for a few days. If it is prescribed for longer, it will be modified with certain supplements to provide more adequate nutrition over the longer term.
Full Liquid Diet - What to Expect
A full liquid diet includes all liquids and foods that become liquid at body temperature. Shakes, milk, frozen yogurt, and creamy soups are allowed, as long as they don’t have any chunks or food particles in them. A full liquid diet is prescribed for similar reasons as the clear liquid diet - to rest the digestive system after illness or surgery and reintroduce it slowly to normal eating - but it’s a less severe diet for less severe cases. Some people need to start on the clear liquid diet first before progressing to the full liquid diet. Those who are preparing for an imaging test will need to stick to clear liquids to keep their digestive tract clear.
When on a full liquid diet, you can eat or drink only things that are liquid, including:
- Water
- Fruit juices, including nectars and juices with pulp
- Butter, margarine, oil, cream, custard, and pudding
- Plain ice cream, frozen yogurt, and sherbet
- Fruit ices and popsicles
- Sugar, honey, and syrups
- Soup broth (bouillon, consommé, and strained cream soups, but no solids)
- Sodas, such as ginger ale and Sprite
- Gelatin (such as Jell-O)
- Boost, Ensure, Resource, and other liquid supplements
- Tea or coffee with cream or milk and sugar or honey
You cannot eat solid foods when you are on a full liquid diet.
Read also: Dietary Habits of Whip-poor-wills
Risks and Considerations
While liquid diets can be effective for weight loss, it's important to consider the potential risks and drawbacks.
Nutritional Deficiencies
Solid foods contain many necessary nutrients. Therefore, it is not recommended to stay on a diet consisting of liquids alone in the long term. Even in studies showing impressive results from liquid meal replacements, solid foods were reintroduced after several weeks or months. Medically prescribed liquid diets like the clear liquid diet or full liquid diet are not meant to be followed in the long term.
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. Eating only a full liquid diet can give you enough energy, protein, and fat, but it does not give you enough fiber. Also, you may not get all the vitamins and minerals you need. So, your provider may recommend that you take certain vitamins and supplements.
Unsustainable for Long-Term Weight Management
Short-term crash diets don’t typically lead to lasting weight loss because they don’t do anything to change your permanent eating habits. Diets that contain solely juices or special beverages are not good long-term strategies. These programs may lead to some rapid weight loss but will probably not lead to lasting fat loss. Focusing on sustainable, long-term dietary changes is a better strategy.
Not Suitable for Everyone
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. Also, if you have diabetes, you may need to discuss this with your healthcare provider before proceeding with the clear liquid diet. You may need to find sugar-free alternatives to some of the liquids, adjust your medications, and monitor your blood sugar carefully during the diet. Also, if you have dysphagia or another swallowing problem, you might need to discuss thickeners with your healthcare provider to thicken your clear liquid diet to a consistency you can more easily swallow.
Commercial meal replacement shakes can often be more expensive than traditional solid foods.
Potential Side Effects
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).
Making Informed Decisions
Before starting a liquid diet for weight loss, it's essential to consult with a healthcare professional or a registered dietitian. They can assess your individual needs, health status, and goals to determine if a liquid diet is appropriate for you. They can also provide guidance on choosing the right type of liquid diet, ensuring adequate nutrient intake, and monitoring for any potential side effects.
If you want to go on one for weight loss, talk to your doctor first about whether a liquid diet is appropriate for you. 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.