With the rising prevalence of obesity in the US, the proportion of liver transplant (LT) candidates who are obese (BMI >30) is expected to increase. Obesity has been identified as an independent risk factor for morbidity and mortality in patients undergoing surgical procedures. However, in LT surgery there is conflicting information pertaining to the BMI threshold that impacts survival. Due to the lack of consensus, there is a wide variation in BMI cut-off used in transplant centers. Therefore the aim of our study is to investigate the BMI categories that impact post-LT survival. Methods: Published studies were identified by systematic literature search of MEDLINE and EMBASE (1995 – 2012). Study eligibility criteria included adult LT studies with BMI categories and survival (in years). BMI categories (kg/m²) were < 30, 30 – 35, 35 – 40 and > 40. The outcome measured was 1 year survival. Meta-analysis was done using random effect model. Results: Overall, 107 studies were identified but only 8 met study criteria. Seven studies were single center (n = 2,836) and one study used large UNOS liver transplant registry (n= 17,172). For meta-analysis we compared 4 different BMI groups:[1] BMI < 30 versus > 30 kg/m² (OR 1.0, p = 0.079), [2] BMI 35 versus > 35kg/m² (OR 1.31, p = 0.001), [3] BMI 35 – 40 versus > 40 kg/m² (p = 0.19) and [4] BMI < 40 versus > 40 kg/m² (OR 1.51, p = 0.001). There was no significant difference in the one-yr survival using a BMI threshold of 30 kg/m². However, we found negative impact on survival once the BMI exceeded 35 kg/m². Subsequent analysis of BMI sub-categories beyond the BMI threshold of 35 kg/m² (i.e. 35 – 40 versus > 35 kg/m²) was not significant. The I² statistics indicated low heterogeneity across the studies. Conclusion: [1] LT candidates with class I obesity (30 – 34.9 kg/m²) have similar outcomes to those who are either normal weight or overweight (25 – 29.9 kg/m²). [2] Pre-transplant BMI > 35 kg/m² (class II and III obesity) has a significant negative impact on liver transplant survival. [3]However, there was no difference in LT outcome between candidates with class II obesity (35 – 40 kg/m²) and class III obesity (>40 kg/m²).

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