Baseline personal, anthropometric and demographic characteristics of children from the SPEEDY study whose data were used in these analyses.

Data are presented as mean ± standard deviation for continuous variables and n (%) for categorical variables. Ref is the reference category. Differences between Girls and Boys (p-value presented) were determined using multilevel linear or logistic regression depending on whether the dependent variable was continuous or categorical. SPEEDY, Sports, Physical activity and Eating behaviour: Environmental Determinants in Young people; BMI, body mass index; GCSE, General certificate of secondary education. *At follow-up one boy and one girl were missing data for weight therefore weight, BMI and weight status at follow-up are out of 317 children (145 boys, 172 girls)