Adolescent boys living in disadvantaged communities are considered a vulnerable group at risk for developing obesity and associated health problems, such as cardiovascular disease, hypertension and type-2 diabetes. While short-term health promotion programmes often produce effective results during the implementation of the intervention, according to self-determination theory (SDT), changes in autonomous motivation are required if programmes are to have sustained effects on health behaviours. This article describes the ATLAS (Active Teen Leaders Avoiding Screen-time) programme, based on SDT, which was developed to engage adolescent boys from low socio-economic backgrounds in physical activity, reduce their consumption of sugar-sweetened beverages and limit recreational screen-time. The article reports a post-hoc analysis of the perceptions and experiences of a representative group of ATLAS participants to investigate whether the boys’ general impressions of the programme reflected the need-supportive teaching strategies on which the programme was based. The results of this analysis suggested that students’ comments about increased feelings of autonomy, competence and relatedness were often linked to corresponding need-supportive teacher behaviours. The findings suggest that embedding health promotion programmes in a need-supportive context can help to foster the motivation and self-regulation that is required to maintain newly adopted healthier behaviours.