Rapid Weight Loss: Does It Work? Is It Safe?

by Marixie Ann Obsioma, MT, undergrad MD on April 20, 2022
Last updated on May 4, 2022

There are so many marketers who promise “rapid weight loss” that it’s difficult to keep track of them all.

Rapid Weight Loss: Does It Work? Is It Safe?

The majority of rapid weight loss pitches fall into one of the following categories:

Diets Based on Deprivation

Beyonce made the so-called “master cleanse” diet popular, which consists of water, lemon juice, maple syrup, and cayenne pepper, among other ingredients. Since at least the 1950s, various variations of these diets have been popularized. They frequently make claims of “detoxification” through the use of colonics or enemas.

Dietary Supplements and Dietary Pills

There are dozens of diet supplements on the market that claim to accelerate weight loss. Most of the time, they claim to either block nutrient absorption, increase metabolism, or help you lose body weight.

Diets with a Very Low-Calorie Intake (VLCDs)

A medically supervised very low-calorie diet has been shown to be an effective method to promote weight loss. The majority of what we know about rapid weight loss comes from studies of people who have followed these diets for a long period of time.

Is It Effective to Lose Body Weight Quickly?

Dietary supplements are regulated by the United States Food and Drug Administration (FDA), but they are treated as foods rather than medications by the agency.

Aside from that, the FDA does not regulate the claims made by manufacturers of over-the-counter weight loss products. In contrast to drug manufacturers, supplement manufacturers are not required to demonstrate that their products are safe or effective before placing them on the market. This means that before dietary supplements can be marketed, they do not need to be approved by the Food and Drug Administration.

Aside from the very low-calorie diet and weight-loss surgery, no other product, pill, or diet has been proven to be effective for rapid weight loss in a safe and healthy manner. There are prescription medications available for weight loss, though none of them are intended for rapid weight loss, and there can be side effects from them.

It is not a pill or a specific type of food that helps you lose weight quickly in any rapid weight loss program. A combination of a significant reduction in calories and physical activity is important for weight management.

What Are the Dangers of Rapid Weight Loss?

Rapid weight loss diets places a physical strain on the body’s resources. The following are examples of serious risks:

  • Malnutrition is caused by a lack of protein in one’s diet for several weeks at a time.
  • Deficiency in fluids can be avoided by consuming plenty of fluids
  • Electrolyte imbalances, which are only rarely life-threatening, are a common occurrence.
  • Gallstones, which occur in 12 percent to 25 percent of people who lose a significant amount of weight over a period of months, are a type of stone.

The following are some of the other side effects of rapid weight loss:

  • Irritability
  • Headaches
  • Fatigue
  • Constipation
  • Dizziness
  • Menstrual irregularities
  • Muscle loss
  • Hair loss

The risks associated with rapid weight loss increase in proportion to the length of time spent on the diet. It does not involved a healthy and balanced diet. It is devoid of protein, and this can be dangerous. Others also do a low carb diet, which is yet another problem. A low carb diet plan also has its own drawbacks.

Is It Ever A Good Idea to Lose Weight in A Short Period of Time?

Rapid weight loss diets can have negative consequences, but so can being overweight. This is why very-low-calorie diets (VLCDs) are considered a reasonable weight-loss option for obese individuals (with a body mass index (BMI) greater than 30), who require rapid weight loss for a specific reason, such as weight loss surgery.

VLCDs are diets that are monitored by a doctor and last for several weeks. The meals are well-balanced nutritionally, but they are expensive; people can end up spending thousands of dollars over the course of a year. In 12 weeks, VLCDs can safely cause a loss of 15 percent to 25 percent of one’s total body weight.

That is for those who complete the program; 25 percent to half of those who begin the program do not complete it. When a diet is discontinued, weight gain occurs quickly; most experts agree that it is preferable to adopt a more sustainable approach to weight loss that is comparable to that of regular diets in order to maintain weight loss.

