Body composition of 4- and 5-year-old New Zealand girls: a DXA study of initial adiposity and subsequent 4-year fat change

BACKGROUND: Dual-energy X-ray information (DXA) quantitating body fat mass and percentage fat in healthy children of preschool age is scarce. Objective: To study the initial variability in body composition and subsequent longitudinal changes in absolute fat mass (kg) and relative adiposity (fat percentage) in a sample of contemporary young New Zealand girls. DESIGN: Cross-sectional study with a longitudinal component. SETTING: University research unit. SUBJECTS: A total of 89 Caucasian girls aged 4-5y were recruited by advertisement at baseline and 4-y changes in body composition were evaluated in 23 of these girls. METHODS: Total body composition was measured by DXA, height and weight by anthropometry. RESULTS: Baseline values for fat mass varied more than values for lean mass or bone mass. Girls from the upper third of our fat percentage distribution (% fat >19.2%) had more than twice the fat mass (5.34 vs 2.31 kg, P < 0.001) of those from the lowest third (% fat < 15.4%). The percentage gain in fat mass over 4y (124 (95% Cl 90-163) also exceeded the percentage gain of lean mass (55 (95% Cl 51-59). In data adjusted for age and height, 63.5% of the variance in percentage body fat at time 2 was explained by fat mass at time one. CONCLUSIONS: In girls, the trajectory of fat gain appears to be established at a young age. Our results support the view that body fatness tracks strongly before puberty. Since preventing the accumulation of excessive fat is preferable to reduction of existing excessive fat stores, it is important to put in place strategies to limit excessive fat gain early in life.