Appearance satisfaction mediates the relationship between recreational screen time and depressive symptoms in adolescents.

BACKGROUND: Research suggests there is an association between high levels of recreational screen time and depression among adolescents; however, mechanisms driving this association remain unknown. The present study examined appearance and weight satisfaction and disordered eating behaviors as mediators in the relationship between recreational screen time and depressive symptoms in adolescents. METHOD: Longitudinal data on screen time, depressive symptoms, disordered eating behaviors, and appearance and weight satisfaction from 304 adolescents (194 females, Mage = 13.40) were analyzed through a moment structure model. RESULTS: Results revealed appearance dissatisfaction mediated the direct effect of recreational screen time on depressive symptoms (Estimate = 0.48, SE = .18, 95% CI [0.12, 0.84]), and that recreational screen time was significantly related to lower appearance satisfaction (Estimate = -0.06, SE = .02, 95% CI [-0.10, -0.01]), which was significantly predictive of more severe depressive symptoms (Estimate = -1.49, SE = .62, 95% CI [-2.71, -0.28]). CONCLUSIONS: These findings suggest that modulating screen time may be an efficacious strategy to reduce appearance dissatisfaction and depressive symptoms during adolescence.

Two-month administration of methylphenidate improves olfactory sensitivity and suppresses appetite in individuals with obesity.

Olfaction contributes to feeding behaviour and is modulated by changes in dopamine levels. Methylphenidate (MPH) increases brain dopamine levels and has been shown to reduce appetite and promote weight loss in patients with attention deficit hyperactivity disorder. The objectives of this study were to test the effect of MPH on olfaction, appetite, energy intake, and body weight (BW) on individuals with obesity. In a randomized, double-blind study, 12 participants (age 28.9 ± 6.7 years) with a body mass index (BMI) of 36.1 ± 4.5 kg/m2 were assigned to MPH (0.5 mg/kg) (n = 5) or placebo (n = 7) twice daily for 2 months. Appetite (visual analog scale), odour threshold (Sniffin' Sticks®), energy intake (food menu), and BW (DEXA scan) were measured at day 1 and day 60. MPH intake significantly increased odour threshold scores (6.3 ± 1.4 vs. 9.4 ± 2.1 and 7.9 ± 2.3 vs. 7.8 ± 1.9, respectively; p = 0.029) versus placebo. There was a significantly greater suppression of appetite sensations (desire to eat (p = 0.001), hunger (p = 0.008), prospective food consumption (p = 0.003)) and an increase in fullness (p = 0.028) over time in the MPH versus placebo. MPH suppressed appetite and improved olfactory sensitivity in individuals with obesity. These data provide novel findings on the favourable effects of MPH on appetite and weight regulation in individuals living with obesity.

The impact of new government childcare accreditation standards on children's in-care physical activity and sedentary time.

BACKGROUND: A new physical activity and sedentary behaviour accreditation standard criterion for childcare settings was introduced by the provincial government in Alberta, Canada. The primary objective of this study was to examine if changes for in-care physical activity and sedentary time (ST) differed between centres in and around Edmonton, Alberta after implementing the new accreditation standards and non-accredited control centres in and around Ottawa, Ontario. Secondary objectives were to examine whether baseline age group (toddler, preschooler) or the childcare environment moderated any group differences in change of the primary outcomes. Furthermore, accreditation and control group differences in change of children's body mass index (BMI) Z-scores or cognitive development as well as educators' perceptions of the primary outcomes were explored. METHODS: Participants were 252 toddlers (19-35 months) and preschoolers (36-60 months) in childcare centres from Alberta (n = 11) and Ontario (n = 8) in the supporting Healthy physical AcTive CHildcare setting (HATCH) study. In-care ST, light-intensity physical activity (LPA), and moderate- to vigorous-intensity physical activity (MVPA) were accelerometer-derived before and 6 months after the implementation of the new standards. At both time points, cognitive development (working memory, expressive vocabulary), heights, and weights were measured, and BMI Z-scores were calculated. Additionally, the childcare environment was observed using the Environment and Policy Assessment and Observation (EPAO) and Movement Environment Rating Scale (MOVERS) tools. Demographic characteristics were parent-reported and weather variables were derived from Environment Canada data. Mixed models were conducted. RESULTS: In adjusted models (n = 241), change in children's in-care ST (B = -0.07, 95%CI: - 1.43,1.29), LPA (B = 0.08, 95%CI: - 0.89,1.05), and log-transformed MVPA (B = 0.01, 95%CI: - 0.09,0.11) were not significantly different between accreditation and control groups. Age group and the childcare environment were not moderators. Significant increases in BMI Z-score (B = 0.19, 95%CI: 0.03,0.35) and high working memory (OR = 3.24, 95%CI: 1.32,7.97) were observed in the accreditation group and significant increases in expressive vocabulary (B = 3.18, 95%CI: 0.05,6.30) were observed in the control group. CONCLUSIONS: The new accreditation criterion may not significantly change physical activity or ST in childcare settings and therefore may not explain findings for BMI Z-scores and cognitive development. Additional training and resources may be needed.

