Why Am I Gaining Weight On A Liquid Diet?

It can feel disappointing to start a diet and not only struggle to lose weight but also gain more. In this article, I will explain everything there is to know about the liquid diet and why people tend to rebound and gain weight back.

Why am I gaining weight on a liquid diet?

In general, you may be gaining weight on a liquid diet because consuming only calories from the liquids lowers energy expenditure. Lack of solid foods strips off any bulk and fiber that increases the thermic effect of food, postprandial satiety, and increases metabolic rate.

So naturally, when you start the liquid-only diet for longer, you may notice temporary weight loss, followed by the jo-jo effect.

Does Going On A Liquid Diet Work?

As a general rule, going on a liquid diet works for people who are about to have gastrointestinal treatment as a part of their intestinal preparation. They’re also used for people seeking out alternative weight-loss strategies as a form to reduce calorie intake.

So liquid diets are mainly used prior to treatment, as a way to clean up the intestines. They are usually supervised by the medical team (source).

However, all liquid diets are also popularized to enhance weight loss goals. Which can work, for some people. But only for a short period of time.

How Liquid Diets Work?

Liquid diets work by replacing solid meals with liquids. These include soups, broths, meal replacements, protein shakes, and creams. By replacing meals with all liquid food, it is an easy way to lower the volume of the food and total daily calorie intake.

So it does work. Going on a liquid diet can dramatically lower your calorie intake.

However, without fully understanding how do liquid diets impact our body over a long time, it is easy to get frustrated when things aren’t working so well anymore and weight is creeping back up.

In a short time, people can notice results. However, those results not gonna last.

After the body loses a significant amount of weight, together with the strict calorie restriction, due to the prolonged calorie deficit, metabolism starts to slow down.

The body is adjusting its process by creating metabolic adaptations that lower the sum of calories we burn.

  • Lower food intake decreases the number of calories burned to digest the food
  • Lower body weight requires fewer calories to be used at rest
  • A calorie deficit will impact our hormonal balance, typically lowering the anabolic hormones and increasing catabolic hormones
  • With steep calorie restrictions, the body will start to increase stress

Can Liquids Cause Weight Gain?

In general, liquids can cause weight gain. Going on a liquid diet eliminates essential nutrients like fiber and starch that play a role in the digestion and absorption of carbohydrates. Lower fiber also leads to a decrease in energy expenditure and an increase in appetite.

In the study done by Dr. Eva Almiron-RoigIn from the The University of Navarra, she said that

Liquids reportedly fail to trigger physiological satiety mechanisms (source)

Initially, after you drink a shake or a smoothie, you may feel full. But studies show that satiety from real foods is much more superior than satiety from liquids.

  • Processed protein have less impact on satiety than protein from whole foods
  • Liquid form calories require less work of the digestion enzymes

Another aspect is that liquid diets are simply hard to maintain over the long term. People get bored and tired of drinking the same thing, without having to eat any real food.

That being said, implementing some liquids into your diet can be an effective way to lower weight. But it must be combined with regular food, too.

Can Liquid Diet Help Lose Weight?

Generally, a liquid diet can help to lose weight. Partial meal replacement, which works by replacing one or two meals per day with a high-quality whey protein to achieve calorie deficit is an effective weight loss strategy that can be maintained over a long time.

So instead of going all in to do only liquids, it is much better to add one or two shakes or soups per day, and still keep the majority of calories coming from foods (source).

Simply skipping one meal a day and substituting it with a shake can be a good start.

  • Make sure your solid foods are rich in protein as they found to have the best satiety impact
  • Adding plenty of colorful veggies with soluble fiber
  • Eating slowly and paying attention to the hunger signals
  • Eating without the distractions

It can also be implemented as intermittent liquid dieting. For one or two days a week, you rely only on the calories from the liquids. For the rest of the week, you eat normally.

Can You Lose Weight On A Liquid Only Diet?

In general, you can lose weight on a liquid-only diet. Lowering the calorie intake and overall food volume is an effective way to weight loss. However, this type of approach is not sustainable because eating the same foods for a period of time is boring.

Initially, it may feel like a good idea. But over time, consuming the same thing over and over again removes all the joy from eating the foods you like.

Is A Liquid Diet Healthy?

In general, a liquid diet is promoted as healthy. Supplements, meal replacement shakes and protein shakes are considered a good choice for people who seek out to reduce weight, in the short term. However, with the lack of solid nutrients, it can fail to be an effective long-term strategy.


Going on a liquid diet beyond the gastrointestinal preparation may initially sound like a good idea. But with just s little extra knowledge, and understanding of how exactly our body process nutrients and deals with appetite, it is much easier to stick to regular food and still lose weight.

Michal Sieroslawski

Michal is a personal trainer and writer at Millennial Hawk. He holds a MSc in Sports and Exercise Science from the University of Central Lancashire. He is an exercise physiologist who enjoys learning about the latest trends in exercise and sports nutrition. Besides his passion for health and fitness, he loves cycling, exploring new hiking trails, and coaching youth soccer teams on weekends.

One thought on “Why Am I Gaining Weight On A Liquid Diet?

  1. I have been on a full liquid diet for 3 years due to habitual small intestine bowel obstructions (9 hospitalizations, 3 major surgeries). However I have been gaining weight this past year and do not understand why. I am looking for possible answers.
    I have multiple issues from my military experience in the Vietnam War. besides setting off a small antipersonnel mine, I have Parkinson’s, prostate cancer and coronary heart disease from my exposure to agent Orange.

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