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Body composition from birth to 6 mo of age in Ethiopian infants: reference data obtained by air-displacement plethysmography.

BACKGROUND
Data on body composition in infancy may improve the understanding of the relation between variability in fetal and infant growth and disease risk through the life course. Although new assessment techniques have recently become available, body composition is rarely described in infants from low-income settings.


OBJECTIVE
The aim of this study was to provide reference data for fat mass (FM) and fat-free mass (FFM) from birth to the age of 6 mo from an urban African population.


DESIGN
We conducted a prospective cohort study among infants from Jimma, Ethiopia. FM and FFM were measured at birth and at 1.5, 2.5, 3.5, 4.5, and 6 mo of age with air-displacement plethysmography (ADP) validated against a stable isotope method in a subsample. Reference charts and reference tables with z scores and percentiles for FM, FFM, FM index (FMI; in kg/m(2)), and FFM index (FFMI: in kg/m(2)) were constructed with the lambda-mu-sigma method.


RESULTS
Body composition growth charts were based on a total of 2026 measurements of body composition obtained from 378 infants. FM and FMI gain progressed in a logarithmic-shaped curve and variation increased with increasing age, whereas FFM increased in an almost linear manner with a minor deceleration at around 3 mo of age. The FFMI curve showed a very modest exponential increase with age.


CONCLUSIONS
By presenting z scores and centile reference charts for an apparently healthy urban Ethiopian infant population, this study represents a first step toward providing reference data on FM and FFM for an urban African context, which is important for future clinical care and research. This study was registered at www.controlled-trials.com as ISRCTN46718296.