[Influence of diet behaviors on height among children and adolescents in China: a multiple level analysis].

OBJECTIVE: To categorize growth and development stages among children and adolescents based on height, and to explore the influences of diet behaviors on height during different growth and development stages. METHODS: Children and adolescents (7 to 18 years) with normal weights were selected using "Reference Norm for Screening Overweight and Obesity in Chinese Child and Adolescent" set up by WGOC in 2003 and "Reference Norm for Screening Underweight in Chinese Child and Adolescent" from the "2010 National Physical Fitness and Health Surveillance" data, and the variables of height and diet behaviors sorted. The growth and development stages were categorized using the hierachical cluster analysis, and the multilevel model was used to analyze influences of diet behaviors on height at different growth and development stages. RESULTS: Basis on height, there were 4 growth and development stages among the children and adolescents. In the boys, growth and development stages included Pre-GSS (growth spurt stage, GSS) including 7 to 10 years, GSS (11 to 12 years), Post-GSS (13 to 14 years), and growth stability stage (15 to 18 years); in the girls, the stages included the fast velocity GS (growth stage, GS) including 7 to 10 years, GS (11 to 12 years), Post-GS (13 to 15 years), and growth stability stage (16 to 18 years). The results of the multilevel model showed that the students' height in the urban areas were higher than in the rural areas (P<0.01), and the trend of difference between the urban and rural areas with the different growth stages was a parabola shape, the highest differences were 3.36 cm and 3.23 cm in the GSS and the fast velocity GS, respectively. There were significant influences of breakfast on height during the Pre-GSS and the fast velocity GS (P<0.01), and increased 0.40 cm and 0.57 cm, respectively. Excluding the stablility growth stage in the girls, drinking milk increased significantly height during the different growth stages (P<0.01), and the increases were gradual downtrend with the growth stages, the highest increase was 0.91 cm and 0.94 cm in Pre-GSS and the fast velocity GS, respectively. Eating eggs increased significantly height during all the growth stages (P<0.01), and the increases were the gradual uptrend with different growth stages. There were interaction effects among breakfast, drinking milk and eating eggs during the different growth stages, which was the gradual downtrend. CONCLUSION: Breakfast and drinking milk are conducive to growth during early adolescence, and the effect of eating eggs on growth is gradual uptrend with different growth stages.

[The association between body mass index, waist circumference with body fat percent, and abdominal fat rate in overweight and obese pupils].

OBJECTIVE: To study the association between body mass index(BMI), waist circumference (WC) with body fat percent, and abdominal fat rate in overweight and obese pupils. METHODS: Using convenience sampling, two primary schools of Dongcheng district in Beijing were selected in May 2010. A total of 162 overweight and obese pupils graded from 2 to 5 who met the criteria of overweight and obese were recruited based on the physical exam record of the school medical department in April. Their physical measurements were taken to measure body fat percent (PBF), abdominal fat rate and visceral fat level and BMI was calculated.Independent-sample t test and Wilcoxon rank sum test were applied to analyze the gender differences. Correlation analysis was used to explore the association between the indexes of fat distribution (PBF, abdominal fat rate and visceral fat level) and BMI and WC.Univariate regression analysis was conducted to determine the variance of three indexes of fat distribution explained by the independent variables. RESULTS: The PBF of overweight and obese pupils was (43.62 ± 2.98) %, the abdominal fat rate of them was (28.06 ± 6.02)%, the visceral fat level of them was 7.51 ± 3.43, BMI was (23.41 ± 2.83) kg/m(2). WC, PBF and abdominal fat rate were (78.57 ± 7.76) cm, (42.36 ± 2.56) % and (26.47 ± 5.39) % in boys and (73.34 ± 7.22) cm, (45.88 ± 2.26) %, (30.92 ± 6.07) % in girls. The difference in gender was significant (t values were -4.218, 8.751, 4.811, respectively, all P values <0.01). The visceral fat level of boys and girls were 8.86 ± 3.42 and 5.09 ± 1.70, with significant difference (Z = -7.08, P < 0.01). The correlation between PBF and BMI and the variance of PBF explained by BMI (r = 0.563, R(2) = 31.7%) were stronger than them with WC (r = 0.402, R(2) = 16.1%) (P < 0.01). The correlation between visceral fat levels and WC and the variance of visceral fat level explained by WC (r = 0.723, R(2) = 57.3%) were higher than them with BMI (r = 0.621, R(2) = 41.7%) (P < 0.01). CONCLUSION: The correlation and prediction ability of BMI and body fat percent were stronger than WC, while the correlation and prediction ability of WC and visceral fat were higher than BMI.

Trends in blood pressure and body mass index among Chinese children and adolescents from 2005 to 2010.

BACKGROUND: The prevalence of obesity, based on body mass index (BMI), among Chinese children and adolescents has increased for decades, but the relationship between trends in blood pressure (BP) and increasing BMI has not been studied. METHODS: BMI and BP measurements of 391,982 children aged 7-17 years were obtained from surveys in 2005 and 2010. The mean change and 95% confidence intervals (CIs) of BP were calculated, and the association between BMI and BP was assessed by using analysis of covariance and direct adjustment with the BMI distribution of 2005 survey. RESULTS: The mean systolic BP (SBP) and diastolic BP (DBP) increased 1.5 mm Hg (95% CI = 1.4-1.7 mm Hg) and 1.1 mm Hg (95%CI = 1.1-1.2 mm Hg) for boys and 1.2 mm Hg (95% CI = 1.1-1.3 mm Hg) and 1.0 mm Hg (95% CI = 1.0-1.1 mm Hg) for girls from 2005 to 2010, respectively. After adjustment for BMI, SBP and DBP in 2010 were 0.8mm Hg (95% CI = 0.8-0.9mm Hg) and 0.8mm Hg (95% CI = 0.7-0.8mm Hg) higher than in 2005, respectively (all P < 0.01). With adjustment for difference in BMI distribution in 2005 and 2010, the mean increase of SBP decreased by 40.5% and that of DBP by 26.9%. CONCLUSIONS: BP among Chinese children and adolescents was on the rise from 2005 to 2010, which was consistent with the hypothesis that the rise in BP was in part attributable to the rise in BMI.