Despite the rising incidence of childhood obesity, international data from Eurostat show that the prevalence of obesity among those aged 15-19 years remains under 5%, which offers an important opportunity for preventing subsequent adult obesity. Young people engage poorly, even obstructively, with conventional health initiatives and are often considered 'hard to reach'. However, when approached in the language of youth, via IT, they express great concern, and unwanted weight gain in young people can be prevented by age-appropriate, independent, online guidance. Additionally, when shown online how 'added value' by industry can generate consumer harms as free market 'externalities', and how obesogenic 'Big Food' production and distribution incur environmental and ethical costs, young people make lasting behavioural changes that attenuate weight gain. This evidence offers a novel approach to obesity prevention, handing the initiative to young people themselves and supporting them with evidence-based methods to develop, propagate and 'own' social movements that can simultaneously address the geopolitical concerns of youth and obesity prevention.