TREating Pediatric Obesity

Inclusion Criteria: 1. Age between 10 and 15 at the start of the study. 2. Obesity defined according to the criteria of the World Health Organization (BMI≥p95) and at least one of the following conditions: 2.1. Hepatic steatosis confirmed by abdominal ultrasound in the previous 12 months. 2.2. Triglycerides\> 150 mg/dl, confirmed in analytical determination in the 4 weeks prior to the start of the study. 2.3. HDL cholesterol \<40 mg/dl, confirmed in analytical determination in the 4 weeks prior to the start of the study. 2.4. LDL cholesterol\> 135 mg/dl, confirmed in analytical determination in the 4 weeks prior to the start of the study. 2.5. Insulin resistance, determined by elevated HOMA-IR confirmed by analytical determination in the 4 weeks prior to the start of the study. 3. Habitual eating window equal to or greater than 13 hours, with a response rate greater than 85%. Habitual eating window will be determined by self-registration during the screening process. Participants must properly record the habitual eating window in at least 12 of the 14 days that self-registration will be requested, and it must be equal to or greather than 13 hours at least 6 days a week. 4. Reporting to have maintained a stable weight and height status during the last two months (changes of less than 2 points in BMI (kg / m2)). 5. Agreement to participate in all phases and procedures of the study. Exclusion Criteria: 1. Being diagnosed with an endocrine disorder, for example, diabetes mellitus under treatment with insulin or oral antidiabetics, thyroid disease, hypercortisolism, congenital adrenal hyperplasia. 2. Being diagnosed with a chronic digestive, rheumatological, neurological, cardiological, pneumological, autoimmune or infectious disease that affects energy metabolism. 3. Having undergone a surgical procedure that chronically alternates digestive or metabolic function. 4. Hypercholesterolemia requiring pharmacological treatment according to the Expert Consensus of the European Society of Arteriosclerosis specific to children. 5. Serum triglyceride concentration\> 500 mg/dl. 6. Systolic or diastolic blood pressure values equal to or greater than the specific 95th percentile for age, sixth, and height, on 3 different occasions \[42\]. 7. Hypertransaminasemia\> 200 IU / L (5 times higher than the upper normal value in the laboratory), which would make it necessary to rule out other causes of liver disease. 8. Being diagnosed with an eating disorder or being at risk of developing these disorders, determined using the SCOFF questionnaire (two or more questions answered positively). 9. Presenting neurological alterations or chromosomopathies. 10. Consuming drugs or supplements that are likely to alter energy metabolism. 11. Being participating in a nutritional intervention or treatment of any kind, or having done so during the previous 3 months. 12. Having a demonstrable personal or professional relationship with any of the members of the investigation team. 13. Any other condition that in the opinion of the research team would contraindicate their participation.