MOVI-daFIT! Intervention: Rationale and design of a cluster randomized controlled trial testing the effects on improving adiposity, cognition, and subclinical atherosclerosis by increasing cardiorespiratory fitness in children

Direct and indirect effects of physiological, psychological and cognitive variables on academic achievement in children

BACKGROUND

Associations between cardiorespiratory fitness (CRF), screen time, psychological well-being, executive functions, and academic achievement have been reported, however, few studies have analysed models considering the effect of all these variables on academic achievement. This study aims to analyse the direct and indirect associations of mothers' education level, CRF, screen time, psychological well-being, executive functions, with academic achievement in schoolchildren, by sex.

METHODS

This was a cross-sectional analysis of MOVI-daFit! study including 519 schoolchildren (49.52% girls) aged 9-11 years old. Executive functions were assessed with the NIH Toolbox, CRF with the 20-m shuttle run test, academic achievement through the final academic grades in language and mathematics and mother's education level, screen time and well-being by questionnaires.

RESULTS

Structural equation modelling revealed that in boys cognitive flexibility had a significant direct effect on academic achievement and screen time a total significant effect on academic achievement. In girls, CRF was associated with inhibition and psychological well-being, and this was associated with academic achievement.

CONCLUSIONS

Physiological, psychological, and behavioural variables act together to impact academic achievement, and that differences by sex might exist. Thus, strategies to enhance academic achievement in schoolchildren should consider psychological well-being, CRF, screen time, and sex differences.

IMPACT

Physiological, psychological, and behavioural variables, such as cardiorespiratory fitness, screen time, psychological well-being, and cognition all together have an impact on academic achievement, with differences by sex. Previous studies have demonstrated the separate effect of these variables, however, to date, this is the first study that analyses all together in the same model their impact on academic achievement, by sex. This study shows that in boys cognitive flexibility and screen time impact academic achievement. In girls, cardiorespiratory fitness is highly associated with psychological well-being, and this, in turn, was associated with academic achievement.

Interventions to prevent obesity in children aged 5 to 11 years old

BACKGROUND

Prevention of obesity in children is an international public health priority given the prevalence of the condition (and its significant impact on health, development and well-being). Interventions that aim to prevent obesity involve behavioural change strategies that promote healthy eating or 'activity' levels (physical activity, sedentary behaviour and/or sleep) or both, and work by reducing energy intake and/or increasing energy expenditure, respectively. There is uncertainty over which approaches are more effective and numerous new studies have been published over the last five years, since the previous version of this Cochrane review.

OBJECTIVES

To assess the effects of interventions that aim to prevent obesity in children by modifying dietary intake or 'activity' levels, or a combination of both, on changes in BMI, zBMI score and serious adverse events.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was February 2023.

SELECTION CRITERIA

Randomised controlled trials in children (mean age 5 years and above but less than 12 years), comparing diet or 'activity' interventions (or both) to prevent obesity with no intervention, usual care, or with another eligible intervention, in any setting. Studies had to measure outcomes at a minimum of 12 weeks post baseline. We excluded interventions designed primarily to improve sporting performance.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our outcomes were body mass index (BMI), zBMI score and serious adverse events, assessed at short- (12 weeks to < 9 months from baseline), medium- (9 months to < 15 months) and long-term (≥ 15 months) follow-up. We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

