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 determine whether adding structured exercise training and a structured fruit and vegetable dietary program to standard multidisciplinary obesity care improves cardiometabolic health in adolescents with obesity enrolled in a weight management program. The main questions it aims to answer are: * Does adding structured exercise training to standard multidisciplinary obesity care improve cardiometabolic health? * Does adding a structured fruit and vegetable dietary program to standard multidisciplinary obesity care improve cardiometabolic health? * Does combining structured exercise training and the fruit and vegetable dietary program with standard multidisciplinary obesity care improve cardiometabolic health? Researchers will compare four groups to evaluate the independent and combined effects of structured exercise training and a structured fruit and vegetable dietary program: * Standard Care Group: Receives standard multidisciplinary obesity care. * Exercise Group: Receives standard care plus a 12-week supervised, structured multicomponent exercise program, weekly exercise counseling, and continuous physical activity monitoring using a tracker. * Dietary Group: Receives standard care plus a 12-week fruit and vegetable enrichment program involving daily smoothie consumption designed to provide one cup of fruit and one cup of vegetables per day, using frozen smoothie ingredient packages delivered to participants' homes, and weekly dietary coaching. * Combined Exercise and Dietary Group: Receives standard care plus both the structured exercise and fruit and vegetable dietary programs. During the 12-week study, participants will complete assessments at baseline, week 6, and week 12. Some procedures may be completed at home or split across more than one day. Assessments may include: * Providing blood, urine, and stool samples. * Completing questionnaires about health, sleep, diet, physical activity, mood, and other health behaviors. * Undergoing body-composition scans to measure fat, lean, and bone mass. * Completing blood-vessel function, liver-fat, and skin-carotenoid assessments. * Completing continuous glucose monitoring. * Assessing resting energy expenditure. * Completing fitness and muscle-strength tests. * Completing a standardized meal-based metabolic assessment. * Completing 3-day dietary records. * Wearing activity and sleep monitors to assess physical activity and sleep patterns.