Body composition among 6–7 years-old children: data from the 2015 Pelotas (Brazil) Birth Cohort Study

Nutritional assessment of children is essential for health, especially given the observed worldwide increase in childhood overweight and obesity. This study aims to describe body composition (fat and lean mass) in children aged 6–7 from the 2015 Pelotas (Brazil) Birth Cohort. Longitudinal study that measured fat mass (FM% and FM in kilograms) and lean mass (LM% and LM in kilograms) using Dual-Energy X-ray Absorptiometry (DEXA) and Air-Displacement Plethysmography (BodPod). Body composition was described in relation to the independent variables. Student t-tests were used for binary variables, and ANOVA was used for categorical and ordinal variables. Of the 4,275 children included in the original cohort, 2,271 had DEXA, and 2,181 had BodPod data at age 6–7 years. Overall, BodPod and DEXA measures presented similar results, with girls having a higher average fat mass percentage in BodPod [25.2% (95%CI 24.7; 25.7) and DEXA [25.9% (95%CI 25.3; 26.4)]. Boys had a higher average lean mass percentage for both equipment [BodPod: 80.5% (95%CI 79.9; 81.1) and DEXA: 74.6% (95%CI 74.1; 75.2)]. Children classified as obese, according to BMI-for-age z-score, had a higher average fat mass percentage (DEXA: 37.2% and BodPod: 34.5%), and this mean was higher among girls. The FM% was higher among girls and LM% among boys. Classifications of body composition in children are needed.