Air Pollution Has a Significant Negative Impact on Intentional Efforts to Lose Weight: A Global Scale Analysis

Background: Air pollution causes many diseases and deaths. It is important to see how air pollution affects obesity, which is common worldwide. Therefore, we analyzed data from a smartphone application for intentional weight loss, and then we validated them. Methods: Our analysis was structured in two parts. We analyzed data from a cohort registered to a smartphone application in 10 large cities of the world and matched it with the annual pollution values. We validated these results using daily pollution data in United States and matching them with user information. Body mass index (BMI) variation between final and initial login time was considered as outcome in the first part, and daily BMI in the validation. We analyzed: daily calories intake, daily weight, daily physical activity, geographical coordinates, seasons, age, gender. Weather Underground application programming interface provided daily climatic values. Annual and daily values of particulate matter PM10 and PM2.5 were extracted. In the first part of the analysis, we used 2,608 users and then 995 users located in United States. Results: Air pollution was highest in Seoul and lowest in Detroit. Users decreased BMI by 2.14 kg/m(2) in average (95% confidence interval, -2.26 to -2.04). From a multilevel model, PM10 (beta= 0.04, P=0.002) and PM2.5 (beta=0.08, P<0.001) had a significant negative effect on weight loss when collected per year. The results were confirmed with the validation (beta(AQI*time)=1.5x10(-5); P<0.001) by mixed effects model. Conclusion: This is the first study that shows how air pollution affects intentional weight loss applied on wider area of the world.