Elevations in serum brain-derived neurotrophic factor following occupational heat stress are not influenced by age or common chronic disease.

With global warming, workers are increasingly exposed to strenuous occupations in hot environments. Given age- and disease-associated declines in thermoregulatory function, older workers are at an elevated risk of developing heat-related injuries. Brain-derived neurotrophic factor (BDNF) is thought to confer neuroprotection during acute exercise, however, the influence of environmental heat on BDNF responses during prolonged work remains unclear. Therefore, we evaluated serum BDNF concentrations before and after 180 min of moderate-intensity treadmill walking (200 W/m2) and after 60 min of post-exercise recovery in temperate (wet-bulb globe temperature (WBGT) 16°C) and hot (WBGT 32°C) environments in 13 healthy young men (mean [SD; 22 [3] years), 12 healthy older men (59 [4] years), 10 men with hypertension (HTN) (60 [4] years), and 9 men with type 2 diabetes (T2D) (60 [5] years). In the temperate condition, all but one participant (1 HTN) completed the 180 min of exercise. While exercise tolerance in the heat was lower in older men with HTN (117 min [45]) and T2D (123 min [42]) compared to healthy older men (159 min [31]) (both p ≤ 0.049), similar end-exercise rectal temperatures (38.9°C [0.4]) were observed across groups, paralleled by similar elevations in serum BDNF across groups at end-exercise (+1106 pg/mL [203]) and end-recovery (+938 pg/mL [146]; all p ≤ 0.01) in the heat. No changes in serum BDNF were observed in the temperate condition. Our findings indicate similar BDNF responses in individuals with HTN or T2D compared to their healthy counterparts, despite exhibiting reduced tolerance to heat.

24-h Movement Guidelines and Substance Use among Adolescents: A School-Based Cross-Sectional Study.

Children and youth are recommended to achieve at least 60 min/day of moderate-to-vigorous physical activity, no more than 2 h/day of recreational screen time, and a sleep duration of 9-11 h/night for 11-13-year-olds or 8-10 h/night for 14-17-year-olds. Meeting the physical activity, screen time, and sleep duration recommendations have previously been associated with substance use among adolescents. However, previous research has mainly examined these factors individually rather than looking at how these indicators could concurrently relate to substance use in this age group. Therefore, this study examined the associations between meeting the 24-h movement guidelines for screen time, sleep duration, and physical activity (independent variables) with substance use outcomes including alcohol consumption, cannabis use, and cigarette smoking (dependent variables) among adolescents. Self-reported data from a cross-sectional and representative sample of 10,236 students (mean age = 15.1 years) in Ontario, Canada were analyzed. Logistic regression models stratified by gender were adjusted for potential confounders. Combinations of 24-h movement guidelines was differentially associated with substance use in boys and girls. Overall, findings showed that meeting 24-h movement guidelines is associated with lower odds of alcohol consumption, cannabis use, and cigarette smoking differentially with type of recommendation met and gender. Given that the associations between 24-h movement guidelines and substance use differ between boys and girls, future efforts should take this into consideration.

Screening for depression in children and adolescents: a protocol for a systematic review update.

