Obesity rates have increased dramatically among children in many parts of the world, especially in North America and several other English-speaking countries. The impact of obesity on pediatric health has become a major prevention initiative by the Obama administration and several public health organizations. Children with obesity are at increased risk for developing asthma, which is already one of the most common chronic diseases among children. The cause underlying obesity's impact on asthma risk is unknown. Commonly cited potential etiologies include airway smooth muscle dysfunction from thoracic restriction, obesity-related circulating inflammation priming the lung, and obesity-related comorbidities mediating asthma symptom development. Each of these theories does not fit precisely with all of the data that have accumulated over the last decade. In this review, I will explore other possible causes including: (1) dietary characteristics common in Westernized countries that might lead to both obesity and asthma; (2) reductions in physical activity; and (3) genetic alterations that increase the propensity to both obesity and asthma together. Next, I will review the current data on how obesity affects common characteristics of asthma such as airway inflammation, lung function, risk of exacerbation, atopy, and response to treatment. Obesity in children with asthma appears to be associated with greater airflow obstruction and a mildly diminished response to inhaled corticosteroids. Little objective evidence in children suggests that obesity significantly heightens the risk of exacerbation or worsens disease stability in children. Lastly, I will discuss the current literature that suggests that obese children with asthma generally should receive the same guidelines-based management as lean children. However, interventions that encourage daily physical activity, weight-loss, normalization of nutrient levels, and monitoring of common obesity-related sequelae should be considered by healthcare providers managing obese children with difficult-to-control asthma.