Does Maximum Pre-operative Weight Loss Predict Weight Loss Surgery Outcomes?

Daniel B Jones, MD, MS, FACS, Caroline Park, MD, MPH, Benjamin E Schneider, MD, FACS, Hussna Wakily, MD. Beth Israel Deaconess Medical Center.

Introduction: Is ‘maximum pre-operative weight loss’ (MPWL), defined as the maximum amount of weight lost prior to surgery, a predictor for post-operative weight loss for patients undergoing weight loss surgery (WLS)? WLS has become a widely accepted and pursued surgical option following medical management for morbidly obese patients. Various pre-operative variables have been investigated, including weight loss, body mass index (BMI), pre-existing comorbidities and socioeconomic status. ‘Maximum pre-operative weight loss’ (MPWL), however, has not been evaluated as a predictor for weight-loss outcomes.

Methods and Procedures: a single institution, retrospective review of 506 patients who underwent WLS, including laparoscopic band, Roux-en-Y gastric bypass, and laparoscopic sleeve gastrectomy from 2004-2012. Patients undergoing WLS who had a recorded MPWL in their pre-operative intake were included in this study; patients whose intake did not include this data were excluded. Follow-up interval was at approximately 3 month, 6 month and 1 year intervals, which respectively are designated ‘short’, ‘intermediate’, and ‘long-term.’ Age, gender, pre-operative body-mass index (BMI) and MPWL were collected for all patients. Post-operative data included: total post-operative weight loss, percent total weight lost, and corresponding BMI at 3 month, 6 month and 1 year intervals. Statistical analysis was performed using STATA (r) ensuring removal of patient identifiers. Tests including t-test, logistic regression, paired correlation and ANOVA.

Results: MPWL was positively correlated with total weight loss and pre-operative BMI across all intervals. Pre-operative BMI was found to be a significant predictor for short-term weight loss (p=0.004, 95% CI), while MPWL was a significant predictor for intermediate weight loss (p=0.035, 95% CI). Both pre-operative BMI and MPWL were positive predictors for post-operative weight loss at one year (p=0.003 and p=0.008 respectively, 95% CI). No specific amount of MPWL was found to be of predictive value of post-operative weight loss or post-operative BMI.

Conclusion: No other studies to our knowledge have explored maximum pre-operative weight loss (MPWL) as a predictor for weight-loss outcomes.This single-institution review of patients undergoing weight-loss surgery demonstrates that maximum pre-operative weight loss is a significant predictor for short-term and long-term weight loss. However, no specific amount of MPWL could be significantly predictive of post-operative weight loss or BMI. These findings emphasize the need for further investigations of weight loss history and tailoring realistic goals and interventions for these patients considering surgery.

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