Obesity is associated with the accumulation of macrophages in adipose tissue, which contributes to inflammation and metabolic complications. A study by Weisberg et al. investigated gene expression in perigonadal adipose tissue from mice with varying levels of adiposity due to sex, diet, and genetic mutations. They found that 1,304 transcripts correlated significantly with body mass, with 30% of the top 100 genes encoding macrophage-specific proteins. Immunohistochemical analysis showed that the percentage of F4/80+ macrophages in adipose tissue was positively correlated with adipocyte size and body mass. Similar findings were observed in human subcutaneous adipose tissue. Bone marrow transplant studies and analysis of macrophage-deficient mice confirmed that these F4/80+ cells are bone marrow-derived and depend on CSF-1. Macrophages in adipose tissue were found to be the primary source of proinflammatory molecules like TNF-α, iNOS, and IL-6. The study suggests that macrophage accumulation in adipose tissue is a key factor in the inflammatory pathways associated with obesity.Obesity is associated with the accumulation of macrophages in adipose tissue, which contributes to inflammation and metabolic complications. A study by Weisberg et al. investigated gene expression in perigonadal adipose tissue from mice with varying levels of adiposity due to sex, diet, and genetic mutations. They found that 1,304 transcripts correlated significantly with body mass, with 30% of the top 100 genes encoding macrophage-specific proteins. Immunohistochemical analysis showed that the percentage of F4/80+ macrophages in adipose tissue was positively correlated with adipocyte size and body mass. Similar findings were observed in human subcutaneous adipose tissue. Bone marrow transplant studies and analysis of macrophage-deficient mice confirmed that these F4/80+ cells are bone marrow-derived and depend on CSF-1. Macrophages in adipose tissue were found to be the primary source of proinflammatory molecules like TNF-α, iNOS, and IL-6. The study suggests that macrophage accumulation in adipose tissue is a key factor in the inflammatory pathways associated with obesity.