Association of the dopamine D2 receptor rs1800497 polymorphism with food addiction, food reinforcement, and eating behavior in Chilean adults.

PURPOSE: The regulation of food intake and body weight involves two interacting systems: (a) The homeostatic system (including biological regulators of hunger and satiety) and (b) the non-homeostatic system, (involving concepts of food reinforcement and food addiction). Studies have established a strong genetic component in eating behavior and obesity. The TaqI A1 polymorphism (rs1800497) has previously been associated with eating behavior, diminished dopamine D2 receptor (DRD2) density, higher body mass, and food reinforcement, but relations to food addiction remain unclear. AIM: To evaluate the association between the polymorphism rs1800497 with eating behavior, food reinforcement and food addiction in Chilean adults. METHODS: This cross-sectional study recruited a convenience sample of 97 obese, 25 overweight and 99 normal-weight adults (18-35 years). Anthropometric measurements were performed by standard procedures. Eating behavior was assessed using the: Yale Food Addiction Scale (YFAS), the Three Factor Eating Behavior Questionnaire and the Food Reinforcement Value Questionnaire (FRVQ). The DRD2 genotype (rs1800497) was determined by taqman assays. RESULTS: Twenty-two percentage of the participants met the criteria for food addiction. Food addiction was higher in women than men (26% vs 10.7%) and in obese compared to non-obese (40% vs 6%). There was no relationship between food addiction and DRD2 genotype. However when stratified by sex and nutritional status, obese female carriers of the A1 allele reported greater scores on emotional eating and snack food reinforcement compared to non-carriers. CONCLUSIONS: The DRD2 polymorphism is associated with some hedonic aspects of eating behavior, namely food reinforcement and emotional eating but not food addiction, and this association may be moderated by sex and obesity status, with obese women who are carriers of this genetic variant at higher risk. LEVEL OF EVIDENCE: Level V: evidence obtained from a cross-sectional descriptive study.

Associations between screen time and cognitive development in preschoolers.

Objectives: To examine the cross-sectional associations between screen time and cognitive development in preschoolers. Methods: Participants were 97 preschoolers (36 to 60 months) in Alberta and Ontario, Canada in the supporting Healthy physical AcTive Childcare setting (HATCH) study. The time that children spent watching television, videos or DVDs (television time) or playing video or computer games (video game time) on a television, computer, or portable device was assessed using a parental questionnaire. Television time and video game time were summed to calculate total screen time. Adherence to the screen time recommendation (≤1 hour/day) of the Canadian 24-Hour Movement Guidelines was calculated. Expressive vocabulary and working memory were assessed using the Early Years Toolbox. Due to the distribution of working memory, it was categorized as a binary variable based on the median score. The associations between screen time and cognitive development were examined using mixed models (expressive vocabulary) or generalized mixed models (working memory). Results: Screen time was not associated with expressive vocabulary. Preschoolers who had higher total screen time were less likely to have better working memory (OR=0.52; 95%CI:0.31, 0.88), despite the null associations for television time (P=0.155) and video game time (P=0.079). Preschoolers who met the screen time recommendation were more likely to have higher working memory capacity (OR=3.48; 95%CI:1.06, 11.47), compared to those who did not meet the recommendation. Conclusion: Limiting total screen time to no more than one hour per day may facilitate working memory development in preschoolers. Screen time may be unrelated to expressive language development in this age group.

