Angela S. Alberga

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.

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.

Video Game Playing Is Independently Associated with Blood Pressure and Lipids in Overweight and Obese Adolescents

Objective To examine the association between duration and type of screen time (TV, video games, computer time) and blood pressure (BP) and lipids in overweight and obese adolescents. Design This is a cross-sectional study of 282 overweight or obese adolescents aged 14–18 years (86 males, 196 females) assessed at baseline prior to beginning a lifestyle intervention study for weight control. Sedentary behaviours, defined as hours per day spent watching TV, playing video games, recreational computer use and total screen time were measured by self-report. We examined the associations between sedentary behaviours and BP and lipids using multiple linear regression. Results Seated video gaming was the only sedentary behaviour associated with elevated BP and lipids before and after adjustment for age, sex, pubertal stage, parental education, body mass index (BMI), caloric intake, percent intake in dietary fat, physical activity (PA) duration, and PA intensity. Specifically, video gaming remained positively associated with systolic BP (adjusted r = 0.13, β = 1.1, p<0.05) and total cholesterol/HDL ratio (adjusted r = 0.12, β = 0.14, p<0.05). Conclusions Playing video games was the only form of sedentary behaviour that was independently associated with increased BP and lipids. Our findings provide support for reducing time spent playing seated video games as a possible means to promote health and prevent the incidence of cardiovascular disease (CVD) risk factors in this high risk group of overweight and obese adolescents. Future research is needed to first replicate these findings and subsequently aim to elucidate the mechanisms linking seated video gaming and elevated BP and lipids in this high risk population. Trial Registration Clinicaltrials.gov NCT00195858

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, whats 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.

The Effect of Exercise Training on Resting Metabolic Rate in Type 2 Diabetes Mellitus

PURPOSE Exercise is a possible means to increase resting energy expenditure, which could offset age-related metabolic declines and facilitate weight management, both of which are particularly important for people who have type 2 diabetes mellitus. We sought to determine the effects of aerobic exercise training and resistance exercise training and the incremental effect of combined aerobic and resistance exercise training on resting metabolic rate (RMR) in previously sedentary individuals with type 2 diabetes. METHODS After a 4-wk run-in period, 103 participants (72 male, 31 female, 39-70 yr, mean +/- SD body mass index = 32.9 +/- 5.7 kg x m(-2)) were randomly assigned to four groups for 22 wk: aerobic training, resistance training, combined aerobic and resistance exercise training, or waiting-list control. Exercise training was performed three times per week at community-based gym facilities. RMR was measured by indirect calorimetry for 30 min after an overnight fast. Body composition was assessed using bioelectrical impedance. These measurements were taken at baseline, at 3 months, and at 6 months of the intervention. RESULTS RMR did not change significantly in any group after accounting for multiple comparisons despite significant improvements in peak oxygen consumption and muscular strength in the exercising groups. Adjusting RMR for age, sex, fat mass, and fat-free mass in various combinations did not alter these results. CONCLUSION These results suggest that RMR was not significantly changed after a 6-month exercise program, regardless of modality, in this sample of adults with type 2 diabetes.

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 bodys lean tissue is related to absolute levels of EI in a sample of inactive adolescents with obesity.

Healthy eating, aerobic and resistance training in youth (HEARTY): Study rationale, design and methods

PURPOSE The objective of the Healthy Eating Aerobic and Resistance Training in Youth (HEARTY) trial (ClinicalTrials.Gov # NCT00195858) was to examine the effects of resistance training, with and without aerobic training, on percent body fat in sedentary, post-pubertal overweight or obese adolescents aged 14-18 years. This paper describes the HEARTY study rationale, design and methods. METHODS After a 4-week supervised low-intensity exercise run-in period, 304 overweight or obese adolescents with a body mass index≥85th percentile for age and sex were randomized to 4 groups for 22 weeks (5 months): diet+aerobic exercise, diet+resistance exercise, diet+combined aerobic and resistance exercise, or a diet only waiting-list control. All participants received dietary counseling designed to promote healthy eating with a maximum daily energy deficit of -250 kcal. OUTCOMES The primary outcome is percent body fat measured by Magnetic Resonance Imaging. Secondary outcomes include changes in anthropometry, regional body composition, resting energy expenditure, cardiorespiratory fitness, musculoskeletal fitness, cardiometabolic risk markers, and psychological health. SUMMARY To our knowledge, HEARTY is the largest clinical trial examining effects of aerobic training, resistance training, and combined aerobic and resistance training on changes in adiposity and cardiometabolic risk markers in overweight and obese adolescents. The findings will have important clinical implications regarding the role that resistance training should play in the management of adolescent obesity and its co-morbidities.

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

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.

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.