Body composition measurement in severe obesity.

PURPOSE OF REVIEW Severe obesity is accompanied by large increases in fat mass and alterations in the composition of fat free mass, in particular total body water and its extracellular compartment. The physical size limitations imposed by severe obesity, and variations in body composition from that of normal weight, pose tremendous challenges to the measurement of body composition. This review focuses on some of the methodological and practical issues associated with the use of common body composition methods, and identifies available published information on feasible methods for use in the severely obese. RECENT FINDINGS There is little published research regarding what body composition methods can be used with confidence in the severely obese populations. A simple three-compartment model combining measurements of body density by air displacement plethysmography and total body water by bio-electrical impedance can provide measurements of percentage body fat in the severely obese that are comparable with a traditional, highly technical three-compartment model requiring facilities such as isotope ratio mass spectrometry along with a substantial technical expertise. SUMMARY This review highlights some of the basic challenges faced by researchers and clinicians when conducting body composition assessments in severely obese patients. A simple three-compartment model that is accurate and easy to perform appears to be promising for use in this population. Further research is needed, however, on this and other feasible methods of body composition assessment in a diverse group of severely obese people.