Obesity, fitness, and brain integrity in adolescence

The Effects of Single-Bout Exercise Interventions with Different Exercise Modalities on Executive Function in Youths

BACKGROUND

This study aimed to investigate how single-bout open-skill exercise (OSE), closed-skill exercise (CSE), and mixed-skill exercise intervention (MSE) influence executive function.

METHOD

A total of 120 students aged between 18 and 25 were separated into three groups: closed-skill exercise, open-skill exercise, and mixed-skill exercise. A task-switching test was performed before and after a single bout of exercise intervention. The simple reaction time, choice reaction time, switch cost, and correction rate were tested in a task-switching test. The results were analyzed via a two-way analysis of variance, with a significance level of α = 0.05, to compare the effects of the intervention.

RESULTS

Only open-skill exercise exhibited a significant effect on the simple reaction time (p < 0.05). In terms of choice reaction time and switch cost, all three intervention groups exhibited significant improvements, with no significant differences observed between the three groups (p < 0.05). The correction rate did not show a significant effect post-intervention, and no significant differences were observed between the groups. The correction rate showed no significant effect after the intervention or between groups.

CONCLUSION

All three types of exercise can shorten choice reaction time and switch cost, but only OSE can reduce simple reaction time.

Triangulating causality between childhood obesity and neurobehavior: Behavioral genetic and longitudinal evidence

Childhood obesity is a serious health concern that is not yet fully understood. Previous research has linked obesity with neurobehavioral factors such as behavior, cognition, and brain morphology. The causal directions of these relationships remain mostly untested. We filled this gap by using the Adolescent Brain Cognitive Development study cohort comprising 11,875 children aged 9-10. First, correlations between the age- and sex-specific 95th BMI percentile (%BMIp95) and neurobehavioral measures were cross-sectionally analyzed. Effects were then aggregated by neurobehavioral domain for causal analyses. Behavioral genetic Direction of Causation modeling was used to test the direction of each relationship. Findings were validated by longitudinal cross-lagged panel modeling. %BMIp95 correlated with impulsivity, motivation, psychopathology, eating behavior, and cognitive tests (executive functioning, language, memory, perception, working memory). Greater %BMIp95 was also associated with reduced cortical thickness in frontal and temporal brain areas but with increased thickness in parietal and occipital areas. Similar although weaker patterns emerged for cortical surface area and volume. Behavioral genetic modeling suggested causal effects of %BMIp95 on eating behavior (β = 0.26), cognition (β = 0.05), cortical thickness (β = 0.15), and cortical surface area (β = 0.07). Personality/psychopathology (β = 0.09) and eating behavior (β = 0.16) appeared to influence %BMIp95. Longitudinal evidence broadly supported these findings. Results regarding cortical volume were inconsistent. Results supported causal effects of obesity on brain functioning and morphology. The present study highlights the importance of physical health for brain development and may inform interventions aimed at preventing or reducing pediatric obesity. RESEARCH HIGHLIGHTS: A continuous measure related to obesity, %BMIp95, has correlations with various measures of brain functioning and structure Behavioral genetic and longitudinal modeling suggest causal links from personality, psychopathology, and eating behavior to %BMIp95 Results also indicate directional links from %BMIp95 to eating behavior, cognition, cortical thickness, and cortical surface area Obesity may play a role for healthy brain development during childhood.

The relationship in early childhood body composition and physical activity levels regarding fundamental motor skill development

BACKGROUND

Fundamental motor skills (FMS) are considered essential for sport participation and might be deficit in obese children. While evidence indicates that physical activity (PA) levels impact motor skill development, the relationship between body composition, PA, and motor competence, particularly in early childhood, is not thoroughly understood. We aimed to determine if PA, fat mass (FM), and fat-free mass (FFM) are predictors of FMS.

METHODS

Preschoolers (n = 47) from two preschools were assessed for FMS, PA, and body composition. Peabody Developmental Motor Scales (PDMS-2) subscale scores were used to assess FMS. PA was assessed with a wrist-worn accelerometer for five days during school. FM and FFM were measured with foot-to-foot bioelectrical impedance.

RESULTS

Linear regressions indicate significant models for stationary skills (SS) (F = 4.57, p = .004) and object manipulation skills (OMS) (F = 4.66, p = .003). FFM was the only significant predictor of SS (t = 3.98, p < .001) and OMS (t = 3.50, p = .001). FM and all intensities of PA were nonsignificant predictors in all models.

CONCLUSIONS

These results indicate that interventions that target improving or maintaining FFM may improve FMS.

Insulin resistance disrupts white matter microstructure and amplitude of functional spontaneous activity in bipolar disorder

BACKGROUND

Bipolar disorder (BD) is linked to several structural and functional brain alterations. In addition, BD patients have a three-fold increased risk of developing insulin resistance, which is associated with neural changes and poorer BD outcomes. Therefore, we investigated the effects of insulin and two derived measures (insulin resistance and sensitivity) on white matter (WM) microstructure, resting-state (rs) functional connectivity (FC), and fractional amplitude of low-frequency fluctuation (fALFF).

