Canadian Senate Report on Obesity: Focusing on Individual Behaviours versus Social Determinants of Health May Promote Weight Stigma

Very little attention has been given to unintended consequences of government reporting on obesity. This paper argues that the 2016 Senate report, "Obesity in Canada: A Whole-Of-Society Approach," exemplifies the systemic public health issue of weight stigma. The purpose of this viewpoint is to critique the approach taken in the Report, by illustrating that it (1) takes a weight-centric approach to health, (2) does not acknowledge important limitations of the definition and measurement of obesity, (3) reifies obesity as a categorical phenomenon that must be prevented, and (4) uses aggressive framing and disrespectful terminology. The Report perpetuates a focus on the individual, thereby failing to recognize the role that governments can play in reducing weight stigma and addressing social determinants of health. If steps are taken to avoid propagating weight stigma, future reports could more constructively address health promotion, equity, and social determinants of health in their policies.

Addressing weight bias and discrimination: moving beyond raising awareness to creating change

Weight discrimination is the unjust treatment of individuals because of their weight. There have been very few interventions to address weight discrimination, due in part to the lack of consensus on key messages and strategies. The objective of the third Canadian Weight Bias Summit was to review current evidence and move towards consensus on key weight bias and obesity discrimination reduction messages and strategies. Using a modified brokered dialogue approach, participants, including researchers, health professionals, policy makers and people living with obesity, reviewed the evidence and moved towards consensus on key messages and strategies for future interventions. Participants agreed to these key messages: (1) Weight bias and obesity discrimination should not be tolerated in education, health care and public policy sectors; (2) obesity should be recognized and treated as a chronic disease in health care and policy sectors; and (3) in the education sector, weight and health need to be decoupled. Consensus on future strategies included (1) creating resources to support policy makers, (2) using personal narratives from people living with obesity to engage audiences and communicate anti-discrimination messages and (3) developing a better clinical definition for obesity. Messages and strategies should be implemented and evaluated using consistent theoretical frameworks and methodologies.

Depressive symptoms, perceived stress, self-efficacy, and outcome expectations: Predict fitness among adolescents with obesity

The objective of the present study was to test if outcome expectancy mediated the relationship between fitness and self-efficacy, perceived stress, and depressive symptoms.Adolescents with obesity (n = 228) completed measures of perceived stress and depressive symptoms at baseline, self-efficacy and outcome expectancy at baseline and 3 months, and fitness at baseline and 6 months. Structural equation modeling was used to analyze the data. Results showed that self-efficacy was positively associated with fitness via outcome expectancies. For females, fewer depressive symptoms were linked to fitness via self-efficacy and outcome expectancies. Exercise interventions that enhance exercise self-efficacy, outcome expectancy, and reduce depressive symptoms may increase fitness.

The use of magnetic resonance imaging to characterize abnormal body composition phenotypes in youth with Prader-Willi syndrome

INTRODUCTION

Magnetic resonance imaging (MRI) provides detailed assessment of body composition compartments. No studies have employed state-of-the-art MRI methods to accurately examine abdominal adipose tissue (AT) and skeletal muscle in youth with Prader-Willi syndrome (PWS). Therefore, this study aimed to describe AT distribution and skeletal muscle in the abdominal region of youth with PWS using MRI.

METHODS

Anthropometric measures and whole-abdominal T1-weighted MRI were performed in sixteen (5 males and 11 females) youth diagnosed with PWS, and seventeen (10 males and 7 females) youth who did not have PWS (controls). Volume of subcutaneous, visceral, intermuscular, and total AT, and skeletal muscle in the abdominal region were quantified using a semiautomatic procedure. Results were summarized using median and interquartile range (IQR, 25th-75th), and ANCOVA test was used (with age and sex as covariates) to examine differences in body composition compartments between PWS and control group.

RESULTS

PWS group had similar age (10.5, 6.6-13.9 vs. 12.8, 10.0-14.4years; P=0.14) and BMI z-score (0.5, 0.2-1.3 vs. 0.2, -0.3 to 1.0; P=0.33) when compared with controls. Significant differences were observed in absolute volumes of total AT (PWS: 4.1, 2.0-6.6L; control: 2.9, 2.0-4.5L; P=0.01), subcutaneous AT (PWS: 2.8, 1.4-4.8L; control: 1.8, 1.1-3.2L; P=0.01), and intermuscular AT (PWS: 0.3, 0.1-0.4L; control: 0.3, 0.2-0.3L; P<0.005). Visceral AT/subcutaneous AT was lower in PWS (0.4, 0.3-0.5) compared to controls (0.5, 0.4-0.6), P=0.01. In addition, skeletal muscle volume was lower in PWS (1.5, 1.0-2.6L) compared to controls (3.1, 1.6-3.9L), P=0.03. Ratios of abdominal AT compartments to skeletal muscle were all higher in PWS compared to controls (all P<0.005).

