'Obesogenic' products, such as energy dense foods, passive entertainment products, cars, and labour-saving devices, are widely available and heavily promoted. Because they are highly consumed and very profitable, obesity becomes the inevitable consequence of their commercial successes. Contemporary market forces heavily favour behaviours for short-term preferences (i.e. over-consumption and underactivity) over long-term preferences (i.e. healthy weight) and this is especially true for children. Hence, if the market, as the main mechanism for determining choices, results in outcomes, which make our children worse off, as is occurring with childhood obesity, then the market has failed to sustain and promote social and individual goals. This is a serious market failure. In the current obesogenic environment, expecting adults, let alone children, to make food and activity choices in their own best long-term interests is, therefore, demonstrably flawed. We argue that significant government intervention is needed to correct this market failure, as has been done for other major health problems.