At one point, almost half of the UK population were cigarette smokers. Today, that figure is closer to one in seven. Decades of action have helped to tackle the nation’s smoking problem and save lives.

Now we face a new public health challenge that demands action: obesity.

Most adults in the UK are now overweight or obese, and our collective weight has been increasing for decades, across the whole of society.

But like smoking, this is a problem we can fix.

At Nesta, our mission is to help more people live a healthy life for longer. We aim to halve the prevalence of obesity by 2030, which means reducing the number of people who are obese by at least 9 million. But we can only do this if we fully understand the problem we’re trying to solve.

Compared to smoking, things are trickier with obesity. We can’t just ban food – we need it to survive, and we get immense joy from eating! So the question is: how can we encourage healthy eating habits in a way that’s easy, accessible and appealing?

The old narrative has been that weight is about willpower and education. This produces an incredibly unhelpful view of personal responsibility. The widespread rise in obesity across the UK shows that many of the factors driving unhealthy weight gain are linked to our environment. And the best evidence suggests there are many many factors outside of our control that drive increased consumption.

So if you are of a healthy weight, it’s probably not actually down to your excellent personal grit and willpower; it’s probably more about the ‘food environment’ you find yourself in. If you found yourself in different circumstances, your weight might be quite different.

When we talk about a food environment, we’re talking about the ways in which we’re exposed to food on a daily basis. Our food choices are guided by what is accessible, convenient and affordable. So what food shops are located near our homes? What kinds of food are affordable and available to us? What are we steered towards by advertising or store design?

People have a lot of competing demands on their time and headspace. Rather than demanding that people pay ever more attention to what they eat, we need to make it easier to eat healthier.

That means driving changes in the food environment.

If the recipe of food is designed to make you eat more, if you see multiple adverts in the street and on your screens every day, if you have to walk past 10 fast food stores to get to somewhere that sells cheap veg, what hope does anyone have?

Changing the food environment could mean working with food retailers to revise store layout and promote healthier options. Or it could mean working with the government to introduce policies like the sugar tax – which has proven so effective at encouraging the food industry to reformulate its products and reduce sugar content.

There’s a double edged sword here. Changes in weight take quite a long time, and the daily calorie difference to gain or lose a few pounds is surprisingly small. This can be problematic for deliberate dieting efforts because people don’t see the progress they want in a few weeks, plus people may not notice slow weight gain over a number of years.

But it can also be a huge positive, because it means that it should be perfectly possible for people to consume fewer calories without massive changes to their lives, and without missing out on the joy of eating. That is why we are cautiously optimistic about our goal.

Nesta’s healthy life team is working with partners across the food industry, public sector and non-profit sector to develop innovative solutions. From portion sizes to food labelling, from digital marketing to local authority initiatives, we’re exploring lots of different routes to improving the nation’s health.

Obesity is the public health challenge of our generation, but we’re not powerless to address it. By working together to truly understand the root causes, we can reverse the trend and ensure a healthier life for all.