Design, Methods, and Pilot Baseline Results of the SEÍSMO Study: A School-Based Cluster Randomized Controlled Trial to Prevent Pediatric Obesity among Disadvantaged Communities in Spain.

Design, Methods, and Pilot Baseline Results of the SEÍSMO Study: A School-Based Cluster Randomized Controlled Trial to Prevent Pediatric Obesity among Disadvantaged Communities in Spain - PMC Skip to main content An official website of the United States government Here's how you know Here's how you know Search Log in Primary site navigation Search Log in Search PMC Full-Text Archive Search in PMC Journal List User Guide As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsement of, or agreement with, the contents by NLM or the National Institutes of Health. Learn more: PMC Disclaimer | PMC Copyright Notice Obes Facts . 2026 Mar 5. Online ahead of print. doi: 10.1159/000551260 Design, Methods, and Pilot Baseline Results of the SEÍSMO Study: A School-Based Cluster Randomized Controlled Trial to Prevent Pediatric Obesity among Disadvantaged Communities in Spain Genís Según a, b , Mar Ribera-Sanuy a , Jan Ródenas-Gálvez a , Paula Berruezo a, c , Pol Soley-Cascales a , Miranda Betés-Suárez a , Sílvia Torres a, d , Clara Homs a, e , Marta Bueno a , Miguel Valiente-Pascual a , Antonio Varajão-Cardoso a , Gisela López-Iglesias a , Mónica Aznar f , Daniel Mateos-Luque a , Berta Mas-Ribera a , Gina Valdés-Querol a , Lluc Fernández-Callao a , Sergi Frías g , Helmut Schröder h, i , Santi F Gómez a, b, h, i, ✉ Author information Article notes Copyright and License information a Gasol Foundation Europe, Sant Boi de Llobregat, Spain b Nursing and Physiotherapy Department, University of Lleida, Lleida, Spain c Public Health and Epidemiology Research Group, School of Medicine, Universidad de Alcalá, Alcalá de Henares, Spain d Research Group on Methodology, Methods, Models and Outcomes of Health and Social Sciences (M 3 O), University of Vic-University Central of Catalonia, Barcelona, Spain e Global Research on Wellbeing (GroW), Faculty of Health Sciences, Blanquerna Ramon Llull University, Barcelona, Spain f Department of Musical, Plastic and Corporal Expression, Faculty of Education, University of Zaragoza, Zaragoza, Spain g Coboi Lab, Sant Boi de Llobregat, Spain h CIBER Epidemiology and Public Health (CIBERESP), Carlos III Health Institute, Barcelona, Spain i Cardiovascular Risk and Nutrition Research Group (CARIN), IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain ✉ Correspondence to: Santi F. Gómez, sgomez@gasolfoundation.org Trial Registration: This study protocol was registered and approved in the ISRCTN registry (ISRCTN10335633) on March 19, 2025. ✉ Corresponding author. Received 2025 Aug 14; Accepted 2026 Feb 18. © 2026 The Author(s). Published by S. Karger AG, Basel This article is licensed under the Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC) ( https://karger.com/Services/OpenAccessLicense ). Usage and distribution for commercial purposes requires written permission. PMC Copyright notice PMCID: PMC13236059  PMID: 41785198 Abstract Introduction Pediatric obesity is a major health issue with a growing worldwide trend since 1990. The present study aims to describe the design, methods, and pilot baseline results of a school-based obesity-prevention intervention implemented in disadvantaged communities. Methods The SEÍSMO study integrates two stages: the first stage includes baseline and follow-up assessments for 11,139 children aged 6–12, evaluated at baseline between 2020 and 2024 in 120 Spanish schools. The second stage is a 6-year cluster randomized controlled trial (RCT) that incorporated the learnings of the first stage to assess from 2024 to 2041 two primary outcomes (z-score body mass index and waist-to-height ratio) and several secondary outcomes (healthy lifestyles, quality of life, academic performance, psychosocial determinants, psychological resilience, and weight stigma) will be evaluated at 12, 24, 36, and 48 months. A sample size of 56 clusters and 4,760 participants is needed, assuming an attrition rate of 35% by 36 months post-baseline, but an oversampling will result in 10,080 participants. In this stage will involve three recruitment editions (2024–2025, 2025–2026, 2026–2027) and will incorporate children aged 3–12 located in Catalonia, Spain. The intervention includes a total of 50 specific action groups. In both study stages, a follow-up will be conducted at 18 years of age, involving a total of 21,219 children. Conclusions SEÍSMO first-stage participants present prevalences of severe obesity and abdominal obesity of 5.4% and 31.3%, respectively. There is an urgent need to have effective obesity-prevention with the capacity to reduce the current inequalities. Keywords: Pediatric obesity, Health promotion, Prevention, Randomized controlled trial, Vulnerable population Introduction Pediatric obesity has become one of the biggest social, economic, and health problems in the world of the 21st century [ 1 , 2 ]. The global prevalence of obesity in young people between 5 and 19 years of age increased from 1.7% in 1990 to 6.9% in 2022 [ 3 ]. In the European context, there is a higher prevalence of obesity among children aged 6–9 in Mediterranean countries [ 4 ], this being 15.9% in Spain [ 5 ], with a figure of 11.6% for the population aged 8–16 years [ 6 ]. Pediatric obesity is multi-determined [ 1 , 7 ] and has biopsychosocial and economic consequences [ 2 , 8 ] in the short [ 9 ], medium [ 10 ], and long term [ 11 , 12 ]. Moreover, children facing socioeconomic inequalities are more likely to present obesity in high-income countries [ 13 ], and Spain is no exception to this [ 14 , 15 ]. Obesity-prevention interventions aimed at promoting healthy habits demonstrate promising positive effects [ 16 , 17 ]. Their approaches should be: (i) multilevel and multicomponent [ 18 ], contemplating healthy eating [ 19 ], physical activity [ 20 , 21 ], psychological well-being [ 22 , 23 ], screen time [ 24 , 25 ], and sleep duration [ 26 , 27 ]; (ii) led by a multidisciplinary team [ 28 , 29 ]; (iii) integrated, equitable, comprehensive, and person-centered [ 30 , 31 ]; (iv) sensitive to social inequalities [ 32 – 34 ]; and (v) grounded in a strong psychosocial theoretical basis [ 35 – 37 ]. School programmes show positive results for single component interventions [ 38 ]. Further research on school-based interventions should consider applying multilevel and multicomponent approaches and include the strategy within the school curriculum [ 39 , 40 ], as suggested by the Schools for Health in Europe Network (SHE) [ 41 ]. A more comprehensive assessment is required based on well-designed cluster randomized controlled trials (RCT) with longer follow-up periods [ 42 ]. The SEÍSMO cluster RCT study aims to: Act as a school-based intervention best practice model, including a multilevel perspective to ensure a political, cultural, and environmental change in the schools based on a multicomponent healthy lifestyle promotion (healthy eating, physical activity, psychological well-being, screen time, and sleep duration) [ 18 ], and foster a comprehensive involvement of the families, teachers, and key agents who accompany children in the school stage. Evaluate the short-, medium-, long-, and very long-term effects of the SEÍSMO intervention. Follow-up school-age participants until adulthood. Methods Study Design and Participants The SEÍSMO study is recruiting participants through schools in two main stages: (1) SEÍSMO first stage and (2) SEÍSMO second stage. SEÍSMO First Stage This was conducted from 2021 to 2024 for piloting the intervention and evaluation methods. It included children aged 6–12 years in primary education schools, prioritizing those located in disadvantaged communities in three Spanish regions: Catalonia, Madrid, and Valencia. It lasted four academic years, including a 1st recruitment round when the intervention and control schools were randomly assigned; 2nd and 3rd non-randomized but controlled recruitment rounds; and a 4th non-controlled recruitment round. The periods between each academic year were dedicated to innovating new intervention and evaluation components. A total of 120 schools participated by receiving progressively more components and making relevant contributions to evolve the method. Of these schools, 75 took part in two or more recruitment rounds, while 45 participated in only one. The first stage involves a cohort of 11,139 children evaluated at the baseline (shown in Fig. 1 ). Gasol Foundation has limited economic and human resources and needed four academic years to develop the complex intervention that is explained in the following subsection. Fig. 1. Open in a new tab Baseline sample size and randomization for each stage and recruitment round of the SEÍSMO study, including expected participants per assessment after baseline for the second stage. IS, intervention school; CS, control school. SEÍSMO Second Stage This has been designed based on the knowledge accumulated during the first stage. The complete SEÍSMO intervention methodology will be evaluated through a cluster RCT during this second stage. Each cluster will be randomly allocated to the intervention or control group using the “list of randomizer” function offered by random.org webpage. The randomization is executed by Gasol Foundation team. During this stage, it will be included children aged 3–12 years at baseline, recruiting schools in three planned rounds in Catalonia, Spain (2024–2025, 2025–2026, and 2026–2027) (shown in Fig. 1 ). Sample Size In both stages are considered each school as a cluster. The first stage did not contemplate a sample size calculation recruiting the school by convenience. For the second stage, the sample size calculation was performed using a two independent cluster means functionality of Granmo tool allocated in the Datarus webpage [ 43 ]. In the long term (36 months), we expect a differential evolution of 0.26 points for the z-score body mass index (zBMI) between the intervention and control schools. An effect size above 0.2 was considered, indicating clinical relevance [ 44 ]. We assumed a 0.05 alpha risk and 0.02 beta risk in a bilateral contrast, a standard deviation (SD) of 1.00, 35% dropout in the long-term assessment, and low heterogeneity by groups on the basis of previous experience of SEÍSMO first stage. A total of 56 clusters and 4,760 participants (85 per cluster) are needed with a statistical power of 80%. A ratio 1:1 will be used, allocating 28 clusters to each group. Nevertheless, a sample size of 180 children per cluster is expected, resulting in 10,080 participants at baseline. This oversampling occurs because the SEÍSMO method is intended to be inclusive for all children and typically schools want to apply the procedures indiscriminately. The same calculation was also performed for the second main outcome: waist-to-height ratio (WHtR). Considering an effect size difference between intervention and control schools of 0.13 (SD = 0.06), the resulting number of clusters and participants per cluster was lower than for the zBMI. For this reason, sufficient statistical power is assumed for WHtR. Inclusion and Exclusion Criteria The first stage enrolment was completed prioritizing schools located in disadvantaged communities with an average annual income per person equal to or lower than 12,292 euros. The second stage participation will be limited to schools located in disadvantaged communities with an average annual income per person equal to or lower than 14,804 euros. These cut-offs refer to the Spanish average per person in 2020 and 2024, respectively [ 45 ]. The value for each selected school has been obtained from the census areas where schools are located according to the Spanish National Statistics Institute [ 46 ]. The exclusion criteria in both stages are: (i) not presenting informed consent signed by the parents/legal guardians, or the participants themselves if 18 years old (follow-up); and (ii) any limitations in terms of completing the assessment related to children or parents/legal guardians with a psychological or