This review includes 172 studies (189,707 participants); 149 studies (160,267 participants) were included in meta-analyses. One hundred forty-six studies were based in high-income countries. The main setting for intervention delivery was schools (111 studies), followed by the community (15 studies), the home (eight studies) and a clinical setting (seven studies); one intervention was conducted by telehealth and 31 studies were conducted in more than one setting. Eighty-six interventions were implemented for less than nine months; the shortest was conducted over one visit and the longest over four years. Non-industry funding was declared by 132 studies; 24 studies were funded in part or wholly by industry. Dietary interventions versus control Dietary interventions, compared with control, may have little to no effect on BMI at short-term follow-up (mean difference (MD) 0, 95% confidence interval (CI) -0.10 to 0.10; 5 studies, 2107 participants; low-certainty evidence) and at medium-term follow-up (MD -0.01, 95% CI -0.15 to 0.12; 9 studies, 6815 participants; low-certainty evidence) or zBMI at long-term follow-up (MD -0.05, 95% CI -0.10 to 0.01; 7 studies, 5285 participants; low-certainty evidence). Dietary interventions, compared with control, probably have little to no effect on BMI at long-term follow-up (MD -0.17, 95% CI -0.48 to 0.13; 2 studies, 945 participants; moderate-certainty evidence) and zBMI at short- or medium-term follow-up (MD -0.06, 95% CI -0.13 to 0.01; 8 studies, 3695 participants; MD -0.04, 95% CI -0.10 to 0.02; 9 studies, 7048 participants; moderate-certainty evidence). Five studies (1913 participants; very low-certainty evidence) reported data on serious adverse events: one reported serious adverse events (e.g. allergy, behavioural problems and abdominal discomfort) that may have occurred as a result of the intervention; four reported no effect. Activity interventions versus control Activity interventions, compared with control, may have little to no effect on BMI and zBMI at short-term or long-term follow-up (BMI short-term: MD -0.02, 95% CI -0.17 to 0.13; 14 studies, 4069 participants; zBMI short-term: MD -0.02, 95% CI -0.07 to 0.02; 6 studies, 3580 participants; low-certainty evidence; BMI long-term: MD -0.07, 95% CI -0.24 to 0.10; 8 studies, 8302 participants; zBMI long-term: MD -0.02, 95% CI -0.09 to 0.04; 6 studies, 6940 participants; low-certainty evidence). Activity interventions likely result in a slight reduction of BMI and zBMI at medium-term follow-up (BMI: MD -0.11, 95% CI -0.18 to -0.05; 16 studies, 21,286 participants; zBMI: MD -0.05, 95% CI -0.09 to -0.02; 13 studies, 20,600 participants; moderate-certainty evidence). Eleven studies (21,278 participants; low-certainty evidence) reported data on serious adverse events; one study reported two minor ankle sprains and one study reported the incident rate of adverse events (e.g. musculoskeletal injuries) that may have occurred as a result of the intervention; nine studies reported no effect. Dietary and activity interventions versus control Dietary and activity interventions, compared with control, may result in a slight reduction in BMI and zBMI at short-term follow-up (BMI: MD -0.11, 95% CI -0.21 to -0.01; 27 studies, 16,066 participants; zBMI: MD -0.03, 95% CI -0.06 to 0.00; 26 studies, 12,784 participants; low-certainty evidence) and likely result in a reduction of BMI and zBMI at medium-term follow-up (BMI: MD -0.11, 95% CI -0.21 to 0.00; 21 studies, 17,547 participants; zBMI: MD -0.05, 95% CI -0.07 to -0.02; 24 studies, 20,998 participants; moderate-certainty evidence). Dietary and activity interventions compared with control may result in little to no difference in BMI and zBMI at long-term follow-up (BMI: MD 0.03, 95% CI -0.11 to 0.16; 16 studies, 22,098 participants; zBMI: MD -0.02, 95% CI -0.06 to 0.01; 22 studies, 23,594 participants; low-certainty evidence). Nineteen studies (27,882 participants; low-certainty evidence) reported data on serious adverse events: four studies reported occurrence of serious adverse events (e.g. injuries, low levels of extreme dieting behaviour); 15 studies reported no effect. Heterogeneity was apparent in the results for all outcomes at the three follow-up times, which could not be explained by the main setting of the interventions (school, home, school and home, other), country income status (high-income versus non-high-income), participants' socioeconomic status (low versus mixed) and duration of the intervention. Most studies excluded children with a mental or physical disability.

AUTHORS' CONCLUSIONS

The body of evidence in this review demonstrates that a range of school-based 'activity' interventions, alone or in combination with dietary interventions, may have a modest beneficial effect on obesity in childhood at short- and medium-term, but not at long-term follow-up. Dietary interventions alone may result in little to no difference. Limited evidence of low quality was identified on the effect of dietary and/or activity interventions on severe adverse events and health inequalities; exploratory analyses of these data suggest no meaningful impact. We identified a dearth of evidence for home and community-based settings (e.g. delivered through local youth groups), for children living with disabilities and indicators of health inequities.

The impact of reduced muscular fitness on cardiometabolic risk factors in children aged 9-11 years

AIM

To analyse the relationships between muscular fitness (MF), fat mass (FM), fat-free mass (FFM) and its combined ratio with cardiometabolic risk (CMR) and whether the relationship between MF and CMR is mediated by body composition in schoolchildren.

METHODS

A cross-sectional study was conducted on schoolchildren from Cuenca, Spain, between September and November 2017. FM and FFM were estimated using bioimpedance analysis. The CMR index was calculated from triglycerides-HDL-c ratio, arterial pressure and fasting insulin. The MF index was assessed using handgrip and standing long jump tests. Analysis of covariance models assessed CMR index differences across the MF index and the FM/FFM ratio categories. Mediation analysis examined whether the MF index and the CMR index association were mediated by FM, FFM or FM/FFM ratio.

