Objectives: We aimed to describe changes in body mass index after kidney transplant and to assess how these changes influence long-term outcomes.
Materials and methods: Data were collected from kidney transplant recipients seen at our center between January 2007 and July 2016. Changes in body mass index over the posttransplant period were modeled using a generalized estimating equation, with changes calculated for each patient from pretransplant to 6 months posttransplant. Calculations were then categorized into 3 body mass index groups: stable (change of ± 1.5 kg/m² or less), reduced (reduction of > 1.5 kg/m²), and increased (increase of > 1.5 kg/m²). Outcomes among groups were compared.
Results: Among 1344 total patients, the geometric mean pretransplant body mass index was 27.3 kg/m². This declined significantly (P < .001) to a geometric mean of 25.6 kg/m² at 1 month posttransplant, before increasing and stabilizing to pretransplant levels by 36 months (geometric mean body mass index of 27.2 kg/m² ; P = .522). Of 822 patients with body mass index measurements at 6 months, 303 had reduced, 388 had stable, and 131 had increased levels relative to pretransplant levels. On multivariate analyses, 12-month creatinine levels were significantly higher in the reduced cohort, with adjusted levels of 160.6 versus 135.0 μmol/L for the stable cohort. However, no significant associations were detected between 6-month body mass index changes and patient survival, graft survival, incidences of posttransplant diabetes and cancer, and a range of other clinical and histologic outcomes (all P > .05).
Conclusions: Our data demonstrated that body mass index was significantly reduced in the first month after kidney transplant before increasing to pretransplant levels during years 3 to 5. Furthermore, patients who retained decreased levels at 6 months had impaired graft function in long-term follow-up. These observations conflict with the existing literature and warrant further investigations.