METHODS

BD patients (n = 92) underwent DTI acquisition, and a subsample (n = 22) underwent rs-fMRI. Blood samples were collected to determine insulin and glucose levels. The Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI) were computed. DTI data were analyzed via tract-based spatial statistics and threshold-free cluster enhancement. From rs-fMRI data, both ROI-to-ROI FC matrices and fALFF maps were extracted.

RESULTS

Insulin showed a widespread negative association with fractional anisotropy (FA) and a positive effect on radial diffusivity (RD) and mean diffusivity (MD). HOMA-IR exerted a significant effect on RD in the right superior longitudinal fasciculus, whereas QUICKI was positively associated with FA and negatively with RD and MD in the left superior longitudinal fasciculus, left anterior corona radiata, and forceps minor. fALFF was negatively modulated by insulin and HOMA-IR and positively associated with QUICKI in the precuneus. No significant results were found in the ROI-to-ROI analysis.

CONCLUSION

Our findings suggest that WM microstructure and functional alterations might underlie the effect of IR on BD pathophysiology, even if the causal mechanisms need to be further investigated.

The Developing Brain: Considering the Multifactorial Effects of Obesity, Physical Activity & Mental Wellbeing in Childhood and Adolescence

Obesity during childhood has been associated with many important physiological and neurological health considerations. Specifically concerning are the associations between youth obesity and declines in mental health, as shown with increasing rates of adolescent depression and anxiety worldwide. The emergence of mental health disorders commonly arises during adolescent development, and approximately half the global population satisfy the criteria for at least one psychiatric disorder in their lifetime, suggesting a need for early intervention. Adolescence is critical time whereby brain structure and functions are not only negatively associated with obesity and declines in mental health, while also coinciding with significant declines in rates of physical activity among individuals in this age group. Physical activity is thus a prime candidate to address the intersection of obesity and mental health crises occurring globally. This review addresses the important considerations between physiological health (obesity, aerobic fitness, physical activity), brain health (structure and function), and mental wellbeing symptomology. Lastly, we pose a theoretical framework which asks important questions regarding the influence of physiological health on the association between brain health and the development of depression and anxiety symptoms in adolescence. Specifically, we hypothesize that obesity is a mediating risk factor on the associations between brain health and psychopathology, whereas physical activity is a mediating protective factor. We conclude with recommendations for promoting physical activity and reducing sedentary time.

Does obesity-associated insulin resistance affect brain structure and function of adolescents differentially by sex?

Metabolic abnormalities affect the adolescent brain. For equivalent abnormalities in metabolism young people exhibit deficits in more cognitive domains than adults. We examine sex differences performance for adolescents with obesity/insulin resistance (IR) and evaluated how sex and IR effected frontal lobe structures and executive functioning. 125 adolescents underwent medical, cognitive, and brain-imaging assessments. Participants were categorized as insulin sensitive (IS) (QUICKI ≥ 0.350) or IR (QUICKI < 0.350). Degree of IR may affect brain and cognition differentially by sex. Females had positive associations between QUICKI and anterior cingulate cortex (ACC) volume, medial orbito-frontal cortex (OFC) thickness, and scores on the Stroop and Digit Symbol Substitution (DSST) tests. Females with IR tended to have thinner insular cortices. No such associations were found in males. In female adolescents, IR may negatively affect brain structure and function. No such effects were found for males. Although needing more development, hormonal effects and inflammation are potential contributors.

The Role of Chronic Physical Activity in Alleviating the Detrimental Relationship of Childhood Obesity on Brain and Cognition

Childhood obesity and its negative relation with children’s brain health has become a growing health concern. Over the last decade, literature has indicated that physical activity attenuates cognitive impairment associated with obesity and excess adiposity in children. However, there is no comprehensive review that considers the extent to which these factors affect different domains of cognition. This narrative review comprehensively summarizes behavioral, neuroimaging, and neuroelectric findings associated with chronic physical activity and fitness on brain and cognition in childhood obesity. Based on the literature reviewed, increased adiposity has a demonstrated relationship with neurocognitive health via mechanisms triggered by central inflammation and insulin resistance, with the most pronounced decrements observed for cognitive domains that are prefrontal- and hippocampal-dependent. Fortunately, physical activity, especially interventions enhancing aerobic fitness and motor coordination, have demonstrated efficacy for attenuating the negative effects of obesity across different subdomains of structural and functional brain imaging, cognition, and multiple academic outcomes in children with overweight or obesity. Such mitigating effects may be accounted for by attenuated central inflammation, improved insulin sensitivity, and increased expression of neurotrophic factors. Lastly, individual differences appear to play a role in this relationship, as the manipulation of physical activity characteristics, the employment of a wide array of cognitive and academic measures, the inclusion of different adiposity measures that are sensitive to neurocognitive function, and the utilization of an inter-disciplinary approach have been found to influence the relationship between physical activity and excess adiposity on brain and cognition.

