Obesity is associated with macrophage accumulation in adipose tissue. This study investigated the relationship between adiposity and macrophage content in adipose tissue using transcriptomic and histological analyses in mice and humans. The researchers found that 1,304 transcripts were significantly correlated with body mass, with 30% of these encoding proteins characteristic of macrophages. Immunohistochemical analysis revealed that the percentage of F4/80-positive macrophages in adipose tissue was positively correlated with adipocyte size and body mass. These macrophages were found to be CSF-1 dependent and derived from bone marrow. Expression analysis showed that adipose tissue macrophages are the primary source of proinflammatory molecules such as TNF-α, iNOS, and IL-6. In humans, CD68 expression in subcutaneous adipose tissue was also significantly correlated with BMI and adipocyte size. These findings suggest that macrophage accumulation in adipose tissue is a key feature of obesity and contributes to the inflammatory processes associated with obesity. The study highlights the role of macrophages in the metabolic complications of obesity and their potential as targets for therapeutic interventions.Obesity is associated with macrophage accumulation in adipose tissue. This study investigated the relationship between adiposity and macrophage content in adipose tissue using transcriptomic and histological analyses in mice and humans. The researchers found that 1,304 transcripts were significantly correlated with body mass, with 30% of these encoding proteins characteristic of macrophages. Immunohistochemical analysis revealed that the percentage of F4/80-positive macrophages in adipose tissue was positively correlated with adipocyte size and body mass. These macrophages were found to be CSF-1 dependent and derived from bone marrow. Expression analysis showed that adipose tissue macrophages are the primary source of proinflammatory molecules such as TNF-α, iNOS, and IL-6. In humans, CD68 expression in subcutaneous adipose tissue was also significantly correlated with BMI and adipocyte size. These findings suggest that macrophage accumulation in adipose tissue is a key feature of obesity and contributes to the inflammatory processes associated with obesity. The study highlights the role of macrophages in the metabolic complications of obesity and their potential as targets for therapeutic interventions.