Introduction: Pediatric obesity has significant impacts on the development of many medical comorbidities into adulthood. While studies have identified the negative effects of obesity on exercise performance and cardiovascular health, the effects of obesity on youth athletes are less studied. Hypothesis: Obesity in youth athletes is associated with decreased activity levels and increased exertional cardiac symptoms. Methods: The HeartBytes National Youth Database produced by Simon’s Heart, a nonprofit organization that organizes sports pre-participation examinations (PPEs) of adolescents, was used for this study. This database contains demographic, exercise-related symptoms, and electrocardiogram data obtained during Simon’s Heart PPEs. BMI values were converted to age- and gender-adjusted percentiles, with obesity defined in accordance with CDC definition BMI ≥ 95th percentile. A chi-squared test with odds ratios (OR) and 95% confidence intervals (CI) were used to evaluate obesity outcomes. Results: Of the 7363 patients in the HeartBytes database with BMI data, the majority were male (60.7%) and White (83.3%). The median age was 15.0 years old (interquartile range 13.5-16.5). Youth athletes within the normal weight range (5th-85th percentile) had higher exercise participation rates in comparison to those who were underweight, overweight, or with obesity (p<0.0001 for each). Athletes with obesity were more likely to have exertional symptoms (OR: 1.63 [CI: 1.36-1.96]; p<0.0001), specific symptoms of easily fatigued (OR: 3.00 [CI: 2.38-3.79]; p<0.0001) and dyspnea (OR: 1.69 [CI: 1.37-2.10]; p<0.0001), compared to those without obesity. Athletes with obesity were more likely to have hypertension (OR: 5.35 [CI: 2.00-14.30]; p=0.0002), high cholesterol (OR: 3.84 [CI: 2.51-5.86]; p<0.0001), and ECG T-wave inversion changes (OR: 2.19 [CI: 1.10-4.33]; p=0.022) than those without obesity. No association was found between obesity and diabetes. Conclusions: In this dataset from a national registry of PPEs, obesity in youth athletes is associated with decreased physical activity and exertional symptoms. Further study is needed to elucidate the cause-effect relationship of these findings.