Characteristics Of Distribution Of Body Fat Of Chinese Children Aged 6-17 Years Old And Its Influencing Factors

Objective:1.To analyze the distribution characteristics of Body Fat Mass(BFM),Body Fat Percentage(BF%),Fat Mass Index(FMI),and Visceral Fat Area(VFA)among Chinese children aged 6-17 years old by urban and rural,gender and age group,2.To understand the status of BF%among Chinese children aged 6-17 years old by body mass index(BMI)group,and to understand the status of VFA among Chinese children aged 6-17 years old by waist circumference(WC)group.3.To analyze the influencing factors of BF%and VFA among Chinses children aged 6-17 years old,such as living environment(urban versus rural),age,pubertal onset timing,energy intake,moderate to high intensity physical activity level(MVPA),sedentary behavior,leisure-time sedentary behavior,sleep duration,parent BMI,and family income.To provide scientific data support for the physical health and prevention of overweight and obesity for Chinese children aged 6-17 years old.Methods:Using multi-stage stratified cluster random sampling method,at 28 survey sites in 14 provinces of 7 regions including East China,North China,Central China,South China,Southwest China,Northwest China,and Northeast China.Using bioelectrical impedance analysis(Biospace,Inbody 770)to measure the body fat of Chinese children aged 6-17 years old,and using uniform devices to measure the height,weight,and waist circumference of students.We designed and conducted multiple types of surveys to capture health-related variables from students regarding demographic characteristics,Tanner stage,diet,physical activity,sedentary behavior,sleep duration,parent BMI,and family income.Data were derived from the survey database as of February 1,2021,where a total of 15,993 children aged 6-17 years and above with complete information on body composition and anthropometric measurements were included to analyze the distribution characteristics of body fat.4,475 children with complete information on diet and physical activity were used to analyze the influencing factors of body fat.SAS 9.4 and SPSS 25 were used for data cleaning and analysis.Quantile Regression model was used to analyze the influencing factors of children’s body fat Percentage and visceral fat area.Results:1.Distribution characteristics of body fat of children aged 6-17 yearsThe median BFM(kg)of boys aged 6-17 years were 4.05,4.90,6.50,8.10,9.80,11.85,10.00,9.00,9.45,10.20,11.40,11.90,respectively.The median BFM(kg)of girls aged 6-17 years were 4.00,5.00,6.10,7.40,8.20,10.40,12.00,13.70,14.90,16.10,16.70,16.90,respectively.According to living environment,gender,and age group,BFM in boys increased significantly between 6-11 years old and decreased slightly afterwards,and increased with age after 13 years old.BFM in girls increased with age.Meanwhile,BFM in boys was higher than that in girls at every quantile between 8-11 years old,and the BFM in girls was higher than that in boys at the 25th to 75th percentiles between 12-17 years old.In general,the median BFM of urban children was higher than rural children in every age group.The median BF%(%)of boys aged 6-17 years were 18.10,19.50,22.05,24.25,25.40,26.25%,20.70,17.90,16.85,17.25,18.15,18.60,respectively.The median BF%(%)of girls aged 6-17 years were 18.80,20.30,22.30,23.80,23.00,24.30,26.40,28.15,29.60,30.40,31.30,31.60,respectively.According to area,gender,and age group,BF%in boys steadily increased between 6-11 years old and decreased with age after 12 years old.BF%in girls increased with age.Meanwhile,BF%in boys were higher than that in girls at the 25th to 90th percentiles between 10-11 years old,and the BF%in girls were higher than that in boys at every quantile between 12-17 years old.In general,the median BF%of urban children was higher than rural children in every age group.The median FMI(kg/m2)of boys aged 6-17 years were 2.80,3.20,3.70,4.30,4.70,5.10,4.00,3.40,3.30,3.50,3.80,4.00,respectively.The median FMI(kg/m2)of girls aged 6-17 years were 2.80,3.20,3.60,3.90,3.90,4.50,5.10,5.50,5.80,6.20,6.50,6.70,respectively.According to living environment,gender,and age group,FMI in boys steadily increased between 6-11 years old,then decreased and remained stable.FMI in girls increased with age.Meanwhile,FMI in boys were higher than that in girls between 9-11 years old,and the FMI in girls were higher than that in boys at all percentiles between 12-17 years old.In general,the median FMI of urban children was higher than rural children in every age group.The median VFA(cm2)of boys aged 6-17 years were 17.65,20.50,25.60,32.00,37.60,45.65,41.25,36.80,37.15,41.65,45.65,47.35,respectively.The median VFA(cm2)of girls aged 6-17 years were 17.50,20.80,25.60,30.70,34.60,43.90,49.30,55.60,60.80,67.10,70.85,72.10,respectively.According to living environment,gender,and age group,VFA in boys and girls all increased with age.Meanwhile,VFA in girls were higher than that in boys at all percentiles between 12-17 years old.In general,the median FMI of urban boys was higher than rural boys in every age group besides 9 years old at the 90th percentile.The median FMI of urban girls was higher than rural girls in every age group.2.Distribution characteristics of body fat in children aged 6-17 years by BMI and WCAccording to BMI,gender,and age group,the median BF%increased from 16.40%to 17.00%in normal weight boys;increased from 17.60%to 30.40%in normal weight girls;increased from 21.10%to 26.00%in overweight boys;increased from 24.70%to 37.70%in overweight girls;increased from 31.85%to 33.55%in obesity boys;increased from 31.75%to 43.40%in obesity girls.The BF%kernel density curves of overweight are