physical limitation that make it impossible to participate in some or all the assessment procedures. Each case will be considered individually, and the Gasol Foundation team will offer different evaluation options to include all the children and families. Intervention Design The SEÍSMO intervention method also has the two aforementioned developmental stages. The SEÍSMO First-Stage Intervention The original intervention was implemented over four editions (1st: 2020/2021; 2nd: 2021/2022; 3rd: 2022/2023; 4th: 2023/2024) lasting 12 months each. The periods between each academic year were dedicated to creating new intervention modules that have progressively been incorporated into the method and piloted to the entire educational community: children, teaching staff, parents and/or legal guardians, nonteaching staff, and school managers. The 1st edition served to pilot the physical education module. The 2nd edition also included the family module. In the 3rd edition, the healthy spaces module was added to the physical education and family modules. Finally, during the 4th edition, the intervention method was rounded out with the additional incorporation of the water promotion module and the healthy eating and sustainable school’s canteen module. Further details on the original intervention design can be found in online supplementary file 1 (for all online suppl. material, see https://doi.org/10.1159/000551260 . The SEÍSMO Second-Stage Intervention All the original intervention modules are currently integrated into the SEÍSMO second-stage intervention. The new intervention will run in each school for a minimum of six consecutive academic years and will be implemented by school staff and coordinated by the multidisciplinary Gasol Foundation team that will promote the implementation of 50 specific action groups ( Table 1 ) structured around three pillars. Competencies pillar: to promote healthy habits as a comprehensive part of the primary school curricular project, aligned with the Spanish educational law [ 47 ]. Educational community pillar: to engage the entire educational community in adopting the SHE approaches. Policy, environment, and cultural pillar: to promote school policies, environment, and culture aimed at fostering healthy lifestyles. Table 1. Number of specific action groups included in the SEÍSMO second-stage intervention by pillars Action type Characteristics per action groups Number of actions per academic year Total actions pillars specific action groups time a , m target implemented/delivered by 1st 2nd 3rd 4th 5th 6th from the 1st to 6th N time, h A. Competencies pillar A1. Physical education activities b 15 C PET 16 32–64 32–64 32–64 16–64 0–64 128–336 32–84 A2. Family letter activity b 30 C TS 1 1 1 1 1 1 6 3 A3. Family home activities b 60 C&F C 6 4 4 4 4 4 26 26 A4. Feedback family home activities b 30 C TS 6 4 4 4 4 4 26 13 A5. Broad activities b 30 C TS 0–16 0–16 16 32 48 64 160–192 80–96 A6. Materials for children b N/E C GF 8 5 5 5 5 5 33 N/E A7. Materials for teaching staff N/E TS GF 6 1 1 1 1 1 11 N/E A8. Materials for families N/E F GF 7 4 4 4 4 4 27 N/E Total actions per pillar 50–66 51–99 67–99 83–115 83–131 83–147 417–657 154–222 B. Educational community pillar B9. Starting presentation 60 SM GF 1 – – – – – 1 1 B10. Creation of healthy governance team N/E SM&SH GF 1 – – – – – 1 N/E B11. Healthy governance team meetings 60 HGT GF – 3 3 3 3 3 15 15 B12. Definition of governance statutes N/E EC HGT – 1 – – – – 1 N/E B13. Annual healthy school event 120 EC GF&HGT 1 1 1 1 1 1 6 12 B14. Incentives for healthy governance team N/E HGT GF 1 1 1 1 1 1 6 N/E B15. Training and follow-up meetings 45 TS GF 6 4 4 4 4 4 26 19.5 B16. Network school meetings 120 TS GF – 1 1 1 1 1 5 10 B17. Comprehensive workshops 120 TS GF – 2 2 2 2 2 10 20 B18. Methodological video training sessions 15 TS GF – 3 – – – – 3 0.75 B19. Theoretical video training sessions 15 TS GF 5 1 1 1 1 1 10 2.5 B20. Complementary training files N/E TS GF 1 1 1 1 1 1 6 N/E B21. Educational guide N/E TS GF 1 1 1 1 1 1 6 N/E B22. Digital platform N/E TS GF 1 1 1 1 1 1 6 N/E B23. Communication materials N/E EC GF 4 0–2 0–2 0–2 0–2 0–2 4–14 N/E B24. Healthy announcements b N/E C&F GF – 4 4 4 4 4 20 N/E B25. Dissemination in social media N/E EC HGT – 4 4 4 4 4 20 N/E B26. School website section N/E EC SM 1 – – – – – 1 N/E B27. Healthy newsletter N/E EC SM 1 – – – – – 1 N/E B28. Dissemination of results N/E EC HGT – – 1 1 1 1 4 N/E Total actions per pillar 24 28–30 25–27 25–27 25–27 25–27 152–162 80.75 C. Policy, environment and cultural pillar C29. Interviews with key agents 60 SM and SH GF 2–4 – 2–4 – 2–4 – 6–12 6–12 C30. Qualitative school observation 60 EC GF 1 – 1 – 1 – 3 3 C31. School surveys – EC GF 2 – 2 – 2 – 6 – C32. Qualitative children's workshops b 60 C TS 1 1 1 1 1 1 6 6 C33. Presentation of comprehensive diagnosis 60 HGT GF – 1 1 1 1 1 5 5 C34. School diagnosis report – EC GF – 1 – 1 – 1 3 – C35. Defining key agents to create an impact team 60 EC HGT and GF – 1 1 1 1 1 5 5 C36. Creation of healthy impact team – C and SH HGT – 1 – – – – 1 – C37. Healthy impact team incentives – HIT GF – 1 1 1 1 1 5 – C38. Healthy impact team co-creation meeting 60 HIT GF – 1 – 1 – 1 3 3 C39. Healthy impact team prioritization meeting 60 HIT GF – 1 – 1 – 1 3 3 C40. Healthy governance team decision-making meeting 120 HGT GF – 1 – 1 – 1 3 6 C41. Presentation of the health-promotion action plan 120 HIT and HGT GF – – 1 – – – 1 2 C42. Final health-promotion action plan report – EC HGT and GF – – 1 – – – 1 – C43. Creation of monitoring committee – HIT and HGT GF – – 1 – – – 1 – C44. Healthy impact team monitoring meetings 60 HIT HGT – – 4 4 4 4 16 16 C45. Individual growth initiatives b N/E C TS and HIT 0–16 16–32 16–32 32–48 32–64 32–64 128–256 N/E C46. Developmental educational community initiatives N/E EC HIT 0–16 16–32 16–32 32–48 32–64 32–64 128–256 N/E C47. Living and equality initiatives N/E EC HIT 0–16 0–32 16–32 32–48 48–64 48–64 144–256 N/E C48. School environment initiatives N/E EC HIT 0–16 0–32 16–32 32–48 48–64 