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 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 doctor 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 doctor agrees that a VLCD is a good idea, the next step is to find a good provider of a VLCD. Your doctor 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?