The evaluation of fat-free mass (FFM) in patients with Duchenne muscular dystrophy (DMD) is useful to investigate disease progression and therapeutic efficacy. This study aimed to validate the Bioelectrical impedance (BIA) method compared with the dual-energy X-ray absorptiometry (DXA) for estimating the %FFM in boys with DMD. This is a cross-sectional study performed with children and adolescents diagnosed with DMD. Resistance and reactance were measured with a BIA analyzer, from which eight predictive equations estimated the %FFM. The %FFM was also determined by DXA and its used as a reference method. Pearson correlation test, coefficient of determination, the root-mean-square error, the interclass correlation coefficient, and linear regression analysis were performed between %FFM values obtained by BIA and DXA. The agreement between these values was verified with the Bland-Altman plot analysis. Forty-six boys aged from 5 to 20 years were enrolled in the study. All the equations showed a correlation between the %FFM estimated by BIA and determined by DXA (p < 0.05). The Bland-Altman method indicated that two equations have a significant bias (p < 0.05) and six equations showed no significant bias of %FFM (p > 0.05). However, one of them has high variation and wide limits of agreement. Five of eight %FFM predictive equations tested in DMD were accurate when compared with the DXA. It can be concluded that BIA is a validity method to evaluate patients with DMD.

Anthropometry and body composition evaluation in boys with Duchenne muscular dystrophy (DMD) are challenging, but crucial methods to evaluate the nutritional status, and better anthropometric reference values and body composition predictive equations are needed for this population. Based on these aspects, this study aimed to investigate the hypothesis that changes in anthropometric parameters and body composition of boys with DMD occur according to age. A cross-sectional study with 49 individuals diagnosed with DMD at the neurological outpatient facility at the Onofre Lopes University Hospital in Natal, Brazil, was performed between September 2016 and March 2019. These individuals underwent anthropometric and body composition evaluation. According to age, the participants were divided into four groups:  G1 (2.6 - 8.2y), G2 (8.5 - 10.8y), G3 (11.0 - 14.0y), and G4 (15.9 - 23.0y). The parameters weight-for-age (W/A) (p=0.025), tricipital skinfold (TSF) (p=0.027), adductor pollicis muscle (p=0.041), and corrected arm muscle area (cAMA) (p=0.005) were different among the groups. Regarding anthropometric parameters, was prevalence in the categories of appropriate W/A and a height-for-age (H/A), and eutrophy for body mass index-for-age (BMI/A). For the TSF, there was a higher frequency of severe malnutrition or obesity. The cAMA indicated severe malnutrition in most individuals. As for %FM, high adiposity was more frequent, increasing over age groups (G1 to G4). The boys with DMD presented different patterns of anthropometric and body composition parameters. An increase of fat mass and a decrease of lean mass with age/disease progression were observed.