Here is the design of a clinical trial:

Official Title: Project LiGHT (Living Green and Healthy for Teens): A Novel Weight Management Program That Emphasizes the Benefits of a Healthy Lifestyle

Included conditions:
- Obesity, Pediatric

Study Armgroups:
- {'label': 'Aim2Be Live Coach', 'type': 'EXPERIMENTAL', 'description': 'Aim2Be app with Live Coach + Fitbit + BMI tracking tools', 'interventionNames': ['Behavioral: Aim2Be app with Live Coach + Fitbit + BMI tracking tools']}
- {'label': 'Aim2Be Waitlist', 'type': 'OTHER', 'description': 'Aim2Be app waitlist + Canadian Health Recommendations + Fitbit + BMI tracking tools for three months, then flip to Aim2Be app with Virtual Coach + Fitbit + BMI tracking tools', 'interventionNames': ['Behavioral: Aim2Be app waitlist + Canadian Health Recommendations + Fitbit + BMI tracking tools, then flip to Aim2Be app with Virtual Coach + Fitbit + BMI tracking tools']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Aim2Be app with Live Coach + Fitbit + BMI tracking tools', 'description': 'Participants will spend six months using the Aim2Be app setting aims, completing tasks, accessing articles, doing self-assessments, and participating in the social wall. They will also complete a series of questionnaires, dietary recalls, BMI tracking using scales and tape measures, and physical activity tracking using Fitbits. Participants in this condition will have access to the Live Coach and the Virtual Coach. The Live Coach has specialized training in lifestyle and motivational interviewing and will support families in changing their health behaviours through in-app messaging and phone calls. The Virtual Coach gives guidance to families through an avatar that has been programmed using motivational interviewing theory.', 'armGroupLabels': ['Aim2Be Live Coach']}
- {'type': 'BEHAVIORAL', 'name': 'Aim2Be app waitlist + Canadian Health Recommendations + Fitbit + BMI tracking tools, then flip to Aim2Be app with Virtual Coach + Fitbit + BMI tracking tools', 'description': 'Participants in this condition will be waitlisted for three months while they receive standard of care (Canadian Health Recommendations for physical activity, dietary habits, screen behaviours, and sleep). Participants will gain access to the Aim2Be app with Virtual Coach after the three month assessment. Participants will then spend three months using the Aim2Be app setting aims, completing tasks, accessing articles, doing self-assessments, and participating in the social wall. For the whole six months, participants will complete a series of questionnaires, dietary recalls, BMI tracking using scales and tape measures, and physical activity tracking using Fitbits. Participants in this condition will have access to the Virtual Coach only. The Virtual Coach gives guidance to families through an avatar that has been programmed using motivational interviewing theory.', 'armGroupLabels': ['Aim2Be Waitlist']}

Primary Outcomes:
- {'measure': 'Change in Body Mass Index z-score (youth)', 'description': 'Change in BMI z-scores will be computed from measured height and weight using World Health Organization (WHO) cut-offs', 'timeFrame': 'Baseline, 3 months, 6 months'}
- {'measure': 'Change in health behaviour knowledge (youth)', 'description': "Survey questions (using a LiGHT-specific tool) will assess teens' knowledge of Canadian recommendations for healthy eating, physical activity, and sedentary behaviours. Knowledge will be reported as an aggregate knowledge score from 0 to 8 (a score of 0 indicates low knowledge and a score of 8 indicates high knowledge), as well as sub-score for each of the knowledge areas (nutrition, physical activity, recreational screen time, sleep).", 'timeFrame': 'Baseline, 3 months, 6 months'}
- {'measure': 'Change in objective dietary behaviour (youth)', 'description': 'Change in mean daily servings of fruits and vegetables and sugar-sweetened beverages consumed over three consecutive 24-hour dietary recalls.', 'timeFrame': 'Baseline, 3 months, 6 months'}
- {'measure': 'Change in number of daily steps (youth)', 'description': 'Change in mean daily steps over a 14-day period at each assessment point, as measured using a Fitbit activity monitor.', 'timeFrame': 'Baseline, 3 months, 6 months'}
- {'measure': 'Change in screen behaviour (youth)', 'description': "Survey questions will assess adolescents' recreational screen time use (using the Take Action survey), and will be reported as the number of self-reported hours of recreational screen time per day.", 'timeFrame': 'Baseline, 3 months, 6 months'}

Please estimate the sample size based on the assumption: 
The study assumes an 80% power, an alpha of .05, a 15% attrition rate from baseline to 3 months, and an 8% rate of families not downloading the Aim2Be app.
Sample size calculation
        Based on previously published data [31], the RCT will have 80% power at an alpha of .05 to detect a .5 decrease in BMI z-score when the sample size in each group is 60. The BMI z-score was used to calculate sample size because this is the most difficult variable to change and requires the largest sample size of all of the primary outcomes. Based on this and accounting for both missing data and attrition, we project needing at least 80 families in each condition. However, to be able to detect a 20% difference in adherence (e.g., secondary aims outcome) between the two intervention groups (odds ratio of 2.33) at an alpha of .05 with 80% power using a one-sided t-test, 77 families are needed in each group. As the waitlist control group will receive the intervention at 3âmonths, we require 100 participants enrolled in each group (this accounts for 15% attrition from baseline to 3-month and the approximately 8% of families who will not download the Aim2Be app). Power calculations were conducted in nQuery (Statsols, USA). Based on these computations, we aim to enroll 200 participants in the RCT.