Effect of ambient temperature on overweight: direct and indirect pathways in a multiple mediation model

Global warming and obesity are two major global challenges. The intricate relationships between climate, lifestyle factors, and their combined impact on overweight remain to be fully elucidated. We aim to estimate the effect of ambient temperature on overweight and examine the role of physical activity and fruit/vegetable consumption as indirect mediating pathways in Argentina. This cross-sectional study was conducted using data from the 2018 National Risk Factors Survey. Average air-temperature at 2m height (from ERA5 reanalysis data) was linked with individual-level data. A multilevel logistic generalized structural equation model was applied to examine the mediating effects of physical activity level and fruit/vegetable consumption on the association between ambient temperature and overweight, adjusted for sex, age, and educational level. The raw difference (95%CI) between the indirect effects was estimated using bootstrapping techniques (sample = 10,000, replicates = 5,000). An inverse association (direct effect) was observed between ambient temperature and overweight (c = -0.019, 95%CI: -0.034; -0.004). A one-unit increase in temperature was associated with higher log odds of fruit/vegetable consumption (a1 = 0.020, 95%CI: 0.005; 0.035) and lower log odds of having moderate (a21 = -0.015, 95%CI: -0.023; -0.007) and high (a22 = -0.059, 95%CI: -0.068; -0.049) physical activity levels, compared to low fruit/vegetable consumption and low physical activity level, respectively. However, the mediating effect of high physical activity level on the temperature-overweight relationship was of greater magnitude. In conclusion, ambient temperature influences fruit/vegetable consumption and physical activity, indirectly affecting nutritional status, with physical activity acting as the key mediator. This underscores the need to prioritize climate change adaptation strategies that promote physical activity.