What is the Very-Low-Calorie Diet? Emergency Weight Loss Guide

Disclaimer: The very-low-calorie diet is not intended for everyday weight loss. The VLCD is for emergencies only and should not be used without guidance and approval from your physician.

When someone wants to lose weight, they often think the faster, the better. People want immediate results, and because of that, something like the very-low-calorie diet plan sounds like a match made in heaven. But what exactly is a very-low-calorie diet, and is it right for you?

Here is everything you need to know about starting a very-low-calorie diet so you can make an informed decision for your health.

What is the Very-Low-Calorie Diet?

A very-low-calorie diet, also known as VLCD, a low-calorie diet, LCD, low-energy diet, very low-energy diet, or rapid weight loss diet, is a specialized diet that requires you to eat a maximum of 800 calories per day and can sometimes go as low as 400 calories, compared to the recommended 1,600 to 2,000 calories per day that most adults need. VLCDs often rely on meal replacements, but it’s also possible to come up with a diet plan that uses prepared foods and dietary supplements. Rapid weight loss diets typically don’t last longer than 12 weeks to ensure patient health.

The first VLCD was established after WWII to treat famine victims facing starvation. The specialized meal plan reintroduced small amounts of food back into victims’ diets to avoid illness from eating too much food at once. Since then, it has been used in clinical settings since the 1980s.

Who Should Go On a Very-Low-Calorie Diet?

Rapid weight loss diets are most commonly prescribed by doctors in special cases, and they are not recommended for everyday use.

VLCDs are most commonly prescribed for obese people with a BMI over 30, especially if they have other health issues such as type 2 diabetes, sleep apnea, or hypertension. These types of diets can also be prescribed as pre-surgery preparation, especially in preparation for bariatric surgery or other surgeries that can be negatively affected by patient weight.

Because very-low-calorie diets can be dangerous, it isn’t recommended to go on one if there isn’t a medical necessity. VLCDs should always be at the recommendation of a doctor.

Who Should Not Go on a Very-Low-Calorie Diet?

There are several groups of people who are not recommended to start a VLCD. These include pregnant women and women who are nursing, teenagers, and seniors. People with a BMI lower than 30 are also not recommended to try a VLCD.

What You Can Eat on the Very-Low-Calorie Diet

Many very-low-calorie diets rely on meal replacement products like shakes, smoothies, and soups. These products are specially made to ensure that you still get all the necessary nutrients from your diet while not eating more calories than necessary.

Follow your doctor’s advice and eat the foods they recommend.

In addition to pre-made shakes and smoothies, your diet may also incorporate simple prepared meals that you can make at home. Meals may include things like eggs, fish, chicken, turkey, lean pork, lean beef, tomatoes, bell peppers, carrots, radishes, chard, beans, low-fat cheese, or low-fat cottage cheese.

Advantages of the Very-Low-Calorie Diet

The very-low-calorie diet can potentially give you several benefits, including rapid weight loss, which can be required to prepare for certain surgeries. Patients using a VLCD may see a loss of three to five pounds per week, which could lead to a loss of up to 60 pounds after 12 weeks. The drop in weight may positively affect other health problems you may have, such as type 2 diabetes, sleep apnea, or hypertension.

Risks of the Very-Low-Calorie Diet

Even when undertaking a VLCD with medical supervision, the diet can still come with risks. Here are some of the risks you should look out for while on a VLCD.

Side Effects You May Experience

When starting a VLCD, you may encounter one or more side effects, such as headaches, weakness, fatigue, nausea, vomiting, constipation, dehydration, low blood sugar, bad breath, diarrhea, or dizziness. Side effects may alleviate within the first few weeks of the diet, but they can potentially persist. Long-term side effects, such as hair loss, may also be something you encounter while on the diet.

Gallstones

Obese patients are at a higher likelihood of developing gallstones, and women have even higher chances. However, gallstones are even more common during rapid weight loss diets, such as VLCD. In order to help prevent gallstones, your doctor may prescribe a medication to stop gallstone formation.

Potential Nutrient Deficiencies

When you’re only eating 20 to 40% of the calories in a normal diet, you won’t get the same nutrients your body needs. This is why many VLCDs rely on nutritional shakes and smoothies that have been carefully balanced to ensure you’re still getting all the vitamins and minerals your body requires. While it is possible to achieve a VLCD with prepared foods, you need to work with your doctor or a dietitian who is familiar with VLCDs to ensure you’re getting proper nutrition to avoid possible health concerns in the future.

