[Developmental characteristics on body composition in Chinese urban children and adolescents aged 3-17 years old].

Objective: To describe the body composition related developmental characteristics in Chinese children and adolescents aged 3-17 years. Methods: Data were obtained from the 'China Child and Adolescent Cardiovascular Health (CCACH) cross-sectional survey' in 2015, which including seven cities. Questionnaire survey, anthropometric measurements were carried out with body composition also measured, using the Hologic Discovery Dual Energy X-ray Absorptiometry (DXA) scanner. BMI, fat mass percentage (FMP), fat mass index (FMI) and fat free mass index (FFMI) were calculated. SAS 9.4 and SPSS 20.0 softwares were used for data analysis. Results: A total of 10 867 participants aged 3-17 years were involved in this study, including 5 512 boys (50.7%). FMP in boys decreased obviously between 10-15 years old[β=-1.811 (95%CI: -1.987 - -1.635)]. FMP in girls decreased between 3-7 years old[β=-0.896 (95%CI: -1.100 - -0.691)] and increased obviously between 12-15 years old [β=0.989 (95%CI: 0.753-1.224)]. In general, FMP in girls were higher than that in boys in every age group, except for the 9 and 10 years old groups ( all P<0.05). FFMI of boys was higher than that in girls at all ages. Differences on FFMI were getting bigger between boys and girls in the 11 years old group and above. FMI increased with age [boys: β=0.033 (95%CI: 0.018-0.048); girls: β=0.192 (95%CI: 0.181-0.204)] and intersected between genders. Adiposity rebound age was earlier in the obese group than that in both overweight and normal weight groups. FMI in normal weight boys decreased with age and remained lower than 5 kg/m(2), while FMI in overweight [β=0.114 (95%CI: 0.091-0.136)] and obese [β=0.211 (95%CI: 0.176-0.245)] boys increased with age. FMP in boys decreased with age from 10 years old in all weight status groups [normal weight: β=-0.836 (95%CI: -0.924 - -0.748); overweight: β=-1.090 (95%CI: -1.269 - -0.910); obese: β=-1.144 (95%CI: -1.321- -0.967)]. BMI, FFMI, FMI in girls changed with age similarly in all weight status groups and increased from 8 years old[normal weight: β=0.174 (95%CI: 0.165- 0.182); overweight: β=0.325 (95%CI: 0.304-0.346); obesity: β=0.447 (95%CI: 0.406-0.488)]. Changes in FMP in girls increased significantly with age after 12 years old [normal weight: β=0.963 (95%CI: 0.851-1.074); overweight: β=0.910 (95%CI: 0.695-1.125); obesity: β=0.895 (95%CI: 0.569-1.221)]. In total, correlation indexes of BMI and FMI were strong (boys: r=0.767; girls: r=0.873) and were different in various weight status groups. Conclusions: The growth chart of BMI presented inconsistently with the different developmental characteristics of body fat, and gender. Measurement on body composition needs to be developed for children and adolescents to give more precisely assessment on growth and development of children.目的： 描述3～17岁儿童青少年体成分（脂肪组织、非脂肪组织）的发育特征。 方法： 采用分层整群抽样方法，分别抽取南方和北方共计7个城市，包括长春、北京、天津、济南、上海、银川、重庆的3～17岁城市汉族儿童青少年10 867例。采用问卷调查收集研究对象基本信息，测量身高、体重，采用双能X线吸收法（DXA）测量身体脂肪组织质量、非脂肪组织质量等。计算BMI、体脂含量百分比（FMP）、脂肪质量指数（FMI）、非脂肪组织质量指数（FFMI）。采用SAS 9.4软件进行数据整理和逻辑核查，采用SPSS 20.0软件进行统计学分析。 结果： 共收集10 867例3～17岁儿童青少年数据，其中男生5 512人（50.7%）。男生FMP在10～15岁组随年龄增长迅速下降[β＝-1.811（95%CI：-1.987～-1.635）]，15岁以后变化不明显；女生FMP在3～7岁组随年龄增长呈下降趋势[β＝-0.896（95%CI：-1.100～-0.691）]，7～12岁变化不明显，12～15岁随年龄增长增速明显[β＝0.989（95%CI：0.753～1.224）]，15岁以后变化不明显。除9岁组和10岁组以外，女生FMP高于男生（均P<0.05）。男生FFMI在3～17岁各个年龄段均明显高于女生（均P<0.05），11岁以后，女生和男生的FFMI差异变大。男生和女生的FMI随年龄变化的生长曲线有交叉，略有随年龄增长而增加的趋势[男生：β＝0.033（95%CI：0.018～0.048）；女生：β＝0.192（95%CI：0.181～0.204）]。脂肪重聚年龄肥胖组小于超重组和正常体重组；男生不同体重状态组BMI、FFMI随年龄变化情况类似；男生正常体重组FMI随年龄增长略有降低，一直保持在5 kg/m(2)以下，超重组[β＝0.114（95%CI：0.091～0.136）]和肥胖组[β＝0.211（95%CI：0.176～0.245）]的FMI有明显随年龄增长而增加的趋势；不同体重状态组男生FMP在10岁以后随年龄增长呈下降趋势[正常体重：β＝-0.836（95%CI：-0.924～-0.748）；超重：β＝-1.090（95%CI：-1.269～-0.910）；肥胖：β＝-1.144（95%CI：-1.321～-0.967）]；不同体重状态组女生的BMI、FFMI、FMI随年龄变化情况类似，在8岁以后呈现随年龄增长而上升的趋势[正常体重组：β＝0.174（95%CI：0.165～0.182）；超重组：β＝0.325（95%CI：0.304～0.346）；肥胖组：β＝0.447（95%CI：0.406～0.488）]；女生FMP的变化12岁以后随年龄增长呈明显增加的趋势[正常体重组：β＝0.963（95%CI：0.851～1.074）；超重组：β＝0.910（95%CI：0.695～1.125）；肥胖组：β＝0.895（95%CI：0.569～1.221）]。总体上来看，BMI和FMI的相关性很强（男生：r＝0.767；女生：r＝0.873），不同体重状态儿童青少年BMI和FMI的r不同。 结论： 儿童脂肪组织和非脂肪组织发育特征不同，且存在性别差异。BMI生长曲线和体脂肪的发育特征不完全一致，且存在性别差异，有必要对生长发育中的儿童进行更精准的体成分评估。.