The moment has arrived for tough decisions by the food industry, starting with the soft drinks sector.

Last week, results from the 2012-13 National Child Measurement Programme showed a third of children are overweight or obese before leaving primary school. They then get fatter in adolescence.

Also last week, the European Food Standards Authority published its assessment of aspartame, the sweetener in most sugar-free soft drinks, after the most thorough review ever. It declared aspartame safe.

The two announcements are linked. Sugar has become the key nutrient of concern in the obesity debate. Soft drinks are the major source of sugar in the diets of most developed countries.

“Many healthier variants are cheaper to produce”

So, health advocates now routinely propose taxes on soft drinks. It is a negative strategy: punish ‘bad’ foods - and the companies that make them. But positive pricing could be a useful weapon against obesity. Instead of moral exhortations to “eat healthily”, consumers need material incentives. Make “good” foods cheaper.

My colleagues and I have set out a radical new strategy to achieve this called Make the Healthy Choice the Cheaper Choice, the full version of which is here.

Most of our diet comes from manufactured products, many high in sugar, fat and calories. Reformulate these mass-market foods to produce healthier variants. Then, give consumers economic incentives to buy the improved versions.

Soft drinks illustrate this strategy well as aspartame and other sugar substitutes make it easy to produce additional healthier variants. They can replace the sugar and calories. They also cost less, so sugar-free drinks are cheaper to produce. Yet no-calorie products always sell at the same price as standard sugared drinks. Companies are in effect charging a “health premium”. Healthier variants are condemned to remain niche products for the affluent. Everyone loses.

We cannot go on like this. Following close behind the obesity epidemic is a diabetes epidemic that would break the bank of any healthcare system in the world. We need effective action.

Change requires tough decisions. Companies have to reformulate brands they have spent millions to establish. Then they have to cut margins to create a price differential with standard products. Why would any company do that? Our paper proves the apparently impossible - companies can sell healthier products at cheaper prices and make more money by doing so.

The fact is that many healthier variants are cheaper to produce and hence more profitable. By cutting part of the extra margin, companies would give consumers a price discount, shift sales and increase revenues.

Many companies engage in CSR. But too many projects are small-scale, cuddly do-goodery. In the age of obesity, real social responsibility for food companies is to produce heathier foods and price them so they sell in volume. Their reward is that they would increase profits in the process.

Jack Winkler co-wrote the report with David Sweanor, Samantha Hogg and Vivian Welch