The present study is based on cross-sectional data from the baseline investigations carried out in OPUS School Meal Study - a randomized crossover study carried out in 9 primary schools in Denmark 2011-2012. Approximately 800 Danish school children from 3rd and 4th grades (8-12 year olds) took part in these baseline investigations of socioeconomic status, pubertal status, growth status, learning abilities, well-being, sleep, physical activity and risk markers of Cardiovascular Disease (CVD), type II diabetes and osteoporosis.