The very low Calorie diet (VLCD) is popular as a treatment for obesity amongst mainstream medical professionals. However, there are problems associated with the use of the VLCD which precludes it as useful tools as part of a health lifestyle. While short-term studies show weight loss in obese individuals using the VLCD, the long-term success rate of the VLCD is poor, with many individuals regaining any weight lost. Many VLCD studies do not report individual components of weight loss and so their results should be interpreted with caution. Weight loss can originate from glycogen stores, water, skeletal muscle mass, as well as body fat. More importantly, weight loss using the VLCD can originate from skeletal bone, thus exposing the individual to future skeletal diseases. Recent research suggests that skeletal changes during weight loss do not reverse on cessation of a VLCD.
For example, researchers1 fed 36 men and women (mean age 50 years) a VLCD (900kcal/d) for 3 months, followed by either a low carbohydrate diet or low fat diet (1600kcal/d) for another 9 months to maintain weight loss. Following this protocol, the average weight loss was 18%, with the average weight regain during the maintenance period being ~3%. In the maintenance phase, there was no significant differences between the low fat or low carbohydrate treatments in terms of weight change. Serum levels of osteocalcin and C-terminal peptide of type I collagen (CTX), markers for bone resorption, increased following the VLCD. However, during weight maintenance the serum levels of the markers remained elevated, suggesting that bone resorption was still occurring, which may indicate reductions in that bone mineral density despite switching to a maintenance energy intake. These results suggest that the VLCD is detrimental to skeletal health.
Previous studies have shown that severe energy restriction causes a reduction in the bone mineral density, but this study provides evidence that this process may continue beyond the end of the restriction. Interestingly, serum parathyroid hormone (PTH) concentrations decreased during the study, whereas an increase in serum concentrations may be expected during times of bone loss as PTH stimulates the resorption process. This may be explained by the low baseline level of vitamin D intake, which increased significantly during the weight loss period. Vitamin D can also be released from fat stores during weight loss. The increase in vitamin D may have increased serum concentrations of 25(OH)D, which in turn increased calcium absorption from the gut, thus forcing down PTH despite active bone resorption. These results have serious implications for the use of the VLCD to treat obesity because serious skeletal ill health may result.
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