Magnetic resonance imaging provides new insights into the characterization of adipose and lean tissue distribution.

Magnetic resonance imaging (MRI) represents a major advance in the study of human body composition and nutritional status. Measurement of whole body and regional adipose tissue (AT) distribution, quantification of lean tissue (LT) and its principal constituent skeletal muscle, and the assessment of visceral AT are among the advantages made possible by MRI. Indeed, the ability to quantify visceral AT has provided the researcher with significant insight into the complex relationships between body composition and health risk. Because there are no known health risks associated with MRI, this methodology is well suited for studying the effects of various nutritional perturbations on both AT and LT, in particular visceral AT and skeletal muscle. An overview of the historical development and current status of MRI within the context of body composition research is provided. Validation studies are reviewed, and new insights into the nature of AT and LT distribution in both sexes and the effects of weight loss on these same parameters are presented. Finally, directions for future MRI research are suggested.