Liquid Diet For Weight Loss: Benefits, Types & Risks In 2024

A liquid diet is when you replace all solid food with liquids, such as meal replacements, shakes, smoothies, juices, or water. Liquid diet for weight loss might seem like a good idea at first, but do they work?

Studies show that liquid diets can help you lose weight in the short-term, but may not be beneficial for long-term sustainable weight loss. Read on to find out the liquid diet benefits and downsides of liquid diets for weight loss, and whether a liquid diet is right for you.

Types Of Liquid Diet For Weight Loss

Liquid diets can either be a full liquid diet or a partial liquid diet. There are different types of liquid diets for weight loss. Here are the most common.

Meal Replacements

Liquid meal replacement diets provide all your daily nutrient needs in the form of a shake. You usually buy them as powders and add milk or water to make a shake. Usually, you’ll replace one meal per day with all meals with shakes. 

There are many commercially available meal replacement shakes and weight loss programs. Your doctor may also prescribe meal replacement therapy for weight loss. 

Detox Liquid Diet

Some people follow a short-term liquid diet – such as a juice cleanse or detox tea regime – for weight loss and detoxification. 

Juice diets provide very few calories and can work for short-term weight loss, but usually lead to weight gain^[1] once resuming normal diet eating. 

Moreover, there’s very little clinical evidence that detox diets work^[2] for toxin elimination. In fact, the loss of toxins usually results from not ingesting them in the first place as part of the diet.

Medically-Prescribed Liquid Diet

Sometimes, liquid diets are prescribed for a medical reason, such as before or after some type of surgery. For instance, liquid diets before bowel surgery can minimize the spillage of bacteria during the procedure.

After any abdominal surgery, the bowels naturally stop moving for a time and a liquid diet prevents a functional obstruction (ileus^[3]) that can occur before normal peristalsis resumes. 

So, you’ll usually follow a liquid diet consisting of pureed foods^[4] for two to three weeks after something like gastric bypass surgery, gallbladder removal, and colorectal surgery^[5].

Clear Liquid Diet

A clear liquid diet consists of water, broth, and some juices (without pulp). They are usually prescribed for patients before certain medical procedures, such as a colonoscopy, to clear the view of the inside of the colon.

What Is A Liquid Diet?

A liquid diet is when you replace solid foods with liquidized foods. This can be smoothies, shakes, juices, or meal replacements. 

Most people follow a liquid diet weight loss program as a personal choice to lose weight. Others may follow a liquid “detox” diet such as a juice cleanse for other health reasons. 

Some people may be prescribed a meal replacement liquid diet for medical reasons if they can’t easily digest solid food, such as those with severe Crohn’s disease, after surgery, or due to intestinal obstruction.

Benefits Of The Liquid Diet

Weight Loss

The main benefit of electively choosing a liquid diet is weight loss. 

Liquid meal replacements usually contain all the nutrients you need and leave out the unhealthy stuff – sugar, saturated fat, unnecessary calories – so it’s no surprise that people lose more weight following a liquid diet compared to a standard low-calorie diet.

Studies show that a high-protein meal replacement liquid diet can lead to 10 kg weight loss^[6] after 16 weeks. In this study, the participants sustained weight loss for a further eight weeks after going back to solid food.

But you may not have to eat a full liquid diet to see weight loss benefits.  A study in obese women found that partial meal replacement (replacing two meals per day) led to an average of 1 kg extra weight loss^[7] after two months compared to a low-calorie diet. 

A further study found that only one meal replacement per day leads to the same amount of weight loss^[8] as two meal replacements per day. 

Better Blood Sugar Balance

Meal replacement therapy can improve blood sugar balance more effectively than standard dietary advice in those with type 2 diabetes. 

Liquid diets automatically remove choice from the equation, so people tend to consume less sugar via meal replacements than when they choose their meals and snacks – even if they’re following a low-calorie diet.

