This study evaluated the preclinical effect of obesity on the ventricular remodeling in adolescents with morbid obesity, and determined if subjects labelled as metabolically healthy obesity (MHO) presented better heart index than those with metabolically unhealthy obesity (MUO). Prospective case-control research of 45 adolescents (14-year-old) with morbid obesity and 25 normal weight adolescents’ gender- and age-matched with Tanner stage 4-5. Left ventricle (LV) was evaluated by conventional Doppler echocardiography, tissue Doppler imaging and two-dimensional speckle tracking echocardiography. Compared to normal-weight subjects, adolescents with morbid obesity presented a high percentage of pathological LV geometry (87%; p<0.01), and systolic and diastolic dysfunctions only detected by E/A ratio (2.0 vs 1.7, p<0.01), global longitudinal strain (-21.0% vs -16.5%, p<0.01), and early diastolic strain rate (3.2 vs 2.2, p<0.01). A correlation was found between impaired cardiac index and body mass index (BMI), high blood pressure, hyperglycemia, low HDL-cholesterol and hypertriglyceridemia. BMI and HDL-cholesterol were the most significant independent variables. No significant differences were found in structural and functional cardiac index when MHO and MUO subjects were compared (global longitudinal strain: -17.0% vs -16.4%, p0.79). Morbidly obese adolescents have an abnormal LV geometry, closely related to BMI, and systolic and diastolic LV dysfunctions. Adolescents labelled as MHO, despite exhibiting better BMI and insulin-resistance values, present the same pathological heart changes as MUO.