Childhood Obesity, Cortical Structure, and Executive Function in Healthy Children

The development of executive function is linked to maturation of prefrontal cortex (PFC) in childhood. Childhood obesity has been associated with changes in brain structure, particularly in PFC, as well as deficits in executive functions. We aimed to determine whether differences in cortical structure mediate the relationship between executive function and childhood obesity. We analyzed MR-derived measures of cortical thickness for 2700 children between the ages of 9 and 11 years, recruited as part of the NIH Adolescent Brain and Cognitive Development (ABCD) study. We related our findings to measures of executive function and body mass index (BMI). In our analysis, increased BMI was associated with significantly reduced mean cortical thickness, as well as specific bilateral reduced cortical thickness in prefrontal cortical regions. This relationship remained after accounting for age, sex, race, parental education, household income, birth-weight, and in-scanner motion. Increased BMI was also associated with lower executive function. Reduced thickness in the rostral medial and superior frontal cortex, the inferior frontal gyrus, and the lateral orbitofrontal cortex partially accounted for reductions in executive function. These results suggest that childhood obesity is associated with compromised executive function. This relationship may be partly explained by BMI-associated reduced cortical thickness in the PFC.

Higher VO2max is associated with thicker cortex and lower grey matter blood flow in older adults

VO₂max (maximal oxygen consumption), a validated measure of aerobic fitness, has been associated with better cerebral artery compliance and measures of brain morphology, such as higher cortical thickness (CT) in frontal, temporal and cingular cortices, and larger grey matter volume (GMV) of the middle temporal gyrus, hippocampus, orbitofrontal cortex and cingulate cortex. Single sessions of physical exercise can promptly enhance cognitive performance and brain activity during executive tasks. However, the immediate effects of exercise on macro-scale properties of the brain’s grey matter remain unclear. We investigated the impact of one session of moderate-intensity physical exercise, compared with rest, on grey matter volume, cortical thickness, working memory performance, and task-related brain activity in older adults. Cross-sectional associations between brain measures and VO₂max were also tested. Exercise did not induce statistically significant changes in brain activity, grey matter volume, or cortical thickness. Cardiovascular fitness, measured by VO₂max, was associated with lower grey matter blood flow in the left hippocampus and thicker cortex in the left superior temporal gyrus. Cortical thickness was reduced at post-test independent of exercise/rest. Our findings support that (1) fitter individuals may need lower grey matter blood flow to meet metabolic oxygen demand, and (2) have thicker cortex.

The Combined Effects of Obesity and Cardiorespiratory Fitness Are Associated with Response Inhibition: An ERP Study

Obesity and cardiorespiratory fitness exhibit negative and positive impacts, respectively, on executive function. Nevertheless, the combined effects of these two factors on executive function remain unclear. This study investigated the combined effects of obesity and cardiorespiratory fitness on response inhibition of executive function from both behavioral and neuroelectric perspectives. Ninety-six young adults aged between 18 and 25 years were recruited and assigned into four groups: the high cardiorespiratory fitness with normal weight (NH), high cardiorespiratory fitness with obesity (OH), low cardiorespiratory fitness with normal weight (NL), and low cardiorespiratory fitness with obesity (OL) groups. The stop-signal task and its induced P3 component of event-related potentials was utilized to index response inhibition. The participants with higher cardiorespiratory fitness (i.e., the NH and OH groups) demonstrated better behavioral performance (i.e., shorter response times and higher accuracy levels), as well as shorter stop-signal response times and larger P3 amplitudes than their counterparts with low cardiorespiratory fitness (i.e., the NL and OL groups). The study provides first-hand evidence of the substantial effects of cardiorespiratory fitness on the response inhibition, including evidence that the detrimental effects of obesity might be overcome by high cardiorespiratory fitness.

Cardiorespiratory and muscular fitness associations with older adolescent cognitive control

BACKGROUND

Participation in physical activity supports greater cardiorespiratory fitness (CRF), a correlate of cognitive control. However, the relationship between muscular fitness (MF) and cognitive control is less clear. The present study investigated the differential relationship of CRF and MF with cognitive control in older adolescents.

METHODS

This cross-sectional study involved students (15-17 years old, n = 541, 43% female) from 20 secondary schools who completed tests of inhibition (modified flanker task), working memory (n-back task), CRF (Progressive Aerobic Cardiovascular Endurance Run), and MF (standing long jump and push-up test). Multilevel analyses tested the association between CRF or MF and cognitive outcomes while accounting for the influence of the other fitness variable and relevant demographic factors.