BACKGROUND: Major depressive disorder is common, debilitating, and affects feelings, thoughts, mood, and behaviors. Childhood and adolescence are critical periods for the development of depression and adolescence is marked by an increased incidence of mental health disorders. This protocol outlines the planned scope and methods for a systematic review update that will evaluate the benefits and harms of screening for depression in children and adolescents. METHODS: This review will update a previously published systematic review by Roseman and colleagues. Eligible studies are randomized controlled trials (RCTs) assessing formal screening in primary care to identify children or adolescents not already self-reporting symptoms of, diagnosed with, or treated for depression. If no or only a single RCT is available, we will consider controlled studies without random assignment. Studies of participants with characteristics associated with an elevated risk of depression will be analyzed separately. Outcomes of interest are symptoms of depression, classification of major depressive disorder based on a validated diagnostic interview, suicidality, health-related quality of life, social function, impact on lifestyle behavior (e.g., substance use, school performance, lost time at work, or school), false-positive results, overdiagnosis, overtreatment, labeling, and other harms such as those arising from treatment. We will search MEDLINE, Embase, PsycINFO, CINAHL, the Cochrane Library, and grey literature sources. Two reviewers will independently screen the titles and abstracts using the liberal accelerated method. Full-text screening will be performed independently by two reviewers using pre-specified eligibility criteria. Data extraction and risk of bias assessments will be performed independently by two reviewers. Pre-planned analyses, including subgroup and sensitivity analyses, are detailed within this protocol. Two independent reviewers will assess and finalize through consensus the certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach, and prepare GRADE evidence profiles and summary of findings tables for each outcome of interest. DISCUSSION: The systematic review will provide a current state of the evidence of benefits and harms of depression screening in children and adolescents. These findings will be used by the Canadian Task Force on Preventive Health Care to inform the development of recommendations on depression screening. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42020150373.

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.

Effects of prenatal exposure to cigarettes on anthropometrics, energy intake, energy expenditure, and screen time in children.

BACKGROUND: Maternal prenatal smoking is associated with downstream childhood obesity. Although animal research suggests reduced resting energy expenditure (REE), decreased physical activity (PA), and increased energy intake as mechanisms, these relationships are unclear in humans. The objectives were to examine the association of prenatal maternal smoking with non-volitional energy expenditure (REE and the thermic effect of feeding [TEF]), child adiposity, energy intake, free-living PA (daily light PA (LPA), daily moderate-to-vigorous PA (MVPA), daily sedentary behavior (SB)), and screen time (television and computer/video game) in children. METHODS: As part of a longitudinal study, 46 children (n = 27 controls and n = 19 smoking exposed) with mean age 7.6 ±â€¯2 years were recruited. Body weight and composition (Bioelectrical Impedance), height (Stadiometer), waist circumference (cm; tape), BMI (kg/m2), REE (kcal/day; indirect calorimetry), PA (minutes; Accelerometry), screen time (hours; self-report) and ad libitum energy intake (lunch buffet; 7-day food log) were measured. Effects sizes were evaluated using Cohen's d. RESULTS: Relative to controls, after controlling for age and family income, children who were exposed to cigarette smoke in utero exhibited greater waist circumference (p = 0.04, Cohen's d = 1.03), percent body fat (%BF; p = 0.02, Cohen's d = 0.97), and a trend for BMI (p = 0.05, Cohen's d = 0.86). Exposed children did not differ in REE (trend for lower: p = 0.1, Cohen's d = 0.42) or TEF but were shown to have significantly higher ad libitum energy intake (p = 0.02, Cohen's D = 0.70) from the palatable lunch buffet, but not from the out of laboratory 7-day energy intake (p = 0.8). Examining screen time behaviors, exposed children spent more time watching television during the week (p = 0.03, Cohen's D = 0.82), and overall television watching (p = 0.02, Cohen's D = 0.80); there were no group differences in any other screen time behaviors. CONCLUSIONS: Children exposed to cigarette smoke in utero exhibit greater adiposity, and this exposure may have as contributing factors higher screen time, ad libitum energy intake, and a trend for reduced REE. The data suggest that lifestyle factors such as diet and screen time represent targets for obesity prevention in a high-risk population of young children exposed to prenatal cigarette smoke. Findings also highlight the need for smoking cessation programs to reduce downstream obesity in offspring.

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.

Children and youth do not compensate for an imposed bout of prolonged sitting by reducing subsequent food intake or increasing physical activity levels: a randomised cross-over study.