CONCLUSIONS

PWS youth have greater abdominal adiposity, particularly subcutaneous AT and intermuscular AT, and lower volume of skeletal muscle compared to controls. The decreased ratio of visceral AT/subcutaneous AT in youth with PWS suggests an improved metabolic profile for the level of adiposity present; however, elevated ratios of AT to skeletal muscle suggest a sarcopenic obesity-like phenotype, which could lead to worse health outcomes.

Effects of aerobic or resistance training or both on health-related quality of life in youth with obesity: the HEARTY Trial

This study examined the effects of aerobic and resistance training, and their combination on health-related quality of life (HRQoL) in adolescents with overweight or obesity. After a 4-week run-in period, 304 (91 males, 213 females) post-pubertal adolescents aged 14-18 years, were randomized to 4 groups for 22 weeks of: aerobic training (n = 75), resistance training (n = 78), combined aerobic and resistance training (n = 75), or nonexercising control (n = 76). All participants received dietary counseling with a daily energy deficit of 250 kcal. Indicators of HRQoL such as overall HRQoL, and physical and psychosocial (an aggregate of emotional, social, and school functioning) HRQoL at baseline and 6 months postintervention were measured by the Pediatric Quality of Life questionnaire. The trial began in March 2005 and was completed in June 2011. In the intention-to-treat analyses, all groups showed significant improvements at 6 months on all HRQoL indicators. The aerobic group showed greater improvements than controls on physical HRQoL (mean differences of 5.5; 95% CI; 1.4-9.6, p = 0.009). In participants with ≥70% adherence, combined training produced greater improvements than control on overall HRQoL (mean differences of 4.8, 95% CI; 0.7-9.0, p = 0.02), physical HRQoL (mean differences of 5.8; 95% CI: 0.6-10.7; p = 0.03), social HRQoL (mean differences of 7.6; 95% CI: 1.0-14.2; p = 0.02), and school-based HRQoL (mean differences of 7.6; 95% CI: 1.0-14.2; p = 0.02). These findings highlight the potential importance of including resistance exercise into traditional aerobic exercise programs to maximize HRQoL in adolescents with obesity.

Weight bias: a call to action

Weight-related issues (including excess weight, disordered eating and body concerns) are often considered as comprising distinct domains of 'obesity' and 'eating disorders'. In this commentary we argue that the concept of weight bias is an important variable when considering wellbeing across the spectrum of weight-related issues. We make the following six points in support of this argument: i) weight bias is common and has adverse health consequences, ii) shaming individuals for their body weight does not motivate positive behaviour change, iii) internalized weight bias is particularly problematic, iv) public health interventions, if not carefully thought out, can perpetuate weight bias, v) weight bias is a manifestation of social inequity, and vi) action on weight bias requires an upstream, population-level approach. To achieve sustainable reductions in weight bias at a population level, substantive modifications and collaborative efforts in multiple settings must be initiated. We provide several examples of population-level interventions to reduce weight bias.

Does exercise training affect resting metabolic rate in adolescents with obesity?

We evaluated the hypothesis that resistance exercise training performed alone or in combination with aerobic exercise training would increase resting metabolic rate (RMR) relative to aerobic-only and nonexercising control groups. Postpubertal adolescents (N = 304) aged 14-18 years with obesity (body mass index (BMI) ≥ 95th percentile) or overweight (BMI ≥ 85th percentile + additional diabetes risk factor(s)) were randomized to 4 groups for 22 weeks: Aerobic exercise training, Resistance exercise training, Combined aerobic and resistance exercise training, or Control. All participants received dietary counselling targeting a daily energy deficit of 250 kcal. RMR was measured by indirect calorimetry and body composition by magnetic resonance imaging. There was no significant change in RMR in any group, in spite of significant within-group increases in fat-free mass in the Aerobic, Resistance, and Combined exercise training groups. RMR at baseline and 6 months were Aerobic: 1972 ± 38 and 1990 ± 41; Resistance: 2024 ± 37 and 1992 ± 41; Combined: 2023 ± 38 and 1995 ± 38; Control: 2075 ± 38 and 2073 ± 39 kcal/day (p > 0.05). There were no between-group differences in RMR after adjustment for total body weight or fat-free mass between groups over time. Per-protocol analyses including only participants with ≥70% adherence, and analyses stratified by sex, also showed no within- or between-group differences in RMR. In conclusion, despite an increase in fat-free mass in all exercise groups, 6 months of aerobic, resistance, or combined training with modest dietary restriction did not increase RMR compared with diet only in adolescents with obesity.

