Preoperative low-energy diets for patients with body mass index >30kg/m2 undergoing non-bariatric surgery: A pilot feasibility randomized clinical trial and a systematic review and meta-analysis of efficacy data

BACKGROUND: The current evidence for preoperative low energy diets (LEDs) for patients with body mass index (BMI) > 30 kg/m2 prior to non-bariatric surgery rests on high-risk of bias studies. A randomized clinical trial (RCT) is warranted to bridge this knowledge gap. Prior to a larger RCT, we conducted a pilot feasibility RCT to address potential hurdles for the larger trial. METHODS: The pilot feasibility multicenter trial was conducted in Canada at four centers between January and October 2024. Patients were randomized (1:1 randomly permuted online blocked allocation) to receive a 3-week LED protocol or standard care. All patients older than 18 years of age with BMI body greater than 30kg/m2 undergoing elective non-bariatric intra-abdominal or orthopedic surgery were evaluated for enrollment. Main exclusion criteria were contraindications to LED and surgery scheduled without at least 3 weeks notice. The primary outcome was descriptive including the following feasibility outcomes: recruitment rate, randomization percentage, intervention adherence, and follow-up completion. Clinical outcomes included anthropometric data. The primary outcome analysis was descriptive. Additionally, a random effects meta-analysis was performed using previously published RCT data for 30-day postoperative morbidity. Last follow-up date was January 14th, 2025. RESULTS: There were 91 patients randomized (LED n=45, control n=46). Out of 373 eligible patients, 57% (95%CI 51.4-63.1%) were randomized. Out of these 91 randomized patients, 81 (89%, 95%CI 80.7-94.6%) had complete follow-up. LED adherence was 81.7% (95%CI 74.1-89.3%). Analysis of covariance suggested patients in the LED group lost more weight during the 3-week intervention period (MD 4.5kg, 95%CI -5.6 to -3.5). The pooled meta-analysis of 5 RCTs suggested a 18% relative risk reduction in postoperative morbidity favouring the intervention (RR 0.82, 95%CI 0.52-1.28, p=0.38, I2=0%). CONCLUSIONS: The feasibility targets of this pilot RCT were not met for recruitment rate, randomization percentage, and complete follow-up. Pooled meta-analysis suggests that LED prior to non-bariatric surgery can effectively induce weight loss with reduced postoperative morbidity, which needs to be validated by a larger noninferiority RCT with additional centers to meet the feasibility targets. TRIAL REGISTRATION: Clinicaltrials.gov: NCT03935451.