In our lab, body composition measurements are generally performed with either the underwater weighting technique or with whole-body dual energy X-ray absorptiometry (DEXA) scanning. For the underwater weighing procedure, we are using the 2 compartment model in which whole-body mass is divided into fat mass and fat free mass. For determining standard subjects’ characteristics in clinical studies, we feel that this represents an appropriate method. In addition, for large cohort studies, we also have the possibility to apply bio-impedance measurements to assess body fat mass. However, in prospective intervention studies, we prefer the use of DEXA scanning. The latter enables to differentiate total body mass into fat mass, lean tissue mass and bone mass (i.e., bone mineral content) on a whole body level and for specific parts of the body. Standard equipment being used is a Lunar Prodigy Advance scanner (GE Healthcare) with enCORE 2005 software.
For determining body composition and/or muscle mass for more specific sub-regions (i.e. cross sectional area measurements in the upper leg), we generally use computed tomography (CT) scanning. Axial image scans are taken with a 16 slice CT scanner (IDT 8000, Philips Medical Systems). AGFA IMPAX imaging software is used to differentiate between fat, muscle and bone tissue, for which the cross-sectional areas are measured. The latter is primarily used to determine cross sectional area of different muscle groups (e.g. quadriceps cross sectional area before and after an exercise training program).
Due to the practical applicability of the BodPod system, we are in the process of buying a Bodpod for easy, non-invasive body composition measurements, which is of particular use in children and the elderly.