We know that obesity is one of the biggest health challenges in the UK. And we know that maintaining a healthy weight is extremely difficult in a world that constantly pushes us towards eating too much. Our healthy life mission is focussed on reversing this trend and is exploring how to promote lower-calorie foods on delivery apps such as Deliveroo and UberEats.

Takeaways tend to contain much more calories than meals cooked at home and are linked with higher weight gains. So what could delivery apps do to enable us to continue enjoying takeaways whilst taking steps to protect our health?

Behavioural sciences suggest that most people are more likely to select options that are presented prominently in online shops, irrespective of food preferences. In the first part of this project we looked at the impact of reordering different portion sizes to assess the impact that might have on overall calorie consumption. Then, we explored if simply repositioning lower-calorie foods more prominently on delivery apps could help people to purchase fewer calories without the need to remove less healthy options.

We invited more than 7,000 adults to do a hypothetical food order using one of four versions of a simulated food delivery app called Take a BITe and compared the number of calories ordered by people using the different versions. The four app versions were completely identical except for the order in which restaurants and foods were displayed:

In the control version, restaurants and foods were positioned at random, irrespective of calorie content.

In the second version, lower-calorie foods were positioned at the top of menus and higher-calorie foods at the bottom. Restaurants continued to be positioned at random.

In the third version, restaurants with lower-calorie mains were positioned at the top and restaurants with higher-calorie mains were positioned at the bottom. Foods were positioned at random on menus.

In the fourth version, restaurants with lower-calorie mains were positioned at the top of the restaurant selection page and lower-calorie foods were positioned at the top of food menus.

Our goal was to give more prominence to lower-calorie options to ensure users did not have to scroll down to get to lower-calorie options.

We asked participants to use the app to do a simulated food order for themselves. The app automatically registered the calories in participants' baskets.

When placing a hypothetical food order on the control app, people ordered a whopping 1,382 kcal. This is approximately 55-70% of an adult’s recommended daily calorie intake in a single takeaway meal. Participants using any of the other three apps ordered significantly fewer calories simply as a result of giving more prominence to lower-calorie options.

Compared to users engaging with the control app, participants using the second app (that repositioned foods) ordered 6% fewer calories and participants using the app that repositioned restaurants (the third version) ordered 12% less calories. This tells us that initiatives that help us to identify healthier restaurants might be more effective than initiatives that help us to identify healthier foods in less healthy restaurants.

Unsurprisingly, the fourth version of the app (that repositioned both restaurants and foods to display lower-calorie options at the top) was the most effective initiative, leading to an approximate 15% reduction in the calorie content of takeaways compared with the control app. Participants using this platform still ordered 1,173 kcal. This is still quite a lot of food but significantly less than the calories ordered by participants using the control version of the app.

Even small reductions in calories can help us move in the right direction. A government tool estimates that if (on average) we all consumed 10kcal less per day, the NHS could save up to £700M per year.This means that we don’t always need to swap our favourite pizza for plain green salad: even initiatives that help us make small changes to what we eat could help to slowly reduce obesity.

In our study, positioning lower-calorie options more prominently on delivery apps also reduced the final basket price. For consumers, this is like “having our takeaway and eating it too”: a win for health and for wallets. But public health scientists need to be realistic: restaurants and delivery apps are unlikely to implement initiatives that cut their bottom line. So can we develop initiatives that ensure consumers are not encouraged to purchase too much food without harming the income of businesses?

In our study, we explored this by asking 1,765 different people to place a hypothetical order using a fifth version of our simulated delivery app. In this version, food options were positioned based on their calorie content and price: restaurants and foods that were lower in calories but higher in price were positioned at the top.

This last initiative reduced the number of excess calories in participants’ takeaways whilst increasing the (hypothetical) price of the takeaway basket. This result could encourage food businesses to implement initiatives that help people maintain a healthy weight. However, we think it is crucial to do further research to ensure that these types of initiatives help us make healthier choices without increasing the negative impact of rising food costs.

For example, we could investigate how to reposition food options in ways that help us to reduce excess calories in our takeaways whilst being neutral on the price of our basket. Or, perhaps, we could explore how to encourage healthy swaps of products with similar prices, since researchers have found swaps to be a promising aid for people looking to make healthier choices in supermarkets.

We are planning to use our simulated delivery app to conduct further experiments and learn more about how we can help us all make healthier choices when ordering takeaways.

We are interested in working with policymakers, retailers, restaurants and delivery platforms of all sizes to explore ways of making services better for our health whilst continuing to be equitable and viable. Testing similar initiatives with real restaurants and delivery apps will be important to see if the effects observed in this simulated study generalise to the real world.

If you have any ideas for how to improve this work or if you want to collaborate with us, please get in touch with [email protected]