• Patients with either vitamin D deficiency [25(OH)D 15–30 ng/ml] or insufficiency [25(OH)D <15 ng/ml] presented higher body fat and weight gain since KTx (p < 0.001 and p < 0.001, respectively). • Waist circumference (p = 0.044), BMI (p = 0.001) and serum leptin (p = 0.001) were higher in patients with vitamin D deficiency. • Body fat (r2 = 0.366, p < 0.001) and serum leptin (r2 = 0.285, p < 0.001) were negatively correlated to serum 25(OH)D. Here, LEP is linked to vitamin D deficiency.