The majority of people who want to lose weight quickly, on the other hand, do so on their own. It’s common for people to lose weight in order to achieve a short-term goal, such as fitting into a dress or looking good on vacation.

It is unquestionably not a good idea to starve yourself. However, if you are otherwise healthy, a brief period of extreme calorie restriction is unlikely to be detrimental to your well-being. You should inform your doctor or wellness professionals of your plans, and you should make sure to include protein in your daily diet (70 to 100 grams per day) and avoid refined carbohydrates. Take a multivitamin, and eat be mindful of your food intake. Go for foods that are high in potassium (tomatoes, oranges, and bananas).

Also keep in mind that crash diets are rarely effective in achieving a long-term, healthy weight. The majority of people gain the weight back immediately.

Is It Harmful to Lose Weight Too Quickly?

It’s normal to want to lose weight as quickly as possible after noticing weight gain.

However, you’ve probably been told that it’s best to lose weight at a slow and steady pace rather than quickly.

This is because the majority of studies have found that people who lose weight gradually are more likely to keep it off in the long run. Slower weight loss also carries with it lower risk of developing health problems.

However, according to the findings of several recent studies, rapid weight loss may be just as effective and safe as slow weight loss.

So, is losing weight quickly actually detrimental to your health? The purpose of this article is to delve into the research and uncover the truth.

So, what exactly qualifies as “fast weight loss”?

Many experts believe that losing 1–2 pounds (0.45–0.9 kg) per week is a healthy and safe rate of weight loss.

It is considered excessive weight loss to lose more than that in a short period of time, and doing so puts you at risk for a variety of health problems such as muscle loss, gallstones, nutritional deficiencies, and decreased metabolism.

The most common ways in which people attempt to lose weight quickly are through intense exercise and by following a “crash diet,” which is only consists of fewer than 800 calories per day, respectively.

The option of eating a very low-calorie diet is often preferred by people, as it is often easier to lose weight by eating less than you would by trying to exercise.

You may, however, lose much more than 2 pounds (0.9 kg) in your first week of following a diet or exercising regimen if you’re just getting started.

When it comes to weight loss, rapid weight loss is perfectly normal during this initial period. During this time period, you will lose water weight, which is a term that is commonly used.

It is when your body consumes less number of calories than it burns fat for energy, which are known as glycogen. When you burn glycogen for fuel, your body also releases the water that has been bound to it during the glycogen storage process.

As a result, you may notice a significant loss of weight during your first week of treatment. Weight loss should stabilize at 1–2 pounds (0.45–0.9 kg) per week once your body has depleted its glycogen reserves.

A healthy and safe weight loss rate is 1–2 pounds (0.45–0.9 kg) per week, according to experts, whereas losing more than this is considered dangerous and unwise. During the first week of an exercise or diet program, you may lose significantly more weight than that.

Is It Possible to Maintain Rapid Weight Loss?

Losing weight is only half of the battle against obesity. The real challenge is in maintaining the weight loss for good.

After only a year on a diet, the majority of people gain back half of the weight they had lost previously. Even worse, nearly everyone who follows a diet will regain all of the weight they have lost within 3–5 years of starting the program.

As a result, losing weight at a slow but steady pace is often recommended by experts. The majority of studies have found that people who lose weight at a slow but steady pace are more likely to maintain their weight loss over the long term.

In addition, plans that encourage slow weight loss typically assist you in developing healthy eating habits such as eating more fruits and vegetables and drinking fewer sugar-sweetened beverages, among other things. These types of behaviors can assist you in maintaining your weight loss over the long term.

Several studies, however, have discovered that rapid weight loss may be just as effective as slow weight loss, even over the long term.

An experimental diet with rapid weight loss for 12 weeks was followed by 97 people who followed a slow but steady weight loss diet for 36 weeks in one study.

