BACKGROUND: TOBEC-derived measurements of body fat-free mass(FFM) and fat have been recently used in infants because safe, fast and valide in altermative to dilution and anthropometric method. The main goal of this study was to determine the agreement of FFM and fat in newborns.

SUBJECTS: 30 healthy, term (37 to 41 weeks) newborns.

METHODS: On day 4 of life anthropometric measurements were taken toghether with skinfold-thickness, thus calculating fat mass following the Weststrate's method. Arm fat area (AFA) and body mass index (BMI) were calculated as well. TOBEC measurements were taken on the same day following a standard procedure. A TOBEC measurement consisted of the mean of 10 readings. Intraindividual coefficient of variation was <3%. Coefficient of correlation was calculated between TOBEC-derived fat (FATT) and skinfold-thickness derived fat (FATWeststrate).

RESULTS: Coefficient of correlation between FATT and FATWeststrate, BMI, AFA were respectively 0.911 (p=0.0001), 0.892(p=0.0001) and 0.839 (p=0.0001). Correlation between FATT and single skinfold-thickness measurements were in the 0.570-0.753 range.

CONCLUSIONS: Correlation between FATT and anthropometric measurements, although statistically significant, were most due to the effect of weight-for-length alone. Skinfold-thickness derived measurements improved the agreement with FATT and seem accurate enough to assess body fat in newborn infants, at least for comparison between groups.