BACKGROUND: A significant long-term nutritional problem after kidney transplantation is obesity. We examined the changes in body composition after transplantation and its determinants.

METHODS: A total of 192-kidney transplant patients (mean age of 48 ± 13 years, 71% male, 73% Caucasian, 37% with diabetes, 69% on maintenance hemodialysis before transplantation, 55% with deceased donor transplant) were included in this prospective study. Body weight, total body fat percentage (TBF%), fat free mass percentage (FFM%), total body water percentage, extracellular water percentage and body cell mass percentage were evaluated by bioelectrical impedance analysis along with clinical parameters at 1, 3, 6, 12 and 24 months following kidney transplantation.

RESULTS: At 1 month post-transplant, mean body weight was 85±22 kg, TBF% was 25% ± 11, FFM% was 75% ± 11, total body water percentage was 55% ± 6, extracellular water percentage was 40% ± 7 and body cell mass percentage was 37% ± 7. Over the 2 year follow up body weight increased by 7.5 kg (95% CI, 4.2, 11, p<0.001), with TBF% significantly increasing [+4.1% (95 % CI; 2.2, 6.1), (p<0.001)] while FFM% significantly declined [-8% (95 % CI; -11, -5.3), p<0.001]. Both total body water percentage and extracellular water percentage decreased significantly by month 12 [-1.5% (95% CI; -2.7, -0.3), p=0.014 and -2.2% (95% CI; -4, -0.4), p=0.015, respectively] and continued to be decreased at month 24 [-2.7% (95% CI; -4.6, -0.9), p=0.005 and -3.8% (95% CI; -6.6, -0.9), p=0.009, respectively]. Body cell mass percentage slightly increased at month 6 [0.76% (95% CI; -0.4, 1.9), p=0.25], further improvement was observed at month 12 [1.7% (95% CI, 0.2, 3.3), p=0.032] and changes of a lower magnitude at month 24 [2.4% (95 %CI, -0.13, 4.9), p=0.094)]. On multivariate analysis Caucasian race and male sex (p<0.05) were predictors of increased TBF%, with male sex (p<0.001) also associated with FFM%.

DISCUSSION: Kidney transplantation leads to changes in body composition that favor increasing body weight driven by fat mass accumulation and lean body mass loss. These changes are accompanied by small but statistically significant increase in body cell mass, indicating an overall improvement in nutrition status. More detailed studies examining the metabolic milieu associated with obesity post transplant is needed to understand the long-term implications of these changes.

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