Impact of a levy on sales of sugar-sweetened beverages within a national chain of restaurants: interrupted time-series analysis

Abstract

BackgroundConsumption of sugar-sweetened beverages (SSBs) is associated with type 2 diabetes, weight gain, and dental caries. Taxes and levies on these beverages have been proposed as a way to reduce their consumption. However, only limited evidence exists for the effectiveness of taxes and levies where implemented. We aimed to assess the impact of a levy of £0·10 per drink on sales of SSBs delivered nationally in the UK within a restaurant setting using electronic point of sale data. MethodsPoint of sale data for non-alcoholic drinks were obtained from all eligible restaurants (n=37) in one restaurant chain between June 23, 2014, and Feb 28, 2016. We conducted an interrupted time-series analysis using linear mixed-models with restaurant as a random effect to assess whether there was a step-change in sales per customer of levy-eligible SSBs at 12 weeks and 6 months after implementation. We assessed effects on non-levied drinks (other soft drinks, juices, bottled waters, and diet cola) to explore substitution effects. Analyses also adjusted for seasonality and clustering. We stratified analyses by sales area (London, the North of the UK, the South of the UK) to assess regional effects. FindingsOverall, compared with the preintervention period, sales per customer of levy-eligible SSBs declined by 11·7% (p=0·002) at 12 weeks and 9·8% (p=0·004) at 6 months. For non-levy drinks, sales per customer of fruit juice (main menu) increased at 12 weeks (+3·3%, p=0·051) and 6 months (+19·7%, p<0·0001). At 6 months, there was a decrease in sales per customer of diet cola (−7·6%, p=0·002) and bottled waters (−6·7%, p=0·009), whereas sales of other non-levied soft drinks increased (+14·6%, p<0·001). We found marked regional variations, with declines in sales of levy-eligible SSBs in London (−14·2%, p<0·001) and the South (−13·8%, p<0·001), but no change in the North. InterpretationTo our knowledge, this is the first study to assess the impact on sales of a levy on SSBs delivered at scale in a national chain of restaurants. We found evidence of substantial declines in sales of levy-eligible SSBs, with the greatest effects seen in London and the South. A levy on SSBs within restaurant settings has the potential to reduce sales and therefore consumption of these beverages. FundingNational Institute for Health Research.