Department of Endocrinology and Metabolism, Peninsula College of Medicine and Dentistry, Plymouth Campus, Plymouth, UK.
Int J Obes (Lond). 2011 Apr;35(4):541-7. doi: 10.1038/ijo.2010.258. Epub 2011 Feb 8.
Several studies suggest that taller children may be wrongly labelled as 'overweight' because body mass index (BMI) is not independent of height (Ht) in childhood, and recommend adjustment to render the index Ht independent. We used objective measures of %body fat and hormonal/metabolic markers of fatness to investigate whether BMI and the corresponding fat mass index (FMI) mislead in childhood, or whether taller children really are fatter.
Longitudinal observational study measuring children annually from age 7 to 12 years.
Two hundred and eighty healthy children (56% boys) from the EarlyBird study.
BMI (body mass (BM)/Ht(2)), FMI (fat mass (FM)/Ht(2)), %body fat ((FM/BM) × 100, where FM was measured by dual-energy X-ray absorptiometry), fasting leptin (a hormonal measure of body fatness) and insulin resistance (a metabolic marker derived from the validated homeostasis model assessment program for insulin resistance--HOMA2-IR) were all analysed in relation to Ht. Alternative Ht-independent indices of BM and FM were compared with BMI and FMI as indicators of true fatness and related health risk.
BMI and FMI correlated with Ht at each annual time point (r0.47 and 0.46, respectively), yet these correlations were similar in strength to those between Ht and %fat (r0.47), leptin (r0.41) and insulin resistance (r0.40). Also, children who grew the most between 7 and 12 years showed greater increases in BMI, FMI, leptin and insulin resistance (tertile 1 vs 3, all p<0.05). BMI and FMI explained ~20% more of the variation in %fat, ~15% more in leptin and ~10% more in insulin resistance than the respective Ht-independent reformulations (BM/Ht(3.5) and FM/Ht(7), both p<0.001).
Taller children really are fatter than their shorter peers, have higher leptin levels and are more insulin resistant. Attempts to render indices of BM or FM independent of Ht in children seem inappropriate if the object of the index is to convey health risk.
有几项研究表明，由于儿童时期的体重指数（BMI）与身高（Ht）不独立，较高的儿童可能会被错误地标记为“超重”，并建议进行调整以使指数与身高无关。我们使用客观的体脂百分比和脂肪相关的激素/代谢标志物来研究儿童时期 BMI 和相应的脂肪质量指数（FMI）是否会产生误导，或者高个子儿童是否真的更胖。
从 7 岁到 12 岁每年对 280 名健康儿童（56%为男孩）进行纵向观察研究。
来自早期鸟类研究的 280 名健康儿童（56%为男孩）。
BMI（体重（BM）/Ht(2)）、FMI（脂肪量（FM）/Ht(2)）、体脂百分比（（FM/BM）×100，其中 FM 通过双能 X 射线吸收法测量）、空腹瘦素（一种衡量体脂的激素）和胰岛素抵抗（一种源自验证的稳态模型评估胰岛素抵抗的代谢标志物- HOMA2-IR）均与 Ht 相关进行分析。比较了替代的与身高无关的 BM 和 FM 指数与 BMI 和 FMI 作为真实脂肪含量和相关健康风险的指标。
在每个年度时间点，BMI 和 FMI 与 Ht 相关（r0.47 和 0.46），但这些相关性与 Ht 与体脂百分比（r0.47）、瘦素（r0.41）和胰岛素抵抗（r0.40）之间的相关性相似。此外，7 岁至 12 岁期间生长最快的儿童，BMI、FMI、瘦素和胰岛素抵抗的增加幅度更大（三分位 1 与 3 相比，均为 p<0.05）。BMI 和 FMI 比各自的与身高无关的重构体（BM/Ht(3.5)和 FM/Ht(7)，均为 p<0.001）能更好地解释体脂百分比、瘦素和胰岛素抵抗变化的20%、15%和~10%。
高个子儿童确实比矮个子儿童更胖，瘦素水平更高，胰岛素抵抗更强。如果 BMI 或 FM 指数的目的是传达健康风险，那么试图使这些指数与身高无关可能是不合适的。
