Cognitive-behavioural health-promotion intervention increases fruit and vegetable consumption and physical activity among South African adolescents: a cluster-randomised controlled trial

Rates of chronic diseases are high among Black South Africans but few studies have tested cognitive-behavioural health-promotion interventions to reduce this problem. We tested the efficacy of such an intervention among adolescents in a cluster-randomised controlled trial. We randomly selected 9 of 17 matched pairs of schools and randomised one school in each pair to the cognitive-behavioural health-promotion intervention designed to encourage health-related behaviours and the other to a human immunodeficiency virus (HIV)/sexually transmitted disease (STD) risk-reduction intervention that served as the control. Interventions were based on social cognitive theory, the theory of planned behaviour and qualitative data from the target population. Data collectors, blind to participants' intervention, administered confidential assessments at baseline and 3, 6 and 12 months post-intervention. Primary outcomes were fruit and vegetable consumption and physical activity. Participants were 1057 grade 6 learners (mean age = 12.4 years), with 96.7% retained at 12-month follow-up. Generalised estimating equations revealed that averaged over the follow-ups, a greater percentage of health-promotion intervention participants than HIV/STD control participants met 5-a-Day fruit and vegetable and physical activity guidelines. The intervention also increased health-promotion knowledge, attitude and intention, but did not decrease substance use or substance-use attitude and intention. The findings suggest that theory based and contextually appropriate interventions may increase health behaviours among young adolescents in sub-Saharan Africa.