Ortiz-Hernández Luis, López Olmedo Nancy Paulina, Genis Gómez Maricarmen Teresa, Melchor López Dulce Paola, Valdés Flores Jesús
Health Care Department, Universidad Autónoma Metropolitana, Unidad Xochimilco, México City, México.
Ann Nutr Metab. 2008;53(3-4):205-14. doi: 10.1159/000181744. Epub 2008 Dec 11.
The validity of body mass index (BMI)-for-age for obesity diagnosis in Latin-American children may be limited due to observed cases of overweight without obesity (i.e. body fat excess), possibly due to certain physical characteristics. In the current study, we investigated whether the usefulness of BMI-for-age in the diagnosis of obesity among Mexican schoolchildren is modified by height, trunk length, muscle mass, body frame, or waist circumference.
Our study cohort comprised 1,015 schoolchildren (aged 6-11 years) from Mexico City. Obesity diagnostics were derived from three classifications of BMI-for-age: percentiles of BMI according to the references of the Centers of Disease Control (CDC), the National Center for Health Statistics and the International Obesity Task Force. The area under the curve (AUC, through receiver-operating characteristic curves) and optimal cutoff points (by Youden index) of each classification were calculated. Body fat percentage, triceps skinfold thickness and blood pressure were used as standards. AUC and optimal cutoff point analysis were stratified according to height-for-age, sitting height, elbow breadth, arm muscle area (AMA) and waist circumference.
For the general population, the CDC reference had the highest values of AUC (0.94 for triceps skinfold thickness and 0.96 for body fat percentage), and the optimal cutoff point was the 85th percentile. Among schoolchildren with large body frames (measured through elbow breadth) or with high muscle mass (assessed by AMA), the optimal cutoff point was the 95th percentile of the CDC reference.
Our results suggest that the percentile cutoff to define obesity in children with high muscle mass or a large body frame should be the 95th percentile, while the 85th percentile can still be used for the other children.
由于观察到超重但无肥胖（即体脂过多）的病例，可能因某些身体特征所致，因此年龄别体重指数（BMI）用于拉丁美洲儿童肥胖诊断的有效性可能有限。在本研究中，我们调查了年龄别BMI在诊断墨西哥学龄儿童肥胖时的效用是否会因身高、躯干长度、肌肉量、体格或腰围而改变。
我们的研究队列包括来自墨西哥城的1015名学龄儿童（6至11岁）。肥胖诊断源自年龄别BMI的三种分类：根据疾病控制中心（CDC）、国家卫生统计中心和国际肥胖特别工作组的参考标准得出的BMI百分位数。计算每种分类的曲线下面积（AUC，通过受试者工作特征曲线）和最佳截断点（通过约登指数）。将体脂百分比、肱三头肌皮褶厚度和血压用作标准。根据年龄别身高、坐高、肘宽、上臂肌肉面积（AMA）和腰围对AUC和最佳截断点分析进行分层。
对于一般人群，CDC参考标准的AUC值最高（肱三头肌皮褶厚度为0.94，体脂百分比为0.96），最佳截断点为第85百分位数。在体格较大（通过肘宽测量）或肌肉量较高（通过AMA评估）的学龄儿童中，最佳截断点为CDC参考标准的第95百分位数。
我们的结果表明，对于肌肉量高或体格大的儿童，定义肥胖的百分位数截断点应为第95百分位数，而第85百分位数仍可用于其他儿童。
