Effect of Preoperative Very Low-Calorie Diets on Hepatic Steatosis, Fibrosis, and Perioperative Outcomes of Bariatric Surgery.

Introduction: Preoperative weight loss through a very low-calorie diet (VLCD) has been shown to reduce liver volume and technical difficulty in patients undergoing metabolic and bariatric surgery (MBS). However, the effect of preoperative VLCD on liver histology and other outcomes is not well demonstrated. Our study aimed to explore the effect of a 2-week preoperative VLCD, compared with no-dietary intervention, on hepatic steatosis, fibrosis, weight loss, and other postoperative outcomes of MBS. Materials and Methods: This retrospective study was conducted at the Chulalongkorn Bariatric and Metabolic Institute, King Chulalongkorn Memorial Hospital, Bangkok, Thailand. The medical records of patients with severe obesity (body mass index ≥50 kg/m 2 ) attending the clinic from January 2005 to December 2020 were reviewed. Clinical data and laboratory investigations were collected at baseline and at each follow-up visit, up to 5 years postoperatively. Hepatic steatosis and fibrosis were assessed by liver biopsy intraoperatively. Results: A total of 181 patients were included in this study. Preoperative VLCD was prescribed in 65 patients (VLCD group) and 116 patients received their usual diet (control group). Mean preoperative weight loss was 9.1 ± 6.1 kg in the VLCD group versus 0.0 ± 0.0 kg in the control group ( P  = .000). The VLCD group had significantly less number of patients with moderate and severe liver steatosis from the liver biopsy specimens (16.2% versus 46.3%; P  = .008). However, there was no significant difference in fibrosis grade between those with VLCD and control (≥F2-fibrosis; 2.7% versus 7.5%; P  = .118). Moreover, preoperative VLCD could reduce operating time in patients who underwent both laparoscopic Roux-en-Y gastric bypass (LRYGB; VLCD 163.4 ± 38.2 minutes versus control 215.1 ± 67.4 minute, P  = .000) and laparoscopic sleeve gastrectomy (LSG; VLCD 110.8 ± 20.0 minutes versus control 131.0 ± 38.1 minutes, P  = .004). During the 5-year follow-up, there were a significant difference of HbA1C between the VLCD and the control group (coefficient: -0.24 with 95% confidence interval [CI]: -0.44 to -0.04, P  = .019), particularly in patients who underwent LRYGB (Coefficient: -0.26 with 95% CI: -0.49 to -0.03, P  = .028), but not LSG. However, long-term weight loss outcomes and other biochemical outcomes were not different between the VLCD and the control group. Conclusion: Preoperative VLCD was associated with reduced liver steatosis and operative time in patients who underwent LRYGB and LSG. Moreover, preoperative VLCD significantly decreased HbA1C during a 5-year follow-up period. Therefore, it should be considered in patients with severe obesity, who will undergo MBS.