Baseline characteristics of children according to treatment arm and participation at follow-up. Values are means (SD) unless stated otherwise.

aMain effects of group and participation and potential interactions between the two age-group and gender specific z-scores were assessed using mixed linear or logistic regression models including indicator variables for participation (part) and group (intervention (INT) vs. controls (CON)), and an interaction term group × participation as well as a random effect for original school class. bCategorization based on WHO z-scores. cPubertal stages are based on Tanner stages: prepubertal (Tanner 1), early pubertal (Tanner 2 and 3), pubertal (Tanner 4 and 5); dboth parents from Eastern or Southern European countries, Africa, Asia, Central or South America, or other less developed countries.