Making healthy food more affordable and more easily available is an urgent public health and economic priority.

The healthy food standard (HFS) is a UK government policy which, if implemented, would mean the top 11 supermarkets in the UK would have to report on the healthiness of their sales and meet a legal health target. In Scotland, only 10 of these supermarkets would be in scope (we refer to the ‘top 10 supermarkets’ in Scotland in reference to this). Nesta analysis shows that rolling out the policy in this sector could reduce obesity prevalence by 26% among children and 18% among adults, which equates to 40,000 fewer children and 300,000 fewer adults living with obesity in Scotland.

While broad population-level impact is critical, it's also important that policy should seek to avoid widening the health gap between richest and poorest, or between different geographies. In the case of the HFS, our analysis explored whether supermarket targets will reach the shops where lower-income households and rural communities across Scotland actually buy their food.

To answer this question, this blog draws on two sources: Nesta's own analysis of Worldpanel consumer data, which tracks where households buy food to eat at home, and new research Nesta commissioned from the University of Edinburgh on journey times to major supermarkets across Scotland. You can find more detail on the methodologies below.

Here are five things we learned:

Our analysis of Worldpanel data looked at food purchases across self-reported household income, social grade (categorisation based on the occupation of the highest income earner) and rural-urban classification. We found that regardless of income, social grade or location, people in Scotland tend to buy the majority (over 91%) of the food they eat at home from the largest supermarkets expected to be within scope of the HFS policy.

This data should give policymakers in Scotland confidence that setting health targets where families buy the vast share of their food offers the greatest scope to improve diets.

When looking at households in Scotland, we observed a slight social gradient in the healthiness of food purchases. Using a sales-weighted converted nutrient profile model (SWA cNPM) we found that higher-income households on average make healthier purchases, with a 2 cNPM point difference in healthiness between the highest and lowest income groups, and between the highest and lowest social grade groups.

Given that lower-income and social grade groups still purchase over 90% of their take-home calories from the 10 major supermarket chains in Scotland, these retailers remain the most direct route available to supporting healthier purchases. These groups also stand to gain the most from how the policy works: by requiring retailers to make small changes to how they sell, promote and develop food, the policy makes the healthier option the easier option - rather than something shoppers have to seek out. Approaches that rely on people changing their behaviour and committing effort are less effective at reducing obesity, and risk widening inequalities.

Research from the University of Edinburgh, commissioned by Nesta, found that 96% of all residential addresses in Scotland are within a 15-minute drive of the 10 supermarket chains expected to be covered by the policy. More than half of addresses are within a 15-minute journey by walking (67%) or public transport (72%).

Based on the place planning principle of 20 minute neighbourhoods, we have considered a 15-minute journey by either car, foot, bike or public transport to be a reasonable journey. In rural areas, where car ownership is higher than urban areas (88% compared to 64%) a 15-minute drive time (or longer) is more likely to be viewed as reasonable compared to urban areas.

When the University of Edinburgh looked at households by Scottish Index of Multiple Deprivation (SIMD) nationally and within local authorities, they found no clear overall trend in access to the 10 largest supermarkets. At the national level, the vast majority across all quintiles can access supermarkets via car within a 15-minute journey time. Crucially, households in the most deprived areas (quintile 1, Q1) had the best access across other modes of transport with 78% able to reach one of the 10 major supermarkets within 15 minutes on foot, 85% by public transport and 98% by bike.

It’s often assumed that people in rural areas struggle to reach major supermarket chains and rely heavily on local convenience stores. In fact the data tells us a different story, suggesting that the HFS will reach the majority of residents in rural areas.

Physical access is somewhat of a mixed picture. The University of Edinburgh research shows distance to a physical store does vary mostly by rurality, rather than deprivation or local authority. A major supermarket is within a 15-minute drive for 94% of addresses in accessible rural areas, falling to 82% in remote small towns and 51% in remote rural areas. And within remote rural areas, journey times vary significantly from one local authority to another.

Even so, Nesta’s own analysis of Worldpanel data shows that rural households still purchase over 90% of their take-home food calories from the major supermarket chains. Most of the remainder comes from bargain stores and freezer centres. This suggests that, despite longer travel times, rural households in Scotland are still accessing the supermarkets likely to be covered by the HFS, either in person or by using online delivery services where available.

The Edinburgh University research did not assess access to the supermarkets through online delivery, but we know it has the potential to widen access further, especially on the mainland. For example, 99.7% of households can receive online deliveries from at least one of the biggest supermarket chains.

Finally, the University of Edinburgh research found that including Scottish retailers such as Spar, Scotmid and Londis within scope of the policy made a very small difference to access by car, raising the share of addresses within a 15-minute drive from 96% to 97% overall. In rural areas it would only slightly increase access: for example, in remote rural areas it would increase the number of addresses within a 15-minute drive from 51% to 55%.

Including additional retailers did somewhat increase access by walking in urban areas. Across Scotland, the number of addresses within a 15-minute journey times on foot to major supermarkets increased from 81% to 88% in large urban areas and from 73% to 82% in other urban areas when including additional retailers. This suggests that bringing these stores within the scope of the policy wouldn’t necessarily increase access for rural households but might in urban areas.

Taken together, our findings suggest that households across Scotland, whatever their location, income or social grade, buy most of the food they eat at home from the largest 10 supermarket chains, and most can reach one of these supermarkets within a reasonable journey time.

This should give policymakers confidence that the HFS will cover the majority of food purchased in Scotland, making it a powerful way to improve health across different income groups. For the biggest gains to health, getting targets right for the largest supermarkets needs to be the priority for implementation, rather than widening the policy to smaller retailers in Scotland. If implemented well, the HFS could mean an estimated 40,000 fewer children and 300,000 fewer adults living with obesity in Scotland, offering a rare opportunity to improve population health while helping to address the health gap across the country.