RESULTS

CRF predicted response accuracy during incongruent flanker trials, the condition requiring greater inhibition. For the working memory task, CRF predicted greater target accuracy and greater d' scores on the 1-back task, requiring lesser amounts of working memory. In the 2-back task, which requires greater amounts of working memory, CRF also predicted greater target and non-target accuracy and d' scores. Comparatively, MF did not predict any cognitive outcomes after adjustment for CRF.

CONCLUSION

CRF was selectively related to better performance during task conditions that require greater amounts of inhibition and working memory. This finding suggests that CRF, but not MF, may benefit cognitive control in older adolescents. This selective influence of CRF on older adolescents' cognition highlights the value of aerobic physical activity.

Prefrontal Cortex and Amygdala Subregion Morphology Are Associated With Obesity and Dietary Self-control in Children and Adolescents

A prefrontal control system that is less mature than the limbic reward system in adolescence is thought to impede self-regulatory abilities, which could contribute to poor dietary choices and obesity. We, therefore, aimed to examine whether structural morphology of the prefrontal cortex (PFC; involved in cognitive control) and the amygdala (a key brain region for reward-related processing) are associated with dietary decisions and obesity in children and adolescents. Seventy-one individuals between the ages of 8-22 years (17.35 ± 4.76 years, 51% female, 56% were overweight or obese) participated in this study; each participant completed a computer-based food choice task and a T1- and T2-weighted structural brain scans. Two indices of obesity were assessed, including age- and sex-specific body mass index (BMIz) and waist-to-height ratio (WHtR). The behavioral task included rating 60 food stimuli for tastiness, healthiness, and liking. Based on each participant's self-ratings, 100 binary food choices were then made utilizing a computer mouse. Dietary "self-control" was calculated as the proportion of trials where the individual chose the healthier food item (vs. the tastier food item) over the total number of trials. Cortical thickness and amygdala subnuclei volumes were quantified using FreeSurfer 6.0 and CIT168 atlas, respectively. We found that WHtR was negatively associated with the thickness of bilateral superior frontal, left superior temporal, right insula, and right inferior temporal regions (p < 0.05, corrected for multiple comparisons). We also found WHtR to be positively associated with the volume of the central nucleus (CEN) region of the amygdala (p = 0.006), after adjusting for the hemisphere, age, sex, and intracranial volumes. A similar data pattern was observed when BMIz was used. Moreover, we found that across all participants, thinner right superior frontal cortex and larger left CEN volumes predicted lower dietary self-control. These results suggest that differential development of the PFC and amygdala relate to obesity and dietary self-control. Further longitudinal studies are merited to determine causal relationships among altered PFC to amygdala neural circuitry, dietary self-control, and obesity.

Objective aerobic fitness level and neuropsychological functioning in healthy adolescents and emerging adults: Unique sex effects

OBJECTIVE

Research suggests positive relationships between aerobic fitness and cognition in older adults; however, limited research has adequately investigated the relationship between objectively measured aerobic fitness and broad cognitive functioning in healthy adolescents and young adults without psychiatric or physical health disorders. Further, studies to date have disproportionately examined males and failed to examine sex differences. Here we examine the relationship between aerobic fitness and neuropsychological functioning in physically healthy youth and whether sex moderates these findings.

DESIGN

Sixty-four healthy emerging adults (16-25 years-old; 32 female) underwent measurement of objective aerobic fitness (VO₂ max) and neuropsychological assessment. Exclusion criteria included: left-handedness, prenatal medical issues or alcohol/illicit drug exposure, Axis-I psychiatric disorders, major medical disorders including metabolic conditions such as diabetes, hypertension, hyperlipidemia, major neurologic disorders, LOS greater than 2 min, intellectual disability or learning disability, regular substance use (e.g., greater than biweekly use of cannabis) or positive drug toxicology testing.

METHOD

Multiple regressions examined VO₂ max, sex, sex*VO₂interaction in relation to neurocognition, controlling for objectively measured body fat percentage.

RESULTS

Prior to including body fat percentage, higher VO₂ max related to improved working memory (Letter-Number Sequencing; p = .03) and selective attention (CPT-II hit response time standard error; p = .03). Aerobic fitness significantly interacted with sex, as higher-fit males had better performance on two sustained attention tasks while females did not demonstrate this pattern (CPT-II variability standard error, p = .047; Ruff 2&7 Total Speed, p = .02). Body fat percentage was positively slower cognitive flexibility (D-KEFS color-word switching/inhibition, p = .046).

CONCLUSIONS

VO₂ independently predicted better working memory and selective attention. Increased aerobic fitness level related to increased performance on sustained attention tasks in males but not females. Therefore, aerobic fitness may be positively related to better cognitive functioning in physically healthy adolescents and emerging adults without metabolic conditions. Further research into factors (e.g., intensity or type of activity) that may relate to beneficial outcomes by sex are needed.