Studies have found that six weeks of meal replacements can balance blood sugar^[9] and improve insulin resistance significantly more effectively than via a traditional low-calorie diet. 

Another study found that 12 weeks of a diabetes-specific meal replacement supplement significantly improved Hb1Ac^[10] – a marker of long-term blood sugar balance – compared to traditional diabetes therapy (i.e., medication and counseling). 

However, as liquid diets don’t help you to change your long-term eating habits, it’s unlikely the changes in blood sugar balance remain after going back to solid foods.

Lower Cholesterol Levels

Following a meal replacement diet could also help lower triglyceride levels. Meal replacements help lower blood fat levels because they usually provide all the healthy essential fats you need without additional or unhealthy fats, such as saturated or trans fats. 

A study in obese women shows that partial meal replacement significantly lowers blood fats^[7] compared to a standard very low-calorie diet. 

Further studies show that partial liquid meal replacement can significantly increase levels of HDL (“good”) cholesterol^[11] after eight weeks and lower total cholesterol levels^[8] after twelve weeks.

Improved Micronutrient Intake

You might not think it, but following a liquid diet could also improve your nutrient intake.

In one study, those following a partial meal replacement diet had higher intakes of vitamins and minerals^[7] than those following a normal low-calorie diet. 

Meal replacements are fortified with all required nutrients to ensure you meet your daily needs, whereas it can be difficult to achieve daily nutrient requirements whilst following a do-it-yourself low-calorie diet.

Better Quality Of Life For Those With Chronic Illnesses

Meal replacement therapy is used to help people with chronic illnesses lose weight and better manage their illnesses. Type 2 diabetes and osteoarthritis are two examples are chronic diseases where meal replacement therapy can help.

Studies show that meal replacement therapy can significantly improve the quality of life in women with knee osteoarthritis^[12] and obese patients with type 2 diabetes^[10] compared to traditional calorie restriction. 

This change could remain in the long term, too. A further study in obese subjects found significantly improved long-term quality of life^[13] after losing weight following a high-protein meal replacement diet for six months, compared to standard lifestyle changes alone.

The improvement in quality of life is most likely down to the more efficient weight loss achieved via meal replacement therapy compared to a standard low-calorie diet. In the end, reducing obesity increases the quality of life, always.

Lower Levels Of Toxin Metals

Some people follow liquid diets for detoxification benefits. However, there’s very little evidence that detox diets work for toxin elimination.

Nevertheless, one study found that four weeks of a liquid detox diet called the “Wellness up diet” – a diet consisting of one meal replacement shake for breakfast, fruit and vegetable juice for lunch, salads for dinner, and nut bars as snacks – led to significantly lower levels of some toxic trace elements in the hair compared to a normal low-calorie diet. 

It must be emphasized, however, that this reduction was felt to be due to the reduced toxins in the diet itself during the study, and not some therapeutic “clearing” of the toxins because of the diet. 

Potential Downsides Of The Liquid Diet

A liquid diet can be a safe and effective method for weight loss if done in the right way.  Long-term studies suggest that both medically-guided^[14] and commercial one-year weight loss programs^[15] are highly effective and safe treatments for obesity with minimal side effects. 

These programs usually consist of 12-week liquid meal replacement therapy followed by several phases of food reintroduction. However, despite the positives of a liquid diet, there can be some downsides to watch out for.

Weight Regain

If you’re following liquid diets to lose weight fast, you might be disappointed long-term.

Studies show that a very low-calorie diet may achieve their weight loss goals initially, but followers tend to gain all the weight back^[16] six to twelve months later. 

There are two main reasons for this: 

(1) Significantly reducing your calorie intake can slow your metabolism to conserve calories, which results in gaining weight again quickly once you start adding more foods to your diet.

(2) Long-term weight loss maintenance requires sustained behavior change^[17]. However, crash diets (i.e., dramatically cutting calories to lose weight fast) don’t help you change your eating habits for sustainable weight management. Psychologically, bad habits will more likely return the more you sacrifice personally; it’s the “Thank goodness that’s over!” mindset when you resume your prior way of life.

