As a population, we are consuming more unhealthy food. As a result, obesity in the UK has doubled since 1990 and two-thirds of adults in the UK are now overweight or obese – more than most other European countries.

At Nesta, we’ve estimated that about an 8.5% nationwide calorie reduction would lead to halving obesity rates, and the huge societal health and wellbeing benefits that go with it. With the right mix of policies, targeted innovation and political support we could get back to this healthier weight distribution.

If we want to get to a better picture nationally then we need a metric of measurement to help us to quantify and compare interventions that could go some way to reducing obesity. Without a comparison metric, it’s hard to know the scale and the type of food-environment interventions that might be most effective.

We need to be able to prioritise interventions, quantifying their likely effect, in order to advocate for measures that will make the biggest contribution to calorie reduction. This is important because most of what has been tried to date has failed. Over the past 30 years, successive governments have initiated 689 government policies targeted at obesity, but the research suggests that they had little impact.

The overwhelming majority of these policies focused on well-meaning individual-level change when what we need is change at the system level. Interventions that place pressure on the individual generally don’t work well in the long term. Broad-brush information provision doesn’t hurt, but has very small (if any) impacts on behaviour for most people. Formal weight management support is generally cost effective, but it would cost huge sums of money to roll out to the whole population.

Understandably calories as a unit of measurement is controversial and can be used to reinforce the failed focus on individual responsibility and willpower. Counting calories is associated with diet culture, weight loss competition TV shows, blaming and shaming individuals and exploitative marketing tactics which prey on insecurities in order to sell us miracle cures. All of this feeds a narrative that the responsibility for tackling obesity sits with individuals.

This type of approach is ineffective for lots of reasons, not least because it perpetuates false stereotypes that people living with obesity are weak willed or lazy. Crucially counting calories simply doesn’t work for most people, our good intentions are rarely a match for the food systems that surround us, and socio economic status.

So for us, we are concerned with counting calories in the system, at what we call the population level. This will allow us to determine if specific interventions can help us remove some of the excess calories that we’ve picked up nationally over the last three decades (halving obesity would get us back to rates we saw as recently as the late 90s). If we remove calories in the system, this will result in individuals consuming less calories and in turn, losing weight.

Much of our eating behaviour is shaped by our environment. Our food environment can be defined as the physical features of our neighbourhood and how they interact with our personal circumstances – the money we can spend on food, for example, or the time we have to prepare it. Taken together they are the availability, accessibility, affordability and advertising of food.

In the UK these elements are stacked heavily against healthy diets. We are interested in population-wide interventions that focus on creating better food environments that make it easier for everyone to eat healthily. We’re in the process of testing the effect size of different interventions to see which of them have the biggest potential to make a difference. It’s likely to be a mix of quite big things like advertising restrictions and relatively small but widespread product changes like reducing the fat content in the skins on sausages (the purpose of a start up we’re supporting).

Without being specific you can’t hold institutions and industry accountable and you can’t judge whether proposed approaches are proportionate to the scale of the challenge.

We need to measure calories at the level of the whole population in order to set out a proportionate plan to halve obesity. We need change to the food environment that look like lots of small changes creating population level changes in what’s sold and consumed in the UK. And we explicitly don’t need individuals feeling more shame or guilt. We appreciate the difficulties that come with this metric, but without a clear target and a road map to get there, we’ll continue to talk in broad terms about ‘healthier food’ without getting to the specifics. And we need specifics if we want to improve health.