Bioelectrical impedance analysis and skinfold thickness for the estimation of body fat: a population-based study in southern Brazil.

Objective: The objective of this study was to compare bioelectrical impedance analysis and skinfold measurements for the estimation of body fat in adults.

Methods: We analyzed data from 292 adult participants enrolled in a cross-sectional population-based study. Four skinfold measurements were performed, and body fat percentage was estimated using the Petroski formula. Bioelectrical impedance analysis was performed using a tetrapolar electrical bioimpedance device. The measurements were compared using Student's t-test, Robinson's coefficient of agreement, Cronbach's alpha, and linear regression models (slope and intercept).

Results: The mean percentage of body fat estimated by skinfold measurements was higher compared to bioelectrical impedance analysis (29.0 vs. 27.9; p<0.001), but the agreement between the methods is good (alpha=0.88; Robinson's coefficient of agreement=0.91). Linear regression models showed a good correlation (r2=0.69). Bland-Altman analysis showed a mean difference of -1.02 (-1.54 vs. -0.50) between the two techniques. The agreement was better in women, those aged 20-39 years, those with a body mass index<25, and those with a waist-to-height ratio<50.

Conclusion: The two methods showed a good agreement between the mean values of body fat percentage and can be used in population studies. However, their results should be considered with caution in men, people aged 40 years and older, overweight people, and those with a waist-to-height ratio≥50.