The behavioural impact of an imposed bout of prolonged sitting is yet to be investigated in the paediatric population. The objective of the present study was to determine the acute effect of prolonged sitting on ad libitum food intake and spontaneous physical activity (PA) levels in healthy children and youth. A total of twenty healthy youth (twelve males and eight females) aged 10-14 years, with a mean BMI of 18·6 (sd 4·3) kg/m², were exposed to three experimental conditions in a random order: (1) a day of uninterrupted sitting (Sedentary); (2) a day of sitting interrupted with a 2 min light-intensity walk break every 20 min (Breaks); (3) a day of sitting interrupted with a 2 min light-intensity walk break every 20 min as well as 2 × 20 min of moderate-intensity PA (Breaks+PA). Food intake (ad libitum buffet meal) and PA (accelerometry for 24 h) were assessed following exposure to each experimental condition. Despite significant differences in sedentary behaviour and activity levels during the three in-laboratory sessions (all P< 0·01), we did not observe any differences in ad libitum food intake immediately following exposure to each experimental condition or any changes in the levels of sedentary behaviour or PA in the 24 h following exposure to each experimental condition (all P>0·25). These findings suggest that children and youth may not compensate for an imposed bout of sedentary behaviour by reducing subsequent food intake or increasing PA levels.

Top 10 practical lessons learned from physical activity interventions in overweight and obese children and adolescents.

Physical activity (PA) interventions targeting overweight and obese children and adolescents have shown only modest success, and dropout is an area of concern. Proper design and implementation of a PA intervention is critical for maximizing adherence and thus increasing the overall health benefits from PA participation. We propose practical advice based on our collective clinical trial experience with support from the literature on best practices related to PA interventions in overweight and obese children and adolescents. The top 10 lessons learned are (i) PA setting-context is important; (ii) choice of fitness trainer matters; (iii) physical activities should be varied and fun; (iv) the role of the parent-guardian should be considered; (v) individual physical and psychosocial characteristics should be accounted for; (vi) realistic goals should be set; (vii) regular reminders should be offered; (viii) a multidisciplinary approach should be taken; (ix) barriers should be identified early and a plan to overcome them developed; and (x) the right message should be communicated: specifically, what's in it for them? The recommendations in this paper can be used in other pediatric PA programs, physical education settings, and public health programs, with the hope of decreasing attrition and increasing the benefits of PA participation to promote health in children and adolescents.

Relative reinforcing value of energy-dense snack foods in overweight and obese adults.

PURPOSE: Obese people find energy-dense food more reinforcing than do their non-obese peers, and reinforcement influences food intake. We examined how the degree of adiposity, measured by body mass index (BMI), is associated with the relative reinforcing value of energy-dense snack foods versus fruits and vegetables in overweight and obese people. METHODS: Ninety-two overweight or obese students in introductory psychology courses completed questionnaires on age, sex, BMI, hunger, smoking status, dietary restraint, and hedonic (liking) ratings for energy-dense snack foods and fruits and vegetables. The questionnaire also was used to evaluate the relative reinforcing value of these snack foods in comparison with fruits and vegetables. RESULTS: The BMI predicted the relative reinforcing value of energy-dense snack food. This positive relationship remained significant after we controlled for age, sex, dietary restraint, hunger, smoking status, and snack food hedonics. CONCLUSIONS: The greater the degree of overweight and obesity, the greater the motivation to obtain energy-dense snack foods. Because the rewarding value of food is a strong determinant of energy intake, a useful approach to preventing and treating obesity may be introducing pharmacological or behavioural nutrition intervention to reduce the rewarding value of energy-dense snack foods, or increasing the rewarding value of fruits and vegetables.

Effects of interactive video game cycling on overweight and obese adolescent health.