Over the course of nearly three years, approximately 70% of people in both groups had regained all of the weight they had lost. Essentially, this means that both diets were equally effective in the long run.

These studies discovered that rapid weight loss was just as effective as slow but steady weight loss overall; however, it is unlikely that a person who loses weight at home would achieve similar results.

During the weight loss and weight maintenance phases, people in the rapid weight loss groups received support from doctors and dietitians who were assigned to them. According to research, having the assistance of a health professional can increase your chances of achieving long-term weight loss success.

In addition, doctors and dietitians work hard to reduce the health risks associated with consuming very few calories on a daily basis. Muscle loss, nutritional deficiencies, and gallstones are just a few of the dangers.

Individuals who attempt these diets on their own run a higher risk of developing these medical conditions.

In a nutshell, losing weight gradually increases your chances of losing weight and keeping it off. This approach will assist you in developing good eating habits that will help you maintain your weight loss. It is also safer than rapid weight loss, especially if you do not have the support of a health professional.

Most studies have found that gradual weight loss is easier to maintain over the long term than rapid weight loss. It aids in the development of healthy eating habits and carries fewer health risks than rapid weight loss does.

The Dangers of Losing Weight Too Quickly

While it may be tempting to try to lose weight very fast, doing so is usually not a good idea.

Diets that promote rapid weight loss are frequently very low in calories and nutrients, as is the case with Atkins. This may put you at risk for a variety of health problems, particularly if you follow a rapid weight loss diet for an extended period of time.

Here are some of the dangers of losing weight abruptly.

  • It is possible that you will lose muscle.
  • It is not always the case that losing weight equates to losing body fat.

While a very low-calorie diet may assist you in losing weight quickly, a large portion of the weight you lose may be made up of muscle and water weight.

In one study, researchers put 25 people on a very low-calorie diet of 500 calories per day for five weeks, and they reported that they felt better. They also put 22 people on a low-calorie diet of 1,250 calories per day for 12 weeks, which they observed to be effective.

Following the study, the researchers discovered that both groups had lost approximately the same amount of weight. People who followed the very low-calorie diet, on the other hand, lost more muscle than those who followed the low-calorie diet by a factor of more than six.

  • It has the potential to slow your metabolism.
  • If you lose weight too quickly, your metabolism may be slowed.

The amount of calories you burn each day is determined by your metabolism. A slower metabolism means that you burn fewer calories per day than you would otherwise.

Several studies have discovered that losing weight abruptly by consuming fewer calories can result in you burning up to 23 percent fewer calories per day than you would otherwise burn.

When you follow a very low-calorie diet, your metabolism slows down for a variety of reasons, including muscle mass loss and a decrease in hormones that regulate your metabolism, such as thyroid hormones.

Unfortunately, this decrease in metabolism may last for a long period of time after you have stopped dieting.

  • It has the potential to cause nutritional deficiencies.
  • If you don’t consume enough calories on a consistent basis, you may be at risk of developing a nutritional deficiency.

This is due to the fact that it is difficult to consume enough essential nutrients such as iron, folate, and vitamin B12 on a low-calorie diet.

Nutritional deficiencies can have a number of negative consequences, as listed below.

Insufficient calorie intake may result in your body not receiving enough nutrients to support hair growth, which may result in hair loss.


When eating very low-calorie diets, you may not be getting enough iron, vitamin B12, and folate, which may put you at risk for extreme fatigue and anemia, as well as other health conditions. Remember that it’s also best to consider your body mass index and body composition, a ratio of fat mass to fat free mass, to make sure you’re losing just enough for a healthy weight management.

A very low energy diet, and not getting enough calories and nutrients can cause your immune system to become weakened, increasing your chances of getting sick.

That’s why to reap the health benefits of doing a rapid weight loss diet, make sure to equip yourself with supplements that can substitute the nourishment you’ll need from regular food. And don’t forget to seek advice from your primary physician before starting this diet.


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