Systemic inflammation is present in children and adults with obesity. Inflammation associated with obesity appears to be central to the development of insulin resistance and atherosclerosis and may be important in the pathogenesis of other comorbid conditions. Although generally considered an inert energy storage tissue, white adipose tissue is a metabolically active organ. It produces a number of inflammatory cytokines and acute-phase reactants. Inflammation associated with obesity declines after weight loss and with exercise. It may also be possible to modify obesity-associated inflammation with medications, reducing comorbidities without weight loss. The study of inflammation in the context of excessive adipose tissue is central to understanding obesity and modifying its impact on patients.