Effects of physical activity interventions on cognitive outcomes and academic performance in adolescents and young adults: A meta-analysis

The aim was to provide a meta-analysis of studies investigating the effects of physical activity interventions on cognitive outcomes and academic performance in adolescents or young adults. A systematic review with meta-analysis was performed using the following databases: Embase, ERIC, MEDLINE, PsycINFO and Web of Science. Studies had to meet the following criteria: controlled study design, investigating the effects of physical activity interventions on cognitive outcomes and academic performance in healthy adolescents or young adults (12-30 years). Results showed that acute interventions (n=44) significantly improved processing speed (ES=0.39), attention (ES=0.34) and, inhibition (ES=0.32). In a subsequent meta-regression, shorter duration of intervention was significantly associated with greater improvements in attention (β=-0.02) and cognitive flexibility (β=-0.04), whereas age, percentage of boys, intensity and dose were not. Chronic interventions (n=27) significantly improved processing speed (ES=0.30), attention (ES=0.50), cognitive flexibility (ES=0.19), working memory (ES=0.59) and language skills (ES=0.31). In the meta-regression, higher percentage of boys was significantly associated with greater improvements in attention (β=0.02) and working memory (β=0.01) whereas age, duration, frequency, dose and load were not. In conclusion, acute and chronic physical activity interventions might be a promising way to improve several cognitive outcomes and language skills in adolescents and young adults.

A hypothesis linking the energy demand of the brain to obesity risk

We propose that variation in brain energy expenditure during childhood is an unexplored but important influence on obesity risk. This hypothesis is supported by evidence that the energy required by the developing brain decreases in later childhood as the rate of body weight gain is increasing. The hypothesis is further supported by findings of genetic and brain imaging research indicating a trade-off between the body mass index (BMI) and the volume of cortical and subcortical structures, and inverse associations between BMI and energetically costly executive cognitive functions. Efforts to quantify variability in brain energy use across children could inspire new educational strategies that increase brain energy demands and thereby reduce obesity risk.

The causes of obesity are complex and multifactorial. We propose that one unconsidered but likely important factor is the energetic demand of brain development, which could constrain energy available for body growth and other functions, including fat deposition. Humans are leanest during early childhood and regain body fat in later childhood. Children reaching this adiposity rebound (AR) early are at risk for adult obesity. In aggregate data, the developing brain consumes a lifetime peak of 66% of resting energy expenditure in the years preceding the AR, and brain energy use is inversely related to body weight gain from infancy until puberty. Building on this finding, we hypothesize that individual variation in childhood brain energy expenditure will help explain variation in the timing of the AR and subsequent obesity risk. The idea that brain energetics constrain fat deposition is consistent with evidence that genes that elevate BMI are expressed in the brain and mediate a trade-off between the size of brain structures and BMI. Variability in energy expended on brain development and function could also help explain widely documented inverse relationships between the BMI and cognitive abilities. We estimate that variability in brain energetics could explain the weight differential separating children at the 50th and 70th BMI-for-age centiles immediately before the AR. Our model proposes a role for brain energetics as a driver of variation within a population’s BMI distribution and suggests that educational interventions that boost global brain energy use during childhood could help reduce the burden of obesity.

The development of executive function in early childhood is inversely related to change in body mass index: Evidence for an energetic tradeoff?

A well-established literature demonstrates executive function (EF) deficits in obese children and adults relative to healthy weight comparisons. EF deficits in obesity are associated with overeating and impulsive consumption of high calorie foods leading to excess weight gain and to problems with metabolic regulation and low-grade inflammation that detrimentally affect the structure and function of prefrontal cortex. Here, we test a complementary explanation for the relation between EF and body mass index (BMI) grounded in the energy demand of the developing brain. Recent work shows that the brain accounts for a lifetime peak of 66% of resting metabolic rate in childhood and that developmental changes in brain energetics and normative changes in body weight gain are closely inversely related. This finding suggests a trade-off in early childhood between energy used to support brain development versus energy used to support physical growth and fat deposition. To test this theorized energetic trade-off, we analyzed data from a large longitudinal sample (N = 1,292) and found that change in EF from age 3 to 5 years, as a proxy for brain development in energetically costly prefrontal cortex, is inversely related to change in BMI from age 2 to 5 years. Greater linear decline in BMI predicted greater linear increase in EF. We interpret this finding as tentative support for a brain-body energetic trade-off in early childhood with implications for lifetime obesity risk.

Pituitary Gland Functional Connectivity and BMI

The pituitary gland (PG) influences body weight through hormonal releases; however, the relation between body weight and PG’s co-activities with other brain regions remains unclear. Here, we aimed to identify (1) the functional connectivity of the PG and (2) PG functional connectivity associated with body mass index by examining resting state functional magnetic resonance imaging data. Using enhanced Nathan Kline Institute-Rockland Sample, PG functional connectivity of 494 individuals was analyzed to assess in voxel-wise fashion. A negative association was found between BMI and PG functional connectivity with the orbitofrontal cortex, hippocampus, putamen, and temporal lobe. Our results show PG dysconnectivity to these regions is associated with higher BMI and implicate that the connectivity between these dopaminergic regions and PG may be associated with body weight maintenance through feeding behavior and growth.