Your Metabolism Will Slow Down

When your body doesn’t get enough calories during the day, it begins to transition into survival mode, and your metabolism will slow down in order to conserve energy. This can lead to you feeling sluggish, cold, and can even cause gastrointestinal abnormalities like constipation. A slow metabolism will also lead to your weight loss slowing as your body tries to conserve energy.

You Will Lose Muscle

A common misconception about very low-energy diets is that you will only lose body fat. However, this isn’t true. When your energy intake isn’t meeting your caloric needs, your body will find that energy wherever it can, and that means it will take from your muscle as well as your fat. This is because your body’s muscle contains glycogen, which is stored glucose intended to be used for energy later. Accessing that stored glucose means losing lean mass.

4 Myths About Very-Low-Calorie Diets

VLCDs are Just Like Fasting

Fasting is a time-restricted eating limit, while VLCDs are not. Fasting tries to help you reduce your caloric intake by reducing the times when you are allowed to eat, but it doesn’t place restrictions on how much you are allowed to eat. On the other hand, VLCDs heavily restrict how much food you can eat, but they allow you to eat on whatever schedule works best for you.

You Can Start a VLCD Without a Doctor.

While you can start a VLCD without a consulting your doctor, you should never do this. VLCDs can be dangerous if you start one without medical guidance to ensure you’re still getting the nutrients your body requires.

VLCDs Are Good for Long-Term Weight Loss

VLCDs are not a long-term diet. When used safely, you only stay on a VLCD for a maximum of 12 weeks, but fewer is more common. VLCDs are not intended for long-term weight loss and should never be used as such.

How to Go on a Very-Low-Calorie Diet Safely

When starting a VLCD, it’s essential to follow your doctor’s instructions exactly, as going against their advice can potentially be harmful to your health.

Whether your doctor prescribes you a set diet plan consisting of meal replacements or guidelines for how to prepare your own reduced-calorie meals, follow their advice and reach out if you ever encounter side effects that impact your day-to-day life.

A Note From DietitianLive

At DietitianLive, we are invested in your health and your goals. Whether you want to lose weight, maintain healthy eating habits, or develop a meal plan that will provide the nutrients you need to live the lifestyle you want, we want to be here to help you along every step of your journey.

For this reason, we cannot advise you to undertake a very-low-calorie diet without specific instruction from your doctor. VLCDs and other rapid weight loss diets with severely limited calories can be extremely dangerous if done without medical supervision.

We recommend that you lose weight slowly for your overall health and for the sustainability of your weight loss. Losing one or two pounds a week is a healthy rate that can provide sustainability and noticeable results without extreme caloric restriction.

Should You Try a Very-Low-Calorie Diet?

Very-low-calorie diets can be dangerous if not undertaken responsibly. For this reason, you should not attempt to go on one unless it’s at the recommendation of your doctor. If you want to lose weight, talking with one of our registered dietitians can be an excellent place to start. Our licensed dietitians can help you come up with a long-term diet strategy and develop healthy eating habits without having to resort to a drastic diet.

If you want to talk to a dietitian about your weight loss goals, sign up for your first session today at no cost to you!

The Very-Low-Calorie Diet: Frequently Asked Questions (FAQ)

Is the Very-Low-Calorie Diet a Fad Diet?

No, VLCDs are not fad diets. They are a medical requirement prescribed by doctors for specific reasons, such as preparation for surgery or relieving symptoms from other health problems.

Has Anyone Ever Died From Rapid Weight Loss Diets?

Yes. In 1978, 58 people died while doing liquid diets intended to achieve rapid weight loss, and since then, there have been more. This is why medical supervision is so important while on a VLCD.

How Long Should I Stay on a VLCD?

As long as your doctor recommends. This may be 12 to 16 weeks, but it could also be less. Always follow your doctor’s recommendation and alert them to any side effects you encounter.

What’s the Difference Between a VLCD and Intermittent Fasting?

A VLCD involves consistently low calorie intake every day, while intermittent fasting focuses on when you eat, not necessarily how many calories. The two approaches serve different purposes and health outcomes.

Is Ketosis Part of the Very-Low-Calorie Diet?

Sometimes. VLCDs can induce ketosis (a metabolic state where the body burns fat for energy), especially if carbs are also limited. However, not all VLCDs are designed to be ketogenic.