RESUMO
BACKGROUND/OBJECTIVE: Anthropometry is a simple, inexpensive method of body composition assessment, but its validity has not been examined adequately in young children. The study therefore compared the body composition estimates using anthropometry with those using dual-energy X-ray absorptiometry (DXA) in infants and young children. METHODS: Body composition estimates using anthropometry and DXA were assessed and compared at 6, 12 and 18 months in a cohort of 137 infants enrolled at birth. RESULTS: Fat mass (FM) and body fat percent (%BF) estimates by anthropometry were lower than those using DXA. Mean differences (DXA-skinfold thickness) in FM, fat free mass (FFM) and %BF were highest at 6 months (350 g, -226 g and 4%, respectively); the differences reduced with increase in age and were lowest at 18 months (46 g, 56 g and 0%, respectively). Bland-Altman analyses showed good agreement between the FM, FFM and %BF estimates by the two methods only at 18 months. Accretion of FM and FFM during follow-up, estimated by the two methods, was significantly different, with agreement between the methods seen only for increment in FFM from 6 to 12 months. CONCLUSIONS: Substantial differences were found in the body composition estimates by anthropometry compared with DXA and also in the longitudinally assessed tissue accretion patterns by the two methods. As the body composition patterns may be influenced by the method used for body composition assessment, results of studies assessing body composition by anthropometry during infancy should be interpreted with caution.
