How to halve obesity

And why we shouldn't fear the politics

I’d like to persuade you, dear reader, that it is entirely feasible to reduce obesity by 25 to 50 per cent in the next decade. Not only that, but we can do so without putting up the price of food, with minimal government spending, and in a way that is politically feasible.

And that if we do so, each year we’d generate enough savings and tax revenue to restore the foreign aid budget back to 0.5% of GDP, as well as cut income tax by 1 pence, and still have another £5bn per year to reinvest in the NHS or new infrastructure projects¹.

Let’s start with understanding the basic maths of the problem. I’ve moaned before on here that many policy discussions forget to quantify the impact of policies, what you might call the ‘dose-response’ relationship. So we get policies that are directionally right, but nowhere near the right level of intensity to get to the desired level of change.

To counter that, my colleagues at Nesta did three things: first, they analysed the degree of calorie reduction needed to halve obesity and how that varies by different population groups; second, they got data from supermarkets and restaurants to understand where people are getting their calories today; third, they reviewed thousands of academic papers on obesity to estimate the cost and impact of 30 obesity policies, before constructing three packages that could halve obesity.

The maths of obesity

The obesity debate starts to go wrong by hugely overestimating the number of calories required to reduce obesity.

The fact that changed my mind most about this issue is this: if the roughly 29 million English adults who are overweight or obese reduced their daily calorie consumption by 8.5% - an average of 216 calories (or 241 calories for men and 190 for women)- we would halve obesity in this country. These changes would need to be sustained, rather than temporary, and might typically take a year before people reach their new equilibrium weight.

To put that into context, 216 calories is similar to the amount of calories in a packet of McCoys crisps, or a small bottle of coke. In writing this I went out to Tesco and bought two very similar meal deals, but one had 300 calories less.

With such a modest change in calories required, you might think we can just rely on informing and educating citizens and asking them to take more personal responsibility over their diet and exercise.

But we know from past policies that this is unlikely to work. Dieting is rarely sustained, because it relies on making effortful, conscious hour-by-hour decisions and summoning enough willpower to constantly resist temptation. It calls on people to swim against the tide of all the promotions and inducements that push people towards eating the ‘wrong’ thing. Exercise too, while good for our health for all sorts of reasons, is of limited value as a policy on obesity. When we exercise we typically burn fewer calories than people imagine, and we typically lose half the benefit by either eating or drinking more after exercise or being less active otherwise.

The behaviour change we should target is not those of individuals making conscious choices. It is the decisions made by supermarkets, manufacturers and restaurants over what recipes to use and what products to stock and promote.

Let’s go back to the 215 calories target. The answer is not to ask people to forgo a snack, or swap crisps for kale. At best a small minority of health conscious people will do this. It is to take out those calories by small, barely noticeable changes across the whole shopping basket and what we eat and drink outside the home, rather than through a single substitute.

How to do it

At Nesta, we’re conducting experiments with supermarkets, delivery platforms and coffee shops to do just this. There are many tactics that can work: changing how stores are laid out, or the choice architecture when buying coffees and snacks; shifting what is promoted or stocked in stores; changing the default portion size when buying food outside the home; offering lower calories substitute products prior to checking out when online; or reformulating products as we saw in soft drinks after the introduction of the Soft Drinks Industry Levy.

What is striking is the power of incrementalism. We are not particularly sensitive to small reductions in salt and sugar, so it is better to take three small steps rather than one big one. When it’s across the whole shopping basket, one product does not suffer in comparison to others. You can make a series of small changes that add up to a lot overall.

I often make comparisons between climate change and obesity, and the contrast between the mental models we have for each issue are intriguing. In the early days of climate change messaging, we’d often suggest every little bit helps. We’d direct energy towards half-filling your kettle, turning off your TV rather than leaving it on stand-by and recycling, when really we have to get rid of boilers and combustion engines. Obesity is the opposite. People’s mental model assumes it requires drastic lifestyle change by individuals, when it’s actually about lots of small tweaks, largely by business.

The policy choices

So how do we drive that behaviour change from business? We reviewed thousands of papers on all policy solutions tackling obesity, reviewing 30 in depth. For each, we assessed the quality of the evidence, the cost to government, and the overall benefits of the policy, including the impact on obesity.

One obvious approach is to use taxation. When the Soft Drinks levy was introduced, its primary effect was not on consumers, but on the soft drinks industry. The levy was carefully calibrated so that drinks could duck under the threshold set by government by reformulating their drinks, which most did.

If we introduced a £3 per Kg tax on sugar, and a £6 per kg tax on salt (sold for use in processed foods and restaurants), we’d see a similar process of reformulation over a much wider set of food and drink. It would reduce obesity by 12%, but it would also raise £7bn per year in tax revenue. While that might keep the Treasury happy, raising revenue through higher food bills takes a brave politician even in better economic conditions.

A more politically palatable alternative is to use regulation. Over 95% of the food sold in the UK is through the 11 main supermarkets. They have huge power to shape the food that is produced - through their own brands and market power - and what is stocked and promoted.

Supermarkets already have data on the ‘healthiness’ of the typical shopping basket (what’s known as the NPM - Nutrient Profile Model). As you can see from the chart below, most supermarkets score around 67 out of 100.

