Objective: To describe the distribution of fat-free mass (FFM) and fat-free mass index (FFMI) in children aged 3-17 years in China. Methods: Data were collected from National Nutrition and Health Systematic Survey in 0-18 years old children in China. By using multi-stage stratified randomized cluster sampling method, the project was conducted in 28 survey points in urban and rural areas in 14 provinces (autonomous regions and municipalities) in 7 regions in China from 2019 to 2021. FFM was measured using bioelectrical impedance meter. Finally, the body composition data of 70 853 children were included in the analysis. M (Q1, Q3) was used to describe the gender and age specific FFM and FFMI of the children in different regions. Kruskal-Wallis H rank sum test was used to compare FFM and FFMI of boys and girls in same age group, boys in different age groups, girls in different age groups, as well as boys in same age group and girls in same age group in different regions. DSCF method was used for pairwise comparisons. Results: After the age of 11 years, the difference of FFMI between boys and girls increased year by year. The FFMI was 14.2 kg/m2 in boys and 13.8 kg/m2 in girls at 11 years old, the difference was significant (χ2=135.86, P<0.001). The difference of FFMI between boys and girls exceed 1.0 kg/m2 from 12 years old, and FFMI was 15.3 kg/m2 in boys and 14.2 kg/m2 in girls at 12 year old, the difference was significant (χ2=597.27, P<0.001). The FFMI was 17.5 kg/m2 in boys and 14.7 kg/m2 in girls at 16 years old, the difference was significant (χ2=2 543.60, P<0.001). The FFMI was higher in boys in northeast China, while the FFMI was lower in both boys and girls in northwest China. Conclusions: Gender specific difference was observed in the increase of FFMI with age. The FFMI was significantly higher in boys than in girls after 11 years old. It is necessary to pay attention to the problem of FFM in children in northeastern and northwestern China.
目的： 描述我国3~17岁儿童去脂体重和去脂体重指数分布特征。 方法： 数据来源于中国0~18岁儿童营养与健康系统调查与应用项目，采用多阶段分层整群随机抽样方法，2019-2021年在全国7个地区、14个省（自治区、直辖市）、城市和农村28个调查点开展调查。利用生物电阻抗仪测定去脂体重，最终儿童70 853人的体成分数据纳入分析。采用M（Q1，Q3）描述不同地区性别、年龄别儿童的去脂体重和去脂体重指数，采用Kruskal-Wallis H秩和检验比较同年龄不同性别、同性别不同年龄、同年龄同性别不同地区儿童去脂体重和去脂体重指数的差异，采用DSCF法进行两两比较。 结果： 11岁后男女童去脂体重指数逐年增大，11岁男女童去脂体重指数分别为14.2 kg/m2和13.8 kg/m2，差异有统计学意义（χ2=135.86，P<0.001）；12岁起，男女童去脂体重指数差异>1.0 kg/m2，12岁男女童去脂体重指数分别为15.3 kg/m2和14.2 kg/m2，差异有统计学意义（χ2=597.27，P<0.001），16岁男女童去脂体重指数分别为17.5 kg/m2和14.7 kg/m2，差异有统计学意义（χ2=2 543.60，P<0.001）。东北地区男童去脂体重指数较高，西北地区男女童去脂体重指数均较低。 结论： 去脂体重指数随年龄增长具有性别差异，11岁后男童去脂体重指数明显高于女童。东北地区和西北地区儿童去脂体重问题需要重点关注。.