The effects of intervening with physical activity in the early years (ages 3-5) on health-related quality of life: a secondary analysis of the Activity Begins in Childhood (ABC) trial.

PURPOSE: Limited research has measured the effect of physical activity (PA) interventions on health-related quality of life (HRQoL) among pre-school-aged children. This study evaluates the effect of the Activity Begins in Childhood (ABC) cluster-randomized controlled trial designed to increase PA in the ages 3-5 years on HRQoL. METHODS: This was a cluster-randomized controlled trial where the intervention group included PA education delivered to daycare providers only, or daycare providers and parents. In the current study, the two PA intervention groups were combined. The comparator group received standard daycare curriculum (COM). A total of 215 children were included (PA n = 161, COM n = 54). Parents completed the proxy Pediatric Quality of Life Inventory Generic Core Scale (PedsQL™ 4.0) to measure HRQoL at baseline and the end of the 6-month trial. HRQoL scores were analyzed as physical, psychosocial, and total domains. Baseline and 6-months measurements were compared for PA and COM groups, and mean changes in scores (95% confidence intervals) were measured using absolute values. RESULTS: No between-group differences were observed for the physical (p = 0.17), psychosocial (p = 0.95) or total scores (p = 0.20). Paired comparisons showed that only the PA group improved psychosocial- (PA mean difference = 2.18 (0.20, 4.15), p = 0.03; COM mean difference = 2.05 (- 1.03, 5.13), p = 0.19) and total-HRQoL scores (PA mean difference = 2.83 (1.83, 3.84), p < 0.001; COM mean difference = 0.19 (- 1.78, 2.16), p = 0.84) after 6 months. CONCLUSION: Although the within-PA group analysis showed an improvement in psychosocial and total HRQoL scores from baseline, no between-group differences were observed in the HRQoL over time among children aged 3-5 years.

The Canadian 24-Hour Movement Guidelines and Psychological Distress among Adolescents: Les Directives canadiennes en matière de mouvement sur 24 heures et la détresse psychologique chez les adolescents.

OBJECTIVE: The Canadian 24-Hour Movement Guidelines for Children and Youth recommend at least 60 minutes of physical activity per day, 2 hours or less of recreational screen time per day, and 9 to 11 hours of sleep per night for 5 to 13 years old and 8 to 10 hours per night for 14 to 17 years old. This study examined the association between meeting these guidelines and psychological distress among adolescents. METHODS: The present cross-sectional sample included 6,364 students aged 11 to 20 years from the 2017 Ontario Student Drug Use and Health Survey. This provincially representative school-based survey is based on a 2-stage cluster design. A confirmatory factor analysis (CFA) was first conducted to confirm the factor structure of the K6, and structural equation modeling adjusted for age, sex, ethnoracial background, subjective socioeconomic status, and body mass index z-score was used to investigate the association between meeting the 24-Hour Movement Guidelines and K6 factors among adolescents. RESULTS: The CFA demonstrated that a 2-factor model (representing anxiety and depressive symptoms) of the K6 fit the data well. The anxiety and depression items demonstrated a composite reliability (Cronbach's α) of 0.86 and 0.83, respectively, indicating a high level of internal consistency. Compared to meeting none of the recommendations, meeting all 3 movement behavior recommendations was associated with lower anxiety (ß = -0.076; P = 0.028) and depressive symptoms (ß = -0.067; P = 0.028). Meeting the screen time + sleep duration recommendations had the strongest association with anxiety (ß = -0.157; P < 0.001) and depressive symptoms (ß = -0.139; P < 0.001), followed by meeting the sleep duration recommendation only for both anxiety (ß = -0.135; P < 0.001) and depressive symptoms (ß = -0.106; P < 0.001). CONCLUSIONS: Meeting the 24-Hour Movement Guidelines was associated with lower anxiety and depressive symptoms among adolescents, and these associations appear mainly driven by meeting the sleep duration recommendation.

Consistent participation in organized physical activity predicts emotional adjustment in children.