If we set mandatory targets for supermarkets to raise their NPM score to 69 out of 100 - about the same as the highest performing supermarkets today - we’d see average calories consumed go down by 80 calories per day, and produce an overall reduction in obesity of around 25%.

The political attraction of this policy is that this change would be delivered without any cost to consumers. Supermarkets could be given 4 years to reach the new standard. During that time, they would already be shifting their store layouts, refreshing their promotions many times over or reformulating products, so this would not be an additional cost. Even if some supermarkets failed to achieve this relatively modest goal, the fines they would pay would not feed into consumer prices given the extremely competitive nature of the UK retail market.

From a business perspective, outcome-based, long term regulation is far preferable to mico-managing the way supermarkets promote their products. It gives them the time and flexibility to adapt so that they can maintain their revenue and profits.

Supermarkets will, of course, rightly say we should also ensure that restaurants, takeaways and delivery platforms should also be captured by robust policy. For example, could a similar regulatory standard be applied to the average food sold through delivery platforms? While hard to implement immediately given the challenge of getting high quality data, this is a solvable problem in the medium term.

Looking at other policies

For now, the key regulations that will drive change in the out of home sector and beyond include the restriction of advertising of products high in fat, sugar and salt - on TV, online, and on public transport. Government are already introducing the TV and online component. This one measure is estimated to reduce obesity by around 16%. Other measures could include banning price promotions of ‘HFSS’ food in out of home businesses and location promotions on food delivery platforms.

What role do we see for weight-loss jabs? If we wanted to solve obesity just through weight-loss jabs, it may be cost-effective and feasible in time, particularly as costs fall. For example, we modelled injecting 3m people per year, which would cost around £42 billion at current prices over 5 years, but produce benefits of £130 billion in that same period.

But we are still in the early stages of understanding the effects of these drugs. They do not work for all people, and have drawbacks that are still emerging. As with dieting, people put weight back on when they come off drugs. They also may limit the joy we gain from eating. As with most health issues, if we can prevent illness it is better for us and cheaper, rather than relying on long-term medication.

For now, our preferred option is to extend the use of GLP1s to people with a BMI of over 35. Rather than see prevention and treatment as in opposition, we should see them as complimentary. The more we can do to improve the food environment, the easier it will be for people to take weight loss drugs temporarily and not regain weight afterwards. If over time we find that the preventative policies outlined above are less effective than hoped, then we may want to substantially extend the focus on treatment.

Managing the politics

The fear of the "nanny state" label has long paralysed meaningful action on obesity.

Yet, as Henry Dimbleby and Dr Dolly Van Tulleken's extensive interviews with former prime ministers, health secretaries, and other politicians show, the political cost of acting on obesity is far lower than feared.

Most people want to be healthy and do not want their kids to grow up obese. They also do not want to have to pay high taxes because of our failure to prevent disease. That is the basis for why action on obesity could command widespread support on the right as well as left.

However, people understandably do not want to pay more for their food, nor do they want to be lectured about lifestyle changes that stop them enjoying food and drink.

The policy approach outlined above ought to be able to meet people where they are at and still achieve huge impact. We should reassure people that policies will not put up the price of food which is why regulation rather than tax is more viable. And we should explain that the route to a healthy weight is not through diets, but small, sustained changes that do not rely on individual behaviour change.

The positive vision is one where businesses are ‘on the side’ of consumers, helping us to make modest changes that keep us healthy, whereas today, the cumulative impact of all the cues we experience is to make eating slightly too much the norm.

It is naive, of course, to ignore the way opponents will try to pull any policy on obesity into the ‘culture war’. But is there any policy area where it is credible to achieve such a dramatic impact, and generate such financial savings for taxpayers, at such little cost? When you see the size of the prize, it is worth threading the political needle.

What I’m reading / listening to / thinking about

Having worked in a humanitarian organisation, it’s been extremely depressing to see the closure of USAID followed by a major cut in UK and French aid. As this article by Nobel Prize winners Abhijit Banerjee and Esther Duflo argues, there are so many misunderstandings about aid, with Americans believing 25% of the federal budget is spent on it (compared to 1% in reality). My suggestions for donors and aid organisations are:

1. If we are to spend only 0.3% on aid, then all of it should actually be spent on helping poorer countries, rather than going on accommodation costs for UK asylum seekers. Let’s at least return some integrity to the UK aid budget.

2. With far fewer resources, it makes sense to focus income more on helping fragile countries affected by conflict and disaster and those fleeing crisis, rather than stable low income countries where trade and other levers can support their growth. We should spend money on humanitarian crises rather than development.

3. Now is the time to double down on innovation, evaluation and greater focus in aid. We should do fewer things but really well. Focus more on cash transfers, digital provision and essential, life-saving health services. And expand rights to work and learn for those fleeing conflict.

4. As Banerjee and Duflo argue, look at new sources of funding. They suggest that if billionaires pay a minimum of 2 per cent of their wealth in tax annually, it could raise up to $250bn annually.

1. Frontier Economics calculates the total annual cost of excess weight in the UK at £98 billion, around a third of which is borne by the NHS or the economy through lost productivity. Excluding costs borne by individuals, halving excess weight could generate total savings/benefits of over £17 billion annually. Restoring the foreign aid budget would cost around £4 billion, and cutting basic income tax by 1p would cost £8 billion, leaving around £5 billion for the NHS.