Impact of a preoperative low calorie diet on liver histology in patients with fatty liver disease undergoing bariatric surgery

Abstract Background A low calorie diet (LCD) prior to bariatric surgery has been shown to reduce liver volume and facilitate ease of operation. It is estimated that 75 -100% of individuals undergoing bariatric surgery have non-alcoholic fatty liver disease (NAFLD). Objectives We aimed to investigate how a LCD affects liver histology in the setting of NAFLD. Setting University Hospital, United States Methods Forty intraoperative liver specimens were analyzed histologically: 20 with and 20 without a preoperative two-week, 1200kcal/day LCD. Weight was measured pre-diet, at surgery, and 6-months after surgery. NAFLD activity score (NAS) was used to grade liver histology at surgery. The NAS scores steatosis, lobular inflammation, hepatocellular ballooning and fibrosis . Results The non-LCD group (n=20) had mean weight at surgery of 136.1 ± 24.1kg. The LCD group (n=20) had initial mean weight of 128.6 ± 25.4kg, with pre-surgical weight loss of 3.43kg (range 0-9.3kg), mean ΔBMI 1.24 kg/m2 (=2.66% total weight loss) on a LCD. The LCD group had significantly less steatosis (p=0.02), fewer foci of lobular inflammation (P=0.01), and less hepatocellular ballooning (p=0.04) compared to the non-LCD group; with no difference in degree of fibrosis. Fewer patients in the LCD group had NASH (p=0.04). Weight loss on a LCD before bariatric surgery was predictive of weight loss 6 months after surgery (p=0.026). Conclusions A two-week LCD prior to bariatric surgery is associated with significant improvement in steatosis, inflammation and hepatocellular ballooning in NAFLD. Among LCD patients, pre-operative weight loss was associated with improved 6-month weight loss and liver function.