BACKGROUND: The objectives of this study were to derive trajectories of childhood participation in organized physical activity (PA) and to examine how these trajectories are associated with pre-existing and subsequent emotional adjustment. METHODS: Trajectories of mother-reported participation in organized PA were derived from age 6 to 10 for 1492 children from the Québec Longitudinal Study of Child Development birth cohort. Parents and teachers reported on internalizing behavior (emotional distress, anxiety, shyness, social withdrawal) at ages 4 and 12, respectively. RESULTS: Longitudinal latent class analysis identified two typical trajectories of participation in organized PA. The Consistent Participation trajectory (61%) included children with elevated probability of participation at all ages. The Low-Inconsistent Participation trajectory (39%) included children who did not participate or participated only once or twice, generally in late childhood. Pre-existing internalizing behavior at age 4 did not predict trajectory membership. However, children in the Low-Inconsistent Participation trajectory showed higher subsequent emotional distress (B = 0.87, 95% confidence interval [CI] = 0.46-1.28), anxiety (B = 0.61, 95% CI = 0.18-1.04), shyness (B = 0.92, 95% CI = 0.39-1.44), and social withdrawal (B = 0.86, 95% CI = 0.37-1.34) at age 12 than those in the Consistent Participation trajectory. CONCLUSIONS: Our findings suggest that early and sustained involvement in organized PA is beneficial for children's emotional development.

Combinations of physical activity, sedentary time, and sleep duration and their associations with depressive symptoms and other mental health problems in children and adolescents: a systematic review.

BACKGROUND: For optimal health benefits, the Canadian 24-Hour Movement Guidelines for Children and Youth (aged 5-17 years) recommend an achievement of high levels of physical activity (≥60 min of moderate-to-vigorous physical activity), low levels of sedentary behaviour (≤2 h of recreational screen time), and sufficient sleep (9-11 h for children or 8-10 h for adolescents) each day. The objective of this systematic review was to examine how combinations of physical activity, sedentary time, and sleep duration relate to depressive symptoms and other mental health indicators among children and adolescents. METHODS: Literature was obtained through searching Medline, EMBASE, PsycINFO, and SportDiscus up to September 30, 2019. Peer-reviewed studies published in English or French were included if they met the following criteria: population (apparently healthy children and adolescents with a mean age of 5-17 years), intervention/exposure (combinations of physical activity, sedentary time, and sleep duration), and outcomes (depressive symptoms and other mental health indicators). A risk of bias assessment was completed for all included studies using the methods described in the Cochrane Handbook. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework was used to assess the quality of evidence for each health indicator. Narrative syntheses were employed to describe the results due to high levels of heterogeneity across studies. RESULTS: A total of 13 cross-sectional studies comprised in 10 papers met inclusion criteria. Data across studies involved 115,540 children and adolescents from 12 countries. Overall, the findings indicated favourable associations between meeting all 3 recommendations and better mental health indicators among children and adolescents when compared with meeting none of the recommendations. There was evidence of a dose-response gradient between an increasing number of recommendations met and better mental health indicators. Meeting the screen time and sleep duration recommendations appeared to be associated with more mental health benefits than meeting the physical activity recommendation. The quality of evidence reviewed was "very low" according to GRADE. CONCLUSIONS: The findings indicate favourable associations between meeting all 3 movement behaviour recommendations in the 24-h guidelines and better mental health indicators among children and adolescents. There is a clear need for high-quality studies that use robust measures of all movement behaviours and validated measures of mental health to increase our understanding in this topic area.

Mediating role of disordered eating in the relationship between screen time and BMI in adolescents: longitudinal findings from the Research on Eating and Adolescent Lifestyles (REAL) study.

