Can a Tax on Sugary Drinks Reduce Obesity?

Professor Mike Rayner, Dr Pete Scarborough and their team in the British Heart Foundation Centre on Population Approaches for Non-Communicable Disease Prevention modelled the effect of a 20% tax on sugary soft drinks in the UK, finding a distinct reduction in rates of obesity, particularly among young people.

Sugary soft drinks are increasingly understood to have negative health effects, especially their contribution to rising rates of obesity. Various ways of reducing their consumption have been suggested including placing a tax on drinks based on their sugar content – if the sugary option is more expensive, then consumers will choose a cheaper, healthier option.

Sweetened soft drinks are said to contain ‘empty calories’: they add extra calories to the diet but provide no nutritional benefits. They can be substituted with lower calorie options with few unintended consequences, such as increases in consumption of other foods as compensation. It is known that drinks don’t make you feel full in the same way as foods, which can lead to over consumption of calories from beverages. This means that when soft drinks are reduced in the diet there is less need to replace the calories from other sources.

Sugar-sweetened and diet options in a supermarket,
photo by Alvimann

In collaboration with the Centre for Food Security at the University of Reading, the researchers set up a food demand model system, which takes data from a survey of actual consumer food purchasing and models how people change their food buying behaviour when prices change. This allows for compensatory behaviour by consumers swapping between sugary soft drinks, diet drinks, fruit juices, milk, tea, coffee and alcoholic beverages.

They then applied a 20% tax on sugary soft drinks and looked at how the model suggested people’s shopping habits would change, with results grouped by both age and income group.


The results, published in the British Medical Journal, showed an average drop of 17 kJ per person per day over the whole UK population. While this does not sound like a lot, it is an average that includes those who did not drink sugary soft drinks at all and those who drink a large quantity of them.

The key result of this drop in calorie intake was a reduction of 180,000 obese people across the UK, around 1.3%, with a greater reduction of obesity among young people under 30, who generally drink more sugary soft drinks.

The tax was estimated to raise around £276m per year. Interestingly, there was little difference in the effect between poorer and richer income groups, most likely because there is not a big difference between the amounts of sugary soft drinks consumed between income groups in the UK.

Wider Interest

The results of this study have been widely cited by those advocating for a soft drink tax in the UK, such as the British Medical Association. Further research that quantifies potential interventions such as a sugar tax is crucial for government policymakers making evidence-based policy on obesity.


The research group that produced this was funded by the British Heart Foundation.

Read more

Diet and Nutrition Research in the Nuffield Department of Population Health

Effects of a fizzy drink tax on obesity rates estimated - Page summarising this research on the NHS website

Photo of drinks cans by Cohdra, Morguefile

Sugar-sweetened and diet options in a supermarket by Alvimann, Morguefile