The mediating role of energy intake on the relationship between screen time behaviour and body mass index in adolescents with obesity: The HEARTY study

Adolescents spend up to 6-8 h/day in sedentary screen behaviour and screen time is an independent risk factor for obesity. However, the mechanisms by which screen time confers obesity risk remain unclear. Via community level recruitment this study examined whether the relationship between screen time behaviours and body mass index (BMI: kg/m²) was mediated by total energy intake or macronutrient consumption. In a cross-sectional study of post-pubertal adolescents (N = 283: 86M, 197F) with overweight or obesity at baseline of an intervention for weight control, we examined self-reported total energy intake (mean Calories from 3 day food diary), macronutrient intake (grams/day of carbohydrate, fat, protein) and total screen time (aggregate of hours/day watching TV, playing seated video games, and recreational computer use). BMI was objectively measured and converted to standardized scores (z-BMI). Simple and multiple mediation analyses were conducted using the bootstrapping approach described by Preacher and Hayes. Covariates included age, sex, ethnicity, parental education, Tanner stage, and self-reported physical activity. The relationship between screen time and z-BMI was significantly mediated by energy intake. Higher levels of carbohydrate intake, but not fat or protein intake, significantly mediated the relationship between screen time and z-BMI (95% bias-corrected and accelerated confidence interval [0.0004, 0.0074]). Higher carbohydrate intake mediated the relationship between TV viewing and z-BMI, and video gaming and z-BMI. In conclusion, the relationship between screen time and BMI appears to be mediated by increased energy intake, primarily in the form of higher carbohydrate intake. It is possible that reducing time spent watching TV and playing video games may reduce food intake and help promote dietary adherence needed for weight management in obese adolescents.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT00195858.

Effects of Child Care Intervention on Physical Activity and Body Composition

INTRODUCTION

This study evaluated whether intervening with child care providers would increase physical activity (PA) and reduce adiposity in preschoolers.

METHODS

This was a two-arm, parallel group, cluster RCT whereby six child care centers were randomly assigned in equal numbers to intervention (n=40 children) or control (n=43 children). Participants were aged 3-5 years and attended licensed child care centers. Child care providers received two 3-hour train-the-trainer workshops and a training manual at program initiation aimed at increasing structured and unstructured PA through active play. Control child care centers implemented their standard curriculum. PA and sedentary behavior were measured by accelerometry, and body composition was measured using bioelectrical impedance at baseline and 6 months. Data were collected in 2011-2012 and analyzed in April 2015.

RESULTS

Linear mixed-effects modeling showed that at 6 months, children in the intervention group demonstrated greater increases in minutes per preschool day spent in overall PA (22.5 minutes, 95% CI=8.9, 36.1, p=0.002), and light-intensity PA (16.1 minutes, 95% CI=5.2, 26.7, p=0.004), but changes between groups in moderate to vigorous PA did not differ. The intervention group showed greater reductions in body fat percentage (-1.9%, 95% CI=-3.5, -0.3, p=0.023) and fat mass (-0.3 kg, 95% CI=-0.7, -0.1, p=0.018), but groups did not differ on fat-free mass, BMI, or z-BMI.

CONCLUSIONS

Provider-led intervention in child care centers increased preschoolers' PA and reduced adiposity, therefore may represent a viable approach to promoting PA and related health benefits in preschool-aged children.

TRIAL REGISTRATION

This study is registered at www.clinicaltrials.gov NCT02293278.

Future research in weight bias: What next?