RESULTS

The analyses involved 485 schoolchildren aged 9-11 years (55.4% girls). Children with a higher MF index had a lower CMR index (p < 0.05). This association did not persist after controlling for FM/FFM. FM, FFM and FM/FFM ratio mediated the relationship between the MF index and the CMR index.

CONCLUSION

Better levels of MF are associated with better cardiometabolic profile, but a healthy body composition is determinant to improve future health.

Process evaluation of school-based high-intensity interval training interventions for children and adolescents: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Several systematic reviews have been published to investigate the effectiveness of high-intensity interval training (HIIT) in schools. However, there has been limited attention given to understanding the functioning of the intervention processes, which is of paramount importance for interpreting and translating the intervention effectiveness. The aim of this systematic review is to determine the extent to which process evaluation is measured in school-based HIIT interventions and to explore the effects of process evaluation and intervention characteristics on cardiorespiratory fitness (CRF), body composition, muscular strength, and blood pressure.

METHODS

A comprehensive search was conducted in SPORT Discus (EBSCOhost), Web of Science, Scopus, Medline (Ovid) and Cochrane Central Register of Controlled Trials. The extent to which process evaluation is measured was narratively reported, alongside with the guidance of process evaluation of complex interventions by UK Medical Research Council. Meta-analyses and meta-regressions were conducted to determine the effects of process evaluation and intervention characteristics to the intervention outcomes.

RESULTS

The literature search identified 77 studies reporting on 45 school-based HIIT interventions. In total, five interventions reported process evaluation in a section or in a separate study, and only one intervention adopted a process evaluation framework. On average, 6 out of 12 process evaluation measures were reported in all interventions. Subgroup analyses did not indicate any beneficial treatment effects for studies with process evaluation group, whereas all pooled data and studies without process evaluation group showed significant improvement for CRF and body composition.

CONCLUSION

Process evaluation is frequently omitted in the literature of school-based HIIT in children and adolescents. Although reporting of process evaluation measures may not directly associate with better intervention outcomes, it allows accurate interpretation of intervention outcomes, thereby enhancing the generalisability and dissemination of the interventions.

Steps per day and health-related quality of life in schoolchildren: the mediator role of cardiorespiratory fitness

To analyse the relationship between steps per day and health-related quality of life (HRQoL) and cardiorespiratory fitness (CRF) and to examine whether the relationship between steps per day and HRQoL is mediated by CRF in schoolchildren. This was a cross-sectional study including 501 schoolchildren (aged 9-12 years, 47% girls), from Cuenca, Spain. Steps per day were measured using the Xiaomi Mi Band 3 Smart Bracelet, HRQoL was estimated by the KIDSCREEN-27 questionnaire, and CRF was assessed using the 20-m shuttle run test. Analysis of covariance and multivariate analysis of covariance models showed that children with a higher mean number of steps per day (> 9000 steps/day) had better HRQoL (global score, and physical and psychological well-being) and higher CRF levels than their peers with a lower number of steps per day (p < 0.05); however, these differences were no longer significant when controlling for sex, age, mother's education level, and CRF (p > 0.05). Linear regression models estimated that each 1000-step increment was associated with better CRF (β = 0.350; 95% CI, 0.192 to 0.508). In addition, the relationship between steps per day and HRQoL was mediated by CRF (p < 0.05).    Conclusion: Steps per day are a good metric to estimate daily physical activity because of its positive relationship with CRF. Moreover, those children taking more than 9000 steps per day are associated with higher levels of physical and psychological well-being. Finally, a substantial part of the improvement in HRQoL achieved through the increase in physical activity (steps per day) is mediated by CRF. What is Known: • Physical activity is known to have a positive impact on health-related quality of life in children. Steps per day are commonly used as a measure of physical activity. • Cardiorespiratory fitness is a recognized indicator of overall health in youth. What is New: • Increments of steps per day were associated with better CRF, with a nonlinear association after approximately 9000 steps/day. • Schoolchildren with > 9000 steps/ day showed better HRQoL.

Differences in quality of life and fitness level among men and women in the adulthood: a cross-sectional analysis

BACKGROUND

This study aimed to examine the associations between physical fitness components and health-related quality of life (HRQoL) among adults stratified by sex and age. In addition, we aimed to examine whether these associations change based on socioeconomic, clinical, and biochemical characteristics.

