A very low calorie diet (VLCD) is a clinically supervised diet plan that involves eating about 800 calories a day or fewer.
The diet usually involves replacing normal food with low-calorie shakes, soups, bars, or porridge containing milk.
VLCDs are typically for adults who are obese – defined as having a BMI over 30 – but should not be the first option to manage obesity.
These diets should only be followed under medical supervision for a maximum of 12 weeks continuously, or intermittently with a low-calorie diet – for example, for two to four days a week.
Most people who want to lose weight do not need to follow a very low calorie diet.
VLCDs are hard to follow
VLCDs may not be nutritionally complete and provide far fewer calories than most people need to maintain a healthy weight.
A daily limit of 800kcal is about a third of the average energy needs for a man (2,500kcal) and half needed for a woman (2,000kcal).
It is not an easy diet to follow. Apart from feeling hungry and low on energy, other side effects can include:
- dry mouth
- constipation or diarrhoea
- hair thinning
While VLCDs can lead to short-term weight loss, most people tend to put the weight back on gradually after coming off the diet.
VLCDs are not a long-term weight management strategy and should only be used as part of a wider weight management plan.
VLCDs aren't suitable for most people
VLCDs aren't routinely recommended by the NHS unless a patient has a medical need, such as needing to lose weight:
- for surgery
- to help manage a health condition, such as diabetes
- to prepare for fertility treatment
However, a range of VLCD plans are available from the private sector for people – typically with a BMI over 30 – struggling to lose weight.
The replacement foods are designed to contain all the nutrients the body needs, while providing 800 calories a day or fewer.
Is a VLCD right for me?
Before you begin a VLCD, see your GP to make sure it's the right choice for you.
VLCDs are the most restrictive form of dieting, severely reducing calorie intake, so medical supervision is important.
A VLCD may be right for you if all three of the following apply:
- You've already made healthy changes to your diet and level of physical activity.
- You're still classed as obese (your BMI is 30 or over).
- You're no longer losing weight.
VLCDs are not recommended for pregnant or breastfeeding women. Find out more about healthy eating in pregnancy.
VLCDs are not suitable for children and people with certain health conditions, such as eating disorders.
They should only be a last resort option and followed under the correct supervision.
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.
You may also be interested in:
- How to diet
- NHS Choices weight loss plan
- Should you lose weight fast?