[Differences between morning and afternoon in the assessment of nutritional status by bioelectric impedance in children].

OBJECTIVE

The aim of this study was to examine if there were differences in the assessment of the nutritional status between values of bioelectric impedance (BI) measured in the morning (08:30) and in the afternoon (17:00).

PATIENTS AND METHODS

We have studied 30 boys between 6.5 and 10.9 years of age. Weight, stature, skinfold thickness and total body impedance (Z) were measured at 08:30 and at 17:00 on the same day.

RESULTS

In 28 of 30 boys, Z at 17:00 was lower than Z at 08:30. The mean decrease in Z was 4.64% of the morning result (p = 0.0001). At 17:00 there was an increase in total body water (TBW) and fat-free mass (FFM) measured by BI, 0.681, and 0.93 Kg, respectively (p = 0.0001), compared with morning values. We did not find differences between skinfold thickness values in the morning and in the afternoon, except for the suprailiac skinfold, which was a bit larger in the afternoon (p = 0.05). In the morning and afternoon there was a high correlation between FFM measured by skinfold thickness and values of TBW and FFM measured by BI.

CONCLUSIONS

Z in boys decrease in the afternoon (17:00) compared with morning values (08:30). This fact must be considered by the pediatrician when IB is used for the assessment of nutritional status in children.