Food selection, cardiorespiratory fitness and the longitudinal association with adiposity among South African school children: ExAMIN Youth SA study

Background: The global pandemic of paediatric obesity, unhealthy diets and physical inactivity are important future health challenges. The purpose of this study was to determine 4-year changes in food selection, cardiorespiratory fitness (CRF), and the longitudinal association withadiposity among South African children. Methods: School children aged 5 to 9 years old in 2017 (n=950) were followed up four years later. Parents indicated selection from healthy and unhealthy food groups in a validated questionnaire. Weight and height of the children were measured, and WHO BMI z-score (BAZ) was calculated. CRF was determined by the 20-m shuttle run test. Changes in food selection frequency, CRF and BAZ were assessed. The association between frequency of food selection, age, household income and CRF with 4-year change in BAZ was determined using mixed linear models. Results: CRF and BAZ increased over four years (both p<0.001). The frequency of sugar-sweetened beverages (p<0.001) and milk intake (p<0.02) decreased, while the intake from fast-foods increased (p=0.001). Daily intakes of vegetables and milk were associated with decreases in BAZ. A trend of a positive association was found between frequency of SSB intake and BAZ. CRF showed a strong negative association with BAZ over time (p<0.001). Conclusions: Higher daily vegetable and milk intakes, as well as higher levels of CRF were protective against increasing adiposity among school-age children, whereas daily SSB intake was associated with an increased adiposity. The promotion of good eating habits and measures to improve CRF among school children are important policy change priorities.