As the prevalence of overweight and obesity in U.S. adults increases to 31.1% and 42.5%, respectively, the associated cardiometabolic risks, including type 2 diabetes and cardiovascular disease, are becoming a growing concern. Sugar-sweetened beverages (SSBs) are a significant source of excess caloric intake that contributes to weight gain.
In response to concerns about SSB consumption, the need to improve health outcomes, and the desire to fund public health initiatives, SSB excise taxes have emerged as a potential solution. This study examines the association between SSB taxes and adult Body mass index (BMI) in California cities with and without such taxes, using electronic health record (EHR) data for more than 8.1 million members representing both regional and statewide populations.
This research analyzed adults aged youths in the age range of 2 to 19 years and 20 to 65 across four cities in California where the SSB taxes were instituted, including Berkeley (in 2015) and San Francisco, Oakland, and Albany (in 2017). In contrast, the same control cities were identified, comprising a total of 328 cities with no SSB tax. Researchers employed the use of EHRs of Kaiser Permanente (KP) to observe BMI trends six years before the introduction of the tax and four to six years after its implementation.
Individuals with conditions impacting BMI, such as cancer or recent bariatric surgery were excluded. Demographic factors like age, sex, race/ethnicity, and socioeconomic indicators were incorporated into the analysis. BMI was classified into overweight (BMI 25 to <30) and obesity (BMI ≥30), allowing the use of adjusted thresholds for Asian patients. A differences-in-differences method was used to compare trends between cities that had enacted an SSB tax and those that hadn’t, controlling population differences.
The study cohort included 1,044,272 individuals: 178,931 participants from four cities with excise taxes (mean [SD] age: 39.7 [11.2] years; 99,501 [55.6%] female) and 865,343 participants from 40 control cities without excise taxes (mean [SD] age: 39.9 [11.6] years; 480,155 [55.5%] female). DID estimates showed a small decline in mean BMI for particular groups in cities with SSB excise taxes. It encompassed adults 20 to 39 years: 20-25 years −0.30; 95% Confidence interval (CI), −0.51 to −0.08; 26-39 years: −0.19; 95% CI, −0.37 to −0.20 and was more significantly expressed in females (−0.19; 95% CI, −0.26 to −0.11), and White (−0.19; 95% CI, −0.35 to −0.04). Interestingly, Berkeley showed a significant reduction in mean BMI (−0.16; 95% CI, −0.27 to −0.04). However, no significant differences were seen in overall BMI or the proportion of individuals with either overweight or obesity.
The results showed diverse associations between SSB taxes and BMI reductions, mostly concentrated in certain demographic groups. Adults aged 20–39 years, the largest consumers of SSBs, experienced the most significant reductions in BMI, as did women and White individuals. Berkeley, the first U.S. city to introduce an SSB tax, had the most pronounced outcomes. However, the population-wide changes in BMI and obesity prevalence across all cities and demographic groups were not statistically significant.
The mean reduction in BMI was equivalent to an estimated weight loss of 0.8-lb for a 5′4″ woman with a BMI of 27, and the effect was modest, even though it was in the expected direction. Although these results are consistent with previous studies demonstrating a reduction in SSB sales following the taxes, the benefits were not evenly distributed. The groups at the highest risk for overweight, obesity, and cardiometabolic conditions did not have the greatest improvements, and this raises questions about equity in the implementation and impact of SSB taxes.
This study examines the complex impact of SSB taxes on adult BMI, showing encouraging outcomes for specific demographic groups, especially younger adults and Berkeley residents. However, the lack of widespread population-level changes highlights the need for further research to refine the fairness and effectiveness of these policies.
Future research should delve into the underlying factors of these demographic differences and explore ways to ensure that SSB taxes deliver wider public health benefits, especially for those most at risk of obesity and related health issues.
Reference: Liu EF, Young DR, Sidell MA, et al. City-level sugar-sweetened beverage taxes and changes in adult body mass index. JAMA Netw Open. 2025;8(1):e2456170. doi:10.1001/jamanetworkopen.2024.56170
