Objective: To examine the acute and chronic effects of reducing prolonged sedentary time (ST) with physical activity (PA) on cognitive and brain health. Design: Systematic review and meta-analysis. Data sources: PubMed, Scopus, CINAHL, PsycINFO, SPORTDiscus, Web of Science, and ProQuest Dissertation and Theses. Eligibility criteria: Randomised controlled trials (RCTs) published from inception to 17 June 2024, with healthy participants without cognitive impairment or neurological conditions that affect cognitive functioning, aged ≥4 years, testing acute and chronic effects of reducing ST and/or prolonged ST by reallocating ST to PA on cognitive function, brain function, and structure. Results: We included 25 RCTs (n=1289) investigating acute (21 studies) and chronic (4 studies) effects on cognitive function (acute: n=20, chronic: n=4) and brain function (acute: n=7, chronic: n=1); there were no studies on brain structure. Acutely interrupting continuous ST with either multiple or a single PA bout improved cognitive function measured from 3 hours to three consecutive days based on 91 effect sizes ( g =0.17, 95% CI: 0.05 to 0.29, p=0.005, I ² =45.5%). When comparing single versus multiple PA bouts, only multiple PA bouts yielded a positive effect on cognitive function based on 72 effect sizes ( g =0.20, 95% CI: 0.06 to 0.35, p=0.006; I ² =48.8%). Chronic studies reported null findings on cognitive function (n=4), with some evidence of improved neural efficiency of the hippocampus (n=1). Conclusion: Interrupting ST with PA acutely improves cognitive function. The evidence from chronic studies remains inconclusive. Systematic review registration: PROSPERO CRD42020200998.

Although obesity has been related to measures of academic achievement and cognition in children, the influence of fat distribution, specifically visceral adiposity, on select aspects of achievement and cognitive function remains poorly characterized among preadolescent children. Purpose: The aim of this study was to evaluate the relation of adiposity, particularly visceral adipose tissue (VAT), on achievement and cognitive function among children. Methods: Children with obesity (ages 8–9 yr old, N = 55, 35 females) completed cognitive and academic tests. Normal weight children (N = 55, 35 females) were matched to this group on demographic characteristics and aerobic fitness. Covariate analyses included age, Brief Intellectual Ability, socioeconomic status, and fat-free V˙O₂ (V˙O₂ peak adjusted for lean mass; mL·kg lean⁻¹·min⁻¹)_. Adiposity (i.e., whole body percent fat, subcutaneous abdominal adipose tissue, and VAT) was assessed using dual-energy x-ray absorptiometry. Results: The results of this study revealed that, relative to their normal weight counterparts, children with obesity had significantly lower performance on tests of reading and math. Analyses revealed that among children with obesity, %Fat and subcutaneous abdominal adipose tissue were not related to cognitive abilities. However, higher VAT was associated with poorer intellectual abilities (Ps ≤ 0.04) and cognitive performance (i.e., thinking ability and cognitive efficiency, Ps ≤ 0.04). However, among normal weight children, VAT was positively associated with intellectual abilities and cognitive efficiency. Conclusion: In conclusion, the results suggest that VAT was selectively and negatively related with cognition among children with obesity. Along with the dangerous metabolic nature of VAT, its detrimental relationship with obese children’s intellectual and cognitive functioning is concerning.

Background: Multi-country studies examining trends in sedentary behaviors among adolescents have mainly focused on high-income or Western countries, and almost no data exists for the rest of the world. Thus, this study aims to examine temporal trends in adolescents’ leisure time sedentary behavior (LTSB) employing nationally representative datasets from 26 countries from five WHO-defined geographical regions.Methods: Data from the Global School-based Student Health Survey 2003–2017 were analyzed in 17,734 adolescents [mean (SD) age: 13.7 (1.0) years; 49.0% boys]. LTSB was self-reported and included all types of sedentary behaviors, excluding time spent at school or doing homework. The prevalence and 95%CI of high LTSB (i.e., ≥3 h/day) was calculated for the overall sample and by sex for each survey. Crude linear trends in high LTSB were assessed by linear regression models. Interaction analyses were conducted to examine differing trends among boys and girls.Results: Temporal variations in LTSB substantially diverged across countries, with results showing increasing (6/26 countries), decreasing (4/26) and stable trends. The sharpest increases in LTSB occurred in United Arab Emirates, Kuwait, and Thailand. Some countries did not show an increase in LTSB prevalence over time but had very high levels of LTSB (i.e., > 40%) across multiple years. Most countries showed no differences in LTSB trends between boys and girls.Conclusions: Data from our study may serve as an important platform for policymakers, as well as local and national stakeholders, to establish country-specific and tailored strategies for reducing LTSB.

There is a growing trend of decreasing physical fitness among adolescents, which may result not only in poorer physical health, but also in poorer academic achievement. Purpose: The purpose of this study was to investigate the changes in aerobic fitness and academic achievement in reading and mathematics during middle school. Methods: This study employed a prospective, longitudinal cross-sectional design. Fifty-two adolescents were followed from sixth grade through eighth grade. In the spring, sixth-, seventh-, and eighth-grade students completed Progressive Aerobic Cardiovascular Endurance Run tests measuring aerobic fitness. In addition, students also completed Illinois Standards Achievement Test academic achievement tests in reading and mathematics. Results: Changes in aerobic fitness between sixth and eighth grade were positively related to changes in academic achievement in both reading and mathematics between sixth and eighth grade. Conclusion: These data suggest that changes in aerobic fitness may modulate changes in academic achievement. These findings highlight the importance of physical activity and have broad relevance for educational systems and policies.