TNF and Obesity: Obesity is characterized by increased levels of circulating proinflammatory cytokines [including interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6], accumulation of leukocytes within the adipose tissue and other organs, activation of macrophages in the liver and fat, and activation of proinflammatory signaling pathways in multiple organs (43, 44).