Two in three adults are living with obesity or excess weight. It’s a disaster for our health. Obesity and excess weight create a greater risk of chronic health conditions like cancer, diabetes and depression. Meanwhile, obesity among children has risen to alarming rates: they are now among the highest in Europe. The condition is also crippling our NHS, costing it more than £19 billion a year.

The good news is that obesity is preventable. And it’s entirely possible to make serious progress in a fairly short period of time. To do that, we need to understand what works and what doesn’t. We know a lot about the sort of approach that’s destined to fail - we’ve relied on treating obesity as a willpower issue for 30 years and in the same time rates have doubled.

Nothing has gone wrong with our willpower in that period. We drink and smoke much less than we used to. What’s changed is that the food that’s around us has become less healthy over time. So even though most of us want to lose weight and make healthier choices, it’s become steadily harder to achieve.

When Nesta conducted a comprehensive analysis of over 30 policies on obesity last year, we found that policies targeting individual behaviour change, like mass media campaigns, education and exercise programmes, would not make a dent in the obesity rate compared with policies that make healthier food more easily available to everyone in the country.

That’s why we’re so pleased to see today’s announcement, which is based on a policy designed by Nesta. It marks a fundamentally different approach to tackling obesity by targeting what’s available and promoted to us in the places where the vast majority of us buy our food - including supermarkets, which is where over 80% of our calorie intake comes from. Today’s announcement recognises that voluntary measures or a focus on willpower hasn’t worked and it builds on growing support in the industry to do more to improve the health of their customers.

The healthy food standard will require food businesses including supermarkets to sell healthier food. The changes they will need to make are modest - this isn't about swapping crisps for carrots. Rather than a big bang change, it’s lots of small changes that accumulate over millions of purchases every day.

The policy has been designed to give each business the freedom to choose their own measures in order to hit the target over several years. Likely tactics will include tweaking own-brand recipes to reduce calories, offering more promotions on healthier options, and using online and store layouts to encourage the sale of healthier products. Supermarkets will retain full control over how they hit the target, and each will be able to play to their individual strengths, within their usual business cycles.

In practical terms, this might mean supermarkets putting healthier yogurts on offer, tweaking the recipe of sandwiches or wraps so they contain slightly less fat or giving more shelf space to cereals that have a bit less sugar.

Over time, these changes can make a huge difference to our nation’s health. By setting a target healthiness score, Nesta estimates that this policy could reduce obesity by around a fifth. This would help over three million people achieve a healthier weight, and generate societal value of about £17 billion. That’s huge.

Crucially, the policy should not drive up costs for consumers or businesses. When developing the policy, a key requirement of our work was that health targets must be achievable without reducing the total value of products sold. This shows is it possible for supermarkets to achieve the targets without affecting their bottom lines. Shoppers don’t need to spend more, and businesses don’t need to sell less. The proposed health score is something supermarkets already have to calculate for the food they sell to comply with existing regulations.

An independent economic analysis found that these improvements are possible without pushing up prices. This is because the policy is not about reducing sales or profits - it’s about small changes to the food that is marketed and sold. Implementation costs are minimal, and the grocery market is highly competitive, which means retailers can find ways to meet the targets in a way that works for and retains their customers. We know this is especially important at a time when household budgets are tight for a lot of people.

Our previous analysis found that there wasn’t a strong link between the health score of a retailer and the average cost of its shopping basket: meaning it isn't the case that the more expensive supermarkets are healthier than the budget ones. In fact, the difference in health scores across different retailers was larger than across incomes. This shows that it doesn't need to cost more to be healthier: it is possible for it to be affordable for all.

But for this policy to have the desired impact, it must be implemented well. We welcome the UK government's commitment to consult and develop this policy with the sector. To ensure progress across all players in the sector, it needs to be mandatory. The voluntary Public Health England reformulation programme aimed to see 20% reductions in sugar across a variety of food categories. Whilst there was some reformulation, total tonnes of sugar increased by 7%. Voluntary measures just don’t work sufficiently well.

To be effective, the policy also needs to use a continuous measure for health, rather than just using a binary ‘healthy’ vs ‘unhealthy’ one. This will give businesses the appropriate flexibility and will incentivise improvements across their portfolios, so that there is value in improving the most unhealthy items. If we care about making our diets healthier, going from chocolate muffins to blueberry muffins is good progress.

If we get this right, then this policy could open a new chapter in our efforts to improve our health and make a meaningful change to obesity in the UK.

The healthy food standard is just one part of the solution, but it’s a crucial one. As the major link between food producers and consumers, large supermarket chains hold considerable power and influence over the whole food system. They've been vocal in their support for customer health - now is their chance to lead the way. If everyone - food retailers, government, the NHS and individuals - plays their part, we can turn the tide on obesity and offer our children a better, healthier future.