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The Facts on Very Low Calorie Diets

Posted in Healthy eating, healthy weight and dieting

What are Very Low Calorie Diets?                        

Very low calorie diets or VLCDs (also known as very low energy diets or VLEDs) are artifical formulas, usually in liquid form, that completely replace all the food you usually eat. They provide 800 calories or less per day and contain protein, carbohydrate, essential fatty acids and the recommended daily allowance for vitamins, minerals and electrolytes. VLCDs are not the same as 'meal replacements' which are portion-controlled products (often liquid shakes or bars), designed to replace one to two meals per day with a low calorie meal and snack(s).

How do VLCDs work?

VLCDs provide a limited amount of energy (calories) for the body to use each day. This isn't enough to meet the energy needs of the body, so the body starts to break down its own fat stores and muscle tissue to produce energy, resulting in weight loss. On a VLCD, about three quarters of the weight you lose is body fat and one quarter is muscle, once a minimum of 50g of protein is consumed each day.

How do VLCDs help people to manage their weight?

How much weight can be lost on a VLCD?

On average, strict use of a VLCD results in 1.0-2.5kg weight loss (2 – 5.5lb per week), which can be very motivating. VLCDs give rapid weight loss at the start but are no better in the long-term (after 1 year) than less restrictive, low calorie diets. That is why it is so important to follow-up a VLCD with a longer term healthy eating and physical activity plan.

What's the best way to maintain weight loss following use of a VLCD?

Studies show a lot of variation in the amount of weight loss that is regained once you have completed the VLCD but, as with all weight loss plans, weight can be regained if lifestyle changes are not kept.

An active follow-up weight maintenance programme, that includes behavioural therapy, nutritional education, exercise and weight loss medications (delivered in a group setting by a team of healthcare professionals) has been shown to improve weight maintenance after a VLCD. 

Are VLCDs safe?

VLCDs are safe and effective when used in the right individuals under careful medical supervision, along side behaviour changes, nutrition education and an exercise programme. 

Who should not use VLCDs?

VLCDs should only be used under medical supervision and your doctor can advise you as to whether a VLCD is suitable for you or not.

VLCDs are not advised in certain population groups and medical conditions. These include:

What kinds of side effects are possible with VLCDs?


There is no magic answer for sustained weight loss. VLCDs may be useful to 'kick start' weight loss when used correctly that is in carefully selected clients under medical supervision. The use of VLCDs should be supported by trained health care professionals who encourage clients through the re-feeding period and beyond, and who teach them about the life-long behaviour and dietary changes needed to keep off the weight lost. Obesity is a long-term condition that needs a lifetime of attention even after a formal weight loss programme ends. The only way to manage weight in the longer term is to commit to permanent changes of healthier eating, regular physical activity and develop a positive and respectful relationship with food.

Created by members of the weight management interest group, August 2013, updated May 2016

Review date: May 2019.

© 2016 Irish Nutrition and Dietetics Institute, INDI. All rights reserved. May be reproduced in its entirety provided the source is acknowledged. This information is not meant to replace advice from your medical doctor or individual counselling with a dietitian. It is intended for educational and informational purposes only.

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