METHODS

A total of 297 participants aged 47.41 (standard deviation: 9.08) years from the "Validity of a Model of Accelerated Vascular Aging as a Cardiovascular Risk Index in Healthy Adults: the EVasCu cross-sectional study" were included in this analysis. HRQoL, physical fitness, socioeconomic status (SES), waist circumference, and blood pressure were measured. Additionally, blood samples were extracted to determine cholesterol, triglyceride, and glycated hemoglobin A1c (HbA1c) levels. Analyses of covariance (ANCOVAs) were estimated to test mean differences in physical and mental health-related health measures (HRQoL) between fitness categories (fixed factors) by sex and age categories.

RESULTS

The physical HRQoL was related to the levels of fitness parameters among women, independent of age, while for men, it was related to better levels of general fitness and cardiorespiratory fitness among men aged < 50 and men aged ≥ 50, respectively. In contrast, mental HRQoL was related to cardiorespiratory fitness only among women aged < 50 years; speed/agility and flexibility among men aged < 50 years; and general fitness, strength, and flexibility among men aged ≥ 50 years. These data did not change when SES, clinical variables, or biochemical determinations were included in the analyses, neither for the physical nor for the mental HRQoL.

CONCLUSION

Gender and age are important factors to be considered when analysing health indicators and influences in the population. In addition, SES, clinical characteristics, and biochemical parameters do not seem to influence the relationship between HRQoL and fitness.

Decrease in the prevalence of hypertension in Spanish schoolchildren from 2010 to 2017: Cuenca Study

AIMS

To examine the secular trends in blood pressure measurements and normal or high blood pressure classification among Spanish schoolchildren from 2010 to 2017, to analyze the persistence in the blood pressure category reported in 2017 compared with 2013 in those children born in 2007-08 and to compare in this cohort the prevalence of high blood pressure using both definitions, the 2004 and 2017 guidelines.

METHODS AND RESULTS

The data for the prevalence/trend analysis were obtained from cross-sectional analyses conducted in 2010, 2013, and 2017 of 2709 schoolchildren aged 4-6 and 8-11 years from 22 schools in the province of Cuenca, Spain. The data for the longitudinal analysis were obtained from cross-sectional analyses of measurements gathered in 2013 and 2017 in the same cohort of children (n = 275). The prevalence of normal blood pressure increased by 5.4% in children aged 4-6 years from 2013 to 2017 and by 2.2% in children aged 8-11 from 2010 to 2017. This increase was mainly driven by a decrease in the children classified in any stage of hypertension by 4.2% and 2.3% in each age range, respectively. In the same birth cohort, there was an increase of 7.6% in normal blood pressure prevalence.

CONCLUSION

The high blood pressure prevalence in Spanish children has clearly decreased over the last decade, but is still important to detect this condition to design specific school-based interventions and the evaluation of children classified as hypertensive who might need medical supervision and treatment.

Sex differences on the relation among gross motor competence, cognition, and academic achievement in children

An association between gross motor competence (GMC) and academic achievement (AA) has been described, but the potential mechanisms behind this association are still unknown. It is not known either whether these mechanisms are similar for boys and girls. The aim of this study was to analyse whether the association between GMC and AA is mediated by executive functions (EFs), and to investigate whether this mediation differs by sex. This cross-sectional study involved 451 children aged 8 to 10 (234 girls; mean age 9.95 ± 0.59). The Movement Assessment Battery for Children-Second Edition (MABC-2), NIH Toolbox, and grades in language and mathematics were used to test GMC, EFs, and AA, respectively. Multifactorial structural equation model (SEM) was used to evaluate a possible relation between variables, controlling for confounders. The differences by sex were examined using a multi-group SEM approach. The results showed that EFs acted as a full mediator of the relationship between GMC and AA in boys (β = 0.14, p = 0.012) but not in girls (β = 0.10, p = 0.326). These results show that the benefit of GMC on AA is mediated by EFs in boys but not in girls. Nevertheless, these conclusions should be carefully considered due to the cross-sectional nature of the study.

