This week, ministers from 53 countries met at a conference in Istanbul to sign a European Char­ter on Counter­acting Obesity. Are boardrooms quaking in their boots? I doubt it. But it's the latest sign that politicians realise obesity is to health what climate change is to the environment - an immense challenge requiring commerce and society to change.

In August, the World Health Organisation produced a devastating report on 48 of the 53 member countries of its European region. Every country had rising obesity. None was winning with efforts to tackle it. The report acknowledges that "improving lifestyles has been mainly considered the responsibility of individuals". That's polite language for saying that blaming consumers hasn't worked. It's bad psychology, too. The report said policymakers need to "make the environment support healthy lifestyles".

Here's the fundamental shift in thinking: if obesity is an inevitable physiological response to an inappropriate environment, dietary change and exercise have to be factored into daily life, not be a choice in personalised health. Forget hype about fat genes, niche products and token projects in schools. As with other issues in the past, today's improvement will only happen today if we alter circumstances.

So does the Istanbul Charter unleash big initiatives? No. To expect it to do so would be to misunderstand the WHO and UN bodies. They are advisory. Conference aims were modest: to raise the issue, to gain high-level commitments, to promote partnerships. These are already there in many, but not all, countries - and are not working.

Was Istanbul just talk, then? No. It's the latest in a series of shadow boxing events where health ministers, deeply worried about obesity's huge fiscal costs, up the stakes. Recently, European Commissioner Kyprianou said he would not regulate on fats, salt and information if companies acted voluntarily. Many big companies have already cut out trans fats. But what about asking them to cut down on total fats and sugars across all products?

The International Business Leaders Forum is busy finalising a draft Code of Conduct, with big company consultation. A recent Eurobarometer poll finds 90% of EU citizens believe junk food and drink advertising influences children. Nine companies have voluntarily ended ads targeting under-12s. The storm clouds are gathering.