What Happens If You Lose Weight Too Fast?

  • Post last modified:August 26, 2021
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Most specialists believe that reducing 0.5-1 kg per week is the best way to maintain a healthy weight over time. Trying to lose too much weight too quickly may result in your weight rebounding to an even heavier weight than you started at.

However, because this slow and steady pace often seems too slow for those who are eager to lose pounds fast, many people do not hesitate to go on a long-term diet or try various weight-loss products at the risk of ruining their health.

Although these unhealthy methods can help you to lose weight in a short period of time, your body is actually unable to keep up with the rhythm of your weight loss. 

As a result, this will inevitably cause some obvious symptoms, such as anxiety, hair loss or insomnia. In the long run, it can seriously affect your physical and mental health.

What really happens if you lose weight too fast? Keep reading and you will find the answer in this article.

What Happens If You Lose Weight Too Fast?

The Risks Of Rapid Weight Loss

1. You may lose muscle

It’s possible to reduce weight drastically in a short period of time by dieting or taking weight-loss pills. However, you may only lose a lot of water instead of body fat. Even worse, rapid weight loss can also cause muscle loss. [*]

If you eat a low-calorie diet for a long time, your body can’t get enough calories from food. To maintain normal metabolism, your body has to get energy by breaking down muscles.

In particular, girls’ muscle mass is inherently less than that of boys. Improper weight loss can accelerate the loss of muscle tissue, which may have a negative impact on metabolism and may cause fatigue, cold hands and feet or other discomforts.

2. May lead to malnutrition and electrolyte imbalance

Low-calorie diets that promote quick weight loss are generally lacking when it comes to nutrition. Following this diet for a long time may inevitably lead to malnutrition and cause electrolyte imbalance in your body.

Most physiological functions of the human body need the regulation of nutrients to work properly. For example, vitamin D can regulate calcium and phosphate levels in your body, thereby maintaining bone health.

Any imbalance in the ratio of these nutrients can be potentially dangerous, especially electrolytes that are vital to the function and integrity of cells. Electrolyte imbalance can lead to diseases such as epilepsy and arrhythmia. [*]

In addition, most people who follow the ketogenic diet have most likely experienced the “keto flu.” The main cause of keto flu is an electrolyte imbalance and the common symptoms are headaches, palpitations, fatigue, nausea and vomiting.

3. Your metabolism may slow down

One thing that many people may not realize is that losing weight too fast can actually slow down your metabolism.

If you have been eating a low-calorie diet, your body could enter a hunger mode due to an insufficient calorie supply.  Your body will then activate self-protection mechanisms.

At this time, in order to save energy consumption, your metabolism slows down and you begin to store excess fat for emergencies. You can think of these as a way for the body to save itself.

However, when you eat a little bit more, your body will turn into a sponge, absorbing as many calories as possible.

This is why many people regain weight after dieting, many times gaining much more weight than they lost. 

4. You may experience endocrine disorders

Losing a lot of weight in a short period of time can often lead to endocrine disorders, such as excessive secretion of adrenaline or insufficient secretion of female hormones.

Symptoms of endocrine disorders include experiencing abnormal menstrual periods or menopause in women.  Other symptoms may include hair loss, acne or rough skin.

If you go on a diet simply to lose weight, but do not exercise properly, it is easy to experience a bloated “puff” body shape. Meaning, even though your weight is normal your body fat percentage is too high.

A study published in “Clinical Endocrinology” in 2014 found that people with normal BMI (body mass index) but higher body fat percentage have a higher risk of metabolic syndrome, high blood pressure, hyperlipidemia and diabetes than people with a normal BMI and body fat percentage.

5. Your mental health may be at risk

Weight loss requires strong self-control. Maintaining a healthy weight should be a long-term goal.

Many people start a diet in order to lose weight quickly. They eat very little food every day. However, this small amount of calories simply cannot meet the basic needs of your body.

Dieters often feel hungry and are regretful or annoyed when they can’t control their appetite and eat more food. Therefore, they often take more extreme measures in order to reduce calorie intake, such as inducing vomiting or taking laxatives.

Such negative emotions are often repeated because the pressure to lose weight quickly keeps getting greater and greater. They may fall into a vicious circle of high expectations and disappointments. Over time, it is easy to suffer from depression and anxiety, overeating or anorexia.

The Risks Of Rapid Weight Loss

How To Lose Weight Through A Healthy Diet

1. Eat less refined carbohydrates

Foods like white bread, cakes and biscuits are very high in refined carbohydrates. They contain almost no dietary fiber and have very low nutritional value.

Regular consumption of these types of foods can easily cause blood sugar spikes, which over time can lead to insulin resistance.

Insulin resistance is the trigger for various health problems including diabetes, obesity or heart disease.

Your daily diet should give priority to foods with complex carbohydrates, such as whole-wheat bread, quinoa, oats, potatoes, corn or beans.

These foods are rich in fiber and other nutrients. Your body needs to spend more time digesting them, so your blood sugar is stable.  

2. Eat enough protein

Protein is an important nutrient for weight loss and improving body appearance.

Even in the case of insufficient calorie intake, eating a lot of protein can help maintain muscle mass.

Eating more protein can not only increase satiety and reduce appetite but also change the levels of several weight-regulating hormones, such as cholecystokinin and ghrelin.

In addition, the reported TEF (the thermic effect ) for protein is 20–30% compared to fat (0–3%) and carbohydrates (5–10%). [*]

The thermic effect of food refers to the calories the body needs to burn during the process of digesting food.

The best sources of protein include eggs, grass-fed beef, chicken breast, fish, seafood, beans, quinoa and seeds.

3. Eat more foods rich in dietary fiber

Dietary fiber contains almost no calories and is not easy to digest. They increase the volume of food and make the food swell in your stomach like a sponge.  This not only prolongs the feeling of fullness but also helps suppress appetite and control weight.

Eating more foods containing dietary fiber can also increase metabolism, promote intestinal health and keep blood sugar stable.

Most fruits, vegetables, beans and grains are rich in fiber.

4. Practice intermittent fasting

Fasting is called “the ancient secret of weight loss.”

Many studies have found that proper fasting can help improve insulin sensitivity, lower blood sugar, control weight, reduce inflammation, fight disease and delay aging.

In addition, fasting can reduce your calorie intake throughout the day.  This can reduce body fat while maintaining muscle mass.

There are many ways to do intermittent fasting. The most common ones include the 16/8 fasting method (this is also the fasting method that most people can tolerate and stick to), the 5:2 fasting method, fasting every other day and one meal a day.

It is important to remember during non-fasting periods, to focus on nutrient-dense foods. In order to achieve a better weight loss effect, it is best to use a low-carb diet or a ketogenic diet as a supplement. This can not only help your body to enter a state of ketosis, accelerate fat burning, but also help reduce hunger, making it easier when fasting.

Before you start trying fasting, please review the 9 Common Negative Effects Of Intermittent Fasting (and How To Fix Them).


Many people believe that bodyweight is the best indicator of their health. Therefore, in order to reach their ideal weight quickly, they do not hesitate to use extreme methods for weight loss. 

Losing weight too fast with these unhealthy methods is very harmful to both your body and your mind.

The best way to lose weight is to change your diet and lifestyle, ensure adequate sleep, exercise properly and reduce stress. These actions help you maintain a fit body over a long period of time and make you more energetic and make you look younger.

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