"Fat but Fit" Paradox and Cardiometabolic Risk in Children: The Role of Physical Activity

Background: The "fat but fit" paradigm suggests that high fitness levels counteract the negative consequences of obesity on cardiometabolic risk, nevertheless, this paradigm has been less studied in children. Objectives: To analyze the relationship between "fat but fit" categories and cardiometabolic risk factors in school children, and to examine whether the intensity of physical activity (PA) is related with the fat but fit (FF) category in which the child is classified. Methods: We analyzed the baseline measurements of 312 school children aged 9-11 years involved in the clinical trial MOVI-daFit!, including adiposity parameters (BMI, waist circumference, and body fat mass percentage), cardiorespiratory fitness (CRF), blood pressure parameters, PA, and biochemical parameters (blood lipid profile, insulin, C-reactive protein, and glycosylated hemoglobin). Results: The cluster analysis of body fat mass percentage and VO₂ max estimate z-scores agreed with the four categories of the "fat but fit" paradigm: fat unfit (FU), unfat unfit (UU), FF, and unfat fit (UF). Analysis of variance (ANOVA) models indicated that children in the FF and UF clusters had better levels of biochemical parameters [high-density lipoprotein cholesterol (HDL-c), triglycerides (TG), TG/HDL-c, insulin], vigorous PA amount and metabolic syndrome (MetS) index than their peers in the FU and UU cluster categories (p < 0.05). Conclusions: Our results reinforce the "fat but fit" paradigm proving that CRF levels can counteract the effect of obesity on some cardiometabolic risk factors (HDL-c, TG, TG/HDL-c, insulin, PA, and MetS) in school children. ClinicalTrials.gov Identifier: NCT03236337.

The effectiveness of a high-intensity interval games intervention in schoolchildren: A cluster-randomized trial

The aim of this study was to assess the effectiveness of a high-intensity interval training (HIIT) intervention based on playground games (MOVI-daFit!) on improvements in adiposity, physical fitness, and cardiometabolic risk factors in schoolchildren. A cluster-randomized controlled trial (RCT) was performed that included 562 schoolchildren (9-11 years) from 10 schools in Cuenca, Spain. The intervention consisted of four 60-min sessions per week in the school setting. Analyses were conducted on the intention-to-treat basis. Changes in physical fitness parameters (cardiorespiratory fitness: main outcome), body composition, blood pressure, and biochemical cardiometabolic risk parameters were analyzed using both mixed linear and logistic regression models, controlling for baseline covariates, Tanner stages, health dietary score index, body mass index, and cluster factor school. In boys, no significant differences in any outcome measure were noted except for the standing long jump test (10.13 cm; 95% CI 2.94 to 17.32; p = 0.006) between the intervention group (IG) and the control group (CG). Improvements in mean arterial pressure (-1.68 mmHg; 95% CI -3.28 to -0.08; p = 0.039), the triglyceride/HDL-c ratio (-0.36 mg/dl; 95% CI -0.59 to -0.13; p = 0.002), C-reactive protein (-0.23 mg/L; 95% CI -0.43 to -0.03), VO₂ max (1.44 ml/kg/min; 95% CI 0.52 to 2.36, p = 0.002), 20-m shuttle run test (3.64 laps; 95% CI 0.51 to 6.78), and standing long jump test (7.04 cm; 95% CI 1.21 to 12.87; p = 0.018) were observed in girls in the IG compared with those in the CG. Body composition parameters did not change significantly in either boys or girls. Additionally, children with lower fitness levels obtained greater improvements than children with higher fitness levels. In conclusion, MOVI-daFit! may represent a good strategy for incorporating HIIT into playground games, although its implementation may need to be improved to extend the benefits to children and enhance its adherence.

The "Fat but Fit" Paradigm from a Children's Health-Related Quality of Life Perspective

Background: The fat but fit paradigm originally argues that the detrimental influence of obesity on cardiovascular risk and mortality could be counterbalanced by normal to high cardiorespiratory fitness (CRF) levels. The aim of the study was to determine whether there is a relationship between categories of the fat but fit conceptual model and health-related quality of life (HRQoL) in children. Materials and Methods: Cross-sectional cluster analyses of the MOVI-daFit! baseline data were conducted in 507 children aged 9 to 11 years in Cuenca, Spain. BMI, body fat percentage, VO₂ max estimate, and HRQoL (measured by the KIDSCREEN questionnaire) were assessed. Results: The cluster analysis of BMI/body fat percentage and VO₂ max estimate z-scores resulted in a four-cluster solution that fit the four categories included in the fat but fit paradigm: fat unfit (FU), unfat unfit (UU), fat but fit (FF), and unfat fit (UF). Analysis of variance (ANOVA) models showed the expected mean trends by cluster category: an increasing trend (FU<UU<FF<UF) in terms of VO₂ max estimate and, conversely, a decreasing trend (FU>FF>UU>UF) in terms of adiposity (p < 0.05). These models also indicated, in the whole sample, that schoolchildren in the FF and UF clusters scored higher on physical well-being, psychological well-being, and total HRQoL scores than their peers in the FU and UU clusters (p < 0.05). The results were similar regardless of gender and whether BMI or body fat percentage was used for clustering. Conclusions: This study reinforces the fat but fit paradigm with respect to a previously unexplored outcome, HRQoL, by indicating that CRF may be mediating in the relationship between obesity and HRQoL. Clinical Trial Registration number: NCT03236337.