Exercise, cognition, and the adolescent brain

BACKGROUND

Few adolescents engage in the recommended levels of physical activity, and daily exercise levels tend to drastically decrease throughout adolescence. Beyond physical health benefits, regular exercise may also have important implications for the teenage brain and cognitive and academic capabilities.

METHODS

This narrative review examines how physical activity and aerobic exercise relate to school performance, cognition, and brain structure and function.

RESULTS

A number of studies have found that habitual exercise and physical activity are associated with academic performance, cognitive function, brain structure, and brain activity in adolescents. We also discuss how additional intervention studies that examine a wide range of neurological and cognitive outcomes are necessary, as well as characterizing the type, frequency, and dose of exercise and identifying individual differences that contribute to how exercise may benefit the teen brain.

CONCLUSIONS

Routine exercise relates to adolescent brain structure and function as well as cognitive performance. Together, these studies suggest that physical activity and aerobic exercise may be important factors for optimal adolescent brain development.

Executive and Reward-Related Function in Pediatric Obesity: A Meta-Analysis

OBJECTIVE

This study examined the effect of pediatric obesity on executive function and reward-related decision-making, cognitive processes that are relevant to obesogenic behaviors, and evaluated their association with sample (e.g., age, gender, intelligence, and socioeconomic status, SES) and study/task (e.g., categorical/continuous variable, food stimuli) characteristics.

METHODS

A random-effects meta-analysis was conducted using Hedge's g effect sizes of published studies from 1960 to 2016, limited to children younger than the age of 21 years without medical comorbidities. Analysis included estimation of heterogeneity (τ²), publication bias (funnel-plot symmetry and fail-safe N), and sensitivity analyses for sample and study/task characteristics.

RESULTS

Across 68 studies with 70 samples, obesity was associated with worse functioning overall (-0.24; 95CI: -0.30 to -0.19; p < 0.001) and for each component process (attention, switching, inhibition, interference, working memory, reward, delay of gratification: -0.19 to -0.38; p's < 0.017), except trait impulsivity (-0.06; 95CI: -0.18 to 0.07). Deficits increased with age and female composition of the sample for inhibition (p = 0.002). No other characteristics moderated effect of obesity.

CONCLUSIONS

Small-to-moderate negative associations with obesity were observed for executive and reward-related performance, but not on reported impulsivity in studies with children younger than the age of 21 years. These results were not moderated by IQ, SES, and study/task characteristics. Age and gender moderated association with inhibition, with a larger obesity-related deficit in older and predominantly female samples. These results suggest cognitive and demographic intervention targets for prevention and mitigation of obesogenic behavior.

Obesity, dyslipidemia and brain age in first-episode psychosis

INTRODUCTION

Obesity and dyslipidemia may negatively affect brain health and are frequent medical comorbidities of schizophrenia and related disorders. Despite the high burden of metabolic disorders, little is known about their effects on brain structure in psychosis. We investigated, whether obesity or dyslipidemia contributed to brain alterations in first-episode psychosis (FEP).

METHODS

120 participants with FEP, who were undergoing their first psychiatric hospitalization, had <24 months of untreated psychosis and were 18-35 years old and 114 controls within the same age range participated in the study. We acquired 3T brain structural MRI, fasting lipids and body mass index. We used machine learning trained on an independent sample of 504 controls to estimate the individual brain age of study participants and calculated the BrainAGE score by subtracting the chronological from the estimated brain age.

RESULTS

In a multiple regression model, the diagnosis of FEP (B = 1.15, SE B = 0.31, p < 0.001) and obesity/overweight (B = 0.92, SE B = 0.35, p = 0.008) were each additively associated with BrainAGE scores (R² = 0.22, F(3, 230) = 21.92, p < 0.001). BrainAGE scores were highest in participants with FEP and obesity/overweight (3.83 years, 95%CI = 2.35-5.31) and lowest in normal weight controls (-0.27 years, 95%CI = -1.22-0.69). LDL-cholesterol, HDL-cholesterol or triglycerides were not associated with BrainAGE scores.

CONCLUSIONS

Overweight/obesity may be an independent risk factor for diffuse brain alterations manifesting as advanced brain age already early in the course of psychosis. These findings raise the possibility that targeting metabolic health and intervening already at the level of overweight/obesity could slow brain ageing in FEP.

