Level Up! (The Combined and Independent Effects of Exercise Training and Dietary Enhancement on Cardiometabolic Health in Adolescents With Obesity)

The goal of this clinical trial is to learn how exercise and diet quality affect the health of adolescents with obesity. The main questions it aims to answer are: * Does exercise improve cardiometabolic health in adolescents with obesity? * Does enriching the diet with fruits and vegetables improve cardiometabolic health in adolescents with obesity? * Do exercise and a fruit and vegetable diet together provide greater health benefits than either one alone in adolescents with obesity? Researchers will compare four groups to see how exercise and diet impact health: * Standard Care Group: Receives the usual care for obesity. * Exercise Group: Receives weekly exercise coaching and participates in a 12-week exercise program. * Diet Group: Receives weekly dietary coaching and eats a diet enriched with fruits and vegetables for 12 weeks. * Combined Exercise and Diet Group: Receives both exercise and dietary programs, namely weekly exercise and dietary coaching, participation in a 12-week exercise program, and daily consumption of fruits and vegetables for 12 weeks. During the 12-week study, participants will attend three study visits to: * Provide blood, stool, and urine samples. * Answer questions about health, sleep, diet, and physical activity. * Undergo body scans to measure fat, lean, and bone mass. * Complete blood vessel function and liver fat content assessments. * Assess resting exergy expenditure. * Complete fitness tests. * Wear a fitness tracker to monitor physical activity and sleep patterns.