The treatment of childhood obesity is challenging. Although dietary and physical activity recommendations are widely known, the willingness to change lifestyles within the family is not easy to be achieved. Motivational interviewing has been shown as a possibly effective method to increase adherence to dietary recommendations in the obese adult.

There is scarce evidence showing whether implementing a motivational interview in obese children could be effective.

The aim of this clinical trial is assessing the effect of a motivational interview, coordinated between the clinical and primary care services on 8 to 14 years old obese children.

In a recent study, the investigators have demonstrated that the motivational therapy approach to treat childhood obesity is highly effective at clinical and metabolic levels. This efficacy has been proved in a clinical outpatient setting. However, a standardized collaborative approach between the clinic and the primary care services would allow a faster and easier approach to childhood obesity treatment. Furthermore, this motivational and educational intervention would benefit from the current technologic facilities, the long term effect of the education at group level, in terms of food shopping plan, healthy, fast and easy cooking methods.

The aim of this clinical trial is to test the efficacy of a multicomponent motivational intervention for the treatment of childhood obesity, coordinated between primary care and hospital specialized services, integrating motivational individual interviews, educational groups and eHealth tools (wearable), compared to the usual intervention performed in paediatrics.

The design will be a clustered randomized control trial, with an intervention group that will receive a multicomponent motivational and educational plan which will be compared to a control group receiving the usual recommendations performed in primary care centres (n=167 per group). The treatment of both study groups will last 12 months and will be performed at the primary care centres. In parallel, the study team will validate the methodology used to assess body composition in obese children as well as the changes produced by the intervention.

Children assigned to the control group receive advices as recommended by the Clinical Practice Guidelines (17). At visits, the family receive explanations about carrying out a balanced diet, divided into 5 meals, in order to provide a moderate energy intake reduction. An increase in physical activity, both in terms of leisure activity, as sports regular practise are recommended. Monthly visits are organized in which weight and height are measured, and compliance with recommendations are actually taking place.

Children assigned to the intervention group receive similar recommendations to those in the control group but under a motivational interview schema. This means that each visit, objectives from the last visit are fulfiled, the therapists try to make the family recongnizing the changes to be done by themselves, rather than imposing by demonstrating ambivalences, and objectives for the next visit are agreed. Furthermore, three workshops as group therapy are organized with the following topics: 1. Increasing physical actty sing an eHEalth monitor, 2. Food choices and dietary balance, and 3. Cooking methods.

Inclusion Criteria:

• Age range between 8 and <14 years at enrolment (so that, children would end the treatment at maximum age of 15 years
• BMI > 97th percentile of Hernandez references from 1988 (Hernández et al., 1988) as indicated by the Guidelines for Clinical Practice of the Spanish Health System (Grupo de trabajo de la Guía de Práctica Clínica sobre la Prevención y el Tratamiento de la Obesidad Infantojuvenil. Ministerio de Ciencia e Innovación [Spanish Ministry of Sciencee and Innovation], 2009) for the diagnose of the childhood obesity.

Exclusion Criteria:

• Children with eating disorders
• Families not available to attend to scheduled visits
• Simultaneous participation in another clinical trial
• Presence of endocrine disorders (GH disorder, hypothyroidism, Cushing's disease, early puberty or other)
• Lack of command of local languages

Given the nature of the intervention participants or researchers could not be blinded.