The 2015 Canadian Weight Bias Summit disseminated the newest research advances and brought together 40 experts, stakeholders, and policy makers in various disciplines in health, education, and public policy to identify future research directions in weight bias. In this paper we aim to share the results of the Summit as well as encourage international and interdisciplinary research collaborations in weight bias reduction. Consensus emerged on six research areas that warrant further investigation in weight bias: costs, causes, measurement, qualitative research and lived experience, interventions, and learning from other models of discrimination. These discussions highlighted three key lessons that were informed by the Summit, namely: language matters, the voices of people living with obesity should be incorporated, and interdisciplinary stakeholders should be included.

Weight bias reduction in health professionals: a systematic review

Innovative and coordinated strategies to address weight bias among health professionals are urgently needed. We conducted a systematic literature review of empirical peer-reviewed published studies to assess the impact of interventions designed to reduce weight bias in students or professionals in a health-related field. Combination sets of keywords based on three themes (1: weight bias/stigma; 2: obesity/overweight; 3: health professional) were searched within nine databases. Our search yielded 1447 individual records, of which 17 intervention studies satisfied the inclusion criteria. Most studies (n = 15) included medical, dietetic, health promotion, psychology and kinesiology students, while the minority included practicing health professionals (n = 2). Studies utilized various bias-reduction strategies. Many studies had methodological weaknesses, including short assessment periods, lack of randomization, lack of control group and small sample sizes. Although many studies reported changes in health professionals' beliefs and knowledge about obesity aetiology, evidence of effectiveness is poor, and long-term effects of intervention strategies on weight bias reduction remain unknown. The findings highlight the lack of experimental research to reduce weight bias among health professionals. Although changes in practice will likely require multiple strategies in various sectors, well-designed trials are needed to test the impact of interventions to decrease weight bias in healthcare settings.

Body composition and energy intake - skeletal muscle mass is the strongest predictor of food intake in obese adolescents: The HEARTY trial

There has been renewed interest in examining the relationship between specific components of energy expenditure and the overall influence on energy intake (EI). The purpose of this cross-sectional analysis was to determine the strongest metabolic and anthropometric predictors of EI. It was hypothesized that resting metabolic rate (RMR) and skeletal muscle mass would be the strongest predictors of EI in a sample of overweight and obese adolescents. 304 post-pubertal adolescents (91 boys, 213 girls) aged 16.1 (±1.4) years with body mass index at or above the 95th percentile for age and sex OR at or above the 85th percentile plus an additional diabetes risk factor were measured for body weight, RMR (kcal/day) by indirect calorimetry, body composition by magnetic resonance imaging (fat free mass (FFM), skeletal muscle mass, fat mass (FM), and percentage body fat), and EI (kcal/day) using 3 day food records. Body weight, RMR, FFM, skeletal muscle mass, and FM were all significantly correlated with EI (p < 0.005). After adjusting the model for age, sex, height, and physical activity, only FFM (β = 21.9, p = 0.007) and skeletal muscle mass (β = 25.8, p = 0.02) remained as significant predictors of EI. FFM and skeletal muscle mass also predicted dietary protein and fat intake (p < 0.05), but not carbohydrate intake. In conclusion, with skeletal muscle mass being the best predictor of EI, our results support the hypothesis that the magnitude of the body's lean tissue is related to absolute levels of EI in a sample of inactive adolescents with obesity.

Positioning of Weight Bias: Moving towards Social Justice

Weight bias is a form of stigma with detrimental effects on the health and wellness of individuals with large bodies. Researchers from various disciplines have recognized weight bias as an important topic for public health and for professional practice. To date, researchers from various areas have approached weight bias from independent perspectives and from differing theoretical orientations. In this paper, we examined the similarities and differences between three perspectives (i.e., weight-centric, non-weight-centric (health-centric), and health at every size) used to understand weight bias and approach weight bias research with regard to (a) language about people with large bodies, (b) theoretical position, (c) identified consequences of weight bias, and (d) identified influences on weight-based social inequity. We suggest that, despite differences, each perspective acknowledges the negative influences that position weight as being within individual control and the negative consequences of weight bias. We call for recognition and discussion of weight bias as a social justice issue in order to change the discourse and professional practices extended towards individuals with large bodies. We advocate for an emphasis on social justice as a uniting framework for interdisciplinary research on weight bias.

