Department of Clinical Medicine, University of Bergen, Bergen, Norway.
Department of Public Health and Primary Care, KU Leuven, University of Leuven, Leuven, Belgium.
Acta Paediatr. 2019 Dec;108(12):2261-2266. doi: 10.1111/apa.14898. Epub 2019 Jul 10.
Body mass index (BMI) metrics are widely used as a proxy for adiposity in children with severe obesity. The BMI expressed as the percentage of a cut-off percentile for overweight or obesity has been proposed as a better alternative than BMI z-scores when monitoring children and adolescents with severe obesity.
Annual changes in BMI, BMI z-score and the percentage above the International Obesity Task Force overweight cut-off (%IOTF-25) were compared with dual-energy X-ray absorptiometry (DXA) derived body fat (%BF-DXA) in 59 children and adolescents with severe obesity.
The change in %BF-DXA was correlated with the change in %IOTF-25 (r = 0.68) and BMI (r = 0.70), and somewhat less with the BMI z-score (r = 0.57). Cohen's Kappa statistic to detect an increase or decrease in %BF-DXA was fair for %IOTF-25 (κ = 0.25; p = 0.04) and BMI (κ = 0.33; p = 0.01), but not for the BMI z-score (κ = 0.08; p = 0.5). The change in BMI was positively biased due to a natural increase with age.
Changes in the BMI metrics included in the study are associated differently with changes in %BF-DXA. The BMI z-score is widely used to monitor changes in adiposity in children and adolescents with severe obesity, but the %IOTF-25 might be a better alternative.
体重指数（BMI）指标广泛用作肥胖儿童肥胖程度的替代指标。与 BMI z 分数相比，将 BMI 表示为超重或肥胖截断百分位数的百分比，被认为是监测严重肥胖儿童和青少年的更好选择。
在 59 名严重肥胖的儿童和青少年中，比较了 BMI、BMI z 分数和超过国际肥胖工作组超重截止值的百分比（%IOTF-25）的年度变化与双能 X 射线吸收法（DXA）测定的体脂肪（%BF-DXA）。
%BF-DXA 的变化与%IOTF-25 的变化（r=0.68）和 BMI 的变化（r=0.70）相关，与 BMI z 分数的变化相关程度稍低（r=0.57）。检测%BF-DXA 增加或减少的 Cohen's Kappa 统计量对于%IOTF-25（κ=0.25；p=0.04）和 BMI（κ=0.33；p=0.01）是公平的，但对于 BMI z 分数则不然（κ=0.08；p=0.5）。BMI 的变化存在正偏差，这是由于其自然随年龄增长而增加。
研究中包含的 BMI 指标的变化与%BF-DXA 的变化相关程度不同。BMI z 分数广泛用于监测严重肥胖儿童和青少年的体脂变化，但%IOTF-25 可能是更好的选择。
