To investigate the prevalence of sarcopenia among people living with HIV (PLWH) in Japan and analyze the relationship between HIV infection and ART effects on the body composition of Japanese PLWH for more appropriate drug selection and lifestyle guidance. Cross-sectional observational study. We included male patients aged ≥ 60 years whose body composition was measured by InBody 570 body composition analyzer during outpatient visits. Patients were classified by body shape based on body mass index (BMI) and body fat percentage measurements and by tenofovir alafenamide administration. Hidden obesity is a condition wherein the BMI is within the standard range but the body fat percentage is higher than the reference. Patients with low muscle mass and strength were considered to have sarcopenia, whereas those with only low muscle strength were considered to have pre-sarcopenia. In total, 87 patients were included. Based on body shape determined by BMI and body fat percentage, most patients had hidden obesity (40 patients, 46.0%). Sarcopenia was detected in 9 patients (10.3%) and pre-sarcopenia in 14 patients (16.1%). The tenofovir alafenamide (TAF) use group had significantly higher BMI, higher skeletal muscle mass, body fat mass, and skeletal muscle mass index relative to the non-TAF use group. Hidden obesity is a risk for lifestyle diseases. It is important to recognize it based on body composition measurements because it can be missed by BMI measurement alone. Tenofovir alafenamide therapy increases skeletal muscle mass, which may result in the prevention of sarcopenia. To clarify how TAF affects the development of sarcopenia and lifestyle diseases, future studies on a larger cohort are warranted.