Effects of aerobic training, resistance training, or both on cardiorespiratory and musculoskeletal fitness in adolescents with obesity: the HEARTY trial

The purpose of this study was to examine the effects of aerobic, resistance, and combined exercise training on cardiorespiratory and musculoskeletal fitness in postpubertal adolescents with obesity. After a 4-week supervised moderate-intensity exercise run-in, 304 adolescents aged 14-18 years with body mass index ≥85th percentile were randomized to 4 groups for 22 weeks of aerobic training, resistance training, combined training, or a nonexercising control. All participants received dietary counselling with a maximum daily energy deficit of 250 kcal. Cardiorespiratory fitness (peak oxygen consumption) was measured by indirect calorimetry using a graded treadmill exercise test. Musculoskeletal fitness was measured using the 2003 Canadian Physical Activity Fitness and Lifestyle Appraisal tests (hand grip, push-ups, partial curl-ups, sit and reach, and vertical jump). Muscular strength was assessed using an 8-repetition maximum test on the bench press, seated row, and leg press machines. A greater increase in peak oxygen consumption in the aerobic exercise group (30.6 ± 0.6 to 33.4 ± 0.7 mLO2/kg/min) was measured relative to the control group (30.6 ± 0.5 to 30.9 ± 0.7 mLO2/kg/min) (p = 0.002). Similarly, the number of partial curl-ups increased in the aerobic group (19 ± 1 to 23 ± 1) while no differences were measured in the control group (19 ± 1 to 20 ± 1) (p = 0.015). Increases in muscular strength and number of push-ups were greatest in the resistance group versus the control and combined groups versus the aerobic group (p < 0.05). In conclusion, aerobic training had the strongest effect on cardiorespiratory fitness, while resistance and combined training improved both muscular strength and endurance more than control and aerobic training alone, respectively, in adolescents with obesity.

Screen time is independently associated with health-related quality of life in overweight and obese adolescents

AIM

Excessive screen time and diminished health-related quality of life (HRQoL) are greater problems for obese than nonobese adolescents, but no research has examined the relationship between these two variables. This study examined the association between screen time and HRQoL in overweight and obese adolescents.

METHODS

A sample of 358 overweight and obese adolescents aged 14-18 years were assessed at baseline between 2005 and 2010 as part of the Canadian Healthy Eating, Aerobic and Resistance Training in Youth (HEARTY) trial. We used the Pediatric Quality of Life (PEDS-QL) and other self-report measures to assess HRQoL and screen time, defined as how long the 261 females and 97 males spent viewing TV, using the computer and playing video games.

RESULTS

After adjusting for socio-demographic variables, adiposity, physical activity and diet, screen time duration was associated with reduced overall HRQoL (adjusted r = -0.16, ß = -0.16, p = 0.009) and psychosocial HRQoL (adjusted r = -0.16, ß = -0.18, p = 0.004), but not physical HRQoL. No differences were found between males and females.

CONCLUSION

Screen time was associated with reduced overall and psychosocial HRQoL in overweight and obese adolescents. Future research should determine whether reducing screen time improves overall and psychosocial HRQoL in obese adolescents.

Effects of aerobic training, resistance training, or both on psychological health in adolescents with obesity: The HEARTY randomized controlled trial

OBJECTIVE

To determine the effects of aerobic training, resistance training, and combined training on mood, body image, and self-esteem in adolescents with obesity.

METHOD

After a 4-week prerandomization treatment, 304 postpubertal adolescents (91 males, 213 females) with obesity ages 14-18 years were randomized to 1 of 4 groups for 22 weeks: aerobic training (n = 75), resistance training (n = 78), combined aerobic and resistance training (n = 75), or nonexercising control (n = 76). All participants received dietary counseling, with a daily energy deficit of 250 kcal. Mood was measured using the Brunel Mood Scale. Body image was assessed using the Multiple Body Self-Relations Questionnaire, and physical self-perceptions and global self-esteem were measured using the Harter Physical Self-Perceptions Questionnaire.

RESULTS

Median adherence was 62%, 56%, and 64% in aerobic, resistance, and combined training, respectively. Resistance and combined training produced greater improvements than control on vigor, and resistance training reduced depressive symptoms. All groups improved on body image and physical self-perceptions, but combined showed greater increases than control on perceived physical conditioning, while only resistance training showed greater increases than controls on global self-esteem. Both combined and resistance training demonstrated greater increases in perceived strength than control. Psychological benefits were more related to better adherence and reductions in body fat than changes in strength or fitness.

CONCLUSION

Resistance training, alone or in combination with aerobic training, may provide psychological benefits in adolescents with overweight or obesity, and therefore could be an alternative to aerobic training for some individuals in the biological and psychological management of adolescent obesity.

