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VLED can Result in Changes in Liver and Abdominal Fat
Abstract & Commentary
By Richard M. Peterson, MD, MPH, Clinical Instructor of Surgery, Department of Surgery, USC. Dr. Peterson reports no financial relationships relevant to this field of study.
Synopsis: Given the observed early reduction in LV and the progressive reduction in VAT, we suggest that the minimum duration for a preoperative VLED be 2 weeks.
Source: Colles SL, et al. Preoperative weight loss with a very-low-energy diet: Quantitation of changes in liver and abdominal fat by serial imaging. Am J Clin Nutr. 2006;84:304-311.
A very low-energy diet (VLED) can result in substantial, rapid weight loss and is increasingly prescribed before obesity surgery to minimize risk and difficulty by reducing liver size and abdominal adiposity. Despite its growing popularity, a VLED in this setting has received little attention.
Colles and colleagues took a concept that is followed by many surgeons in bariatric surgery and were able to establish a means to quantify the use of a VLED and its impact on liver size. Several concepts surrounding pre-operative weight loss exist. Some surgeons require a mandatory preoperative weight loss before surgery, whereas some have not found a correlation. For some, the loss of weight preoperatively signifies the patient's commitment to their surgery and their new lifestyle. There are studies to both support and refute this claim. This study identifies another reason for the weight loss. In our practice we have found that mandatory preoperative weight loss confers an advantage to the surgeon, technically, which translates to increased patient safety. We have not statistically correlated this with operative times, but anecdotally it seems that our performance is improved in these settings. Additionally, in those patients who have not lost weight preoperatively, these have been the cases that had large livers and were technically more difficult.
Colles et al, in their study, were able to quantify a reduction in the size of the liver in those patients that were compliant with their VLED. Thirty-two subjects were enrolled in the study and were followed for a 12-week period. The outcomes measured during this time were changes in liver volume and visceral and subcutaneous adipose tissue. CT scans and MRI were used to measure and follow the progression of these factors at baseline, 2, 4, 8, and 12 weeks.
They found that 80% of the liver volume change occurred in the first 2 weeks in their study population, and a maximal liver volume reduction was achieved at 8 weeks. The change in visceral adipose tissue was uniform over the 12-week period.
The study strengths were an ability to track and confirm compliance of the patients with the VLED. Additionally, they were able to quantify with radiographic evidence the reduction in the size of the liver and visceral adipose tissue. The weakness of the study is in its patient size and its generalizability to the population at large, which Colles et al point out. A study of a larger size would improve the power and generalizability of their results. It would also be helpful to know if these same patients did translate to "technically easier" patients as they underwent surgery.
The recommendations by Colles et al for surgeons to place their patients on a VLED prior to surgery for 6 weeks addresses the time frame for the majority of the reduction of liver volume. Additionally, with a shorter time period (less than 12 weeks), patient compliance is more likely possible.