The Change4Life initiative is a step in the right direction, but we need to do more to tackle the issue, says Sue Davies

National Obesity Week starts on Monday, an important reminder that a quarter of us in the UK are now obese. Add to this rates of diet-related disease and it's clear that many struggle to make healthier choices.

The Great Swapathon, part of the government's Change4Life campaign, aims to encourage people to swap unhealthy habits for healthier ones, starting off with vouchers available from Asda and through the News of the World.

It's encouraging to see a greater focus on making healthier choices cheaper, but this shouldn't detract from the need to take more decisive action on other fronts. There have been numerous strategies to tackle obesity and an unprecedented level of debate about food and health over the past few years. Work around salt reduction and the introduction of traffic-light labelling stand out.

But we have to be more ambitious. While many companies provide front-of-pack labelling, there is little consistency. Only Asda and McCain use traffic lights, along with percentage GDAs and descriptors, the scheme shown to work best. EU legislation should enable progressive discussions about shifting to a common UK scheme.

Health claims regulation has also failed to live up to aspirations. Evaluations by the European Food Safety Authority show that about 80% of health claims assessed so far can't be substantiated, but these products can still legally be sold. The principle that you shouldn't be able to make a 'health' claim on an unhealthy product is also under threat, with vigorous lobbying by some companies, and robust nutrient profiles are urgently needed.

Another problem is the number of unhealthy promotions targeting children. Standards to ensure healthy school food have been introduced, but there's been less progress in other key public institutions.

The government's Responsibility Deal is an opportunity to reinvigorate discussions and go further with work already under way. Voucher schemes are a start, but a lot more can be done around supermarket promotions. Obesity statistics speak for themselves. We can't be complacent until healthier food choices start to become the norm.

Sue Davies is chief policy adviser of Which?.