In multivariable models, race/ethnicity, income, sexual orientation, and CD4 count were significant correlates of obesity in HIV-infected men receiving medical care; those with annual income under $50,000 but over $20,000, heterosexual men, and those with CD4 count greater than 200 cells/μL were more likely to be obese. The gene discussed is CD4; the disease is obesity due to melanocortin 4 receptor deficiency.