The UK government’s sugar reduction programme has been described as “world leading” among the increasing number of policies that target reducing sugar consumption around the world. This programme was announced in 2016 and challenged the food industry to work with Public Health England to achieve by 2020 a 20% reduction in the sugar content of the foods that—together with sugary drinks—make up 50% of children’s intake of free sugars. These foods, such as cakes and biscuits, also make up a large percentage of adults’ sugar intake, so the policy could also have important health benefits for adults.

Our new modelling study estimated that if these targets were met and did not lead to unanticipated changes in consumer or industry behaviour, then the average reduction to sugar intake in England could amount to 25kcal (105kJ) per day for 4-10 year olds and 11-18 year olds, and 19kcal (79kJ) per day for adults. These averages hide broad variation, with high consumers receiving a greater health benefit. We accounted for this by estimating calorie change and BMI at the individual level before modelling health impacts across the population.

We found that the obese population in England could fall by more than one in 20 obese younger children (4-10 years) and adults, but that for older children (11-18 years) the benefits would be smaller—at around one in 50. Health benefits from obesity related illness in adults could be substantial, with our results suggesting that more than 150 000 cases of type 2 diabetes could be prevented over 10 years, plus nearly 6000 cases of both cirrhosis and colorectal cancer, accounting for savings to the NHS in England of £285m.

We know that sugar consumption is higher and obesity is more prevalent in lower socioeconomic groups, so this policy may help to address health inequalities. Inequalities could be further reduced by this kind of “upstream” policy approach because it targets health risk separately from health behaviour. People in more deprived socioeconomic groups may be less likely to achieve positive behaviour change, so this policy may help to reduce health inequalities precisely because it circumvents refractory unhealthy behaviours.

Achieving these potential benefits will be heavily reliant on how industry and consumers respond. The plan involves sugar being removed from diets by reformulating products, reducing their size, and/or shifting the balance of sales to products with lower sugar content. We don’t yet know if reformulation will successfully reduce the calorie content and we also don’t yet know if a food item’s size is reduced that consumers will not simply eat a greater number of them.

Furthermore, we have little indication of how industry intends to shift the balance of sales. A lack of strong consensus in the research around eating behaviours prevents us from being certain of consumer responses to the plan. To maximise our ability to design consistent, effective policy, more investment is needed in these research areas.

If the sugar reduction programme’s targets are hit, it would go some way to help tackle obesity in England, but is not going to solve the current crisis. The Public Health Responsibility Deal shows us that success cannot be assumed.

Whatever happens, we will need multiple interrelated interventions to solve the complexity of the obesity problem. These policies are likely to need to include approaches that are sector specific, such as regulating price promotions and advertising. Yet we also need to achieve cultural change around food and physical activity, attitudinal change across our public bodies to systematically deliver health in all policies (from town planning and transport, to education on healthy eating and cooking), and to address poverty. Only through systemic change can we start to address the alarming rise in chronic diseases related to poor nutrition.

Ben Amies-Cull is a doctoral student at the Nuffield Department of Population Health, University of Oxford, and a practising GP in Manchester. His academic interests are in the health economics of non-communicable disease prevention, population approaches to non-communicable disease prevention, and health inequalities. Twitter @ben_amies

Competing interests: Ben Amies-Cull was supported by grants from the National Institute of Health Research and Medical Research Council.