School-based physical activity programs for promoting physical activity and fitness in children and adolescents aged 6 to 18

BACKGROUND

Physical activity among children and adolescents is associated with lower adiposity, improved cardio-metabolic health, and improved fitness. Worldwide, fewer than 30% of children and adolescents meet global physical activity recommendations of at least 60 minutes of moderate to vigorous physical activity per day. Schools may be ideal sites for interventions given that children and adolescents in most parts of the world spend a substantial amount of time in transit to and from school or attending school.

OBJECTIVES

The purpose of this review update is to summarise the evidence on effectiveness of school-based interventions in increasing moderate to vigorous physical activity and improving fitness among children and adolescents 6 to 18 years of age. Specific objectives are: • to evaluate the effects of school-based interventions on increasing physical activity and improving fitness among children and adolescents; • to evaluate the effects of school-based interventions on improving body composition; and • to determine whether certain combinations or components (or both) of school-based interventions are more effective than others in promoting physical activity and fitness in this target population.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, CINAHL, PsycINFO, BIOSIS, SPORTDiscus, and Sociological Abstracts to 1 June 2020, without language restrictions. We screened reference lists of included articles and relevant systematic reviews. We contacted primary authors of studies to ask for additional information.

SELECTION CRITERIA

Eligible interventions were relevant to public health practice (i.e. were not delivered by a clinician), were implemented in the school setting, and aimed to increase physical activity among all school-attending children and adolescents (aged 6 to 18) for at least 12 weeks. The review was limited to randomised controlled trials. For this update, we have added two new criteria: the primary aim of the study was to increase physical activity or fitness, and the study used an objective measure of physical activity or fitness. Primary outcomes included proportion of participants meeting physical activity guidelines and duration of moderate to vigorous physical activity and sedentary time (new to this update). Secondary outcomes included measured body mass index (BMI), physical fitness, health-related quality of life (new to this update), and adverse events (new to this update). Television viewing time, blood cholesterol, and blood pressure have been removed from this update.  DATA COLLECTION AND ANALYSIS: Two independent review authors used standardised forms to assess each study for relevance, to extract data, and to assess risk of bias. When discrepancies existed, discussion occurred until consensus was reached. Certainty of evidence was assessed according to GRADE. A random-effects meta-analysis based on the inverse variance method was conducted with participants stratified by age (children versus adolescents) when sufficient data were reported. Subgroup analyses explored effects by intervention type.

MAIN RESULTS

Based on the three new inclusion criteria, we excluded 16 of the 44 studies included in the previous version of this review. We screened an additional 9968 titles (search October 2011 to June 2020), of which 978 unique studies were potentially relevant and 61 met all criteria for this update. We included a total of 89 studies representing complete data for 66,752 study participants. Most studies included children only (n = 56), followed by adolescents only (n = 22), and both (n = 10); one study did not report student age. Multi-component interventions were most common (n = 40), followed by schooltime physical activity (n = 19), enhanced physical education (n = 15), and before and after school programmes (n = 14); one study explored both enhanced physical education and an after school programme. Lack of blinding of participants, personnel, and outcome assessors and loss to follow-up were the most common sources of bias.  Results show that school-based physical activity interventions probably result in little to no increase in time engaged in moderate to vigorous physical activity (mean difference (MD) 0.73 minutes/d, 95% confidence interval (CI) 0.16 to 1.30; 33 studies; moderate-certainty evidence) and may lead to little to no decrease in sedentary time (MD -3.78 minutes/d, 95% CI -7.80 to 0.24; 16 studies; low-certainty evidence). School-based physical activity interventions may improve physical fitness reported as maximal oxygen uptake (VO₂max) (MD 1.19 mL/kg/min, 95% CI 0.57 to 1.82; 13 studies; low-certainty evidence). School-based physical activity interventions may result in a very small decrease in BMI z-scores (MD -0.06, 95% CI -0.09 to -0.02; 21 studies; low-certainty evidence) and may not impact BMI expressed as kg/m² (MD -0.07, 95% CI -0.15 to 0.01; 50 studies; low-certainty evidence). We are very uncertain whether school-based physical activity interventions impact health-related quality of life or adverse events.