OBJECTIVE: This study investigated whether the duration and type of screen time (ST) (TV viewing, recreational computer use, video gaming) is longitudinally associated with z-BMI and if these relationships are mediated by disordered eating (emotional, restrained). DESIGN: At baseline, participants were n 1197 (T1; 60 % female) adolescents (mean age = 13·51 years) who completed surveys over 2 years. ST was assessed by a self-reported measure created by the investigative team, while emotional and restrained eating was measured by the Dutch Eating Behaviour Questionnaire (DEB-Q). Height and weight were objectively measured to quantify z-BMI. SETTING: Thirty-one public and two private schools from the region of Ottawa, Canada. PARTICIPANTS: Students in grades 7-12. RESULTS: Parallel multiple mediation analyses revealed that more time spent watching TV at baseline is associated with higher z-BMI at T3 (total effect; B = 0·19, se = 0·07, P = 0·01, 95 % CI 0·05, 0·34), but no relationships were observed for total ST exposure or other types of ST and z-BMI. Disordered eating did not mediate the positive association between baseline TV viewing and z-BMI at T3. CONCLUSIONS: TV viewing was longitudinally associated with higher z-BMI in a community-based sample of adolescents, but disordered eating behaviours did not mediate this relationship. However, other non-pathological eating behaviours may mediate the association between ST and obesity and warrant further investigation. Finding suggests that targeting reduction in youth's TV viewing may be an effective component in the prevention of childhood obesity.

Physical activity, screen time and sleep duration: Combined associations with psychosocial health among Canadian children and youth.

BACKGROUND: Canada recently adopted the 24-Hour Movement Guidelines for Children and Youth (24-Hour Guidelines) for young people aged 5 to 17 years-an international first, providing integrated recommendations for physical activity, sedentary time and sleep. Since the release of the guidelines, very few studies have examined the associations of adherence to the 24-Hour Guidelines with health outcomes-and none focus on psychosocial health. Therefore, the objective of this study was to assess the associations of meeting the 24-Hour Guidelines and their behaviour-specific recommendations with psychosocial health among Canadian children and youth. DATA AND METHODS: This cross-sectional study included 4,250 children and youth aged 5 to 17 years with valid accelerometer data. The study data were collected from 2009 to 2015 with the Canadian Health Measures Survey and pooled. Moderate-to-vigorous physical activity was measured using accelerometers; screen time, sleep duration and measures of psychosocial health were self- or proxy-reported. Multivariate logistic regression models were used to examine the associations of meeting individual or different combined recommendations from the 24-Hour Guidelines with psychosocial health. RESULTS: There was low overall adherence to all three 24-Hour Guidelines recommendations, especially among youth (children: 13.9%, youth: 4.8%). Meeting two or more of the recommendations was associated with higher odds of positive psychosocial health among youth (odds ratio [OR] = 3.10; 95% confidence interval [CI]: 1.17-8.19). Sleep duration and screen time were strongly associated with social behaviour and psychosocial health among Canadian youth. DISCUSSION: Adherence to the 24-Hour Guidelines was significantly associated with better psychosocial health among Canadian youth.

Evaluating the psychometric properties of the parent-rated Strengths and Difficulties Questionnaire in a nationally representative sample of Canadian children and adolescents aged 6 to 17 years.

BACKGROUND: The Strengths and Difficulties Questionnaire (SDQ) is a brief measure of children's and adolescents' mental health. There are different versions of the questionnaire: a version for children and adolescents to complete by self-reporting, a version for parents and guardians to complete ("parent-rated"), and a version for teachers to complete. The purpose of this study was to examine the psychometric properties of the parent-rated SDQ with a nationally representative sample of Canadian children and adolescents. DATA AND METHODS: Data are from cycle 1 (2007 to 2009), cycle 2 (2009 to 2011), cycle 3 (2012 to 2013) and cycle 4 (2014 to 2015) of the Canadian Health Measures Survey. Data include 7,451 Canadian children and adolescents aged 6 to 17 years (49.3% female). Parents and guardians completed the SDQ by reflecting on their child's behaviour over the past six months. Factorial validity was examined via confirmatory factor analysis, which included testing the original five-factor SDQ model and alternative three-factor and higher-order models. Reliability was assessed through composite reliability scores. Measurement invariance across subgroups was also assessed. RESULTS: The original five-factor (i.e., emotional symptoms, conduct problems, peer problems, hyperactivity and prosocial behaviour) SDQ fit the data satisfactorily, demonstrated evidence of reliability, and was invariant across sex (male vs. female), age (children vs. adolescents) and survey language (English vs. French). The higher-order solution fit the data acceptably, and the three-factor solution did not fit the data well. DISCUSSION: The original five-factor, parent-rated SDQ demonstrates evidence of factorial validity and reliability as a population measure of mental health difficulties among Canadian children and adolescents.

