Sugar-sweetened beverage taxes reduce child and adolescent BMI

By Pooja Toshniwal PahariaReviewed by Benedette Cuffari, M.Sc.Aug 5 2024

A recent study published in JAMA Network Open investigates whether city-level sugar-sweetened beverage (SSB) taxation affects child and adolescent body mass index (BMI) values in California between 2009 and 2020.

Study: City-Level Sugar-Sweetened Beverage Taxes and Youth Body Mass Index Percentile. Image Credit: Daisy Daisy / Shutterstock.com

Are SSB taxes effective?

In 2019, the American Academy of Pediatrics (AAP) proposed economic solutions like SSB taxes to reduce the consumption of these beverages to prevent obesity among children and young adults. Previous studies examining the efficacy of public health strategies to reduce the consumption of SSBs among children and young adults have produced mixed outcomes; however, a tendency toward weight loss has been reported.

Following taxation, SSB purchases and consumption decreased in several cities, which helped support public health and equality programs. Nevertheless, the effect of these taxes on weight-related outcomes in children remains unclear. Understanding the potential efficacy of SSB taxation is crucial for towns contemplating imposing similar strategies to reduce overweight and obesity among children.

About the study

The researchers compared the effects of SSB tax implementation in Berkeley, Albany, San Francisco, and Oakland cities of California to 40 control cities. Exposure and control cities were matched based on Euclidean distances of variables according to five-year averages of the United States Census American Community Survey, provided four years before SSB tax implementation.

The variables included population density, total population, female percentage, age distributions, education, ethnicity, race, insurance status, household poverty percentage, and the percentage of Kaiser Permanente (KP) members. The researchers excluded control cities matched to exposure cities by their geographical proximity.

The study sample comprised KP members between two and 19 years of age residing in the selected Californian cities with one or more pre- and post-tax BMI values documented in their digital medical records. The researchers excluded individuals with metastatic cancers, pregnancy, history of bariatric surgery in the previous five years, and palliative care recipients.

Primary outcomes included U.S. Centers for Disease Control and Prevention (CDC) sex and age-specific BMI percentiles, as well as the percentage of overweight or obese youth before and four to six years after SSB tax implementation.

BMI percentiles exceeding the 85^th percentile reflected overweight, whereas BMI percentiles above the 95^th percentile reflected obesity. All study participants were stratified by age into two to five, six to 11, and 12 to 19 years.

Data were analyzed between January 2021 and May 2023 using the difference-in-differences (DID) approach. Sensitivity analyses were conducted using the synthetic control method (SCM) and aggregated city-year data rather than patient-year health records to re-estimate SSB taxation outcomes.

Study findings

A total of 44,771 individuals, 50% of whom were female, were included in the current study, with a mean age of 6.4 years. All study participants residing across four California cities that taxed SSB exhibited significant decreases in mean sex—and age-specific BMI values after SSB tax implementation compared to 345,428 children with a mean age of 6.9 years, 50% of whom were female, residing in matched control cities.

SSB tax implementation led to an overall reduction of 1.6% in mean BMI percentile change between study exposure cities and matched controls. However, no statistically significant differences were observed in the proportion of overweight or obese youth compared to control cities.

The DID method yielded statistically significant estimates for exposure city residents in terms of BMI percentile reductions. More specifically, 2% and 2.8% reductions were observed in children between two and five years of age and those aged six to 11 years, respectively.

Significant reductions were also observed in the percentage of overweight or obese youth, 5.5% and 4.2% in children two to five years and six to 11 years of age, respectively. Obese youth percentages were also reduced by 1.9% in children between two and 11 years of age.

Compared to control cities, mean BMI percentile reductions were statistically significant for Asian, male, and White children at 1.6%, 2%, and 2.5%, respectively. Young white children also exhibited significant reductions in the percentages of those who were overweight or obese by 3.7% and those with adiposity by 2.8%. Sensitivity analyses yielded similar results.

Conclusions

SSB taxes were found to significantly reduce youth BMI percentiles, especially among male, White, and obese Asians 12 years of age and younger residing in San Francisco and Berkeley. These findings indicate that governments should explore imposing SSB legislation to reduce childhood obesity and the burden of chronic illness among children 12 years of age and younger.