BackgroundObesity rates among children and adults continue to accelerate in the U.S., particularly among marginalized and low-income populations. Obesity prevention and reduction policies can significantly impact population health by improving environmental conditions and increasing access to health-promoting resources. Limited research has been conducted to examine state obesity policy change over time. The primary aim of this study is to examine legislative approaches used to prevent and reduce obesity in the state of California (U.S.).MethodsWe used quantitative policy surveillance methods to develop a state database of obesity-related legislation (bills, resolutions) introduced in California’s legislature between 1999 and 2020. Descriptive statistics were used to examine trends of introduced and enacted policy by legislative and policy characteristics. Chi-square tests were used to determine differences in characteristics between enacted and non-enacted legislation. Legislative session and policy characteristics found to be associated with enactment were used to predict adoption in a logistic regression.ResultsA total of 284 obesity-related bills and resolutions were introduced in California’s legislature between 1999 and 2020 with a peak of 43 in 2005–2006. On average, 25.8 bills and resolutions were introduced each 2-year legislative cycle. Findings indicate that (a) children and schools were the most frequently specified population and setting; (b) the most common policy topics were nutrition (45%) and physical activity (33%); and (c) only 15% of legislation mentioned race/ethnicity. Overall, 24.9% of bills were enacted compared to 82.1% of resolutions adopted. Legislation to raise awareness about obesity had 5.4 times the odds of being passed compared to other topics. Yet this difference was not statistically significant in a sensitivity analysis when we excluded resolutions.ConclusionsThis database can be leveraged to advance our knowledge of effective and equitable policy instruments to prevent and reduce obesity. Results reveal important policy elements that may impact legislative success, including policy topic, and contribute to a nascent evidence base for public health law research, legal epidemiology, and practice. Future work should investigate the role of policy effectiveness research and evidence on legislative policymaking.