The purpose of this study is to determine if Facebook can be used as a motivating factor for obese or overweight adolescents in a weight-reduction program.

This study is a randomized controlled trial. There will be two randomly assigned groups of obese or overweight adolescents (WHO definition). Both groups will be enrolled in a 12 week weight reduction program which includes personal nutritional evaluation and food plan and exercise routine. Follow-up appointments will be held every 3 weeks. One group will be encouraged to update their Facebook status at least once a day, regarding their healthy lifestyle changes (exercise routine, healthy food choice, "checking-in" at the wellness center, kilograms lost, etc). The control group will be asked not to share information about their program on Facebook for 12 weeks. Facebook follow-up will be held by the investigators on the study's Facebook account. Teenagers will be thoroughly explained on how to set the account to a limited profile if they want to. At the end of the program both groups will be compared regarding weight loss and mean BMI.

Inclusion Criteria:

• Adolescents between 13 and 19 years old.
• Obese or overweight according to the IOTF.
• No physical or medical impediment for performing physical activity.
• No risk for eating disorders (SCOFF questionnaire).
• Report less than 20 minutes of physical activity per day.
• Have an active Facebook account and use it more than 20 minutes per day.
• Low-risk in the Gatehouse Bullying Scale.

Exclusion Criteria:

• Physical or medical impediment for performing physical activity.
• Answer "yes" at least twice on the SCOFF questionnaire.
• Report more than 20 minutes of exercise per day.
• Not having an active Facebook account or using it less than 20 minutes per day.
• "High Risk" on the Gatehouse Bullying Scale.