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Infant growth and body composition from birth to 24 months: are infants developing the same?
Shane A Norris1,2, Lukhanyo H Nyati3,4, Alexia Murphy-Alford5
1SAMRC Developmental Pathways for Health Research Unit, Department of Pediatrics, University of the Witwatersrand, Johannesburg, South Africa.
Insights
Infant body composition varied significantly across six diverse countries, even among those with ideal length. Factors beyond height-for-age Z-scores influence fat mass in early childhood.
Area of Science:
- Pediatric Nutrition
- Growth and Development
- Body Composition Analysis
Background:
- Infancy is crucial for establishing growth trajectories with long-term health implications.
- Longitudinal body composition in infants across diverse global settings remains under-investigated.
Purpose of the Study:
- To investigate longitudinal body composition in infants from six economically and ethnically diverse countries.
- To assess the influence of height-for-age Z-scores on body composition parameters.
Main Methods:
- Recruited mother-infant dyads using WHO Multicenter Growth Reference Study criteria.
- Measured fat-free mass (FFM), fat mass (FM), fat mass index (FMI), and fat-free mass index (FFMI) from birth to 24 months.
- Computed height-for-age (HAZ), weight-for-age (WAZ), and weight-for-length (WHZ) Z-scores; compared groups based on HAZ.
Main Results:
- Height-for-age Z-scores showed variable performance between 0-6 and 3-24 months.
- Stunting prevalence peaked at 10.3% for boys and 7.8% for girls at 24 months.
- Girls had 10% greater FMI than boys by 24 months; significant FFM and FM differences existed based on HAZ categories.
Conclusions:
- Body composition was heterogeneous among infants with ideal length in a multi-country sample.
- A HAZ close to the WHO standard reduced FFM heterogeneity but not FM, indicating other factors influence adiposity.
Background:
Given the importance of infancy for establishing growth trajectories, with later-life health consequences, we investigated longitudinal body composition among infants from six economically and ethnically diverse countries.
Methods:
We recruited mother-infant dyads using the WHO Multicenter Growth Reference Study criteria. We measured fat-free mass (FFM) in 1393 (49% female) infants from birth to 6 months of age (Australia, India, and South Africa; n = 468), 3-24 months of age (Brazil, Pakistan, South Africa, and Sri Lanka; n = 925), and derived fat mass (FM), fat mass index (FMI), and fat-free mass index (FFMI). Height-for-age (HAZ), weight-for-age (WAZ), and weight-for-length (WHZ) Z-scores were computed. Sex differences were assessed using a t-test, and country differences using a one-way analysis of covariance. We further compared subsamples of children with average (-0.25 > HAZ < +0.25), below-average (≤-0.25) and above-average (≥+0.25) HAZ.
Results:
HAZ performed well between 0 and 6 months, but less so between 3 and 24 months. The stunting prevalence peaked at 10.3% for boys and 7.8% for girls, at 24 months. By 24 months, girls had greater FMI (10%) than boys. There were significant differences in FFM (both sexes in all countries) and FM (Brazilian boys, Pakistani and South African girls) by 24 months of age between infants with average, above-average, and below-average HAZ.
Conclusion:
In a multi-country sample representing more ideal maternal conditions, body composition was heterogeneous even among infants who exhibited ideal length. Having a mean HAZ close to the median of the WHO standard for length reduced FFM between-country heterogeneity but not FM, suggesting that other factors may influence adiposity.
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