Obesity and type 2 diabetes mellitus (T2D) are global pandemics. Worldwide, the prevalence of obesity has nearly tripled since 1975 and the prevalence of T2D has almost doubled since 1980. Both obesity and T2D are indolent and chronic diseases that develop gradually, with cellular physiologic changes occurring before the clinical signs and symptoms of the diseases become apparent. Individuals with obesity and T2D are physiologically frail and have an increased risk of infections and mortality from sepsis. Improvement in the morbidity and mortality of these at-risk populations would provide a great societal benefit. We believe that the worsened outcomes observed in these patient populations is due to immune system dysfunction that is triggered by the chronic low-grade inflammation present in both diseases. As immune modulatory therapies have been utilized in other chronic inflammatory diseases, there is an emerging role for immune modulatory therapies that target the chronically affected immune pathways in obese and T2D patients. Additionally, bariatric surgery is currently the most successful treatment for obesity and is the only weight loss method that also causes a sustained, substantial improvement of T2D. Consequently, bariatric surgery may also have a role in improving immunity in these patient populations.