The current project is a randomized controlled multi-centre clinical trial, in a cohort of children aged 3 to 6 years at baseline and being at obesity risk. The main objective consists on assessing the efficacy of an intervention during early childhood, considering a healthy lifestyle based on the promotion of a Mediterranean dietary pattern and regular physical activity, compared with a control group, on decreasing obesity incidence 5 and 10 years after the beginning of the intervention. It is envisaged to include 738 children, aged 3 to 6 years, having at baseline a body mass index (BMI) < than the equivalent to 30 kg/m2 in adults, and at least one parent having a BMI > 25 kg/m2. The clinical trial will have two arms and will be performed in Primary Health centres in 3 cities: Córdoba, Santiago de Compostela and Zaragoza. The control group will receive usual care by healthcare professionals. The intervention group, will receive education on Mediterranean lifestyle (Mediterranean diet and physical activity promotion), combined with the provision of extra-virgin olive oil and fish, in order to be consumed at least 3 times per week. Physical activity sessions with a physical activity monitor will also be offered for free to the children (2 sessions of 60 minutes of moderate-vigorous physical activity, per week). The participants' degree of compliance with the intervention will be periodically monitored. The main outcome is the incidence of obesity and the secondary outcomes are changes in body composition, physical fitness and cardiovascular risk factors. We are targeting for a 10 year follow-up.

Hypothesis A healthy lifestyle, based on the promotion of the Mediterranean dietary pattern and regular physical activity, decrease the likelihood of developing obesity and cardio-metabolic abnormalities during childhood and adolescence.

Objectives

To assess, in a cohort of children at high risk of obesity, if an intervention during childhood and adolescence, considering a healthy lifestyle based on the promotion of Mediterranean dietary pattern and regular physical activity, when compared with a control group Main objective

1. To decrease obesity incidence 5 and 10 years after the start of the intervention Secondary objectives
2. To improve body composition (Body mass index z-score, Fat mass index z-score, waist circumference) assessed in a yearly basis
3. To improve health-related physical fitness assessed in a yearly basis
4. To improve cardiovascular risk factor (classic and omics) associated with obesity 1, 3, 5 and 10 years after the start of the intervention Intermediary objectives
5. To increase the adherence to a Mediterranean dietary pattern 1, 3, 5 and 10 years after the start of the intervention
6. To increase the adherence to age-specific physical activity recommendations 1, 3, 5 and 10 years after the start of the intervention

Inclusion Criteria:

• Children > 3 years and < 7 years, with at least one parent having a BMI ≥ 25 kg/m2, with no disease responsible for the high BMI.
• Children with normal- or over weight, following the IOTF criteria (Cole TJ, Lobstein T. Pediatr Obes 2012; 7: 284-294).

Exclusion Criteria:

• Children < 3, or > 7 yearss, or both parents Having BMI <25 kg/m2.
• Children with chornic diseases or following a therapeutic diet .
• Children from families having dietary habits not fitting with the characteristics of the dietary intervention.
• Children from families having difficulties to follow the protocol.

The plan is to allow other researchers to use the data obtained in the study is this is approved byut the corresponding responsible persons.

At the end of the trial

Approval of an analysis protocol by the study's steering committee