Very-low-energy diets prior to nonbariatric surgery: a systematic review and meta-analysis

Background: Very-low-energy diets (VLEDs) serve as an intensive approach to weight loss in a short period of time. While the preoperative use of VLEDs to optimize obese patients before bariatric surgery is well established, the evidence for VLEDs before other types of surgery remains unclear. The aim of this review was to determine the impact of preoperative VLEDs on perioperative outcomes in nonbariatric surgery, particularly for patients undergoing oncologic resection. Medline, EMBASE, CENTRAL, and PubMed were systematically searched. Methods: Articles were included if they evaluated VLED utilization before any type of nonbariatric surgery. The primary outcome was postoperative morbidity. Secondary outcomes included compliance, safety, and preoperative weight loss. A pairwise meta-analyses using inverse variance random effects was performed. From 792 citations, 13 studies (4 randomized controlled trials) with 395 patients (mean age 56.5 yr, 55.8% female) receiving VLED preoperatively in preparation for nonbariatric surgery were included. Results: Hepatectomy and gastrectomy were the most common surgical interventions. Mean duration of preoperative VLED was 6.6 weeks. The most employed liquid VLED formulation was Optifast. Target daily caloric intake ranged from 450 kcal to 1400 kcal. Compliance with VLED ranged from 94% to 100%. Mean preoperative weight loss ranged from 3.2 kg to 19.2 kg. There were no significant differences in post-operative morbidity (odds ratio [OR] 1.10, 95% confidence interval [CI] 0.64 to 1.91, p = 0.72), operative time (standardized mean difference [SMD] -0.35, 95% CI -1.13 to 0.43, p = 0.38), or postoperative length of stay (SMD 0.40, 95% CI -0.11 to 0.91, p = 0.12) for patients receiving VLEDs compared with those not receiving VLEDs. Six studies evaluated patients undergoing oncologic operations, and there were no significant differences in these data compared with data from operations for benign disease. Conclusion: While currently available evidence is heterogeneous, preoperative VLEDs are safe, well tolerated, and effectively induce preoperative weight loss in patients undergoing nonbariatric surgery for both benign and malignant disease. Further prospective studies are warranted.