Most murine studies are skewed toward the use of male mice to study obesity-induced metabolic dysfunction because of similar protection in female mice. We have investigated dietary obesity in a mouse model and have directly compared inflammatory responses in males and females. In this review we will summarize what is known about sex differences in diet-induced inflammation and will summarize our data on this topic. It is clear that sex differences in high-fat diet-induced inflammatory activation are due to cell intrinsic differences in hematopoietic responses to obesogenic cues, but further research is needed to understand what leads to sexually dimorphic responses. diabetes; high-fat diet; myelopoisis; obesity; sexual dimorphism GLOBAL OBESITY RATES have risen drastically in the past several decades with around one in every three individuals currently categorized as obese (34). The overall incidence of obesityrelated diseases such as diabetes and cardiovascular disease (CVD) also continues to rise as a result (3a). Obesity manifests as the result of an imbalance of caloric intake and energy expenditure. A major contributing factor to the increase in obesity rates is an increase in the consumption of calorie-dense foods rich in saturated fatty acids (4). With increased consumption of high-fat foods, individuals accrue body fat and thus have an elevated risk of developing obesity-related diseases. In this brief review we will emphasize the effects of diet-induced obesity, focusing primarily on sexually dimorphic responses of high-fat diet (HFD) priming of the immune system. An individual's response to HFD is dependent on several factors including sex, age, and ethnicity. What has become increasingly striking is that there is a clear sexual dimorphism in obesity and diabetes rates. While obesity rates are higher in women (34), men have higher rates of cardiovascular disease (CVD) and Type 2 diabetes (30, 36), suggesting that females are protected from the adverse effects of obesity (30). This is of particular importance because when investigating diabetes and CVD, many preclinical studies have been performed in males alone, leaving gaps in our knowledge of sexually dimorphic responses to obesity (45). Therefore, guidelines and therapies are being created based on investigations in males but are being implemented in men and women (13).It is important to investigate males and females to understand the contributing factors to these sex-specific differences. Previous studies have focused on altered hormone environments, anatomical fat distribution (17, 19), and energy expenditure differences. Women have been found to have 10% higher total body fat content compared with males of the same body mass index (BMI) (15). This dimorphism is especially profound in poor socioeconomic conditions, whereas richer environments show a smaller variance in adiposity between the sexes (11). This suggests that estrogen largely influences fat accumulation regardless of socioeconomic status (11). Additionally, when adiposity matched, fema...