A new body composition index (BCI) based on BMI and impedentiometric parameter (reactance): trend observed in the first year of life.

Observational studies have highlighted the lack of specificity of body mass index (BMI) as indicator of body composition. Body mass is heterogeneous and includes both fat and fat-free components, although in different proportions. Thus, variations in BMI among individuals reflect differences in both compositional variables, not only fat mass. The bioelectrical impedance index reactance (Xc) is representative of the quantity of cell membranes and consequently of body cell mass (BCM). The relation between BMl and Xe standardized by the subject's height, could provide a more reliable body composition index, because it takes in account not only the body weight but also the contribution represented by fat-free mass. Aim: To evaluate the trend of body composition index (BCI) in the first year of life in a sample of healty infants.