AUTHORS' CONCLUSIONS

Given the variability of results and the overall small effects, school staff and public health professionals must give the matter considerable thought before implementing school-based physical activity interventions. Given the heterogeneity of effects, the risk of bias, and findings that the magnitude of effect is generally small, results should be interpreted cautiously.

Obesity and thinness prevalence trends in Spanish schoolchildren: are they two convergent epidemics?

BACKGROUND

The objective of this study was to analyse the secular trends in body composition variables and weight status among Spanish schoolchildren from 1992 to 2017, and to examine the persistence in the same weight status category from 2013 to 2017 of the birth cohort in 2007-08.

METHODS

The data for the prevalence/trend analysis were taken from cross-sectional analyses conducted in 1992 (n = 308), 1996 (n = 307), 1998 (n = 275), 2004 (n = 1119), 2010 (n = 912), 2013 (n = 352) and 2017 (n = 275) using similar procedure methods among schoolchildren (aged 4-6 y and 8-11 years) from 22 public schools in the province of Cuenca, Spain. The data for the longitudinal analysis were obtained from cross-sectional analyses of measurements gathered in 2013 and 2017 in the same cohort of children (n = 275) born in 2007 and 2008. Weight, height, body fat percentage (by electronic bioimpedance) and waist circumference were measured by trained personnel. Weight status was defined according to the BMI cut-offs proposed by the International obesity task force (IOTF) criteria.

RESULTS

In schoolchildren, the overall prevalence of thinness increased from 5.9% in 1992 to 14.5% in 2017, P < 0.001. Whereas, the overall prevalence of obesity/overweight remained relatively steady between the same time period (from 25.2% to 26.9%), P = 0.599. In relation to the longitudinal analyses, we observed that 70.9% of schoolchildren in 2017 remained in the same weight status category as in 2013.

CONCLUSIONS

The child obesity epidemic in Spain has remained relatively stable over the last two decades. However, the prevalence of thinness shows a worrying upward trend.

Maternal Education and Academic Achievement in Schoolchildren: The Role of Cardiorespiratory Fitness

OBJECTIVES

To examine the relationship between maternal education, cardiorespiratory fitness, and academic achievement in schoolchildren, specifically whether the association between maternal education and academic achievement is mediated by cardiorespiratory fitness.

STUDY DESIGN

This is a secondary analysis of a cross-sectional study including 478 Spanish schoolchildren aged 8-11 years. ANOVA was used to test differences in cardiorespiratory fitness by maternal education level. ANCOVA was used to test the differences in academic achievement by the educational level of mothers and the cardiorespiratory fitness of children, controlling for each other. A mediation analysis was used to test if the relationship between maternal education and academic achievement was explained by cardiorespiratory fitness.

RESULTS

A higher level of maternal education was associated with a higher cardiorespiratory fitness level and academic achievement in children; moreover, the cardiorespiratory fitness level in children was associated with better academic achievement (P < .05). Finally, cardiorespiratory fitness acted as a partial mediator of the relationship between maternal education and academic achievement in boys (z = 1.81; P = .03) but not in girls (z = 0.86; P = .19), explaining 6.54% of this relationship for the total sample and 6.67% for boys.

CONCLUSIONS

This study suggests that the benefits of maternal education on academic achievement are partially explained by the mediating role of cardiorespiratory fitness.

A Cluster Mediation Analysis Confirms the Validity of the "Fat but Fit" Paradigm in Children's Cognitive Function and Academic Achievement

OBJECTIVE

To evaluate the fat but fit conceptual model, testing whether this paradigm for body mass index (BMI) and maximum rate of oxygen consumption (VO_2max) exists in schoolchildren and whether executive functions mediate the relationship between fat but fit categories and academic achievement.

STUDY DESIGN

Cluster cross-sectional analyses of data from 554 children aged 9-11 from Cuenca, Spain. BMI, VO_2max, core executive functions (inhibition, working memory, and cognitive flexibility) and academic achievement (language and mathematics).

