Purpose: Although obesity is a risk factor for hip osteoarthritis (OA), the role of body composition, if any, is unclear. This study examines whether obesity and body composition are associated with hip cartilage changes using magnetic resonance imaging (MRI) in community-based adults. Methods: 141 community-based participants with no clinical hip disease, including OA, had BMI and body composition (fat mass and fat free mass) measured at baseline (1990 to 1994), and BMI measured and 3.0T MRI performed at follow-up (2009-2010). Femoral head cartilage volume was measured and femoral head cartilage defects were scored in the different hip regions. Results: For females, baseline BMI (b¼-26mm 3 , 95% CI-47 to-6mm 3 , p¼0.01) and fat mass (b¼-11mm 3 , 95% CI-21 to-1mm 3 , p¼0.03) were negatively associated with femoral head cartilage volume. Also, while increased baseline fat mass was associated with an increased risk of cartilage defects in the central superolateral region of the femoral head (OR¼ 1.08, 95% CI 1.00-1.15, p¼0.04), increased baseline fat free mass was associated with a reduced risk of cartilage defects in this region (OR¼0.82, 95% CI 0.67-0.99; p¼0.04). For males, baseline fat free mass was associated with increased femoral head cartilage volume (b¼ 40mm 3 , 95% CI 6 to 74mm 3 , p¼0.02) Conclusions: Increased fat mass was associated with adverse hip cartilage changes for females, while increased fat free mass was associated with beneficial cartilage changes for both genders. Further work is required to determine whether modifying obesity and in particular body composition alters the development of hip OA.