Background: This systematic review identifies programs, policies, and built-environment changes targeting prevention and control of adult obesity and evaluates their effectiveness.
Methods: We searched PubMed, CINAHL, PsycINFO, and EconLit from January 2000 to March 2018. We included natural experiment studies evaluating a program, policy, or built-environment change targeting adult obesity and reporting weight/body mass index (BMI). Studies were categorized by primary intervention target: physical activity/built environment, food/beverage, messaging, or multiple. Two reviewers independently assessed the risk of bias for each study using the Effective Public Health Practice Project tool.
Results: Of 158 natural experiments targeting obesity, 17 reported adult weight/BMI outcomes. Four of 9 studies reporting on physical activity/built environment demonstrated reduced weight/BMI, although effect sizes were small with low strength of evidence and high risk of bias. None of the 5 studies targeting the food/beverage environment decreased weight/BMI; strength of evidence was low, and 2 studies were rated high risk of bias.
Discussion: We identified few natural experiments reporting on the effectiveness of programs, policies, and built-environment changes on adult obesity. Overall, we found no evidence that policies intending to promote physical activity and healthy eating had beneficial effects on weight/BMI and most studies had a high risk of bias. Limitations include few studies met our inclusion criteria; excluded studies in children and those not reporting on weight/BMI outcomes; weight/BMI reporting was very heterogeneous. More high-quality research, including natural experiments studies, is critical for informing the population-level effectiveness of obesity prevention and control initiatives in adults.
Keywords: obesity; prevention; systematic reviews.