The effect of a meal on measures of impedance and percent body fat estimated using contact-electrode bioelectrical impedance technology.

BACKGROUND/

objectivesTo determine the effect of a meal on impedance and percent body fat (%BF) determined using contact-electrode bioelectrical impedance analysis (BIA) technology. SUBJECTS/

methodsForty-three adults (23 women and 20 men) volunteered to participate in this study (age=20.5±1.1 years; body mass index=24.1±3.8 kg/m(2)). Body composition was assessed using three BIA analyzers: leg-to-leg (LBIA), segmental (SBIA) and multi-frequency (MFBIA), on two separate occasions. After a baseline measurement, subjects consumed a meal or received nothing, which served as the control (CON). Subjects were reassessed 20, 40 and 60 min following (POST) the baseline measure in each condition.

resultsTwenty minutes after eating (3847±900 kJ), body mass (LBIA=0.8 kg, SBIA=0.8 kg, MFBIA=0.7 kg, P<0.05), impedance (LBIA=6.0 Ω, SBIA=17.9 Ω, MFBIA=27.1 Ω, P<0.05) and %BF (LBIA=0.9%, SBIA=1.7%, MFBIA=0.8%, P<0.05) increased significantly and remained elevated at 60 min POST. During the CON trial, a consistent body mass reduction (60-80 g) and impedance increase (4-9 Ω) was observed over time resulting in a small increase in %BF (0.3-0.7%) 60 min POST (P<0.05).

conclusionsTwenty minutes after eating, %BF increased due to elevations in impedance and body mass. As such, when precision is critical, we recommend adhering to the pretest fasting guidelines to avoid meal-induced alterations in %BF estimates. In addition, use of a consistent testing schedule may minimize normal %BF variation over time.