Over the past decade a common picture on the aetiology of obesity has become largely agreed. After years of competing analyses, most people now accept that obesity is the result of a complex multifactoral interplay.1 2 It is not either food intake or physical activity but both. It is not just food oversupply or pricing or domestic culture or food marketing or poor consumer choice or genetic potential. In fact, it is all of these and more. At last, scientific advisers have accepted that they have an analysis to share with politicians and can begin the tortuous process of crafting frameworks for action.3

So why is the British government quietly breaking with this consensus and putting so much weight behind nudge thinking? Nudge is being presented as a new change mechanism from which public health gain will follow and …