Objective: To explore the relative importance of different food attributes and levels in food decision making of school aged children, and to understand their meal preferences, so as to provide the evidence for formulating precise intervention strategies for dietary behaviours of school aged children. Methods: From May to June 2024, a total of 854 children aged 11 to 15 years old were selected from 2 middle schools (each school in urban and rural areas) in both Hubei Province and Anhui Province by stratified cluster random sampling method to conduct a D-optimal discrete choice experiment. The mixed Logit model was used to analyze children s preference for meal attributes and different levels, and to calculate the relative importance (RI) of attributes and willingness to pay (WTP) in meal choices. Results: The included five food attributes had statistical significance on meal choice of school aged children ( P <0.05). The relative importance of food attributes affecting the meal choices of school aged children in descending order were dining mode ( RI =31.26%), food varieties ( RI =30.56%), cooking method( RI =23.84%), taste( RI =8.06%) and price ( RI =6.27%). Among them, school aged children preferred home cooked meals ( β =0.74) (WTP=86.3 yuan),varied foods(grain/tubers+vegetables+fish, meat, eggs and beans) ( β =0.61) (WTP=71.9 yuan), fried/roasted cooking ( β =0.51) and spicy taste ( β =0.33).Price was negatively correlated with meal choices( β =-0.01) ( P <0.05). Based on residential area and body mass index (BMI), the stratified analysis showed that dining mode was highest in the relative importance for rural children with overweight and obese children ( RI =31.28%,34.17%), both of whom preferred home cooked meals ( β =0.76, 0.91), and meals containing fish, meat, eggs and beans with grain/tubers or grain/tubers and vegetables in terms of food choice (area: β =0.53, 0.53 ; BMI: β =0.55, 0.56) ( P <0.05). Conclusions School aged children have different preferences for different attributes of meals. The quality of school meals should be improved,the cost of buying healthy meals should be reduced,targeted family health education should be carried out,and healthy cooking methods should be advocated.

Objective:To investigate the influence of environmental factors on body mass index of children and adolescents in China.Methods:Using data from the China Health and Nutrition Survey, the research object to 7 - 17 years old children and adolescents who participated in 2000, 2006, 2011, and 2015 round of survey with complete data, a total of 6 626 children and adolescents (male 3 473, female 3 153) were investigated under univariate analysis for each environmental factor variable before using Partial Least Square Regression fitting a linear model for further screening. Finally, we fitted a three-level linear mixed-effects model distinct by urban and rural area for analysis.Results:The three-level null model, log likelihood=-17 034.68, χ 2=483.06, P<0.001. Intern-class correlation coefficient ( ICC) showed that community-level was 9.97%, and both community and individual were 39.38%. The three-level model also showed that urban model's urbanization index ( β=-0.05, 95% CI: -0.09--0.01, P<0.05), the park location ( β=-0.88, 95% CI: -1.72 - -0.04, P<0.05), 15 - 17 age group ( β=-1.04, 95% CI:-1.78 - -0.30, P<0.05) were negatively correlated with BMI. The distance to the gym ( β=0.12, 95% CI: 0.02 - 0.22, P<0.05), the number of home TV sets ( β=0.50, 95% CI: 0.08 - 0.92, P<0.05) and the frequency of parents' alarm of fiction TV program contents ( β=1.85, 95% CI: 0.70 - 3.00, P<0.05) were correlated with BMI. Rural urbanization index ( β=-0.04, 95% CI:-0.07 - -0.01, P<0.05). Rural per capita income ( β=-7.29e -4, 95% CI:-1.00e -3 - -6.77e -5, P<0.05), parents' restricted frequency of watching TV ( β=-1.29, 95% CI:-2.36 - -0.21, P<0.05), adipo-energy ratio ( β=-0.03, 95% CI:-0.06 - -1.00e -3, P<0.05) were negatively correlated with the BMI. Factors as the frequency of parents' alarm of fiction TV program contents ( β=3.01, 95% CI: 0.03 - 6.00, P<0.05), the survey time was 2015 ( β=4.83, 95% CI: 1.96 - 7.69, P<0.05) were correlated with BMI. Conclusions:Environmental factors could indirectly influence the change of BMI of children and adolescents to different degrees and various aspects. Urbanization index and rural per capita income had a slight protective effect on increasing BMI of children and adolescents. At the community level, attention should be paid to the setting of activity places around the living environment of children and adolescents. Family members should also guide their children and adolescents to develop nice behavior in watching TV.