- A VLCD provides 800 calories or fewer per day through nutritionally complete meal replacements
- Medically supervised VLCDs promote rapid weight loss through ketosis while ensuring all macronutrient and micronutrient needs are met
- VLCDs can be used as a standalone treatment or in combination with medical or surgical weight loss interventions
- A common use is pre-bariatric surgery — to shrink the liver and make the operation safer and more straightforward
- VLCDs are not appropriate for everyone and require professional guidance before starting
What Is a VLCD?
A Very Low Calorie Diet (VLCD) is a structured, nutritionally complete eating program that provides 800 calories or fewer per day — typically through meal replacement products rather than conventional food.
Unlike crash diets or unstructured calorie restriction, a properly formulated VLCD is designed to be a total food replacement — providing all required daily levels of protein, essential fatty acids, carbohydrates, vitamins, and minerals, despite the dramatically reduced calorie intake. This nutritional completeness is what distinguishes a medically appropriate VLCD from an unsafe starvation diet.
VLCD meal replacements are available in a range of formats to suit different preferences:
What Does a VLCD Contain?
A medically approved VLCD product is formulated to meet all essential nutritional needs — not just reduce calories. The six key nutritional components are:
The extremely low carbohydrate intake induces ketosis — the same metabolic state as in a ketogenic diet — which promotes rapid fat-burning and natural appetite suppression through ketone production.
How Are VLCDs Used?
VLCDs are a versatile tool in weight management — they can be used in several different clinical contexts:
Used as a primary treatment approach for overweight or obesity — typically under medical supervision for a defined period, followed by a carefully managed transition back to conventional food.
One of the most common uses of a VLCD. In the weeks before bariatric surgery, patients often undertake a VLCD to reduce liver size — a fatty, enlarged liver makes laparoscopic surgery technically more difficult and increases surgical risk. Shrinking the liver significantly improves operative safety and outcomes.
Used alongside weight loss medications, behavioural therapy, or exercise programmes as part of a comprehensive, supervised treatment plan — particularly when rapid initial weight loss is clinically indicated.
Important: VLCDs Are Not for Everyone
VLCDs are not appropriate for everyone. People with certain medical conditions — including Type 1 Diabetes, active eating disorders, pregnancy, severe kidney or liver disease, and several others — may not be suitable candidates. It is essential to discuss your individual circumstances with your GP, Bariatric Doctor, or Dietitian before starting a VLCD program.
When medically supervised, VLCDs are safe and effective. Your MedSurg Weight Loss doctor and dietitian will assess your suitability, explain what to expect, help you transition safely in and out of the program, and monitor your health throughout.
If you'd like to know whether a VLCD could be appropriate for you, our team can assess your suitability and develop a medically supervised plan. No referral is necessary. Get in touch or explore our Medical Weight Loss and Dietitian services to learn more.
Medical disclaimer: This article is for general informational purposes only. Very low calorie diets should only be undertaken under medical supervision. Please consult your doctor or dietitian before starting any VLCD program.