Greater body mass index is associated with reduced frontal cortical volumes among adolescents with bipolar disorder

BACKGROUND

Higher body mass index (BMI) and obesity is common among youth with bipolar disorder (BD) and is associated with greater psychiatric illness severity, including suicidality. Obesity has been associated with frontal, temporal and subcortical volumetric reductions in adults with BD. We examined the neurostructural correlates of BMI in adolescents early in their course of BD.

METHODS

We processed T1-weighted images of adolescents with BD and psychiatrically healthy controls using FreeSurfer to derive a priori region of interest (ROI) volumes/cortical thickness for the frontal lobe (FL), prefrontal cortex (PFC) and orbitofrontal cortex (OFC) as well as volumes for the amygdala and hippocampus. General linear models assessed the association between BMI and the ROIs, controlling for age, sex and intracranial volume. We also conducted exploratory within-BD group and whole brain vertex-wise analyses.

RESULTS

We included 40 adolescents with BD and 48 controls in our analyses. In addition to a main effect of BMI on the ROIs, there were significant diagnosis × BMI interaction effects on FL volumes. In the BD group only, BMI was negatively associated with FL, OFC and PFC cortical thickness. Whole brain analysis of BMI-volume correlations revealed 2 significant interaction clusters: 1 in the medial OFC and 1 in the caudal anterior cingulate cortex, with BD showing a stronger negative correlation.

LIMITATIONS

Reliance on BMI rather than a more nuanced measure of obesity may have influenced the findings.

CONCLUSION

Our results suggest that elevated BMI among adolescents with BD is associated with frontal neurostructural differences that are not observed in controls. Prospective studies examining the direction of the observed associations and the effect of BMI optimization on brain structure in adolescents with BD are warranted.

Executive functions in adolescents with binge-eating disorder and obesity

OBJECTIVE

Binge-eating disorder (BED) in adults is associated with alterations in executive functions (EF) and obesity. Much less is known about these relationships in adolescents, including whether poor EF are associated with eating disorder psychopathology and/or elevated body mass index. This study examined EF in response to neutral stimuli in youth with BED.

METHOD

Adolescents with BED and obesity (n = 22), individually matched adolescents with obesity (n = 22), and normal weight (n = 22) completed neuropsychological tests targeting inhibition (Color-Word Interference Test), sustained attention (D2 Concentration Endurance Test), cognitive flexibility (Comprehensive Trail Making Test), and decision-making (Iowa Gambling Task).

RESULTS

Adolescents with BED and obesity displayed significantly poorer inhibitory control compared to normal-weight adolescents. This effect persisted after controlling for the level of secondary education. However, initial differences between adolescents with obesity and normal-weight controls regarding inhibitory control and sustained attention vanished after controlling for education. The three groups did not differ regarding cognitive flexibility and decision-making. Moreover, adolescents with BED and obesity did not perform worse than adolescents with obesity on any of the neuropsychological tests.

DISCUSSION

Overall, our results indicate that adolescent BED is associated with only a few alterations in general EF, specifically inhibitory control, and underline BED and educational level as confounding factors in neuropsychological research on obesity. To further delineate EF profiles of adolescents with BED, future research should focus on EF in response to disorder-related stimuli and experimental settings with high ecological validity.

Insulin Sensitivity and Inflammation Mediate the Impact of Fitness on Cerebrovascular Health in Adolescents

BACKGROUND/OBJECTIVES

To investigate in adolescents the relationships between retinal vessel diameter, physical fitness, insulin sensitivity, and systemic inflammation.

METHODS

We evaluated 157 adolescents, 112 with excessive weight and 45 lean, all without type 2 diabetes mellitus. All received detailed evaluations, including measurements of retinal vessel diameter, insulin sensitivity, levels of inflammation, and physical fitness.

RESULTS

Overweight/obese adolescents had significantly narrower retinal arteriolar and wider venular diameters, significantly lower insulin sensitivity, and physical fitness. They also had decreased levels of anti-inflammatory and increased levels of proinflammatory markers as well as an overall higher inflammation balance score. Fitness was associated with larger retinal arteriolar and narrower venular diameters and these relationships were mediated by insulin sensitivity. We demonstrate that inflammation also mediates the relationship between fitness and retinal venular, but not arterial diameter; insulin sensitivity and inflammation balance score jointly mediate this relationship with little overlap in their effects.

CONCLUSIONS

Increasing fitness and insulin sensitivity and reducing inflammation among adolescents carrying excess weight may improve microvascular integrity. Interventions to improve physical fitness and insulin function and reduce inflammation in adolescents, a group likely to benefit from such interventions, may reduce not only cardiovascular disease in middle age, but also improve cerebrovascular function later in life.

