Climate Change, Air Pollution and the Global Obesity Syndemic: a Review of Current Evidence

Climate change and obesity are two converging global crises with complex and interrelated pathways. This review aims to synthesize recent evidence linking climate-related exposures, including rising ambient temperatures, air pollution, and urbanization to the pathogenesis of obesity. It also explores how obesity itself increases vulnerability to heat injury and environmental stress, highlighting the bidirectional nature of this syndemic.

Epidemiologic evidence has supported associations between air pollution and increased body mass index, central adiposity, and metabolic dysfunction across the lifespan. Mechanistic research implicates impaired thermogenesis, chronic inflammation and oxidative stress, endocrine disruption, hypothalamic inflammation, and microbiome dysbiosis as key pathways linking environmental exposures to adiposity. Obesity further amplifies the physiological burden of climate-related stressors, such as heatwaves, due to reduced heat dissipation and altered hormonal responses. Anti-obesity medications may exacerbate heat-related risks via dehydration and gastrointestinal side effects. Urban greenness appears to offer a partial protective effect, modulating the obesogenic impact of air pollution and heat, particularly in low-income settings. Obesity and climate change share common socioeconomic, behavioral, and environmental drivers. Addressing this dual burden requires integrated strategies that promote environmental sustainability and metabolic health. These include green infrastructure, active transportation, climate-adapted clinical care, and public health strategies that reflect planetary health principles. Recognizing obesity not only as a medical condition but also as an environmentally influenced disorder is essential for effective, future-oriented prevention and intervention efforts.