48–64 144–256 N/E C49. Cultural, socioeconomic, and policy initiatives N/E EC HGT 0–16 0–32 16–32 32–48 48–64 48–64 144–256 N/E C50. Annual evaluation report N/E HGT HIT and GF – 1 1 1 1 1 5 N/E Total actions per pillar 6–88 42–170 97–179 173–253 222–336 221–333 761–1,359 55–61 Open in a new tab C, children; PET, physical education teacher; TS, teaching staff; F, families; GF, Gasol Foundation team; SM, school manager; SH, stakeholders; HGT, healthy governance team; EC, educational community (children, families, teaching staff, and non-teaching staff); HIT, healthy impact team. N/E = Cannot be estimated because most of them are resources that benefit each target population, but they do not have a specific predefined participation time. a Total time dedicated to each action in minutes per target population. b Direct intervention actions addressed at each child. Bold values represent the total number of expected actions across all pillars. The relationship with the three pillars is shown in Figure 2 . The main goal was to establish school governance mechanisms [ 48 ] to transform them into health-promoting schools [ 41 ]. This transformation involves developing a school-based action plan to promote healthy lifestyles and psychological resilience through an equity-orientated approach. It seeks to address multiple intersecting inequality axes, such as gender, socioeconomic status, migration status, and physical condition, which contribute to unequal exposure to health risks and weight stigma [ 49 ]. The plan incorporates school-level strategies and protocols aimed at reducing weight bias and mitigating social pressures related to body weight, thereby addressing weight stigma as both a social determinant of health and a barrier to effective obesity prevention. Fig. 2. Open in a new tab Three main pillars of the SEÍSMO second-stage intervention that integrates the five pilot modules, including target population, progression, and timeline. To achieve this, the complete intervention will be progressively implemented, involving between 1,330 and 2,178 actions, and between 289.75 and 363.75 h of implementation ( Table 2 ). Nine specific groups of actions are directly addressed at children, while 41 are indirect ( Table 1 ). The indirect actions aim to gradually increase the autonomy and empowerment of each school, reducing their dependence on guidance from the Gasol Foundation team. Further details on the intervention design can be found in online supplementary file 1. Table 2. Number and implementation hours of direct and indirect actions per academic year Action type Academic years 1st 2nd 3rd 4th 5th 6th From the 1st to 6th N time, h N time, h N time, h N time, h N time, h N time, h N time, h Direct 38–70 14.5–22.5 67–131 15.5–31.5 83–131 23.5–31.5 115–163 31.5–39.5 115–195 35.5–47.5 115–211 39.5–55.5 533–901 160–228 Indirect 42–108 11.75–13.75 54–168 21 106–174 25.25–27.25 166–232 24.25–24.25 211–299 23.25–25.25 214–296 24.25 793–1,277 129.75–135.75 Complete intervention 80–178 26.25–36.25 121–299 36.5–52.5 189–305 48.75–58.75 281–395 55.75–63.75 326–494 58.75–72.75 329–507 63.75–79.75 1,330–2178 289.75–363.75 Open in a new tab The four theoretical bases of the SEÍSMO intervention are the: (i) I-Change model [ 50 ]; (ii) Healthy Galaxy metaphor [ 34 , 51 ]; (iii) Resiliency Theory [ 52 ], operationalized by the Search Institute through 40 developmental assets [ 53 ]; and (iv) the motivation interviewing tool [ 54 ]. The intervention logical framework is shown in Figure 3 and the extended information is included in the online supplementary file 2. Fig. 3. Open in a new tab Logical framework of the SEÍSMO intervention. GF, Gasol Foundation; BMI, body mass index; WHtR, waist-to-height ratio. Implication of Control Group Schools The following actions will be implemented: (a) an evaluation plan; (b) an annual health-related event (shown in Table 1 action B13); (c) a comprehensive school diagnosis during the first academic year (shown in Table 1 actions C29–C31); (d) a total of three follow-up meetings are planned for the first and second academic years, and four for the subsequent academic years (shown in Table 1 action B15) to ensure adherence and define the actions that will be progressively implemented; (e) a set of national and regional public resources, including training, guidelines, advisory services, health-related materials, and other initiatives, will be promoted equally in the intervention and control group (shown in Table 1 , C45–C49). Outcomes The main outcomes are the anthropometric variables zBMI and WHtR for both stages. The secondary outcomes are different for each stage: (1) SEÍSMO first stage considers incidence of obesity, healthy lifestyles, quality of life, and psychosocial determinants; (2) SEÍSMO second stage will additionally measure the academic performance, psychological resilience, and weight stigma. These outcomes are grouped according to the following variable groups ( Table 3 ). Anthropometrics: weight (kg), height (cm/m), and waist circumference (cm) will be measured by the Gasol Foundation-trained team to calculate the incidence of obesity, the zBMI, and the WHtR. This training includes a relevant component to be aware of and prevent weight stigma when carrying out the measurements and when communicating with each child participant. Lifestyles: diet quality [ 55 ], physical activity (min) [ 56 ], physical fitness [ 57 ], screens (min) [ 58 ], and sleep (h) [ 59 ] will be measured using validated questionnaires. From preschoolers up to the 3rd grade, the questionnaires will be filled out by parents/legal guardians, while participants in the 4th, 5th, and 6th grades will self-report. The baseline will be applied from preschoolers to 5th grade and the second, third, and fourth assessments will be carried out when participants are in the 4th, 5th, and 6th grades, respectively. The exception will be participants in the 4th or 5th grade at baseline, as they will participate in three or two assessments, respectively, plus the follow-up at 18 years of age. Quality