Childhood obesity is a global public health issue, with rising prevalence rates. In Spain, the problem is significant, particularly in the southern regions. Factors contributing to childhood obesity include dietary habits, lack of physical activity, and socioeconomic influences.

Efforts to address childhood obesity in Spain include various programs focusing on dietary modification, increased physical activity, and family involvement. Despite these initiatives, there is a need for continued intervention, as changing dietary and lifestyle patterns have led to reduced fruit and vegetable consumption and increased sedentary behavior among children.

Childhood obesity has concerning health implications, including heart-related issues. Echocardiography plays a vital role in early detection.

Given the limited research on the impact of childhood obesity on musculoskeletal development and mobility, a comprehensive study is needed to analyze its prevalence and associated factors. The study aims to assess the effectiveness of nutritional interventions administered by school nurses.

In summary, childhood obesity in Spain is a growing concern, with multifaceted causes and health implications. Ongoing efforts are required to combat this issue and promote healthier lifestyles among children.

An elevated Body Mass Index (BMI) in the child population represents a significant global public health concern. According to the World Health Organization (WHO), overweight occurs in children aged 6-19 when the BMI exceeds one or more standard deviations from the median established in WHO child growth patterns.

Epidemiological data reflects that since the late 20th century, childhood obesity has increased from 4.9% (31.5 million) to 6% (40.6 million) worldwide. According to data from the Childhood Obesity Surveillance Initiative (COSI) within the European Union (EU), children in Spain aged 6-9 have a 42% overweight rate and a 19% obesity rate. In comparison, girls have a 41% overweight rate and a 17% obesity rate, positioning Spain as the fourth EU country with the highest prevalence of overweight and obesity in children.

Within the national territory, 4 out of 10 schoolchildren have excess weight, with the highest prevalence in the southern regions. The autonomous community with the lowest incidence of childhood overweight is Navarra, with 15%, and the highest is the Region of Murcia, with 40%. Andalusians present a high prevalence rate of 33.4%. In general, the country's northern regions have lower figures, while the southern region has the highest rates of childhood overweight. It has also been observed that there is a higher likelihood of being overweight in rural areas than in urban areas.

This could be due to regional differences in habits during the three critical periods for the development of childhood obesity: the preconception period involving maternal factors, the first 1000 days of life (9 months of pregnancy + 2 years of life), and the adiposity rebound between 5-7 years. Childhood overweight is also highly influenced by factors such as maternal overweight, early introduction of complementary feeding before 6 months of age, smoking during pregnancy, low parental educational levels, and the excessive use of screens such as mobile phones or tablets at an early age.

The most relevant factors in overweight are diet, physical inactivity, physical activity, and lifestyle habits. However, when it comes to minors, all these factors are strongly influenced by the cultural, social, and institutional environment, as well as the family's socioeconomic level.

In Spain, Andalusia is one of the autonomous communities with a lower income index (0.67) and a lower average expenditure on public health at 0.33%. However, the community puts in the most effort to implement policies against obesity, with a score of 5.19.

Numerous campaigns have been launched to prevent childhood obesity, developed by the Spanish Agency for Consumer Affairs, Food Safety, and Nutrition (AECOSAN) as part of the nutrition, physical activity, and obesity prevention (NAOS) strategy. Additionally, the Andalusian Ministry of Health and Families has implemented plans such as "Growing in Health," "Evaluation of Food Offer in Andalusian Schools 2019-2020," and the "Health throughout Life" campaign.

All these programs coincide on three fundamental aspects when addressing childhood obesity: interventions to modify dietary habits promoting balanced and healthy eating, increasing fruit and vegetable consumption while minimizing sugar intake; interventions to promote physical activity, encouraging at least one hour of exercise daily; and, lastly, family involvement interventions to achieve proper adherence to these changes.

These interventions are necessary today because, over the past decades, there have been changes in eating patterns and diets, resulting in a decrease in the consumption of fruits, vegetables, legumes, and fresh products, as well as an increase in the consumption of processed foods with higher sugar, fat, salt content, and poorer nutritional quality. According to COSI initiative data, Spain is where children consume the least fruits and vegetables daily. There have also been changes in physical activity, with studies showing that 25% of Spanish children are sedentary.

One of the direct consequences of childhood overweight is morphological heart alterations, reflected in left ventricular hypertrophy and cardiac diastolic alterations. Numerous scientific studies have established a close relationship between obesity in children and adolescents and an increase in epicardial fat, which can lead to cardiac and vascular abnormalities. In fact, having a high BMI at a young age has become a significant risk factor for the premature development of cardiovascular diseases that were previously considered exclusive to adults. These changes are visible through echocardiography, especially in epicardial fat.

As a non-invasive diagnostic tool, Echocardiography has gained a fundamental role in early detection of these alterations in the pediatric population affected by an increase in epicardial fat. Its early implementation allows for precise cardiac and vascular function assessment, improving these young patients' quality of life and prognosis. These measurements and modifications have been analyzed recently, although more data on younger populations and post-pandemic needs to be collected. Furthermore, to address this growing challenge, it is crucial to raise awareness about the importance of maintaining a healthy weight early and promote research and the application of preventive and intervention strategies to reduce epicardial fat in the pediatric population.

Due to all the aforementioned reasons, coupled with the limited number of current publications that deeply analyze the consequences of childhood obesity on the development of the musculoskeletal system and children's mobility, it is essential to conduct a study of the population and subsequently intervene to promote healthy growth and development in children.

Therefore, the objective is to establish the impact of a nutritional intervention by a school nurse on a group of schoolchildren.

Inclusion Criteria:

• Students from the school
• Pediatric from age 6 to 16
• Students from the school that confirmed approval
• Signed informed consent by the minor
• Signed informed consent by the minor's parents or guardians.

Exclusion Criteria:

• Presence of HbA1c levels below 5.7%
• Presence of HbA1c levels above 6.4%
• Presence of pathological metabolic diseases, such as diabetes or metabolic syndrome
• Presence of other diseases related to intestinal integrity or skin issues.
• Lack of the signed informed consent by the minor and legal guardian

The data of the participants will be made available to other researchers under consideration and analysis of the research committee.

The randomisation will be conducted based on an artificial model, utilising a coding system that assigns numerical identifiers to names, postal codes, and grade levels. This approach ensures a systematic and unbiased selection process, allowing for a fair representation of participants across various demographic factors.

The sampling has been estimaited by Epidat program. The experimental group, receiving nutritional intervention, will consist of approximately 50% of the total sample, equivalent to 215 participants. Meanwhile, the control group, not receiving the intervention, will comprise the remaining 50% of the sample, also around 215 participants. This distribution will enable an effective comparison of results between the two groups and assess the effectiveness of the nutritional intervention.