Projected impact of the Portuguese sugar-sweetened beverage tax on obesity incidence across different age groups: A modelling study

Background: Excessive consumption of sugar has a well-established link with obesity. Preliminary results show that a tax levied on sugar-sweetened beverages (SSBs) by the Portuguese government in 2017 led to a drop in sales and reformulation of these products. This study models the impact the market changes triggered by the tax levied on SSBs had on obesity incidence across various age groups in Portugal. Methods and findings: We performed a national market analysis and population-wide modelling study using market data for the years 2014–2018 from the Portuguese Association of Non-Alcoholic Drinks (GlobalData and Nielsen Consumer Panel), dietary data from a national survey (IAN-AF 2015–2016), and obesity incidence data from several cohort studies. Dietary energy density from SSBs was calculated by dividing the energy content (kcal/gram) of all SSBs by the total food consumption (in grams). We used the potential impact fraction (PIF) equation to model the projected impact of the tax-triggered change in sugar consumption on obesity incidence, through both volume reduction and reformulation. Results showed a reduction of 6.6 million litres of SSBs sold per year. Product reformulation led to a decrease in the average energy density of SSBs by 3.1 kcal/100 ml. This is estimated to have prevented around 40–78 cases of obesity per year between 2016 and 2018, with the biggest projected impact observed in adolescents 10 to