of life: this will be measured using the EuroQol (EQ-5D-5L) [ 60 ] following the same pattern of assessments as explained for healthy lifestyles. Academic performance: each academic year, school managers will report the participants’ school grades to the Gasol Foundation team. At the age of 18, academic level will be self-reported. Psychosocial determinants: these will be measured using an ad hoc questionnaire based on the Attitude, Social influence, self-Efficacy (ASE) model [ 61 ]. At baseline, participants in the 4th and 5th grades will self-report. The 4th graders will answer these surveys in the short and medium term, while the 5th graders will complete only one (short term). All the children who stay at the participant schools will complete the same questionnaire when they reach the 4th grade. Psychological resilience: this will be measured using the Developmental Assets Profile (DAP) [ 62 , 63 ], following the same procedures as outlined for psychosocial determinants, with an additional follow-up at 18 years of age. Weight stigma: this will be measured using the Modified Weight Bias Internalization Scale (WBIS-M) [ 64 ], following the same procedure as for psychological resilience. Table 3. Measurements of SEÍSMO study by variable groups and age range for each term and stage ​ Number of repeated measurements stage first second terms baseline short follow-up baseline short medium long very long follow-up months after baseline 0 8–12 72–144 0 11–19 20–29 30–43 44–105 72–180 age range (years) 6–12 18 3–12 8–12 18 Anthropometrics a 3–18 1 2 3 1 2 3 4 5 6 Lifestyles b 1 2 3 1 2 3 4 5 6 Quality of life c 1 2 3 1 2 3 4 5 6 Academic performance d 6–18 – – – 1 2 3 4 5 6 Psychosocial determinants e 8–12 1 2 3 1 2 – – – – Psychological resilience f 8–18 – – – 1 2 3 – – 4 Weight stigma g – – – 1 2 3 – – 4 Open in a new tab a Anthropometric measurements include weight, height, and waist circumference. b Lifestyles include diet quality measured by Mediterranean Diet Quality Index (KIDMED) [ 55 ], physical activity measured by Physical Activity Unit 7 item Screener (PAU7S) [ 56 ], physical condition measured by International Fitness Scale (IFIS) [ 57 ], screen time measured by Screen time-based Sedentary Behavior Questionnaire (SSBQ) [ 58 ], and hours of sleep measured by Sleep Habits Survey for Adolescents (SHSA) [ 59 ]. c Quality of life is measured by EUROQOL (EQ-5D-5L) [ 60 ]. d Measured by the school curricular ratings [ 47 ] and academic level at the age of 18. e Psychosocial determinants measured using an ad hoc questionnaire based on the Attitude, Social Influence, Efficacy (ASE) model [ 61 ]. f Psychological resilience measured by Developmental Assets Profile (DAP) [ 62 ]. g Weight stigma focusing on the weight bias internalization measured by the Modified Weight Bias Internalization Scale (WBIS-M) [ 64 ]. Additionally, we will collect other data reported by parents/legal guardians at baseline. Children: birth weight, pregnancy duration, breastfeeding, and adverse childhood experiences [ 65 , 66 ]. Parents/legal guardians: self-reported sociodemographic characteristics, weight and height, academic level, labor market status, and home address. Finally, the teaching staff will self-report their sociodemographic characteristics, academic level, motivation, knowledge, and awareness level toward health-promoting schools. The data collection is explained in online supplementary file 3. Follow-Up The SEÍSMO first stage was evaluated in the short term (8–12 months) to analyze the piloted method. Additionally, in the SEÍSMO second stage, a total of 7,056, 6,272, 5,096, and 3,360 participants are expected to be analyzed in the short (11–19 months), medium (20–29 months), long (30–43 months), and very long term (44–105 months), respectively (shown in Fig. 1 ). The participants in both stages will also be followed up when they are 18 years old. Table 4 shows the total number of participants per recruitment round and year until 2041. Table 4. Number of participants that will be invited to the follow-up at 18 years old Stage Recruitment edition 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 Total First 1st (2020–2021) 1 37 560 724 616 563 473 475 1 – – – – – – – – 3,450 2nd (2021–2022) 11 5 28 467 729 868 715 571 780 146 1 – – – – – – 4,321 3rd (2022–2023) – 1 1 63 407 476 405 447 512 839 95 – – – – – – 3,246 4th (2023–2024) – – – 1 2 15 22 16 30 32 4 – – – – – – 122 Subtotal a 12 43 589 1,255 1,754 1,922 1,615 1,509 1,323 1,017 100 – – – – – – 11,139 Second 5th (2024–2025) – – – – – – 160 160 160 160 160 160 160 160 160 – – 1,440 6th (2024–2025) – – – – – – – 480 480 480 480 480 480 480 480 480 – 4,320 7th (2024–2025) – – – – – – – – 480 480 480 480 480 480 480 480 480 4,320 Subtotal b – – – – – – 160 640 1,120 1,120 1,120 1,120 1,120 1,120 1,120 960 480 10,080 Total 12 43 589 1,255 1,754 1,922 1,775 2,149 2,443 2,137 1,220 1,120 1,120 1,120 1,120 960 480 21,219 Open in a new tab a SEÍSMO first stage participants according to their baseline birthdate. b SEÍSMO second stage participants according to an estimation of 20 children per classroom in each cluster. Bold values highlight the total number of expected participants who are followed up in adulthood. Attrition Rate SEÍSMO first stage presented a dropout rate of 10% in the short-term. For SEÍSMO second stage, the following dropout rates are expected: short term = 10%; medium = 20%; long = 35%; and very long term = 50%. For both stages, 60% dropout is expected by the follow-up at 18 years old. To minimize the attrition and monitor the SEÍSMO full intervention fidelity data, the following actions will be undertaken: (i) regular follow-up meetings with the stakeholders and educational community organized by the Gasol Foundation team; (ii) registration of each child’s attendance at intervention actions; (iii) qualitative evaluation of governance mechanism activation at the end of each academic year to track progress made toward being a health-promoting school; (iv) Healthy Eating Physical activity in Schools project (HEPS) quality checklist