To evaluate a whole body rapid imaging technique to calculate neonatal lean body mass and percentage adiposity using 3.0 Tesla chemical shift Magnetic Resonance Imaging (MRI). A rapid 2-Point Dixon MRI technique was used to calculate whole body fat and water images at 3.0 Tesla in term (n=10) and preterm (n=15) infants in 42 seconds/scan. MRI calculated whole body mass correlated closely with measured body weight (R2=0.87;p<0.001). Scan-rescan analysis demonstrated a 95% limit of agreement of 1.3% adiposity. At term corrected age, former preterm infants had significantly reduced lean body mass compared to term born controls 1935g versus 2416g (p=0.002).