Moreover, some liquid diet regimes may recommend the use of laxatives for fast weight loss^[18]. This can lead to a loss of water weight^[19] rather than fat mass, meaning fast weight regain after eating normal foods again. 

Worse, during periods of water loss, you may negatively impact your electrolyte levels which can adversely affect kidney function and heart rhythm.

As most types of liquid diets such as meal replacements tend to be fewer calories, there’s a high risk of regaining all the weight you worked so hard to lose for the above reasons.

Nutrient Deficiencies

Meal replacement shakes and other types of liquid diets tend to be low in calories, which can lead to nutrient deficiencies.

However, if you’re following a medically prescribed liquid diet or using well-balanced fortified meal replacement powders, there’s a low risk of nutrient deficiencies.

Moreover, using liquid diets to lose weight results in essential fatty acids being released^[20] from adipose tissue, reducing the need for meal replacements to be supplemented with essential fats – especially omega-6. 

This can upset the balance between omega-6s and omega-3s, whose ratio should be, ideally, 1:1 to 2:1, respectively, to optimize cholesterol metabolism.

You can also take a nutritional whole food supplement to reduce the risk of deficiencies while following a liquid diet, but it’s probably not necessary. Commercial products are backed by adequate research and quality control to avoid deficiencies.

Gallstones

Very low-calorie diets can increase the risk of developing gallstones^[21], which are hardened balls of cholesterol fats in your gallbladder.

This usually happens as a result of not getting enough essential fats^[20] in the diet. Liquid meal replacements should provide a minimum of 20 grams of fat per day to reduce gallstone risk.

Gastrointestinal Symptoms

Using liquid meal replacements may lead to overconsuming magnesium in some cases. 

Whilst this isn’t a major health risk, it can lead to diarrhea^[20] when consuming more than 350 milligrams (mg) of magnesium per day. If you’re experiencing gut issues, make sure you’re not consuming more than 350 mg of magnesium per day through meal replacements and nutritional supplements.

Low Blood Sodium Levels

Studies show that overconsuming “detox” teas can lead to hyponatremia^[22], the scientific term for very low sodium levels in the blood. Severe hyponatremia can kill. 

A couple of case studies have been reported. One case study describes a 67-year-old man who developed severe hyponatremia^[23] after a five-day kidney detox tea regime. 

What To Include In Liquid Diet Meal Plan?

If following a liquid diet for weight loss, we recommend following a liquid diet plan supported by your doctor or healthcare provider.

However, if you want to try a self-directed liquid diet for weight loss at home, we recommend including the following:

• Avoid a full-liquid diet. Replace one or two meals per day with high-protein meal replacement shakes offered by commercial companies. Make sure the company you choose provides a balanced meal replacement with all essential vitamins, minerals, and fats.
• Include fruit and vegetable smoothies as a snack or meal. Make sure to include a variety of fresh fruits and vegetables as well as sources of proteins and fats, such as nut butter, yogurt, soy milk, or protein powders.
• We recommend following a partially liquid diet, eating one solid-food meal, such as salads, and snacks such as fruit and nut bars.
• Avoid detox teas; opt for normal herbal teas instead.

Final Thought

Liquid diets replace some or all of your meals with liquids such as shakes, smoothies, and teas. They’re usually fewer calories, so many people use them for weight loss. Studies show that liquid diets can work for long-term weight loss when done in the right way. 

However, doing your own liquid diet at home can lead to harmful side effects and weight regain if not done properly. Worse, without the scientific background of companies that specialize in these products, you can be putting yourself in extreme danger.

If you want to lose weight, we recommend following a short-term liquid diet that replaces only one or two meals per day and incorporates more solid foods as part of a phased program. This helps you to change your eating habits for sustainable weight management. 

Remember, for a diet to work, don’t just change the way you eat during the diet, but for your whole life.

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