Very low calorie diets (VLCDs)

Very low calorie diets (VLCDs) are designed to completely replace usual food intake. By definition a diet is described as very low calorie if it provides less than 800 kcal per day.33 It is important that VLCDs provide sufficient protein and meet the daily requirements for vitamins, erectile minerals, electrolytes and fatty acids. VLCDs are usually provided in the form of liquid supplements. Small amounts of low calorie foods such as vegetables may be incorporated into a VLCD. Due to the severe calorie restriction and the potential side effects, VLCDs should not be followed for periods greater than 12-16 weeks. Patients could expect to lose 1.0-2.5 kg per week when strictly adhering to a VLCD.


The National Task Force on the Prevention and Treatment of Obesity,34 recommend that VLCDs are restricted to those:

  • With a BMI of >30
  • Who are well motivated
  • Who have failed at more conservative approaches
  • Have a medical condition that would be immediately improved with rapid weight loss e.g. severe obstructive sleep apnoea.

Contraindications to VLCDs include:

  • Unstable cardiac or cerebrovascular disease
  • Acute and chronic renal failure
  • Severe or end stage liver disease
  • Psychiatric disorder that could interfere with compliance
The side effects of VLCDs may include fatigue or weakness, dizziness, constipation, diarrohea, dry skin, hair loss, menstrual changes and cold intolerance. More serious side effects include the development of gout and gallstones, however, it is well recognised that any form of weight loss increases the likelihood of gallstone development..
VLCDs in the past were associated with cardiac disturbances, however, modern VLCDs are now appropriately constituted and there is no evidence that there is an association between their use and cardiac disturbance.

It is important that patients are medically assessed prior to undergoing a VLCD and that they are monitored closely throughout the treatment. Although it has been shown that VLCDs can produce greater initial weight loss, the long-term results achieved do not appear to substantially differ from those achieved using other dietary methods.1 For this reason there should be strong emphasis on weight maintenance strategies following a period of a VLCD.

The National Obesity Forum recommends that VLCDs are used only under close clinical and dietetic supervision.