Perspectives of Canadian fitness professionals on exercise and possible anorexia nervosa

BACKGROUND

Many individuals with eating disorders, including anorexia nervosa (AN), engage in overexercise. Little is known about fitness professionals' perceptions of their responsibilities when interacting with clients with possible AN. The purpose of the current study was to examine Alberta fitness professionals' experiences with clients suspected of having AN, and their views on related ethical issues. Specifically, we aimed to examine (1) their experiences with fitness clients suspected of having AN; (2) their opinions about related ethical responsibilities of fitness professionals; and (3) their views on related training and ethical issues.

METHODS

We administered a 21-item online survey to 143 Canadian fitness professionals about their experiences and perspectives on encountering individuals with possible AN in exercise classes and at their exercise facilities.

RESULTS

Sixty-two percent of respondents had encountered a client they believed had AN. Three-quarters had never received any training on managing clients with AN and felt inadequately prepared for such situations. Although most felt ethically obliged to intervene with such a client, more than two-thirds reported no relevant guidelines in their professional training.

CONCLUSIONS

Many fitness professionals are faced with clients with possible AN, have the desire to help, feel ethically obligated to take action, but do not know what course of action to take, if any. Work is needed to clarify ethical issues and related training needs for certification programs for fitness professionals regarding AN.

Effects of aerobic training, resistance training, or both on percentage body fat and cardiometabolic risk markers in obese adolescents: the healthy eating aerobic and resistance training in youth randomized clinical trial

IMPORTANCE

Little evidence exists on which exercise modality is optimal for obese adolescents.

OBJECTIVE

To determine the effects of aerobic training, resistance training, and combined training on percentage body fat in overweight and obese adolescents.

DESIGN, SETTING, AND PARTICIPANTS

Randomized, parallel-group clinical trial at community-based exercise facilities in Ottawa (Ontario) and Gatineau (Quebec), Canada, among previously inactive postpubertal adolescents aged 14 to 18 years (Tanner stage IV or V) with body mass index at or above the 95th percentile for age and sex or at or above the 85th percentile plus an additional diabetes mellitus or cardiovascular risk factor.

INTERVENTIONS

After a 4-week run-in period, 304 participants were randomized to the following 4 groups for 22 weeks: aerobic training (n = 75), resistance training (n = 78), combined aerobic and resistance training (n = 75), or nonexercising control (n = 76). All participants received dietary counseling, with a daily energy deficit of 250 kcal.

MAIN OUTCOMES AND MEASURES

The primary outcome was percentage body fat measured by magnetic resonance imaging at baseline and 6 months. We hypothesized that aerobic training and resistance training would each yield greater decreases than the control and that combined training would cause greater decreases than aerobic or resistance training alone.

RESULTS

Decreases in percentage body fat were -0.3 (95% CI, -0.9 to 0.3) in the control group, -1.1 (95% CI, -1.7 to -0.5) in the aerobic training group (P = .06 vs controls), and -1.6 (95% CI, -2.2 to -1.0) in the resistance training group (P = .002 vs controls). The -1.4 (95% CI, -2.0 to -0.8) decrease in the combined training group did not differ significantly from that in the aerobic or resistance training group. Waist circumference changes were -0.2 (95% CI, -1.7 to 1.2) cm in the control group, -3.0 (95% CI, -4.4 to -1.6) cm in the aerobic group (P = .006 vs controls), -2.2 (95% CI -3.7 to -0.8) cm in the resistance training group (P = .048 vs controls), and -4.1 (95% CI, -5.5 to -2.7) cm in the combined training group. In per-protocol analyses (≥ 70% adherence), the combined training group had greater changes in percentage body fat (-2.4, 95% CI, -3.2 to -1.6) vs the aerobic group (-1.2; 95% CI, -2.0 to -0.5; P = .04 vs the combined group) but not the resistance group (-1.6; 95% CI, -2.5 to -0.8).

CONCLUSIONS AND RELEVANCE

Aerobic, resistance, and combined training reduced total body fat and waist circumference in obese adolescents. In more adherent participants, combined training may cause greater decreases than aerobic or resistance training alone.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00195858.

The effects of resistance exercise training on body composition and strength in obese prepubertal children

OBJECTIVE

To assess the effects of resistance exercise training on body composition and muscular strength in obese prepubertal children.

