Background: Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterized by progressive muscle weakness and degeneration. Cardiomyopathy, defined as disease of the heart muscle, is universal in Duchenne muscular dystrophy (DMD). Previous studies reported no correlation of body mass index (BMI) on cardiomyopathy onset in DMD (1). Obesity (OB) is a well-established risk factor for cardiovascular disease (CVD) in the general population. A recent large study reported that being underweight (UW, BMI < 18.5 kg/m) was the actually strongest risk factor for CVD (2). Objectives: We sought to determine the impact of BMI on non-ambulatory DMD patients on the prevalence of myocardial disease, measured by late gadolinium enhancement (LGE), and cardiomyopathy by Cardiac MRI (CMR). A retrospective review was performed of CMRs of DMD patient ≥ 15 years with LGE and LVEF data. Patients were divided into underweight (UW, BMI <18.5 kg/m), normal (NW, BMI = 18.5 < 24.9 kg/m), overweight (OW, BMI = 25 < 30 kg/m) and obese (OB, BMI = 30 kg/m) groups. The prevalence of LGE and LVEF was compared between the groups. Results: Two hundred and seventy-three DMD patients who met inclusion criteria are detailed in Table 1. There is no difference in age between groups with an expected difference in weight and BMI. Left ventricular dilation is uncommon but LGE is prevalent in all groups (UW=87.8%, NW=79.8%, OW=94.7% and OB=79.4%). LVEF has the lowest prevalence in the UW group compared to both the NW and OW groups (49.8±11.5 vs 53.8±9.5 vs 54.8±10.3%, p =0.02 and 0.006 respectively) with no difference compared to the OB group (52.4±11.9%, p = 0.15). Conclusion: Being underweight (UW) is associated with a lower LVEF and more cardiomyopathy compared to normal weight (NW) or overweight (OW) DMD patients. This study highlights the importance of lower BMI's in patients as a potential clinical sign of advanced disease. Future longitudinal study is needed to better understand how BMI affects cardiomyopathy in DMD.