Higher Adolescent Body Mass Index Is Associated with Lower Regional Gray and White Matter Volumes and Lower Levels of Positive Emotionality

Adolescent obesity is associated with an increased chance of developing serious health risks later in life. Identifying the neurobiological and personality factors related to increases in adiposity is important to understanding what drives maladaptive consummatory and exercise behaviors that result in obesity. Previous research has largely focused on adults with few findings published on interactions among adiposity, brain structure, and personality. In this study, Voxel Based Morphometry (VBM) was used to identify associations between gray and white matter volumes and increasing adiposity, as measured by Body Mass Index percentile (BMI%), in 137 adolescents (age range: 9–20 years, BMI% range: 5.16–99.56). Variations in gray and white matter volume and BMI% were then linked to individual differences in personality measures from the Multidimensional Personality Questionnaire (MPQ). After controlling for age and other covariates, BMI% correlated negatively with gray matter volume in the bilateral caudate (right: partial r = −0.338, left: r = −0.404), medial prefrontal cortex (partial r = −0.339), anterior cingulate (partial r = −0.312), bilateral frontal pole (right: partial r = −0.368, left: r = −0.316), and uncus (partial r = −0.475) as well as white matter volume bilaterally in the anterior limb of the internal capsule (right: partial r = −0.34, left: r = −0.386), extending to the left middle frontal subgyral white matter. Agentic Positive Emotionality (PEM-AG) was correlated negatively with BMI% (partial r = −0.384). PEM-AG was correlated positively with gray matter volume in the right uncus (partial r = 0.329). These results suggest that higher levels of adiposity in adolescents are associated with lower trait levels in reward-related personality domains, as well as structural variations in brain regions associated with reward processing, control, and sensory integration.

Altered Brain Response to Drinking Glucose and Fructose in Obese Adolescents

Increased sugar-sweetened beverage consumption has been linked to higher rates of obesity. Using functional MRI, we assessed brain perfusion responses to drinking two commonly consumed monosaccharides, glucose and fructose, in obese and lean adolescents. Marked differences were observed. In response to drinking glucose, obese adolescents exhibited decreased brain perfusion in brain regions involved in executive function (prefrontal cortex [PFC]) and increased perfusion in homeostatic appetite regions of the brain (hypothalamus). Conversely, in response to drinking glucose, lean adolescents demonstrated increased PFC brain perfusion and no change in perfusion in the hypothalamus. In addition, obese adolescents demonstrated attenuated suppression of serum acyl-ghrelin and increased circulating insulin level after glucose ingestion; furthermore, the change in acyl-ghrelin and insulin levels after both glucose and fructose ingestion was associated with increased hypothalamic, thalamic, and hippocampal blood flow in obese relative to lean adolescents. Additionally, in all subjects there was greater perfusion in the ventral striatum with fructose relative to glucose ingestion. Finally, reduced connectivity between executive, homeostatic, and hedonic brain regions was observed in obese adolescents. These data demonstrate that obese adolescents have impaired prefrontal executive control responses to drinking glucose and fructose, while their homeostatic and hedonic responses appear to be heightened. Thus, obesity-related brain adaptations to glucose and fructose consumption in obese adolescents may contribute to excessive consumption of glucose and fructose, thereby promoting further weight gain.

Fitness, insulin sensitivity, and frontal lobe integrity in adults with overweight and obesity

OBJECTIVE

To formally test whether insulin sensitivity mediates the relationship between fitness and brain integrity.

METHODS

Eighty-four middle-aged participants without diabetes received a 6-min walk test from which maximal oxygen uptake (VO2 max) was derived, a structural magnetic resonance scan, and a medical evaluation including fasting glucose and insulin levels.

RESULTS

This study showed significant associations between fitness, abdominal obesity, and insulin sensitivity and anterior cingulate cortex (ACC) volume as well as between ACC thickness and quantitative insulin-sensitivity check index (QUICKI). The relationship between ACC volume and VO2 max was completely mediated through QUICKI. Further, this strong association was confirmed by a single and very significant cluster on the ACC linking gray matter volume and QUICKI in a voxel-based morphometry analysis.

CONCLUSIONS

As expected, increased abdominal obesity was associated with reductions in fitness, ACC volumes, and insulin sensitivity. Importantly, this study demonstrated a significant mediation of the relationship between VO2 max and ACC volume by QUICKI. This suggests that the links between impaired insulin sensitivity and brain abnormalities in adults carrying excess weight could be alleviated through increased physical activity and fitness.

Physical Activity Interventions for Neurocognitive and Academic Performance in Overweight and Obese Youth: A Systematic Review

This article examines cognitive, academic, and brain outcomes of physical activity in overweight or obese youth, with attention to minority youth who experience health disparities. Physically active academic lessons may have greater immediate cognitive and academic benefits among overweight and obese children than normal-weight children. Quasi-experimental studies testing physical activity programs in overweight and obese youth show promise; a few randomized controlled trials including African Americans show efficacy. Thus, making academic lessons physically active may improve inhibition and attentiveness, particularly in overweight youngsters. Regular physical activity may be efficacious for improving neurologic, cognitive, and achievement outcomes in overweight or obese youth.