The purpose of this study was to examine the efficacy of interactive video game stationary cycling (GameBike) in comparison with stationary cycling to music on adherence, energy expenditure measures, submaximal aerobic fitness, body composition, and cardiovascular disease risk markers in overweight and obese adolescents, using a randomized controlled trial design. Thirty overweight (with at least 1 metabolic complication) or obese adolescents aged 12-17 years were stratified by gender and randomized to video game or music condition, with 4 participants (2 per group) failing to complete the twice weekly 60 min sessions of the 10-week trial. The music group had a higher rate of attendance compared with the video game group (92% vs. 86%, p < 0.05). Time spent in minutes per session at vigorous intensity (80%-100% of predicted peak heart rate) (24.9 ± 20 min vs. 13.7 ± 12.8 min, p < 0.05) and average distance (km) pedaled per session (12.5 ± 2.8 km vs. 10.2 ± 2.2 km, p < 0.05) also favoured the music group. However, both interventions produced significant improvements in submaximal indicators of aerobic fitness as measured by a graded cycle ergometer protocol. Also, when collapsed, the exercise modalities reduced body fat percentage and total cholesterol. The present study indicates that cycling to music was just as effective as stationary cycling while playing video games at improving fitness, body composition, and cholesterol profiles in overweight and obese teens, and resulted in increased attendance, vigorous intensity of physical activity, and distance pedaled. Therefore, our data support the superiority of cycling to music and indicate investing in the more expensive GameBike may not be worth the cost.

Effects of dietary restraint and body mass index on the relative reinforcing value of snack food.

The present study examined the independent and interactive association between dietary restraint, body mass index (BMI) and the relative reinforcing value of food. Four hundred and three introductory psychology students completed questionnaires assessing age, gender, BMI, hunger, smoking status, nicotine dependence, dietary restraint, hedonic ratings for snack food and fruits and vegetables and the relative reinforcing value of snack food and fruits and vegetables. In the overall sample, results indicated a dietary restraint x BMI interaction after controlling for age, hunger, nicotine dependence, and hedonics. However, when regression models were separated by gender, the BMI x restraint interaction emerged only for females and not for males. Findings suggest that BMI moderates the relationship between dietary restraint and snack food reinforcement in females only, such that restraint and snack food reinforcement are inversely correlated in females with lower BMI, but restraint is positively correlated with snack food reinforcement in females with higher BMI. Theoretical and clinical implications of these findings are discussed.

Smoking, dietary restraint, gender, and the relative reinforcing value of snack food in a large university sample.

The present study examined the independent and interactive association between smoking, gender, dietary restraint and the relative reinforcing value of snack food in a university sample. Four hundred and three introductory psychology students completed questionnaires assessing age, gender, BMI, hunger, smoking status, nicotine dependence, dietary restraint, hedonic ratings and the relative reinforcing value of snack food and fruits and vegetables. The relative reinforcing value of snack food was determined by the number of button presses subjects would be willing to do to obtain (100g) of snack food versus 100g of fruits and vegetables. Multiple regression analyses yielded a significant three-way interaction of gender, restraint, and smoking in predicting the relative reinforcing value of snack food indicating that in female smokers, dietary restraint was inversely associated with the relative reinforcing value of snack food, whereas in male smokers, restraint was not significantly related with the reinforcing value of snacks. These findings remained significant after controlling for BMI, hunger, and hedonics, suggesting that there are gender differences in relationship between smoking, dietary restraint, and snack food reinforcement. Among female university students, smoking moderates the relationship between dietary restraint and food reinforcement whereby high-restraint female smokers appear to be at lower risk of over-consuming energy dense snack food compared to low-restraint female smokers, while high-restraint male smokers may not be at higher risk than low-restraint male smokers.

Can fruits and vegetables and activities substitute for snack foods?

This study investigated the choice of snack foods versus fruits and vegetables and enjoyable sedentary behaviors using a computerized behavioral choice task. Thirty-nine participants were provided the choice of earning points for snack foods or fruits and vegetables (Condition 1) or snack foods or enjoyable sedentary behaviors (Condition 2). The behavioral cost to gain access to snacks increased across trials, whereas the behavioral costs to obtain alternatives to snack foods remained constant across trials. Results showed that when costs for snack foods and alternatives were equal, participants chose snack foods, but as the behavioral costs increased, participants shifted choice to the alternatives. The switch point for both alternatives was equal. Results suggest that fruits and vegetables and sedentary activities can substitute for snack foods when the behavioral cost for snack foods is increased.