DESIGN

Study participants, who were between the ages of 8 and 12 years, met Tanner I (stage) criteria, had a body mass index ≥ 95th percentile for age and sex, were randomized to either high-repetition, moderate-intensity resistance training (n = 12) or to the non-intervention control group (n = 7) for 12 weeks. Exercise training was performed twice a week for 75 minutes per session. Body composition was assessed using dual energy x-ray absorptiometry and muscular strength was evaluated using a 1-repetition-maximum test.

RESULTS

Exercise-group participants attended 98% of the 24 total sessions and showed a significant increase in body weight (57.6± 13.5 vs 59.6± 14.1 kg), height (144.9± 9 vs 146.6± 10.4 cm), lean body mass (32.6± 6.8 vs 34.0± 7.0 kg), lean body mass index (lean body mass in kg/height2; 15.3± 1.6 vs 15.6± 1.5 kg/m2), arm strength (28.4± 5.8 vs 31.2± 6.0 kg), and leg strength (89.4± 31.7 vs 113.4± 34 2 kg) from baseline measures (P < 0.05). Control group participants also showed significant increases in weight, height, and lean body mass from baseline measures (P < 0.05) but not in arm or leg strength. When the changes in participant body composition and muscular strength were compared between the exercise and control groups, significant differences were found in leg lean mass and leg strength (P < 0.05). There were no changes in percent body fat and fat mass index [FM/height2(kg/m2)] in either group.

CONCLUSION

Resistance training increases leg lean mass and leg strength in obese prepubertal youth and may have a positive effect on overall physical activity and health.

A review of randomized controlled trials of aerobic exercise training on fitness and cardiometabolic risk factors in obese adolescents

Aerobic training is the most prescribed exercise modality for the management of pediatric obesity. There is strong evidence that it decreases waist circumference, percent body fat and visceral fat, increases cardiorespiratory fitness, and decreases blood pressure in obese adolescents. However, the independent effects of aerobic exercise training on other cardiometabolic risk factors (ie, insulin resistance markers, plasma lipid levels, and inflammatory markers) are limited and yield inconsistent findings. Our article reviews randomized controlled trials evaluating the effects of aerobic exercise training on body composition, fitness, lipid levels, and insulin resistance in obese adolescents (aged 13-18 years) and outlines future research directions for this population.

Screen viewing and diabetes risk factors in overweight and obese adolescents

BACKGROUND

Sedentary behavior has been associated with deleterious cardiometabolic health indicators in adults, but very little research has examined this relationship in youth.

PURPOSE

To examine the association between the duration and type of sedentary screen behavior with diabetes risk factors (fasting glucose, insulin, homeostasis model-insulin resistance [HOMA-IR], 2-hour postload glucose, hemoglobin A1c) in a sample of overweight and obese adolescents.

METHODS

A cross-sectional study of 307 overweight or obese adolescents aged 14-18 years (90 boys, 217 girls) assessed at baseline of a lifestyle intervention for weight control conducted from 2005 to 2010. Sedentary screen behaviors, defined as hours per day spent watching TV, playing seated video games, recreational computer use, and total screen time were measured by self-report. Data were analyzed using linear regression analyses in 2012.

RESULTS

TV viewing was the only type of sedentary screen behavior associated with elevated diabetes risk factors before and after adjustment for confounders. Specifically, TV viewing remained positively associated with fasting insulin (adjusted r=0.11, β=0.10, p=0.048) and HOMA-IR (adjusted r=0.11, β=0.10, p=0.05) after adjustment for age, gender, waist-to-hip ratio, caloric intake, percentage of intake in carbohydrates, physical activity duration, and physical activity intensity.

CONCLUSIONS

TV watching may be independently associated with an increase in diabetes risk factors in a high-risk sample of overweight and obese adolescents. These findings provide support for interventions designed to reduce time spent watching TV as a possible means to attenuating diabetes risk factors in this high-risk population.

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.

Overweight and obese teenagers: why is adolescence a critical period?

This paper discusses the critical period of adolescence and its potential role in the development and persistence of obesity. The adolescent years are characteristic of changes in body composition (location and quantity of body fat), physical fitness and decreased insulin sensitivity during puberty. This period of growth and maturation is also marked with behavioural changes in diet, physical activity, sedentary behaviour and psychological health. Physical activity and sport participation decline during adolescence especially in teenage girls, while sedentary behaviour, risk for depression and body esteem issues increase during the teenage years. These physiological and behavioural changes during adolescence warrant the attention of health practitioners to prevent the onset and continuation of obesity throughout the lifespan.