to evaluate the intervention according to the four quality dimensions of concept, structure, process, and results [ 67 ]; (v) level of intervention satisfaction after each academic year reported by children, families, and teaching staff; and (vi) qualitative voice audios after each action led by Gasol Foundation team to monitor implementation quality. Data Management Study data will be collected and managed using Qualtrics ® , an online platform that adheres to data protection laws (specifically referring to Law 2/2018). Access to the datasets will be password-protected, and children and parents/legal guardians will be identified by a 10-digit number to ensure confidentiality before, during, and after the study. Data Monitoring The data monitoring committee will be formed by researchers of Gasol Foundation with no conflict of interest. This committee will compose by the research officer, a data management manager, project officer, research and programs coordinator, and director of research and programs. Statistical Methods We will analyze the pooled data from both SEÍSMO stages. Data clean-up will be performed to minimize errors. To compare groups, we will use the Student’s t test or U of Mann Whitney for continuous variables and the chi-square test for categorical variables. Furthermore, for baseline and short, medium, long, and very long assessments, a descriptive analysis of the weight status, sleep, screen time, diet, physical activity, quality of life, psychosocial determinants, academic performance, psychological resilience, and weight stigma of children will be performed. For the quantitative variables, the usual central tendency and dispersion statistics (mean and SD, and median and interquartile range) will be obtained, and qualitative variables will be summarized by frequency and percentage for each category. We will estimate the statistical significance of the differences between baseline and short, medium, long, and very long assessments within each participation group. We will be paired tests for continuous variables and McNemar’s tests for categorical variables. To analyze significant differences in the outcome’s evolution between control and intervention groups, mixed models will be used. These mixed models will adjust for each dependent variable (linear for continuous variables and logit for dichotomous). Several covariables will be adjusted in the models, as well as time (baseline/final), group (intervention/control), and time-group interaction that also will be adjusted as fixed factors, and subject and school will be set as random factors. Participants with missing data will be excluded from de analysis. All analyses will be carried out using SPSS V26.0, R Studio 4.5.0, and Stata 17.0, and a significance level of 5% will be considered for all tests. Results SEÍSMO first stage has allowed us to analyze the baseline characteristics, mean values of anthropometric measurements, and prevalence of different weight status categories [ 68 , 69 ] among the participants in each group ( Table 5 ). A total of 11,139 participants were assessed, with 5,028 and 6,111 being assigned to the control and intervention groups, respectively. Furthermore, no statistically significant differences were found for age, gender of children and also for parents’ university degrees comparing both groups. However, participants in the intervention group had a significantly lower mean average income per person [ 46 ] and labor market status of parents/legal guardians than those in the intervention group. In addition, the intervention group has a statistically significant higher mean of WHtR compared to the control group. As explained, SEÍSMO prioritizes disadvantaged communities where prevalences of overweight, severe obesity and abdominal obesity were alarmingly high in both groups. Table 5. Baseline characteristics of participants in the SEÍSMO first stage by allocation group and overall Baseline characteristics a Overall, N = 11,139 Control, N = 5,028 Intervention, N = 6,111 p value b Age 9.0 (1.8) 8.9 (1.9) 9.0 (1.8) 0.140 Girls 48.9 48.5 49.1 0.533 Annual average income per person (EUR) c 12,224.8 (3,486.4) 12,954.7 (4,496.5) 11,624.3 (2,173.5) 0.000* Parental socioeconomic status University degree 29.2 29.5 28.9 0.479 Working 73.1 74.0 72.3 0.050 Weight, kg 35.1 (11.7) 35.0 (11.8) 35.1 (11.6) 0.742 Height, m 1.35 (0.1) 1.35 (0.1) 1.35 (0.1) 0.263 Body mass index, kg/m 2 18.8 (3.7) 18.8 (3.7) 18.8 (3.8) 0.807 Waist, cm 64.6 (10.7) 64.8 (10.8) 64.5 (10.6) 0.255 WHtR 0.48 (0.062) 0.47 (0.061) 0.48 (0.062) 0.008* Weight status Excessive weight d 46.6 46.4 46.8 0.606 Overweight 24.0 23.6 24.3 0.389 Obesity 17.3 17.5 17.1 0.571 Severe obesity 5.4 5.3 5.4 0.643 Abdominal obesity e 31.3 32.0 30.8 0.180 Open in a new tab *Statistical significance p < 0.05. a Continuous data are presented as mean and standard deviation [mean (SD)], and categorical data are presented as percentage (%). b Obtained a comparison between participation groups by data. p value non-applicable in the overall description. c According to the census area of school allocation by the Spanish National Statistics Institute (2022) [ 46 ]. d Calculated according to the WHO’s growth standards [ 68 ]. e According to the Taylor cut off criteria, ≥0.5 [ 69 ]. Discussion Pediatric obesity was highly prevalent within disadvantaged communities that participated in the SEÍSMO first stage. These results highlight the importance of implementing school-based intervention methodologies, such as the SEÍSMO full intervention, to reduce the strong health inequalities evidenced by previous research carried out in Spain. On the one hand, it showed a lower likelihood of presenting obesity (OR: 0.28; 95% CI: 0.16–0.48), severe obesity (OR: 0.20; 95% CI: 0.05–0.81), and abdominal obesity (OR: 0.36; 95% CI: 0.23–0.54) of the most socioeconomically advantaged population compared with the most disadvantaged [ 14 ]. On the other hand, although the overall prevalence of pediatric obesity presents a positive trend between 2006 and 2016, the most deprived