## 2 Materials and Methods
### Assessment of Study Methodology and Risk of Bias  
The Physiotherapy Evidence Database (PEDro) scale was utilised to evaluate the methodological quality of pre-test post-test studies with experimental (EXP) and control (CON) groups that were randomly selected. The scale employs a range of 0 (low methodological quality) to 10 (high methodological quality) to score the internal study validity. The score that each section is awarded can range from 0 (\"no\") to 1 (\"yes\"), depending on the quality obtained by each point. The quality of the studies were categorized according to the following cut-off points: excellent (9-10), good (6-8), fair (4-5), and poor (<3) [38]. The scale in question comprises ten items.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Criterion** & **Inclusion** & **Exclusion** & **Search Coherence** \\ \hline \multirow{4}{*}{_(1) Population_} & Preschool and school & Children out of preschool or & _“early childhood” OR_ \\  & school-aged children & Children under & _preschool OR kindergarten_ \\  & & medical treatment & _OR school_* _OR “primary_ \\  & & Children out of school doing & _“elementary education”_ \\  & & physical activity program & _(nutriation intervention could_ \\  & & & _food_* _OR DIET_* _AND_ \\  & Children in schools involved & be at home) & _(exercise OR “Physical_ \\ \multirow{4}{*}{_(2) Intervention or Exposure_} & in a multifaceted (nutrition & Children not involved in a & _activity_” OR _“physical_ \\  & and exercise) intervention & multifaceted program & _education” OR sport OR_ \\  & program (exercise should be & Children involved in & _fitness OR aerobic OR_ \\  & in school) & programs with & _movement_) _AND_ (_program_* \\  & & supplementation & _OR intervention_) \\  & & & _Study protocols_ \\  & & & - & - \\ \multirow{4}{*}{_(3) Comparation_} & \multirow{4}{*}{-} & \multirow{4}{*}{-} & \multirow{4}{*}{-} \\  & Outcomes extracted from & & & \\ \cline{1-1}  & children’s blood analysis & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & Randomized controlled trial & Non randomized & _“randomized controlled trial_* \\ \cline{1-1}  & Peer-reviewed full-text studies & Non-peer reviewed & \\ \cline{1-1}  & published in original journal & journal articles. & & \\ \cline{1-1}  & articles, without & Non original full-text studies & \\ \cline{1-1}  & language restrictions. & (conference papers...). & \\ \hline \hline \end{tabular}  
* serves as an truncation operator to capture all word variations with the specified root term. For instance, “school” retrieves “schools,” “schooling,” “school-age,” “schoolchildren,” and related variations. This truncation technique is an standard practice in systematic database searching to ensure comprehensive retrieval of relevant literature while maintaining search precision and reproducibility, as recommended by established systematic review guidelines.  
\end{table}
Table 1: Inclusion and exclusion criteria.  
Additionally, the Risk of Bias 2.0 (RoB 2.0) tool was employed to provide a comprehensive assessment of bias across five key domains: randomization process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of the reported result [39]. Each domain was evaluated and classified as \"low risk,\" \"some concerns,\" or \"high risk\" based on predefined criteria. Two authors conducted both PEDro and RoB 2.0 assessments (M.R.-G. and A.M.-V), with disagreements resolved through discussion or consultation with a third author (C.D.G.-C). The combination of both assessment tools provided a robust evaluation of study quality and internal validity, enabling a more comprehensive understanding of potential biases that could affect the reliability of the findings. Assessment of publication bias through funnel plots and [PERSON]'s test was not conducted due to substantial methodological heterogeneity preventing formal meta-analysis.