Changes in Weight-Related Outcomes Among Adolescents Following Consumer Price Increases of Taxed Sugar-Sweetened Beverages

Abstract

Importance: Following the implementation of a tax on sugar-sweetened beverages (SSBs) in Mexico in 2014, SSB prices increased by about 10% on average, but differently across cities. It remains unclear how observed SSB price changes are associated with adolescent weight-related outcomes.

Objective: To compare weight-related outcomes among adolescents living in cities with differential SSB price changes before and after the SSB tax was implemented in Mexico.

Design, setting, and participants: Associations between differential SSB price changes and changes in weight-related outcomes were examined overall and by sex among 12 654 adolescents aged 10 to 18 years born between 1999 and 2002 living in 39 cities in Mexico. Multivariate regressions with individual fixed effects were applied on longitudinal individual-level yearly clinical data (height and weight) from 2012 to 2017 collected by the Instituto Mexicano del Seguro Social (IMSS) and merged with city-level SSB price data from 2011 to 2016 collected by the National Institute of Statistics and Geography (INEGI). Data were analyzed from July 2018 to July 2021.

Exposures: Yearly city-level changes in SSB prices between 2011 and 2016.

Main outcomes and measures: Age- and sex-specific body mass index (BMI; calculated as weight in kilograms divided by height in meters squared) percentile and indicator for overweight or obesity if BMI was at or above the 85th percentile.

Results: Before 2014, 46% of 12 654 adolescents (6850 girls and 5804 boys) included in this study had obesity or overweight. The mean (SD) age was 11.38 (1.08) years. Among girls, a 10% SSB price increase was associated with a 1.3 percentage point absolute decrease (95% CI, -2.19 to -0.36; P = .008) or a 3% relative decrease in overweight or obesity prevalence within 2 years of a price change. For girls with BMI at or above the 75th percentile pretax, this price increase was associated with a 0.59 lower BMI percentile (95% CI, -1.08 to -0.10; P = .02) or a 0.67% relative decrease. Improved outcomes for girls were observed in cities where price increases were greater than 10% after the tax. No such associations were observed for boys.

Conclusions and relevance: In this study, increased SSB prices were associated with decreased overweight or obesity prevalence among girls but not among boys. Improvements in outcomes were small, and mostly observed for girls with heavier weight and in cities where price increases after the tax were greater than 10%.

Figure 1.. Changes in Sugar-Sweetened Beverage (SSB) Prices Over Time and Across Cities

A, Unweighted mean prices of carbonated SSBs expressed per product per 1 L per year between 2011 and 2016. Nominal prices were deflated using the January 2011 consumer price index. To convert 2011 Mex$ to 2011 US$, multiply by 0.08. The dashed line indicates implementation of the SSB tax in January 2014. B, Percent change in real prices of carbonated SSBs before and after the tax. Price changes following the tax were >10% in 23 cities (4169 adolescents), 5%-10% in 7 cities (6986 adolescents), and <5% in 9 cities (1499 adolescents).

Figure 2.. Unadjusted Trends in Prevalence of Adolescents at Risk for Overweight or Obesity by Areas With Differential Price Change Following the Sugar-Sweetened Beverage (SSB) Tax

A, Mean prevalence at risk for overweight or obesity (OWOB) among all adolescents included in the study. Sample is restricted to a cohort of adolescents living in cities who were born between 1999 and 2002 and whose weight and height were measured at an Instituto Mexicano del Seguro Social clinic at least once per year between 2012 and 2017. Price changes following the tax were >10% in 23 cities (4169 adolescents), 5%-10% in 7 cities (6986 adolescents), and <5% in 9 cities (1499 adolescents). The dashed line indicates the start of the SSB tax in January 2014. B, Mean prevalence of at risk for OWOB for girls. C, Mean prevalence of at risk for OWOB for boys.