areas in urban settings present an increase in the prevalence ratios, especially for girls (1.59 [95% CI: 1.46–1.74]–2.03 [95% CI: 1.88–2.19]) [ 15 ]. These gender and socioeconomic status inequalities are considered by SEÍSMO second stage to produce positive effects on the worrying current epidemiological pattern. Furthermore, these innovative school-based interventions should be evaluated through well-designed RCTs, including high-quality long-term follow-up targeting disadvantaged communities with robust evaluation methods to demonstrate intervention effects [ 42 ], as detailed in the SEÍSMO study. Our study includes two primary outcomes (zBMI and WHtR) and several secondary outcomes (healthy lifestyles, quality of life, academic performance, psychological determinants, psychological resilience, and weight stigma) that enable us to study the effects of a pediatric obesity preventative intervention beyond the classical weight-centrism [ 49 ]. The strengths of the evaluation method are: Study design: cluster RCT school-based intervention over six academic years [ 70 , 71 ], and following up until adulthood [ 42 ]. Several main and secondary outcomes: zBMI and WHtR are used to assess the intervention impact, with WHtR being a reliable complement or alternative to zBMI [ 72 ]. The obesity-prevention interventions are likely to affect several secondary outcomes which are also evaluated in this study. Sample size calculation and oversampling: the statistical power of the study is enhanced by the oversampling. The process, fidelity, and quality of the intervention monitored [ 67 ]. Strengths of the intervention method: Addressed at schools located in disadvantaged communities: schools have the opportunity of universally promoting health [ 73 ], independently of inequality axes [ 32 , 33 , 49 , 74 , 75 ]. The SEÍSMO second-stage intervention approach: this is coordinated, inclusive, equitable, and collaborative [ 30 , 40 , 76 , 77 ]. SHE pillars [ 41 ] are incorporated, transforming the school policies, culture, and environment to make them health-promoting schools [ 78 ]. The healthy and equitable school-based action plan: addressing obesity requires school-based strategies that consider intersecting inequality axes, such as gender, socioeconomic status, migration, and physical condition, which influence unequal health risks. The action plan aims to reduce weight stigma and inequality axes, recognizing them both as a social determinant and as a barrier to effective obesity prevention. Tackling stigma and addressing it from the perspective of social determinants is essential for achieving positive outcomes and reducing inequalities in health. Robust psychosocial theoretical background: the intervention model applies motivational interviewing principles [ 36 , 79 ] and promotes child resilience [ 53 ]. Previous research has shown that adverse childhood experiences predict weight status evolution [ 37 ] and higher levels of child resilience are associated with a lower risk of obesity, independently of the socioeconomic status [ 80 ]. Family and environmental factors to boost each participant resilience are intervened [ 81 , 82 ]. Tailored intervention: Table 4 outlines the intervention components, which are adapted to each school’s needs, expectations, motivation, and stage of change [ 83 ]. In addition, the involvement of a number of key actors in each school is positive when tailoring the design. We will monitor this heterogeneity through process evaluation and make appropriate adjustments when analyzing the main effects. Sustainability and scalability: the generation of governance mechanisms guarantees the sustainability and scalability [ 30 , 41 , 78 ]. Control group implication: regular public health initiatives will be promoted as part of the intervention but also within the control schools, ensuring ethics compliance and their enrolment in the long term [ 42 ]. The SEISMO first-stage intervention pilot: the pilot editions have allowed us to progressively distil the complex intervention method. The current intervention integrates all five pilot modules and incorporates all the learnings regarding governance mechanisms. This study does have some potential limitations: Selection bias: first, the cluster selection criteria based on the mean income of the census area where the schools are located may not correspond with individual socioeconomic status. Nevertheless, most disadvantaged children in Spain live in the same census area as their public/partially-funded school, as this is one of the priority assignment criteria [ 84 ]. Second, some epidemiological studies report high nonparticipation rates in disadvantaged communities [ 85 ]. To try to overcome, this individual selection bias adequate communication strategies will be proposed to participant schools that will spearhead the recruitment. Information bias: the limitations inherent in using self-reported questionnaires to measure secondary outcomes are assumed and should affect both participation groups equally. Scientifically validated tools will be applied, and the participants will receive support to fill out the questionnaires. Should be highlighted that the physical activity questionnaire is already validated for population aged 8–16 while the version for 3–8 years old children is pending to be published. Similarly, the Spanish version of the WBIS-M questionnaire is only validated for secondary education students. Missing data: large epidemiological studies, such as SEÍSMO, are more likely to accumulate high rates of missing data. The governance mechanisms contemplate one Gasol Foundation professional being fully dedicated to ensuring data quality in coordination with a research technician, and a project manager. Retention: to deploy all the 50 specific action groups, a commitment lasting six academic years is expected from each school. This complicates the retention rate in the SEÍSMO second-stage intervention, the continuity of schools, and thus the dose of intervention that each child receives over the years. Weight-based