"The global challenge is clear - make physical activity a public health priority throughout the world to improve health and reduce the burden of disease."
Prof Lindsey Davies, president of the UK Faculty of Public Health, agreed:
"We need to do all we can to make it easy for people to look after their health and get active as part of their daily lives.
"Our environment has a significant part to play. For example, people who feel unsafe in their local park will be less likely to use it."
But others questioned equating smoking with inactivity.
While smoking and inactivity kill a similar number of people, smoking rates are much lower than the number of inactive people, making smoking more risky to the individual.
Dr Claire Knight, of Cancer Research UK, said: "When it comes to preventing cancer, stopping smoking is by far the most important thing you can do."