With the demand for weight-loss interventions likely to continue its upward trend over the next decades, the question remains on how to continuously monitor and support overweight and obese adolescents, particularly in the long-term. Moreover, as the burden of the obesity rates increases in health care centers, the development of alternative delivering strategies gains attention. In an environment of limited resources, the development of new-technology based programs seems a promising area to deliver cost-effective interventions to a wide number of individuals. However, the existing studies present several limitations and a challenging aspect of treating obesity in adolescents is the presence of high rates of disordered eating behaviors.

The objective of this study is to develop and test the effectiveness of a web-based Cognitive Behavioral Therapy intervention, for adolescents with overweight/obesity. A Randomized Controlled Trial will compare a control group receiving medical treatment as usual (TAU), and an intervention group receiving TAU plus a psychological/behavioral intervention delivered via the internet.

This research project intends to examine the effectiveness of a Cognitive Behavioral Therapy and psychoeducational based program for adolescents with overweight and obesity delivered as a web-based intervention: APOLO-Teens. Therefore, a randomized controlled trial will compare a control group receiving medical treatment as usual for pediatric obesity in public health care centers in Portugal, and an intervention group receiving TAU plus the APOLO-Teens web-based intervention.

The APOLO-Teens web-based intervention was designed to optimize treatment as usual for pediatric obesity, promoting the adoption of healthy eating habits and lifestyle behaviors. Particularly it aims to promote higher consumption of fruits and vegetables, increase physical activity levels, reduce sedentary time, enhance psychological well-being, and facilitating weight loss.

All participants will be assessed at baseline, 3 months after the beginning of the research protocol/intervention, end of the web-based intervention, and at 6 and 12 months follow-up. All the assessments will be conducted in Qualtrics: Online Survey Software. Repeated Paired Samples T-test will explore differences between the two groups across the assessment times. Multiple linear regression analysis will be applied to explore predictors of weight loss and weight regain, and survival analyses to identify participants with the highest probability to regain weight. Additionally, 3-Level Hierarchical Linear Models will be conducted to explore the temporal occurrence and patterns of change of eating-related variables, physical activity, and BMI z-score in participants from the two groups.

It is expected that the intervention group participants will present a higher frequency of healthy food consumption (fruit/vegetables) and increased physical activity levels at the end of the web-based intervention when compared with TAU group participants. We further expect, differences between the groups regarding eating behavior-related variables, as well as in the psychological features assessed throughout the different assessment points, and ultimately in weight maintenance or regain, with the intervention group presenting lower scores/weight.

Inclusion Criteria:

• Participants with overweight or obesity (BMI z-score ≥ 1/BMI percentile ≥ 85th);
• Enrolled in ambulatory treatment for overweight/obesity in a public Portuguese health care center;
• Having a Facebook® account;
• Having access to the Internet at least three times per week.

Exclusion Criteria:

• Medical conditions that affect weight;
• Intellectual disabilities (Specific learning difficulties that prevented adolescents from reading and understanding written text);
• Ambulatory movement limitations (e.g., use of the walking stick, morpho-functional alterations as lower limb amputation, etc.);
• Not being under other interventions for weight loss at the time of enrollment.

The type of data to collect include sensitive and personal health information protected by the Portuguese Law.

Randomization is performed by a researcher not involved in data management. The researcher who evaluates the outcomes of interest is masked.