Very low calorie diets

If you’re trying to lose weight, eating healthily and being physically active are the key. In a few cases, though, a very low calorie diet (VLCD) could be the right choice. But these should only be followed for a limited time, so talk to your GP before you start. They can help to support you.

To see whether you are a healthy weight, use our Healthy weight calculator to find your body mass index (BMI). Your BMI is a measure of whether you are a healthy weight for your height.

Achieving a healthy weight is all about striking the right balance between the energy that you put into your body, and the energy that you use.

To lose weight, you have to use more energy than you consume in food and drinks throughout the day.

You can do this by making healthy changes to your eating habits, and building more physical activity into your daily life. In many cases, this will be enough to achieve a healthy weight.

You can learn more about changing your diet in Healthy eating, and get advice on becoming more active in Fitness.

However, if you have made these changes already and the weight loss you’ve experienced has not resulted in a healthy weight, you may benefit from a very low calorie diet.

VLCDs are not available on prescription from the NHS, but are offered by a range of private organisations in England, at a cost. The proven benefits are short-lived; there is limited evidence of long-term benefit.

Before you begin a VLCD, make sure that it is the right choice for you. It’s also important that the diet you choose is safe, and that you follow it properly. That means talking to your GP for more advice.

What is a VLCD?

Examples of very low calorie diet plans offered privately include: Medifast, Optifast and the Cambridge diet.

A very low calorie diet is any diet that involves eating 800 calories a day or fewer. It should only be undertaken for 12 continuous weeks, or intermittently – for example, every two or three days – along with a low calorie or normal diet.

The recommended daily calorie intake is 2,000 for women, and 2,500 for men. This means that VLCDs contain far fewer calories than most people need to be able to maintain a stable, healthy weight. For that reason, eating a very low calorie diet can cause more rapid weight loss than a conventional weight loss programme.

It’s important that VLCDs are only used by people who need them and that the diet is safe and followed properly. Cutting calories significantly can cause health problems such as gallstones, heart problems, and other issues associated with not getting the nutrition you need, such as tiredness and anaemia. A proper VLCD will ensure that you continue to get all the nutrients you need, and is typically followed under supervision, so that action can be taken if health problems occur.

In England, a range of private organisations sell very low calorie diet plans. During a typical VLCD the person undertaking the diet will stop eating all normal foods, and replace them with special drinks, soups, bars or porridge containing milk- , soy- or egg-based protein. The replacement foods are designed to contain all the nutrients that we need, while providing 800 calories a day or fewer.

The person undertaking the diet will also meet regularly with a trained member of staff from the organisation – usually called a counsellor or consultant – who will monitor their progress.

Who should use a VLCD?

VLCDs are only suitable for people who are very overweight (obese), and have remained very overweight despite making healthy changes to their diet and lifestyle.

Most people who want to lose weight do not need to eat a very low calorie diet.

However, it may be right for you if all three of the following statements apply to you:

  • You have already made healthy changes to your diet and level of physical activity.
  • You are still very overweight (your BMI is 30 or over).
  • You are no longer losing weight.

VLCDs are not recommended for pregnant or breastfeeding women, and they are not suitable for children. Find out more about healthy eating in pregnancy.

How to use a VLCD

If you think a VLCD may be right for you, the first step is to talk to your GP. They can provide advice on whether a VLCD will help: they may measure your BMI and talk to you about other steps you’ve taken to lose weight. VLCDs are not suitable for people with certain health conditions, such as eating disorders and epilepsy, and your GP can also talk to you about this.

If your GP agrees that a VLCD is a good idea, the next step is to find a good provider of a VLCD. Your GP may be able to help with this, too.

At your first session, a counsellor from the VLCD organisation will talk to you about how the diet works, the weight loss you can expect and the side effects that may occur while you are on the diet. These are usually minor, and can include fatigue, diarrhoea, constipation and nausea.

Typically, you’ll be asked to keep a record of your weight loss and any side effects.

Your counsellor will refer you to a GP if you encounter any health problems during the diet.

Page last reviewed: 17/10/2014

Next review due: 17/10/2016


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