BigO is a research study open to children and teenagers aged 9-16 years on the W82GO programme. Many children and teenagers do not exercise enough. We are interested in finding out if measuring activity using a smart watch improves treatment. We are also studying the effect of food adverts and are asking participants to capture images so we can measure the types of adverts you see. With this information BigO will be able to advise clinics and public health authorities on how to develop and plan effective programmes and policies in an attempt to reduce childhood obesity. For more information please see the BigO website and information leaflet above.