Social media use and parent-child relationship: A cross-sectional study of adolescents.

We examined the association between social media use and parent-child relationship quality and tested whether this association is independent of total screen time. Data on 9,732 students (48.4% female) aged 11-20 years were obtained from a provincially representative school-based survey. Heavy use of social media (daily use of more than 2 hr) was associated with greater odds of negative relationships between mother-daughter (odds ratio [OR] = 1.79; 95% confidence interval [CI]: 1.27-2.52), father-daughter (OR = 1.56; 95% CI: 1.16-2.09), father-son (OR = 2.19; 95% CI: 1.58-3.05) but not mother-son (OR = 1.17; 95% CI: 0.88-1.55). Results were similar after further adjusting for total screen time. There were no significant associations between regular use of social media (2 hr or less) and parent-child relationships. These findings suggest that heavy use of social media is associated with negative parent-child relationships. Longitudinal research is necessary to disentangle the pathways between social media use and the parent-child relationship.

Bingeing, Purging, and Suicidal Ideation in Clinical and Non-Clinical Samples of Youth.

Suicidal ideation is a serious mental health concern reported by adolescents. Despite understanding of increased suicidal ideation in patients with eating disorders (EDs) and obesity, few studies have compared how disordered eating (bingeing, vomiting and over exercising) is associated with suicidal ideation in clinical and non-clinical samples of youth across the ED and weight spectrum. The present study aimed to 1) comparatively examine rates of suicidal ideation and disordered eating behaviors in clinical samples of youth with EDs, complex obesity, or from the community, and 2) examine whether disordered eating was associated with suicidal ideation above and beyond age, body mass index, diagnosis, treatment-seeking status, and depressive symptoms in large samples of males vs. females in an attempt to understand whether these behaviors should lead to concern regarding suicidal ideation. Data from charts on treatment-seeking adolescents diagnosed with either an ED (N = 315), severe complex obesity (N = 212), and from the community (N = 3036) were pooled together for comparative purposes. Results showed that suicidal ideation was higher in youth seeking treatment for an ED (50.2%) and obesity (23.7%) as compared to youth from the community (13%). Binary logistic regression analyses revealed that vomiting (OR = 1.73 for females, 8.17 for males) and over-exercising (OR = 1.47 for females, 1.68 for males) was significantly associated with suicidal ideation in both males and females. Findings underscore the importance of screening for suicidal ideation in youth who report vomiting or over-exercising despite diagnostic presentation, age, weight, or treatment setting.

Development of the Ottawa Disordered Eating Screen for Youth: The ODES-Y.

OBJECTIVE: To develop a concise screening tool that allows for early identification of disordered eating in youth. STUDY DESIGN: In this 2-step classification accuracy study, questions for the Ottawa Disordered Eating Screen-Youth, a 2-question screening tool (index test), were conceptualized by clinician-scientists from tertiary care pediatric eating disorder and weight-related clinics, and was validated using retrospective data (2004-2010) from a community-based study, the Research on Eating and Adolescent Lifestyles (REAL) study. RESULTS: Analyses of contrast between the index test and the reference standard using data from 2892 (1714 females) students between grade 7 and grade 12 revealed classification statistics of 67.1% for sensitivity, 85.9% for specificity, 4.7 for positive likelihood ratio, 0.38 for negative likelihood ratio, 50.6% for positive predictive value, and 92.4% for negative predictive value for females and 61.1% for sensitivity, 93.9% for specificity, and 9.9 for positive likelihood ratio, 0.41 for negative likelihood ratio, 32.3% for positive predictive value, and 98.0% for negative predictive value for males. CONCLUSIONS: Our findings suggest that the index test has utility as a short and accurate screening tool for earlier detection of disordered eating thoughts and behaviors in youth. Additional research is needed to best determine how the index test can be administered to youth across various health care, school, public health, and surveillance settings in clinically sensitive pragmatic ways.

Brain on Fire: Incentive Salience, Hedonic Hot Spots, Dopamine, Obesity, and Other Hunger Games.

