A study led by the University of Queensland analyzed how genetic factors affect body mass index (BMI) in children from age 1 to 18. Published in Nature Communications, the research used data from 6,291 children in the Avon Longitudinal Study of Parents and Children, with 65,930 repeated BMI measurements.
Key Findings
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Common genetic variation explains approximately 25% of BMI variation at different ages and 25% of the variation in BMI change rate from ages 1 to 18.
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Genetic correlation between BMI in infancy and late adolescence is weak, indicating that early body size may not reflect the same biological processes as later BMI.
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BMI around age 10 and overall growth trajectory (rate of change from 1 to 18 years) showed significant genetic links to adult cardiometabolic traits such as type 2 diabetes and cardiovascular disease.
"Genetics explain about 25% of the variation in how a child’s BMI changes over time, but a baby’s size is not strongly linked to their size as a teenager."
Implications
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The findings suggest caution in interpreting infant BMI as a lifelong risk marker for obesity. What drives growth in the first year of life may be biologically different from what drives weight gain in adolescence.
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Growth should be viewed as a trajectory rather than a single measurement in research and clinical settings, with the rate of change—especially around age 10—offering the strongest clues about future cardiometabolic health.
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The study's limitations include a predominantly European ancestry cohort, limiting generalizability to diverse populations, and BMI being an imperfect proxy for adiposity.
Next Steps
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Future research should focus on growth trajectories and key developmental phases to identify children at greater long-term health risk.
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Increased investment in longitudinal child health data collection and method development in Australia is recommended to enable more diverse and robust analyses in the future.