RESULTS

Cluster analysis of BMI and VO_2max z-scores resulted in a 4-cluster solution that could be interpreted according to fat unfit, unfat unfit, fat fit, and unfat fit categories. ANCOVA models confirmed an increasing trend by cluster category in terms of VO_2max levels and, conversely, a decreasing trend in terms of adiposity variables. These models also confirmed that children in the fat fit and unfat fit categories scored higher than their peers in the fat unfit and unfat unfit categories. Mediation analyses using fat but fit clusters as multicategory independent variable, executive functions as mediators, and academic achievement as outcome variable showed that the positive association between the BMI-VO_2max clusters and academic achievement was mediated by inhibition levels in fat fit and unfat fit individuals, by working memory levels only in those classified as fat fit, and by cognitive flexibility only in unfat fit individuals.

CONCLUSIONS

This study confirms the validity of the 4-cluster conceptual model regarding BMI and VO_2max and reinforces the predictive validity, proving that fitness levels are able to counteract the detrimental effect of obesity on academic achievement.

Relationship between exclusive breastfeeding and brain-derived neurotrophic factor in children

Objective

A positive relationship between breastfeeding and brain-derived neurotrophic factor (BDNF) in infants has been suggested due to the presence of BDNF in human milk. This study aimed to determine the relationship between exclusive breastfeeding and BDNF serum levels in Spanish schoolchildren.

Methods

A cross-sectional analysis including 202 schoolchildren, aged eight to 11 years, from Cuenca, Spain, was conducted. Information on sociodemographic and anthropometric variables, sexual maturation, birth weight and exclusive breastfeeding (‘no exclusive breastfeeding’, and exclusive breastfeeding for ≤6 and >6 months), and BDNF serum levels using an ELISA method were obtained. Covariance analyses (ANCOVA) were conducted to examine the relationship between serological BDNF and exclusive breastfeeding after controlling for potential confounders.

Results

ANCOVA models showed no significant differences in BDNF levels between children who were exclusively breastfed for more than six months versus those who were not (p > 0.05). No significant differences were observed by age group (eight to nine years versus 10 to 11 years; p > 0.05). Additionally, no clear negative trend in BDNF serum levels according to sexual maturation categories was found (p > 0.05).

Conclusion

These findings suggest that exclusive breastfeeding does not have a significant positive association on BDNF from eight to 11 years, since children who were exclusively breastfed did not have significantly higher BDNF levels than those who were not exclusively breastfed. Likewise, BDNF levels were not found to be negatively affected by hormonal development. Future research should examine the influence of exclusive breastfeeding on BDNF over the different developmental stages.

Executive functions mediate the relationship between cardiorespiratory fitness and academic achievement in Spanish schoolchildren aged 8 to 11 years

OBJECTIVES

Previous research has studied the influence of physical fitness on academic achievement through executive functions. However, the nature of this relationship remains unclear. This study aimed to analyze how cardiorespiratory fitness (CRF) and executive functions are associated with academic achievement and to examine whether the relationship between CRF and academic achievement is mediated by executive functions in schoolchildren.

METHODS

This was a cross-sectional study including 570 schoolchildren, aged 8 to 11 years, from Cuenca, Spain. Data were collected from September to October 2017. Sociodemographic variables, family socioeconomic status, pubertal status, academic achievement, CRF (20-meter shuttle run test) and executive functions (inhibition, cognitive flexibility and working memory, NIH Toolbox battery in Spanish, v 1.8; iPad Pro, Apple, Inc.) were measured.

RESULTS

Overall, ANCOVA models controlling for age, gender and mother educational level showed higher scores in language and mathematics in children in higher categories of CRF, inhibition, cognitive flexibility and working memory than in children in lower categories. The effect sizes were moderate (p < 0.05, partial eta squared: from 0.05 to 0.12). Moreover, the mediation analysis showed that inhibition partially mediated the relationship between CRF and language (c' = 0.058; IC = [0.005; 0.028]) and mathematics (c' = 0.064; IC = [0.005; 0.030]) grades. Similarly, cognitive flexibility mediated CRF's relationship with language (c' = 0.059; IC = [0.003; 0.028]) and with mathematics (c' = 0.066; IC = [0.003; 0.029]); however, a significant relationship remained. For working memory, mediation analysis showed no significant results (c' = 0.92; IC = [-0.002;0.025] P > 0.05 in language; c' = 0.103; IC = [-0.002;0.029] P > 0.05 in mathematics). Mediation ranged from 13.38% to 36%.

CONCLUSIONS

Children in higher categories of both CRF and executive function showed higher grades in mathematics and language. The findings indicated that a significant proportion of the positive influence of CRF on academic achievement was mediated by improvements in inhibition and cognitive flexibility. Thus, this study supports the hypothesis that improvements in CRF may contribute to increasing academic achievement not only through a direct mechanism but also through improvements in executive functions.