From the Guidelines
No, a very low calorie diet (VLCD) is not a sustainable weight loss plan for most people. VLCDs typically provide only 800 calories or fewer per day and while they can produce rapid initial weight loss, they are designed for short-term use (usually up to 3 months) under medical supervision 1. These diets often come in the form of meal replacements like shakes or bars and are generally recommended only for individuals with a high risk of complications, such as those requiring weight loss and/or glycemic management before a needed surgery, if the benefits exceed the potential risks 1.
The unsustainability of VLCDs stems from several factors, including:
- Significant side effects, such as electrolyte abnormalities, severe fatigue, and cardiac arrhythmias 1
- Muscle loss alongside fat loss
- Weight regain once normal eating resumes
- Lack of teaching long-term dietary and lifestyle changes necessary for maintaining weight loss
A more sustainable approach involves:
- Moderate calorie reduction (typically 500-1000 calories below maintenance)
- Regular physical activity
- Behavioral changes that can be maintained indefinitely This slower approach (1-2 pounds of weight loss per week) allows for adequate nutrition and is more likely to result in lasting weight management 1.
It's also important to note that comprehensive weight loss maintenance may be indicated in cases of documented surgery, additional pharmacologic agents, and structured lifestyle management programs, which should include long-term, comprehensive weight maintenance strategies and counseling to maintain weight loss and behavioral changes 1.
From the Research
Sustainability of Very Low Calorie Diets for Weight Loss
- Very low calorie diets (VLCDs) are defined as diets with an energy intake of 800 kcal/day or less, and are often used for rapid weight loss in obese individuals 2.
- Studies have shown that VLCDs can result in significant short-term weight loss, with an average weight loss of 1.5 to 2.5 kg/week, and a total weight loss of 20 kg after 12 to 16 weeks 2, 3.
- However, the long-term maintenance of weight loss with VLCDs is not very satisfactory, and is no better than with other forms of obesity treatment 2, 3.
- Incorporating behavioral therapy and physical activity into VLCD treatment programs may improve long-term weight loss maintenance 2.
Comparison with Other Diets
- VLCDs have been compared to conventional low-calorie diets (LCDs) in several studies, with results showing that VLCDs induce greater short-term weight losses, but similar long-term losses 3.
- A study found that VLCDs did not produce greater long-term weight losses than LCDs, and that the use of liquid meal replacements as part of a 1000 to 1500 kcal/day diet may provide an effective and less expensive alternative to VLCDs 3.
- Other dietary approaches, such as low-fat diets, low-carbohydrate diets, and high-protein diets, have also been recommended for weight loss, but the optimal dietary strategy for sustainable weight loss is still debated 4, 5.
Safety and Efficacy
- VLCDs are generally safe when used under proper medical supervision in moderately and severely obese patients, but can be associated with serious complications such as cholelithiasis 2.
- A study found that long-term management with low-calorie diets (900 kcal/day) in severely obese patients who were non-eligible for surgery resulted in substantial and sustained improvements in glucose homeostasis, blood pressure, and lipid profile, with minor self-limited side effects 6.
- The safety and efficacy of VLCDs depend on various factors, including the individual's health status, the duration of the diet, and the level of medical supervision 2, 6.