Study On Correlation Between BMI,Waist Circumference And Physical Fitness Index Of Children And Adolescents

ObjectsIn recent decades,the tremendous changes in lifestyle have led to the emergence of social and public health problems such as excessive nutrition intake,inadequate physical activity and increased sedentary time,resulting in an increase in the incidence of abnormal body composition among children and adolescents in China,which is mainly manifested in the detection rate of overweight and obesity,especially the detection rate of "central obesity" has shown a rapid upward trend.Most studies on the relationship between body composition and physical fitness use body mass index(BMI)to determine body composition,and then explore the relationship between body composition and physical fitness.However,BMI indicators reflect the body fat status of individuals,and it is difficult to objectively reflect the relationship between the two.Compared with BMI,waist circumference(WC)can more scientifically reflect the accumulation of visceral fat in children and adolescents,and it is more objective to judge "central obesity".Based on this,this study used BMI and WC to determine the body composition of children and adolescents,and explored the relationship between BMI,WC and physical fitness index(PFI)respectively.On this basis,the effects of "central obesity" and "peripheral obesity" on physical fitness index were analyzed in depth.The purpose of this study is to explore the relationship between BMI,waist circumference and physical fitness index of Chinese children and adolescents,so as to provide scientific basis and theoretical basis for improving the nutritional and physical fitness status of Chinese children and adolescents.MethodsAccording to the division of administrative regions in China,the researchers adopted the method of ?stratified cluster random sampling?from 2015 to 2016 to select some cities in various administrative districts(northeast,north,northwest,southwest,central and south,East China).In each age group of students aged 7-18 years in each city,about 100 boys and girls were randomly selected,a total of 13582 students were selected as the research objects.The percentile distribution characteristics of body mass index,waist circumference and physical fitness index of children and adolescents were constructed by LMS method;the physical fitness index of children and adolescents was calculated by Z-score method and analyzed by radar chart;the dose-effect relationship between BMI-Z grouping,WC-Z score,different obesity types and physical fitness was explored by logistic multivariate regression method;and the linear regression method was used to construct different body composition and physical fitness of exponential regression equation.Results(1)The basic characteristics of BMI,WC and PFI:(1)The percentile values of BMI and WC of children and adolescents increase with age.The mean BMI and WC of boys ranged from 16.36 to 20.91 kg/m2 and 54.34 to 74.39 cm respectively,while those of girls ranged from 16.37 to 20.29 kg/m2 and 53.69 to 67.34 cm,respectively.PFI P50 values of boys and girls and adolescents were between-0.26~0.28 and-0.31~-0.21,respectively.(2)Detection rates of BMI and WC grouping: The detection rates of overweight and obesity of boys and girls were 14.95% and 11.38%,9.35% and 7.03%,respectively.The detection rates of normal waist circumference,normal high waist circumference and high waist circumference were 61.71%,19.44% and 18.85% for boys and 65.28%,17.94% and 16.78% for girls respectively.(3)The detection rates of different obesity types were 77.53% and 22.47% for boys and 74.23% and 25.77% for girls.(2)Comparison of PFI in different body composition assessment groups:(1)On the general level,the PFI of boys in lean,normal,overweight and obese groups were-0.50,0.33,-0.20 and-1.02,while that of girls were-0.46,-0.01,-0.29 and-0.54,respectively.There were significant differences in different nutritional status(P < 0.05).(2)On the whole,the PFI values of boys in normal waist circumference,normal high waist circumference and high waist circumference groups were 0.11,0.23 and-0.60,respectively,and those of girls were-0.06,-0.01 and-0.44,respectively.There was statistical significance in different waist circumference(P < 0.05).(3)On the whole,the PFI values of male central obesity and peripheral obesity were-1.13 and-0.61,respectively,and that of female students were-0.79 and 0.24.There was statistical significance in different obesity status(P < 0.05).(3)Comparison of different BMI-Z and WC-Z:(1)Compared with BMI-Z grouping,F-values of boys,girls and the whole group were 10.266,1.821 and 9.486,respectively,with statistical significance between different genders and the whole group(P<0.05);(2)Compared with WC-Z grouping,F-values of boys,girls and the whole group were 11.247,4.385,13.466,respectively.There was statistical agreement between different genders and the whole group.Meaning(P < 0.05).(4)Comprehensive evaluation of various physical fitness indicators:(1)Comprehensive evaluation values of physical fitness at different BMI levels: the comprehensive evaluation values of thin,normal,overweight and obese boys were 0.9556,0.9952,0.9598 and 0.8840,and girls were0.9559?0.9955?0.9675 and 0.9070,respectively;(2)Comprehensive evaluation values of physical fitness at different WC levels: normal or low waist circumference,normal waist height and high waist circumference for boys were 0.9959?0.9780?0.9719,respectively,0.9943,0.9912 and 0.9815 for girls respectively.(3)The comprehensive evaluation values of central obesity and peripheral obesity for boys were 0.9417,0.9948,0.9721 and 0.9922 for girls,respectively.(5)Logistic regression analysis of the correlation between different body components and physical performance:(1)With obesity as the reference,the detection rate of high-grade PFI in normal group and overweight group was 1.208 and 1.13 times(P < 0.05);(2)With high waist circumference as the reference,the detection rate of high-grade PFI in normal waist circumference was 1.148 times(P < 0.05);3.With central obesity as the reference,the detection rate of high-grade PFI in peripheral obesity group was 1.148 times(P < 0.05).192 times(P < 0.05).Conclusions(1)With BMI as the evaluation benchmark,the physical fitness index of obese children and adolescents is the worst;with WC as the evaluation benchmark,the physical fitness index of high waist circumference children and adolescents is the worst;compared with the peripheral obese group,the physical fitness index of central obese children and adolescents is worse.(2)Obesity(especially central obesity)is a risk factor of high-level physical fitness index in children and adolescents.