Comparison of air displacement plethysmograph and bioelectrical impedance for assessing body composition changes during weight loss in Japanese women.

Objective:  To investigate the difference between air displacement plethysmograph (ADP) and bioelectrical impedance (BI) for assessing body composition changes during weight loss in Japanese women. Design:  Cross-sectional and longitudinal investigation study. Subjects:  In a first cross-sectional study, we used data of 7380 Japanese women aged 14–83 years [body mass index (BMI): 22.6 ± 3.7 kg/m2] at baseline. Among the participants, we used data of 54 women (BMI: 25.9 ± 3.9 kg/m2) for a 5-month follow-up study. Measurements:  Body fat percentage was evaluated by ADP and BI, and body fat (kg) and lean body mass (kg) were calculated. Anthropometric parameters, such as height, weight, BMI, waist circumference, hip circumference and waist hip ratio, were also measured. In a second longitudinal study, they were also investigated before and after the study. Results:  In a first cross-sectional study, body fat percentage was 31.2 ± 7.0% in ADP and 25.7 ± 6.8% in BI. A significant relationship was observed between ADP and BI (r = 0.761, p < 0.01). In a second longitudinal study, body weight was significantly reduced. There were significant method (ADP vs. BI) and time (pre and post) effects but no interactions in assessing body fat percentage. There was a significant relationship between ADP and BI in body fat percentage, body fat and lean body mass. Delta body fat percentage (r = 0.386, p < 0.01) and delta body fat (r = 0.556, p < 0.01) measured by ADP were weakly correlated with those measured by BI. However, delta lean body mass measured by ADP was not correlated with that measured by BI. Conclusion:  There was a discrepancy between ADP and BI for assessing body composition changes in Japanese women. ADP is preferentially recommended for evaluating body composition.