assessment: There is a risk that using body weight as an outcome could unintentionally contribute to increased weight stigma. We acknowledge this risk and have therefore incorporated specific strategies into the intervention to prevent and mitigate weight bias internalization. The actions implemented to reduce this risk include informing families through the informed consent and developing a protocol for collecting this variable through a highly trained and sensitive team. Moreover, we also ensure that the weight displayed on the scale is not visible and that participants are not informed of their weight, thereby minimizing the potential for weight-based teasing or bias [ 49 ]. Furthermore, we will consider other relevant secondary outcomes to understand obesity more broadly, not just focusing on weight. School setting: school-based obesity-prevention interventions are part of the solution, but not the only part [ 29 ]. An advocacy task for local health policies and a multisectoral approach is also needed [ 18 , 86 ]. Conclusions The high rates of obesity in disadvantaged communities corroborated in the SEÍSMO first stage baseline results reflect an urgent need to design more innovative interventions to reduce health inequalities for preventing pediatric obesity in the school setting. The school-based obesity-prevention interventions should be the first step within a global strategy that also should intervene through other settings and include incidence on public policies addressed to promote healthy lifestyles from a perspective sensitive to social inequalities. Acknowledgments The authors gratefully acknowledge the invaluable contributions of children, families, teachers, and schools. We acknowledge the Coboi Lab of the Ajuntament de Sant Boi de Llobregat City Council for hosting us during our scientific production periods and Fernández Global Fruit Group for donating fruit to all the healthy school events in the first stage. Also, we thank Grupo IFA and major and individual donors of Gasol Foundation for providing structural funds to our entity. Statement of Ethics The study protocol was approved by the Ethics Committee (CEIm) of Fundació Sant Joan de Déu, Barcelona, Spain (CI PIC-255-20) with the principles of the Declaration of Helsinki. Potential benefits are associated with improved participant lifestyle, academic performance, individual resilience, and reduced incidence of pediatric obesity following the SEISMO second-stage intervention. There is a risk that using weight as a measure might actually make obesity rates worse, so we plan to include the issue of weight bias internalization to study and reduce weight stigma in our intervention, while also adding other important factors to better understand obesity without focusing only on weight. Any modification of the study protocol will be amended in the trial registration system (ISRCTN10335633). Written informed consent is requested from each participating family and signed by the parent or children’s legal guardian. Children and their families can leave the study at any time, and their data will be deleted. The data collected will be kept strictly private. Conflict of Interest Statement The authors declare that they have no competing interests. Funding Sources SEÍSMO study is financially supported by BNP Paribas Cardif, Barça Foundation, Aigües de Barcelona & AGBAR, Agència de Salut Pública de Barcelona (ASPB), Ajuntament de Barcelona, Ajuntament de Pineda de Mar, Ajuntament de Balaguer, and Ajuntament de Lleida. The Gasol Foundation also received structural funds from Grupo IFA and major or individual donors that contribute to any initiative of the entity. All these funders had no role in the design, data collection, data analysis, and reporting of this study. Author Contributions S.F.G. and G.S., contributed to the conception, design, and development of the initial trial protocol. S.F.G. and H.S. have served as the Principal Investigators. H.S. has been a member of the steering committee, overseeing participant safety, study design, and trial integrity. M.R.-S. and G.V.-Q. have coordinated the daily operations of the study. S.F.G., G.S., and J.R.-G. have led the data management and monitoring. The data collection and implementation of actions have been conducted by M.R.-S., J.R.-G., M.V.-P., P.S.-C., M.B.-S., P.B., A.V.-C., G.L.-I., M.B., D.M.-L., B.M.-R., L.F.-C., and S.T. They also contributed relevantly to progressively enrich the intervention and evaluation methodology during the first stage until reaching the current stage. S.F. and M.A. have made significant conceptual contributions to the intervention and evaluation methodologies presented in this study protocol. Additionally, all authors critically reviewed the protocol for important content. G.S. served as study coordinator, with the support of the C.H. on the coordination from 2020 to 2022 and drafted both the protocol and the manuscript, and after thorough review of the intellectual content, all co-authors approved the final versions of both. Funding Statement SEÍSMO study is financially supported by BNP Paribas Cardif, Barça Foundation, Aigües de Barcelona & AGBAR, Agència de Salut Pública de Barcelona (ASPB), Ajuntament de Barcelona, Ajuntament de Pineda de Mar, Ajuntament de Balaguer, and Ajuntament de Lleida. The Gasol Foundation also received structural funds from Grupo IFA and major or individual donors that contribute to any initiative of the entity. All these funders had no role in the design, data collection, data analysis, and reporting of this study. Data Availability Statement The data that support the findings of this study are not publicly available due to privacy reasons but are available from the corresponding author upon request, after agreement of the sharing conditions by the steering committee of the SEISMO study. Supplementary Material. Supplementary_material-Suppl.1-s1.docx (3.5MB, docx) Supplementary Material. Supplementary_material-Suppl.2-s2.pdf (1.5MB, pdf) Supplementary Material. 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