What Happens If You Only Drink Meal Replacement Shakes?

By Matt Smith

Published: April 9, 2025

Meal replacement shakes are a fantastic way to improve your health and nutrition. They make meal times easier to prepare and can even help to save you money. But what happens if you only drink meal replacement shakes and nothing else? This article will explore the results.

Drinking only meal replacement shakes is likely to lead to weight loss as most shakes contain just 400 calories per serving. There can be side effects to following an all-liquid diet, and meal replacement shake diets such as this are mostly used by doctors treating people with obesity.

Now that we know that consuming an all-shake diet is safe but not advisable let’s take a closer look at why this is.

What Are Meal Replacement Shakes?

A meal replacement shake can be quite hard to define. It is normally a powdered shake that you mix with water or milk. Unlike a protein shake, meal replacement shakes are often made to have a balance of proteins, fats, and carbohydrates.

But they are not always powdered. There has been a marked increase in ready-made meal replacement shakes that you can purchase in bottled form. Obviously, these end up costing quite a lot more, and their environmental impact is a lot more severe, but they still count as meal replacement shakes.

Many people in the past have stated that meal replacement shakes should not be considered food, but this is a confusing way to discuss food. For example, soup is 95% water, yet is obviously food, as are stews and foods such as oatmeal.

Meal replacement shakes are often made from oats, a protein source, and healthy fats. The only difference is that they are dehydrated into powder form, making them easier to transport, cheaper to buy, and longer-lasting.

There is a surprisingly long history of meal replacement shakes, but the modern meal replacement shake has been around since the early 2000s. Before that, you had shakes such as SlimFast and Herbalife, which were low in quality and didn’t have particularly good macronutrient ratios.

Why Do Some People Follow Shake-Only Diets?

The vast majority of meal replacement shakes have been designed to replace one or two meals per day. But some people are known to have taken meal replacement shakes throughout the day instead of eating anything else.

This is what meal replacement shakes were originally intended for, and they have been used in a clinical setting for a long time. You can find a number of studies that looked at MRS shake diets for significant periods of time.

These are used for weight loss purposes and are usually restricted to people who are severely overweight or obese. At this point, the risk/reward ratio for this diet swings towards the “reward” side, with the potential health benefits outweighing the risks and side effects.

This type of diet can work in a clinical setting because the people undertaking the diet have a lot of support from experts. They have their vitals checked, they may also get education and support from dieticians, and their doctor knows exactly what is going on, and why.

There are some people who attempt to follow this diet without the help of their doctors, and this is where the risk/reward ratio swings towards risk.

Are Shake-Only Diets Safe?

A shake-only diet can be as safe or unsafe as any diet, it all depends on how you implement it. The major risk is that you spend a prolonged period of time in an extreme calorie deficit, which can lead to malnutrition.

But, if you consumed enough meal replacement shakes to hit your maintenance calories, then the diet is perfectly safe. You may notice some gastrointestinal discomfort as your body gets used to a liquid diet, but nothing that should cause you any real danger.

This would end up being quite expensive, though, as an average male would need five shakes per day to hit 2,000 calories (more if the shakes are 200-300 calories). This could work out cheaper for some people, but many people would find it to be quite expensive, particularly if they have a large family.

Bottom Line: Drinking only meal replacement shakes is safe, provided you are consuming enough calories to lead an active lifestyle. There are few risks, just some unpleasant side effects. It is ultimately a better option only to replace 1-2 meals per day with shakes and create healthy meals for the remaining calories.

Do Doctors Recommend Shake-Only Diets?

In September 2020, the NHS put 2,000 people who had Type II diabetes on a soup-and-shake diet. The soups and shakes were used instead of meals for a 3-month period [1]. After three months, participants slowly reintroduced foods.

The study lasted over two years, and the average weight loss over this period was 7.2 kg in the first month and 13.4 kg by month three. But where the results really stood out was in the following months, where participants were able to prevent the weight regain that so often affects dieters.

The study was so successful that it was rolled out across England, available to people 18-65 who have had Type II diabetes for at least two years as well as other health factors.

Does this mean that a doctor would recommend an all-shake diet to anyone who walked into their office? No. There are specific criteria for implementing the diet, and it would not work well for people who are not overweight.

The answer to this question is that a doctor might recommend a shake-only diet, but only in certain circumstances. It is definitely a good idea to talk to your doctor before attempting, and you should first consider whether a 1-2 shake per day diet would be a better option.

What Happens if You Only Drink Meal Replacement Shakes?

You will most likely create a large calorie deficit and see a significant drop in body fat over a three-month period. However, you may also experience side effects such as gastrointestinal issues, fatigue, low energy, and tedium.

Most people who decide to follow a shake-only diet would actually benefit more from taking 1-2 shakes per day and adding a third meal that they prepare themselves.

Should You Follow a Shake-Only Diet?

Probably not, the benefits of doing so will be outweighed by the downsides. This form of diet can be boring and you will either be very hungry due to a massive calorie deficit, or you will be spending a lot of money on shakes each day.

Meal replacement shakes work best when they are combined with regular meals. Swap out a problem meal (such as lunch or breakfast) with a shake, and then cook yourself a delicious evening meal. That way you are saving yourself time and money, while also allowing you the option to lose weight, maintain a healthy weight, or gain weight (if that is what you want to do).

How to Get the Most out of Your Meal Replacement Shake

Rootana is a plant-based meal replacement shake that avoids artificial sweeteners and prioritises top quality ingredients. You can get the most out of it by using to replace one or two meals per day, ideally meals that you struggle with due to time constraints, the availability of fresh food, or other reasons.

We have a number of helpful articles on preparing delicious Rootana shakes, which you can check out here.

References

[1] https://www.diabetes.org.uk/about_us/news/nhs-soup-and-shake-diet-to-help-people-with-type-2-into-remission

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Complete Nutrition: Perfect Balance of Macros, Vitamins & Minerals

Rootana is a perfectly balanced combination of complex carbohydrates for slow energy release, the right amount of protein for a balanced meal and all 27 vitamins and minerals.

No Half Measures: 400 Calories Per Serving

Many meal shakes are simply too low in calories and too high in protein to be a complete meal, meaning they're little more than a protein shake. Rootana fuels you effectively and has the perfect macro split for a balanced meal.

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No Sweeteners: No Stevia, No Sucralose, No Aspartame, No Acesulfame K, No Monk Fruit

We don't include any sweeteners as they don't provide any nutritional benefit and may have short or long-term unwanted effects. Rootana is naturally flavored with a small amount of coconut sugar.

Tastes Like Real Food: Because It Is Real Food

With no sweeteners like acesulfame k, aspartame, stevia or sucralose (Splenda), Rootana tastes like real food. That means no artificial after taste and none of that bloated feeling that many sweeteners cause.