This review examines human feeding behavior in light of psychological motivational theory and highlights the importance of midbrain dopamine (DA). Prospective evidence of both reward surfeit and reward deficit pathways to increased body weight are evaluated, and we argue that it is more complex than an either/or scenario when examining DA's role in reward sensitivity, eating, and obesity. The Taq1A genotype is a common thread that ties the contrasting models of DA reward and obesity; this genotype related to striatal DA is not associated with obesity class per se but may nevertheless confer an increased risk of weight gain. We also critically examine the concept of so-called food addiction, and despite growing evidence, we argue that there is currently insufficient human data to warrant this diagnostic label. The surgical and pharmacological treatments of obesity are discussed, and evidence is presented for the selective use of DA-class drugs in obesity treatment.

Changes in the Brain-Derived Neurotrophic Factor Are Associated with Improvements in Diabetes Risk Factors after Exercise Training in Adolescents with Obesity: The HEARTY Randomized Controlled Trial.

Obesity in youth increases the risk of type 2 diabetes (T2D), and both are risk factors for neurocognitive deficits. Exercise attenuates the risk of obesity and T2D while improving cognitive function. In adults, these benefits are associated with the actions of the brain-derived neurotrophic factor (BDNF), a protein critical in modulating neuroplasticity, glucose regulation, fat oxidation, and appetite regulation in adults. However, little research exists in youth. This study examined the associations between changes in diabetes risk factors and changes in BDNF levels after 6 months of exercise training in adolescents with obesity. The sample consisted of 202 postpubertal adolescents with obesity (70% females) aged 14-18 years who were randomized to 6 months of aerobic and/or resistance training or nonexercise control. All participants received a healthy eating plan designed to induce a 250/kcal deficit per day. Resting serum BDNF levels and diabetes risk factors, such as fasting glucose, insulin, homeostasis model assessment (HOMA-B-beta cell insulin secretory capacity) and (HOMA-IS-insulin sensitivity), and hemoglobin A1c (HbA1c), were measured after an overnight fast at baseline and 6 months. There were no significant intergroup differences on changes in BDNF or diabetes risk factors. In the exercise group, increases in BDNF were associated with reductions in fasting glucose (ß = -6.57, SE = 3.37, p = 0.05) and increases in HOMA-B (ß = 0.093, SE = 0.03, p = 0.004) after controlling for confounders. No associations were found between changes in diabetes risk factors and BDNF in controls. In conclusion, exercise-induced reductions in some diabetes risk factors were associated with increases in BDNF in adolescents with obesity, suggesting that exercise training may be an effective strategy to promote metabolic health and increases in BDNF, a protein favoring neuroplasticity. This trial is registered with ClinicalTrials.gov NCT00195858, September 12, 2005 (funded by the Canadian Institutes of Health Research).

Systematic review of the relationships between sedentary behaviour and health indicators in the early years (0-4 years).

BACKGROUND: The purpose of this systematic review was to examine the relationships between sedentary behaviour (SB) and health indicators in children aged 0 to 4 years, and to determine what doses of SB (i.e., duration, patterns [frequency, interruptions], and type) were associated with health indicators. METHODS: Online databases were searched for peer-reviewed studies that met the a priori inclusion criteria: population (apparently healthy, 1 month to 4.99 years), intervention/exposure and comparator (durations, patterns, and types of SB), and outcome/health indicator (critical: adiposity, motor development, psychosocial health, cognitive development; important: bone and skeletal health, cardiometabolic health, fitness, risks/harm). The quality of the evidence was assessed by study design and outcome using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. RESULTS: Due to heterogeneity, meta-analyses were not possible; instead, narrative syntheses were conducted, structured around the health indicator and type of SB. A total of 96 studies were included (195,430 participants from 33 countries). Study designs were: randomized controlled trial (n = 1), case-control (n = 3), longitudinal (n = 25), longitudinal with additional cross-sectional analyses (n = 5), and cross-sectional (n = 62). Evidence quality ranged from "very low" to "moderate". Associations between objectively measured total sedentary time and indicators of adiposity and motor development were predominantly null. Associations between screen time and indicators of adiposity, motor or cognitive development, and psychosocial health were primarily unfavourable or null. Associations between reading/storytelling and indicators of cognitive development were favourable or null. Associations between time spent seated (e.g., in car seats or strollers) or in the supine position, and indicators of adiposity and motor development, were primarily unfavourable or null. Data were scarce for other outcomes. CONCLUSIONS: These findings continue to support the importance of minimizing screen time for disease prevention and health promotion in the early years, but also highlight the potential cognitive benefits of interactive non-screen-based sedentary behaviours such as reading and storytelling. Additional high-quality research using valid and reliable measures is needed to more definitively establish the relationships between durations, patterns, and types of SB and health indicators, and to provide insight into the appropriate dose of SB for optimal health in the early years.

