Childhood obesity is a growing public health issue affecting millions of children worldwide, increasing the risk of metabolic and cardiovascular diseases in adulthood. This problem is particularly concerning in children and adolescents with Down syndrome (trisomy 21, T21), who have a higher predisposition to fat accumulation due to genetic, metabolic, and behavioral factors. However, assessing their nutritional status and body composition is challenging, as conventional tools such as body mass index (BMI) may not accurately reflect adiposity in this population.

One of the most severe risks associated with obesity in children with T21 is non-alcoholic fatty liver disease (NAFLD). This condition is characterized by fat accumulation in the liver without significant alcohol consumption and is closely linked to insulin resistance, dyslipidemia, and pro-inflammatory states. If not detected early, NAFLD can progress to more severe liver diseases such as fibrosis or cirrhosis. In individuals with T21, the prevalence of NAFLD may be underestimated due to the difficulty in properly assessing body composition and metabolism.

Since NAFLD diagnosis traditionally requires invasive procedures such as liver biopsy, this study proposes using non-invasive techniques, such as liver elastography, to assess liver health in children and adolescents with T21. Additionally, dietary habits will be analyzed using standardized tools to establish the relationship between nutrition, body composition, and NAFLD risk in this population.

Study Hypothesis:

The main hypothesis is that obesity and inadequate dietary patterns increase the risk of NAFLD in our participants with T21. The investigators also believe that liver elastography will enable the early detection of fat accumulation in the liver and other signs of liver disease, facilitating timely intervention.

Study Objectives:

The primary objective of this study is to evaluate the presence and severity of NAFLD in children and adolescents with T21 using non-invasive diagnostic techniques and nutritional assessment methods.

Specifically, the study will analyze:

• Liver health: Measurement of liver fat and stiffness using elastography. Body composition: Anthropometric evaluation and adiposity analysis. Dietary habits: 24-hour food recall and KIDMED questionnaire to assess adherence to the Mediterranean diet.
• Relationship between obesity and NAFLD: Identification of metabolic and behavioral risk factors.

1. Study Design

   This is an observational cross-sectional study in which participants with T21, with and without obesity, will be evaluated without direct therapeutic intervention.

2. Registration and Evaluation Procedures

   2.1 Clinical Assessments

   • Liver Elastography: Assessment of liver stiffness using FibroScan. Hepatic elastography is a non-invasive imaging technique used to assess liver stiffness and fat content, which correlates with liver fibrosis. It is particularly useful in pediatric populations for evaluating liver diseases such as non-alcoholic fatty liver disease (NAFLD), viral hepatitis, and other chronic liver conditions. FibroScan measures ultrasound signal attenuation due to liver fat content. Higher values (db/m) indicate more fat deposition.
   • Anthropometric Measurements: Weight, height, body mass index (BMI), abdominal circumference.
   • Body composition parameters measured by bioimpedance:

   Adipose tissue %, muscle mass (kg) and visceral fat index.

   2.2. Nutritional Evaluation:

   • 24-hour dietary recall. To estimate nutrient consumption, dietary intake from the 24-hour dietary recall will be converted given the use of nutritional composition tables and validated food composition software (DIAL).
   • KIDMED questionnaire for adherence to the Mediterranean diet.

   The KIDMED (Mediterranean Diet Quality Index) questionnaire is a widely used tool to assess adherence to the Mediterranean diet among children and adolescents. It consists of 16 items that evaluate various dietary habits. Each item is scored as follows:

   Positive connotation items (reflecting healthy Mediterranean dietary habits): Each receives a score of +1.

   Negative connotation items (indicating departure from Mediterranean dietary principles): Each receives a score of -1.

   The total KIDMED score ranges from -4 to 12. Based on the total score, adherence to the Mediterranean diet is categorized into three levels:

   High adherence: Scores of ≥8. Medium adherence: Scores between 4 and 7. Low adherence: Scores of ≤3.

3. Quality Assurance Plan

   Electronic data management system with automatic validations to prevent data entry errors.

4. Sample Size Evaluation

   It is estimated that a sample of 17 participants with T21 and 17 participants in the control group reaches 80% statistical power in detecting significant differences in the detection of fatty liver.

5. Statistical Analysis Plan

   • Descriptive statistics will be used to characterize the sample.
   • Correlation tests and logistic regression will be performed to assess the relationship between NAFLD and metabolic factors.
   • Analysis of variance (ANOVA) will be used to compare parameters among subgroups.

6. Ethical and Safety Considerations

   • Approval from the Research Ethics Committee.
   • Data management in compliance with the General Data Protection Regulation (GDPR).

This protocol will allow us to evaluate the relationship between obesity, dietary patterns, and NAFLD in children with T21, providing key information for future preventive strategies.

Inclusion Criteria:

• Children (5-10 years), and adolescents (11-19) andyoung adults (20-22 years) of bothSexes
• 5 to 22 years old
• Diagnosis of trisomy 21 or other intellectual disability of genetic origin for the group of the cases.
• BMI: 17-40 Kg/m2
• Signing of the informed consent by the parents or guardians.

Exclusion Criteria:

• Not meeting the inclusion criteria
• Have previous liver pathology.
• Be under any medical treatment that
• Modify composition parameters Body: GLP-1 analogues and derivatives.

Participants will be selected who are patients at the Jerome Lejeune Foundation center or students in special education centers who wish to participate. For the control group, dissemination will be carried out among workers with children of the required age range.

Relevant data obtained on the relationship of fatty liver in the studied population