2.3. Measures

Mode of transport to school was captured by the responses to the question, ‘How do you usually get to school?’ which allowed for multiple responses. There were five alternatives: public transport, cycling, walking, car (including private cars and taxi), and bike as a passenger (including bicycles, motorbikes, and electric bikes).

Body weight and height were measured by the health workers in school, in units of 0.1 cm and 0.1 kg, respectively. Determination of being overweight and obese was based on age adjusted Body Mass Index (BMI, weight/height²) with Chinese standard classifications in children and adolescents by Working Group of Obesity in China [15,16].

Family sociodemographic information included the educational level and occupation of both parents. A total of three options, ‘up to secondary education (year 12),’ ‘junior college degree,’ and ‘bachelor or above’ were used to determine the family education level. A series of options describing occupation (‘administrative staff,’ ‘technicians,’ ‘clerical staff,’ ‘business people,’ and so on) were listed and participants selected one only.