Exposure to man-made combustion products, including secondhand tobacco smoke, maternal smoking during pregnancy, and near-roadway air pollution (NRAP), have been associated with increased body mass index and obesity in children and have been shown to result in excess weight gain in animal models. Potential mechanisms include pro-inflammatory central nervous system effects of airborne particles on appetite control, resulting in increased caloric intake, or changes in basal metabolism due to effects on mitochondria and brown adipose tissue. Combustion-derived polyaromatic hydrocarbons have also been linked to altered lipid metabolism, epigenetic effects on PPARγ expression, particle-induced estrogenic effects, and alterations in the distribution of visceral fat. Emerging evidence that a broad spectrum of environmental chemicals have “obesogenic” properties and alter the metabolic profile of adipose tissue challenges the prevailing model that the childhood obesity epidemic is explained solely by increased caloric density of food and decreased physical activity. Research on environmental obesogens could identify novel targets for intervention and yield public health benefits, since NRAP and SHS exposure are both common in populations most at-risk for development of obesity.