Nudge-Based Exercise Intervention for Adolescents With Obesity

Body weight and height will be measured at baseline and approximately 3 months after baseline. Weight in kilograms and height in meters will be combined to report a single BMI value using the formula: BMI = weight (kg) / [height (m)]^2. Body weight and height are component measurements used to derive BMI for this endpoint and are not separate outcome measures. Change in BMI will be calculated as the BMI value at approximately 3 months after baseline minus the baseline BMI value. The reported unit of measure is kg/m^2.

Physical activity will be assessed using the Chinese version of the International Physical Activity Questionnaire-Short Form (IPAQ-SF). The questionnaire records walking, moderate-intensity, and vigorous-intensity physical activity during the previous 7 days. The activity-specific values will be converted to metabolic equivalent of task minutes per week (MET-minutes/week) and summed according to the IPAQ-SF scoring method to generate a single total physical activity score. The individual activity categories are components of the total score and are not separate outcome measures under this endpoint. Change in physical activity from baseline to the follow-up assessment will be evaluated.

Sedentary behavior will be assessed using a questionnaire that records time spent in common sedentary activities outside school hours on each day of a typical week, including screen-based activities, homework and reading, tutoring, motorized transportation, sedentary hobbies, social activities, and playing musical instruments. Total sedentary time will be summarized as average minutes per day. Change from baseline to follow-up will be evaluated.

Body fat percentage will be measured by bioelectrical impedance analysis using the InBody H30 body composition analyzer and reported as a percentage (%). Change from baseline to follow-up will be evaluated.

Skeletal muscle mass will be measured by bioelectrical impedance analysis using the InBody H30 body composition analyzer and reported in kilograms (kg). Change from baseline to follow-up will be evaluated.

Exercise self-efficacy will be assessed using the Exercise Self-Efficacy Scale (ESES), which evaluates participants' confidence in maintaining regular exercise when facing barriers such as fatigue, lack of time, or unfavorable weather. Higher scores indicate greater exercise self-efficacy. Change from baseline to follow-up will be evaluated.

Health-related quality of life will be assessed using the Chinese version of the Pediatric Quality of Life Inventory Generic Core Scales. The scale contains 23 items covering physical, emotional, social, and school functioning. Scores are transformed to a 0-100 scale, with higher scores indicating better health-related quality of life. Change in the total score from baseline to follow-up will be evaluated.

Fasting blood glucose will be assessed by laboratory testing after an overnight fast. Change will be calculated as the follow-up value minus the baseline value.

Fasting insulin will be assessed by laboratory testing after an overnight fast. Change will be calculated as the follow-up value minus the baseline value.

Insulin resistance will be estimated using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), calculated from fasting glucose and fasting insulin concentrations. Higher values indicate greater insulin resistance. Change will be calculated as the follow-up value minus the baseline value.

Glycated hemoglobin (HbA1c) will be assessed by laboratory testing and reported as a percentage (%). Change will be calculated as the follow-up value minus the baseline value.

When available, total cholesterol concentration will be recorded from routine clinical laboratory testing performed during clinical re-examination and reported in millimoles per liter (mmol/L). Change from baseline will be calculated as the value at approximately 3 months after baseline minus the baseline value.

Triglyceride concentration will be recorded from routine clinical laboratory testing conducted as part of routine clinical re-examination and reported in millimoles per liter (mmol/L). No additional blood sample will be collected solely for this study. Change from baseline will be calculated as the value at approximately 3 months after baseline minus the baseline value.

Low-density lipoprotein cholesterol (LDL-C) concentration will be recorded from routine clinical laboratory testing conducted as part of routine clinical re-examination and reported in millimoles per liter (mmol/L). No additional blood sample will be collected solely for this study. Change from baseline will be calculated as the value at approximately 3 months after baseline minus the baseline value.

High-density lipoprotein cholesterol (HDL-C) concentration will be recorded from routine clinical laboratory testing conducted as part of routine clinical re-examination and reported in millimoles per liter (mmol/L). No additional blood sample will be collected solely for this study. Change from baseline will be calculated as the value at approximately 3 months after baseline minus the baseline value.

Alanine aminotransferase (ALT) activity will be recorded from routine clinical laboratory testing conducted as part of routine clinical re-examination and reported in units per liter (U/L). No additional blood sample will be collected solely for this study. Change from baseline will be calculated as the value at approximately 3 months after baseline minus the baseline value.

Aspartate aminotransferase (AST) activity will be recorded from routine clinical laboratory testing conducted as part of routine clinical re-examination and reported in units per liter (U/L). No additional blood sample will be collected solely for this study. Change from baseline will be calculated as the value at approximately 3 months after baseline minus the baseline value.

Serum uric acid concentration will be recorded from routine clinical laboratory testing conducted as part of routine clinical re-examination and reported in micromoles per liter (μmol/L). No additional blood sample will be collected solely for this study. Change from baseline will be calculated as the value at approximately 3 months after baseline minus the baseline value.