Food selection, cardiorespiratory fitness and the longitudinal association with adiposity among South African school children: the 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 with the development of adiposity among South African primary school-age children. METHODS: School children aged 5-9 years old in 2017 (n = 950) were followed up for four years. 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 (20-m SRT). Changes in food selection frequency, CRF and BAZ were assessed. The association between frequency of food group selection, age, household income and CRF with 4-year change in BAZ was determined using mixed linear models. RESULTS: BAZ (p < 0.001) and age-adjusted performance in the 20-m SRT of boys (p = 0.04) increased at follow-up. 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. The promotion of healthy eating and measures to improve CRF among school children are important priorities.