Canadian 24-Hour Movement Guidelines for the Early Years (0-4 years): An Integration of Physical Activity, Sedentary Behaviour, and Sleep.

BACKGROUND: The Canadian Society for Exercise Physiology convened representatives of national organizations, research experts, methodologists, stakeholders, and end-users who followed rigorous and transparent guideline development procedures to create the Canadian 24-Hour Movement Guidelines for the Early Years (0-4 years): An Integration of Physical Activity, Sedentary Behaviour, and Sleep. These novel guidelines for children of the early years embrace the natural and intuitive integration of movement behaviours across the whole day (24-h period). METHODS: The development process was guided by the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument. Four systematic reviews (physical activity, sedentary behaviour, sleep, combined behaviours) examining the relationships within and among movement behaviours and several health indicators were completed and interpreted by a Guideline Development Panel. The systematic reviews that were conducted to inform the development of the guidelines, and the framework that was applied to develop the recommendations, followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology. Complementary compositional analyses were performed using data from the Canadian Health Measures Survey to examine the relationships between movement behaviours and indicators of adiposity. A review of the evidence on the cost effectiveness and resource use associated with the implementation of the proposed guidelines was also undertaken. A stakeholder survey (n = 546), 10 key informant interviews, and 14 focus groups (n = 92 participants) were completed to gather feedback on draft guidelines and their dissemination. RESULTS: The guidelines provide evidence-informed recommendations as to the combinations of light-, moderate- and vigorous-intensity physical activity, sedentary behaviours, and sleep that infants (<1 year), toddlers (1-2 years) and preschoolers (3-4 years) should achieve for a healthy day (24 h). Proactive dissemination, promotion, implementation, and evaluation plans were prepared to optimize uptake and activation of the new guidelines. CONCLUSIONS: These guidelines represent a sensible evolution of public health guidelines whereby optimal health is framed within the balance of movement behaviours across the whole day, while respecting preferences of end-users. Future research should consider the integrated relationships among movement behaviours, and similar integrated guidelines for other age groups should be developed.

Examining the bidirectional relationship between physical activity, screen time, and symptoms of anxiety and depression over time during adolescence.

More physical activity (PA) and less screen time (ST) are positively associated with mental health in adolescents; however, research is limited by short-term designs and the exclusion of ST when examining PA. We examined: (a) changes in PA, ST, symptoms of depression, and symptoms of anxiety over four assessments spanning 11years, and (b) bidirectional relationships between initial PA, ST, and symptoms of depression and anxiety as predictors of change in each other during adolescence. Between 2006 and 2010, participants from Ottawa Canada (Time1; N=1160, Mean age=13.54years) completed questionnaires at four points covering the ages from 10 to 21years. Latent growth modeling was used. PA decreased over time whereas ST and symptoms of depression and anxiety increased over time. Controlling for sex, ethnicity, school location, zBMI, birth year, and parents' education, initially higher anxiety was associated with initially higher ST (covariance=.88, p<.05) and initially lower PA (covariance=-6.84, p=.07) independent of initial symptoms of depression. Higher initial depression was associated with higher initial ST (covariance=2.55, p<.05). Increases in anxiety were associated with increases in ST (covariance=.07, p=.06) and increases in depression (covariance=.41, p<.05). Examining bidirectional relationships, higher initial symptoms of depression predicted greater decreases in PA (b=-.28, p<.05). No other significant findings between initial PA, ST, anxiety, or depression were found as predictors of change in each other. Interventions targeting depression around age 13 may be useful to prevent further declines in PA. Similarly, interventions to reduce ST may be beneficial for concurrent reductions in symptoms of depression and anxiety, irrespective of PA.