located between the curves of normal weight and of obesity in each age group.BF%in boys steadily increased and decreased slightly,and remained stable with age after 11 years old in every BMI group.BF%in girls increased with age in every BMI group.Meanwhile,BF%in normal weight and overweight girls were higher than that in boys at every quantile,while BF%in obesity boys was higher than that in girls in 11 years old at all quantiles.Differences on BF%were getting greater between boys and girls in the 12 years old group and above.According to WC,gender,and age group,the median VFA increased from 17.10 cm2 to 37.80 cm2 in normal WC boys,and increased from 17.00 cm2 to 66.20 cm2 in normal WC girls,and increased from 56.70 cm2 to 103.40 cm2 in central obesity boys,and increased from 42.10 cm2 to 140.60 cm2 in central obesity girls.The VFA kernel density curves of central obesity are located on the right side of the normal WC in each age group.VFA in normal WC girls were higher than that in normal WC boys at all percentiles,and the differences on VFA were getting bigger between boys and girls in the 13 years group and above.VFA in central obesity girls were higher than that in central obesity boys between 12-17 years at all quantiles,and the differences on VFA were getting larger between boys and girls in the 12 years group and above.3.Influencing factors of body fat of children aged 6-17 by BMI and WC3.1 Body Fat PercentageThe coefficients estimated by quantile regression analyses were negative between age and BF%at the 10th,25th,50th,and 75th percentiles for normal-weight boys.Pubertal timing was negatively associated with boys’ BF%,and its influence was gradually increasing.MVPA was negatively associated with boys’ BF%in high percentiles(P50 and P75).Parental BMI was positively associated with BF%of boys and girls,and the influence was gradually increasing.Pubertal timing and age had a positive association with girls’ BF%at all percentiles.The coefficients estimated by quantile regression analyses were negative between age and BF%for overweight boys,while were positive for girls.Sedentary behavior,leisure-time sedentary behavior had a positive association with boys at the 25th and 90th percentiles of the BF%.The coefficients were negative between energy intake and BF%at 90th percentiles for overweight girls,while MVPA,sedentary behavior,and sleep duration had a positive association with girls’ BF%at low percentiles.The coefficients were positive between father’ s BMI and BF%for overweight boys at low percentiles,while were negative for girls at high percentile.Mother’ s BMI had a negative association with boys’ BF%at the 50th percentile,while had a positive association with girls’BF%at the 25th percentile.The coefficients estimated by quantile regression analyses were negative between age and BF%at all percentiles for obesity boys,while were positive for girls.The coefficients were negative between pubertal timing and BF%at high percentile.Negative coefficients were found in energy intake and boys’ BF%.3.2 Visceral Fat AreaThe coefficients estimated by quantile regression analyses were negative between living environment and VFA at low percentile for normal WC boys and girls.The coefficients were positive between age and VFA at all percentile for boys and girls and between parents’ BMI and VFA at 25th to 75th percentiles and its influence was gradually increasing.Family income had a negative association with girls’VFA at high percentiles and its influence was gradually increasing.The coefficients estimated by quantile regression analyses were negative between MVPA and VFA at low percentiles for central obesity boys.Parents’ BMI and energy intake had a positive association with boys at different percentiles.Age and mother’s BMI had a positive association with girls at all percentiles,and pubertal timing had a positive association with girls at the 25th percentile.Conclusion:Body fat mass,body fat percentage fat mass index,and visceral fat area among Chinese children aged 6-17 years old were influenced by living environment,gender,and age group.For most age groups,body fat of urban children was higher than rural children.Body fat in boys increased significantly between 6-11 years old,and remained stable or decreased slightly with age after 11 years old.While body fat in girls increased with age,and the differences on body fat were getting greater between boys and girls in the 12 years old group and above.The median BF%of overweight children was between normal weight and obesity.For most age groups,the BF%of normal-weight and overweight girls were higher than that of boys,while the BF%of obesity boys were higher than that of girls in 11 years old.In addition,the median VFA of central obesity children was higher than that of normal WC.The VFA of normal WC of girls was higher than that of boys,while central obesity of boys was higher than girls at 6-11 years old.Pubertal timing were important factors affecting the body fat of children aged 6-17 years old.Innovation and limitations:For the first time,to analyze the distribution characteristics of BFM,BF%,FMI,and VFA among Chinese children aged 6-17 years old.Using,better robustness model,the Quantile Regression model to analyze influencing factors of BF%and VFA,including diet,physical activity,sedentary behavior,family factors.For the first time,the influence of pubertal timing on children’s BF%and VFA was considered.In this study,dietary factors only considered energy intake,so the effects of dietary factors on children’s body fat have not been fully explored.It is recommended to analyze the effects of macronutrient intake and dietary energy sources.