Objectives: HIV infection alters the composition of the gut microbiota.However, investigations of HIV infection and the gut microbiome have not considered the contributions of dietary intake and obesity to microbial diversity.Our objective was to demonstrate how response to HIV antiretroviral therapy (CD4 + T-cell count), dietary intake, and obesity [body mass index (BMI) ≥30 kg/m 2 ] impacts the microbiome in adults with HIV aged >50 y, who are considered older adults in the HIV community owing to possible accelerated aging.Methods: We recruited 60 HIV-infected persons ≥50 y old with controlled viremia for >1 y.Groups were determined based on a CD4 + count either 500 (high, n = 30) cells/mm 3 and a BMI ≥30 kg/m 2 (obese) or <30 (not obese): 1) Low CD4/Not Obese, 2) Low CD4/Obese, 3) High CD4/Not Obese, and 4) High CD4/Obese.Participants had no underlying gastrointestinal disease or antibiotic use for 60 d pre-enrollment.Dietary intake was assessed as the average of three 24-h diet recalls.The fecal microbiome was analyzed using 16S rRNA gene sequencing with the use of MiSeqTM and QIIME bioinformatics.Results: The median age was 56 y (range 50-72 y); 30% were women; and the median BMI was 28 kg/m 2 .A negative correlation was observed between BMI >30 kg/m 2 and diversity (Shannon r = -0.24,P = 0.11; Simpson r = -0.23,P = 0.04).A low CD4 count was associated with increased Synergistetes and decreased Bifidobacteriales.Protein intake adjusted for body weight was positively correlated with Fusobacteria and Prevotella operational taxonomic units.Participants in the High CD4/Not Obese group had higher Bacteroidetes and lower Firmicutes composition than both Obese groups (both P < 0.05), whereas the Low CD4/Not Obese group had Bacteroidetes and Firmicutes composition similar to both Obese groups.Conclusions: In this preliminary study, the gut microbiomes of obese adults with HIV were less diverse, whereas dietary protein intake impacts the gut microbiome composition even in the presence of HIV infection.However, individuals infected with HIV-1 in the Low CD4/Not Obese group display a gut microbe profile similar to HIV-infected obese persons.Understanding the relation between body weight, gut microbe composition, and chronic viral infection will facilitate the development of novel interventions for gut dysbiosis and its consequences in people living with HIV.