CD4 and AIDS: Although immune reconstitution is a major goal of ART, it is unclear why higher baseline BMI levels positively affect CD4+ T-cell gain, and our study shows that peripheral CD4+ T cells in HIV/AIDS patients receiving ART are associated with the potential relevance of fat metabolism, which is critical for a better understanding of the biological determinants of immune reconstitution, especially in patients with poor immune reconstitution and underweight.