Very low calorie diet effects
Pro Research Analysisby 
Searched over 200M research papers
Weight Loss and Body Composition Effects of Very Low Calorie Diets (VLCDs)
Very low calorie diets (VLCDs), typically providing 800 kcal/day or less, are highly effective for rapid short-term weight loss, with average weekly losses of 1.5 to 2.5 kg and total losses of about 20 kg over 12 to 16 weeks. These results are significantly better than standard low-calorie diets, which usually result in 0.4 to 0.5 kg of weight loss per week and a total of 6 to 8 kg over the same period Atkinson1993Tsai2006Wadden1983. VLCDs also lead to improvements in body composition, including reductions in body mass index (BMI), waist circumference, and fat mass, while helping to preserve lean body mass when adequate protein is included Muscogiuri2021Di Rosa2020Basolo2025+1 MORE.
Metabolic and Health Benefits of VLCDs
VLCDs, including very low calorie ketogenic diets (VLCKDs), have been shown to improve glycemic control, lipid profiles, and insulin resistance, making them beneficial for individuals with obesity-related conditions such as type 2 diabetes and polycystic ovary syndrome (PCOS) Muscogiuri2021Basolo2025Monda2020+2 MORE. These diets can also reduce inflammation markers and improve adiponectin levels, which are linked to better metabolic and inflammatory health . In women with PCOS, VLCDs result in greater weight loss and more pronounced improvements in hyperandrogenism and metabolic parameters compared to moderate energy deficit diets .
Safety and Side Effects of Very Low Calorie Diets
Modern VLCDs are generally safe when used under proper medical supervision for up to three months, especially in individuals with a body mass index (BMI) over 30. Serious complications are rare, with gallstones (cholelithiasis) being the most common side effect. Most other side effects are mild and manageable, such as increased satiety and reduced desire to eat, and recovery is usually spontaneous Atkinson1993Muscogiuri2021Di Rosa2020+1 MORE. Earlier versions of VLCDs, particularly those based on poor-quality protein, were associated with significant risks, but current formulations with high-quality protein have not been linked to diet-related fatalities in large case series .
Comparison with Other Diets and Long-Term Outcomes
While VLCDs produce greater short-term weight loss than conventional low-calorie diets, long-term weight maintenance is challenging and not significantly better than with other dietary approaches. Incorporating behavioral therapy and physical activity into VLCD programs can help improve long-term weight maintenance Atkinson1993Tsai2006. There is no clinical advantage to using VLCDs with fewer than 800 kcal/day compared to those at the 800 kcal/day level, as weight loss and body composition changes are similar across this range .
Special Considerations and Recommendations
VLCDs are most effective and safest when personalized and supervised by healthcare professionals, especially for individuals with obesity and related health conditions. They are not recommended for everyone and should be used with caution, considering potential contraindications . Further research is needed to understand the effects of VLCDs on gut microbiota and other long-term health outcomes .
Conclusion
Very low calorie diets are a powerful tool for rapid short-term weight loss and improvement in obesity-related health conditions. They are generally safe under medical supervision, but long-term weight maintenance remains a challenge. Personalization and comprehensive support, including behavioral and physical activity interventions, are key to maximizing the benefits and minimizing the risks of VLCDs.
Sources and full results
Most relevant research papers on this topic