Centiles for energy costs of tissue deposition in infancy, childhood and adolescence: calculations based on reanalysis of UK body composition reference data.

BACKGROUND: The World Health Organization (WHO) recommends that pediatric energy requirements be estimated as the sum of total energy expenditure and the energy content of tissue deposited through growth. WHO growth estimates for children aged 2+ years are based on an assumed 2 kcal/g tissue gained, and do not address age or sex variability in the composition of accreted tissue. We revisited growth costs using objective body composition data. METHODS: We conducted secondary data analysis of UK reference data. Using seven centiles for fat-free mass and fat mass, we calculated fat and protein deposition rates and their energy costs. We generated new centiles for total body energy content from body composition data, where velocities indicate total growth energy costs. Median values were compared with WHO reference values. RESULTS: Compared to WHO values, the median UK child deposits more energy in infancy, and through childhood from 2 years in females. Median protein deposition declines through infancy before rising in adolescence, peaking at 12 years (females) and 14 years (males). Median fat deposition declines through infancy and is relatively constant in both sexes through childhood, though higher centiles differ by sex. UK children have higher median growth costs than WHO values for males in late infancy and for females at most ages. Older children, measured more recently (2001-2010), had greater adiposity and growth costs than younger children (1987-1996). Individual children showed a degree of trade-off between fat and protein deposition. CONCLUSIONS: We provide new centiles for total energy costs of growth, and for fat and protein accretion rates and costs. Growth energy requirements in UK children, especially females, differ from WHO values, due primarily to greater fat deposition in more recent cohorts. Our approach may be applied to other centile data, to improve understanding of variability in growth costs across populations and time periods.