Estimating the health impacts of sugar-sweetened beverage tax for informing policy decisions about the obesity burden in Vietnam

Background Considered a "best buy" intervention to cope with the obesity burden, a tax on sugar-sweetened beverage (SSB) has been adopted in more than 40 countries. In Vietnam, a tax on SSBs has been proposed several times (most recently in 2017). This study aimed to estimate the health impacts of different SSB tax plans currently under discussion to provide an evidence base to inform decision-making about a SSB tax policy in Vietnam. Method Five tax scenarios were modelled, representing three levels of price increase: 5%, 11% and 19-20%. Scenarios of the highest price increase were assessed across three different tax designs: ad valorem, volume-based specific tax & sugar based specific tax. In each case we modelled SSB consumption in each tax scenario; how this reduction in consumption translates to a reduction in total energy intake and how this relationship in turn translates to an average change in body weight and obesity status among adults by applying the calorie-to weight conversion factor. Changes in diabetes type 2 diabetes burden were then calculated based on the change in average body mass index of the modelled cohort. A Monte Carlo simulation approach was applied on the conversion factor of weight change and diabetes risk reduction for the sensitivity analysis. Results While the impact of a 5% price increase arising from a tax was relatively small, increasing SSBs price up to 20% appeared likely to impact substantially on national overweight and obesity rates. The greatest reduction in rates was observed for the population who were categorised as being overweight and obesity grade 1. The decline in overweight and obesity prevalence rates was slightly higher for women than men. Differences were evident across the three tax designs considered with a specific tax based on sugar density achieving greatest effects .