Objective: Bioimpedance analysis (BIA) is a potential field and clinical method for evaluating skeletal muscle mass (SM) and %fat. A new BIA system has 8-(two on each hand and foot) rather than 4-contact electrodes allowing for rapid 'whole-body' and regional body composition evaluation. Design: This study evaluated the 50 kHz BC-418 8-contact electrode and TBF-310 4-contact electrode foot-foot BIA systems (Tanita Corp., Tokyo, Japan). Subjects: There were 40 subject evaluations in males (n ¼ 20) and females (n ¼ 20) ranging in age from 6 to 64 y. BIA was evaluated in each subject and compared to reference lean soft-tissue (LST) and %fat estimates in the appendages and remainder (trunk þ head) provided by dual-energy X-ray absorptiometry (DXA). Appendicular LST (ALST) estimates from both BIA and DXA were used to derive total body SM mass. Results: The highest correlation between total body LST by DXA and impedance index (Ht 2 /Z) by BC-418 was for the foot-hand segments (r ¼ 0.986; left side only) compared to the arm (r ¼ 0.970-0.979) and leg segments (r ¼ 0.942-0.957)(all Po0.001).The within-and between-day coefficient of variation for %fat and ALST evaluated in five subjects was o1% and B1-3.7%, respectively. The correlations between 8-electrode predicted and DXA appendicular (arms, legs, total) and trunk þ head LST were strong and highly significant (all rX0.95, Po0.001) and group means did not differ across methods. Skeletal muscle mass calculated (Kim equation) from total ALST by DXA (X7s.d.)(23.779.7 kg) was not significantly different and highly correlated with BC-418 estimates (25.279.6 kg; r ¼ 0.96, Po0.001). There was a good correlation between total body %fat by 8-electrode BIA vs DXA (r ¼ 0.87, Po0.001) that exceeded the corresponding association with 4-electrode BIA (r ¼ 0.82, Po0.001). Group mean segmental %fat estimates from BC-418 did not differ significantly from corresponding DXA estimates. No betweenmethod bias was detected in the whole body, ALST, and skeletal muscle analyses. Conclusions:The new 8-electrode BIA system offers an important new opportunity of evaluating SM in research and clinical settings. The additional electrodes of the new BIA system also improve the association with DXA %fat estimates over those provided by the conventional foot-foot BIA.

Similarly, percent fat estimates from UWW and ADP using the two-compartment Siri equation were highly correlated (r ϭ 0.94, standard error of the estimate ϭ 3.58%, p Ͻ 0.001). Bland-Altman analysis showed no significant bias between D b measured by UWW and ADP. After controlling for D b measured by ADP, no additional between-subject variation in D b by UWW was accounted for by subject age, sex, or BMI. Discussion: Body density, an important physical property used in human body composition models, can be accurately measured by ADP in overweight and obese subjects.

ST-ONGE, MARIE-PIERRE, FREDERICK RUBIANO, ALFREDO JONES, JR., AND STEVEN B. HEYMSFIELD.A new hand-held indirect calorimeter to measure postprandial energy expenditure. Obes Res. 2004;12: 704 -709. Objective: To verify the accuracy of a new hand-held metabolic rate measuring device (MedGem) in quantifying postprandial energy expenditure (PP EE). MedGem measurements were compared to measurements obtained with a conventional indirect calorimeter (Delta-Trac). Research Methods and Procedures:The resting metabolic rate of 15 healthy subjects was measured for 20 minutes using Delta-Trac followed by a 10-minute measurement period using MedGem. EE was again measured for 7 hours after consumption of a 2510-kJ breakfast. Measurements were read from the Delta-Trac for the initial 50 minutes of each hour followed by a single reading from the MedGem after 5 to 10 minutes of measurement. Measured EE was calculated as the average of the total measurement period for Delta-Trac and for eight readings using MedGem; PP EE was calculated as the average of all measurements obtained after breakfast consumption. Results: There was no difference in resting metabolic rate between the two methods (6455.1 Ϯ 417.6 vs. 6468.5 Ϯ 337.2 kJ/d for Delta-Trac and MedGem, respectively). Measured EE and PP EE values with Delta-Trac (7019.1 Ϯ 400.8 and 7099.8 Ϯ 399.2 kJ/d, respectively) and MedGem (6775.6 Ϯ 372.0 and 6819.5 Ϯ 379.9 kJ/d, respectively) were not significantly different. There was no bias detected in any of the measurements made with MedGem compared with those of Delta-Trac. Discussion: The new hand-held EE measuring device can accurately track PP EE relative to a conventional indirect calorimetry system and, therefore, provides a new opportunity to assess PP EE in research settings and large-scale trials.