Mental health 3 categories
0 = mental health
1 = Mental subhealth symptoms
2 = Mental subhealth

Video time 3 categories
1 = Less than 1 hour
2 = 1 to 2 hours
3 = More than 2 hours

Workout time 3 categories
1 = Less than 30 minutes
2 = 30 to 60 minutes
3 = > 60 minutes

6 categories of ways to go to and from school
1 = walk
2 = cycling
3 = Bus or Taxi
4 = subway
5 = Parents take
6 = other

Video time 4 categories
1 = Less than 1 hour
2 = More than 1 hour and less than 2 hours
3 = More than 2 hours and less than 3 hours
4 = More than 3 hours

Workout time 4 categories
1 = Less than 30 minutes
2 = More than 30 minutes and less than 1 hour
3 = More than 1 hour and less than 2 hours
4 = More than 2 hours

Video time 3 classification in turn
1 = More than 2 hours
2 = 1 to 2 hours
3 = Less than 1 hour

Workout time 3 categories in turn
1 = > 60 minutes
2 = 30-60 minutes per hour
3 = Less than 30 minutes

Sleep time is reversed
1 = More than 8 hours
2 = 6 to 8 hours
3 = Less than 6 hours

Sleep time 2 classification in turn
1 = > 6 hours
2 = Less than 6 hours

Workout time 2 classification in turn
1 = > 30 minutes
2 = Less than 30 minutes

milk and dairy products
1 = Eat almost all (more than 4 times a week)）
2 = Eat occasionally (2-3 times per week)
3 = Eat almost nothing (less than once a week)

Parent Occupation F
1 = civil servant
2 = worker
3 = company employee
4 = go into business
5 = peasant
6 = other

Parent's education F
1 = primary school
2 = junior high school
3 = High school/technical secondary school
4 = University or above

Emotional sub-health 2 categories
0 = emotional health
1 = Emotional subhealth

Behavior sub-health 2 classification
0 = Conduct health
1 = Moral subhealth

Social adaptation sub-health 2 classification
0 = Socially adapted health
1 = Social adaptation to sub-health

Mental health 2 categories
0 = mental health
1 = psychological subhealth

Ways to go to and from school
0 = A positive way
1 = Negative way

sleeping time
1 = Sleep time < 8h/d
2 = Sleep time ≥8h/d

video time
1 = Video time < 2h/d
2 = Video time ≥2h/d

exercise frequency
1 = No exercise (0 times/week)
2 = Occasionally (1-2 times/week)
3 = Frequently (3-7 times/week)

exercise time
1 = Exercise time < 60min/d
2 = Exercise time ≥60min/d

Participate in extracurricular exercises
1 = yes
2 = N0

breakfast
1 = Eat almost all (more than 4 times a week)
2 = Eat occasionally (2-3 times per week)
3 = Eat almost nothing (less than once a week)

picky eater
1 = Hardly picky about food
2 = Occasionally picky eaters
3 = Often picky eaters

gender
1 = boys
2 = Girls

School section
1 = Junior middle school, 13 to 15
2 = High school 16 to 18

urban and rural
1 = city
2 = countryside

father occupation
1 = civil servant
2 = company employee
3 = Other

father's education
1 = Junior high and below
2 = senior high school
3 = Junior college or above

monthly household income
1 = ＜2000
2 = 2001-5000
3 = 5001-8000
4 = ＞8000

Grip strength quartiles
1 = ≤P25
2 = P26-50
3 = P51-75
4 = ＞P75