*Purpose: Describe changes in body mass index (BMI) before and after kidney transplant and determine the association between BMI and graft loss or mortality.

*Methods: Single center, retrospective study of adult patients undergoing kidney transplant from June 2012-June 2016. Patients were excluded if they received a repeat or multi-organ transplant, experienced death or graft loss prior to three months post-transplant, were lost to follow up, became pregnant, or underwent a weight-loss surgery. BMI at time of listing, time of transplant and post-transplant at 3 months, 1 year, 2 years, and 3 years were documented. The changes in BMI over time were analyzed using paired sample t-test. The association of BMI with graft loss and mortality were analyzed using logistic regression.

*Results: A total of 202 patients met inclusion criteria; 171 patients were alive with a functioning renal graft at 3 years post-transplant. The average age at time of transplant was 54 years-old (SD 13), and the majority of subjects were African American males who received a deceased donor transplant. The average BMI at transplant listing was 29.7 kg/m² (SD 5.9), which significantly decreased to 29 kg/m² (SD 5.3) by the time of transplant (p=0.02). BMI increased post-transplant to 29.1 kg/m² (SD 5.3) at 3 months (p=0.69); 30.8 kg/m² (SD 5.6) at 1 year (p<0.01); 31.1 kg/m² (SD 5.6) at 2 years (p<0.01); and 31.1 kg/m² (SD 5.8) at 3 years (p<0.01) as compared to the time of transplant. The increase in BMI from the second year to third year after transplant was not significant. None of the baseline patient characteristics were significantly associated with extent of BMI change. The average BMI at the time of transplant for subjects who experienced graft loss (n=14) was higher than those who did not [32 kg/m² (SD 5.3) vs 29 kg/m² (SD 4.2), (p=0.02)]. The average BMI at the time of transplant for subjects who died during follow up (n=18) was similar to subjects who survived [29.6 kg/m² (SD 4.6) vs 29.2 kg/m² (SD 5.3), (p=0.76)].

*Conclusions: Patients lost weight while on the wait list for kidney transplant and then gained weight post-transplant. Weight gain became significant at 1 year post-transplant and continued to increase until 2 years post-transplant, after which it plateaued. Higher BMI at transplant was associated with increased graft loss. There was no association between BMI at transplant and 3 year post-transplant mortality.

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