Effect of physical training and its cessation on percent fat and bone density of children with obesity

The path less traveled: Using structural equation modeling to investigate factors influencing bone functional morphology

OBJECTIVES

The relationship between an organism's mechanical environment and its bone strength has been long established by experimental research. Multiple intrinsic and extrinsic factors, including body mass, muscle strength, genetic background, and nutritional and/or hormonal status, are likely to influence bone deposition and resorption throughout the lifespan, complicating this relationship. Structural equation modeling (SEM) is uniquely positioned to parse this complex set of influences.

MATERIALS AND METHODS

Data from the Third National Health and Nutrition Examination Survey, including sex, total body mass, lean body mass, exercise frequency, peak body mass, and age, were analyzed using SEM to determine how they affect bone strength both individually and combined.

RESULTS

Body mass is typically the driver of cross-sectional area, but body mass and lean mass have similar effects on the polar moment of area (J). Peak body mass had a strong direct effect on J, despite decreasing strongly with increases in lean mass. Exercise also did not confer a large direct effect on cross-sectional area or J but did modify body mass and lean mass. In females, intentional weight loss was associated with decreased exercise levels.

DISCUSSION

SEM is a useful tool for parsing complex systems in bone functional morphology and has the potential to uncover causal links in the study of skeletal remodeling, including factors like weight loss or exercise that may have secondary effects.

The Benefits to Bone Health in Children and Pre-School Children with Additional Exercise Interventions: A Systematic Review and Meta-Analysis

OBJECTIVE

Determine if exercise interventions, beyond what is already provided to children and preschool children, improve bone health and reduce fracture incidence.

DESIGN

Systematic review and meta-analysis reported using the PRISMA guidelines. Certainty of evidence was assessed using GRADE recommendations.

DATA SOURCES

Five electronic databases were searched for records: PUBMED; CINAHL; CENTRAL; SPORTDiscus; Web of Science.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised, quasi-randomised and non-randomised controlled trials (including cluster-randomised) assessing the impact of additional exercise interventions (e.g., increased physical education classes or specific jumping programs) on bone health in children (6-12 years) and pre-school children (2-5 years) without dietary intervention.

RESULTS

Thirty-one records representing 16 distinct clinical trials were included. Dual-energy X-ray Absorptiometry (DXA) and/or peripheral Quantitative Computed Tomography (pQCT) were used to quantify bone health. Increased femoral neck bone mineral content in children with additional exercise interventions (n = 790, SMD = 0.55, 95% CI = 0.01 to 1.09) was reported, however this was not significant following sensitivity analysis. Other DXA and pQCT measures, as well as fracture incidence, did not appear to significantly differ over time between intervention and control groups. No studies reported adverse events. Studies failed to report all domains within the TIDieR checklist. All studies were at high risk of bias using the Cochrane RoB Tool 2.0. The certainty of the evidence was very low.

CONCLUSIONS

The addition of exercise interventions, beyond what is provided to children, does not appear to improve DXA and pQCT measures of bone health. The effect of additional exercise interventions on bone health in pre-school children is largely unknown. Future trials should ensure adherence is clearly reported and controlled for within analysis as well as including reports of adverse events (e.g., apophysitis) that occur due to increased exercise interventions.

Abnormal Cortical and Trabecular Bone in Youth With Type 1 Diabetes and Celiac Disease

OBJECTIVE

This study compared bone health in youth with type 1 diabetes and celiac disease (CD) versus type 1 diabetes alone.

RESEARCH DESIGN AND METHODS

This was a case-control study of 42 youth with coexisting type 1 diabetes and CD and 40 with type 1 diabetes matched for age, sex, diabetes duration, and HbA_1c. Bone mineral density (BMD), bone mineral content (BMC), and BMC-to-lean tissue mass (LTM) ratio were measured using DXA and reported as z-scores for height. Total, trabecular, and cortical bone and muscle parameters were measured using peripheral quantitative computed tomography (pQCT) and reported as z-scores for age.

RESULTS

Mean age at assessment was 14.3 ± 3.1 years; diabetes duration, 8.0 ± 3.5 years; HbA_1c, 8.2 ± 1.5% (66 ± 5 mmol/mol); and 25-hydroxy vitamin D, 71 ± 21 nmol/L. Comparing youth with coexisting CD versus type 1 diabetes alone, DXA showed lower BMC-to-LTM ratio (0.37 ± 1.12 vs. 0.73 ± 2.23, P = 0.007) but no difference in total BMD. Youth with coexisting CD also had lower BMC-to-LTM ratio versus the general population (P = 0.04). Radial pQCT showed lower total BMC (-0.92 ± 1.40 vs. -0.26 ± 1.23, P = 0.03) despite similar bone and muscle cross-sectional area. In multivariable linear regression, lower BMC was associated with higher insulin dose (P = 0.03) but not HbA_1c.

CONCLUSIONS

Youth with both type 1 diabetes and CD have lower BMC relative to LTM and lower BMC, indicating abnormal trabecular and cortical bone development despite similar bone and muscle size. These findings suggest that the two conditions confer a lower bone turnover state. We recommend further examination of bone health in this population; future research should examine early interventions to improve bone health.

WITHDRAWN: Interventions for treating obesity in children

BACKGROUND

Child and adolescent obesity is increasingly prevalent, and can be associated with significant short- and long-term health consequences.

OBJECTIVES

To assess the efficacy of lifestyle, drug and surgical interventions for treating obesity in childhood.

SEARCH METHODS

We searched CENTRAL on The Cochrane Library Issue 2 2008, MEDLINE, EMBASE, CINAHL, PsycINFO, ISI Web of Science, DARE and NHS EED. Searches were undertaken from 1985 to May 2008. References were checked. No language restrictions were applied.

SELECTION CRITERIA

We selected randomised controlled trials (RCTs) of lifestyle (i.e. dietary, physical activity and/or behavioural therapy), drug and surgical interventions for treating obesity in children (mean age under 18 years) with or without the support of family members, with a minimum of six months follow up (three months for actual drug therapy). Interventions that specifically dealt with the treatment of eating disorders or type 2 diabetes, or included participants with a secondary or syndromic cause of obesity were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data following the Cochrane Handbook. Where necessary authors were contacted for additional information.

MAIN RESULTS

We included 64 RCTs (5230 participants). Lifestyle interventions focused on physical activity and sedentary behaviour in 12 studies, diet in 6 studies, and 36 concentrated on behaviorally orientated treatment programs. Three types of drug interventions (metformin, orlistat and sibutramine) were found in 10 studies. No surgical intervention was eligible for inclusion. The studies included varied greatly in intervention design, outcome measurements and methodological quality.Meta-analyses indicated a reduction in overweight at 6 and 12 months follow up in: i) lifestyle interventions involving children; and ii) lifestyle interventions in adolescents with or without the addition of orlistat or sibutramine. A range of adverse effects was noted in drug RCTs.

AUTHORS' CONCLUSIONS

While there is limited quality data to recommend one treatment program to be favoured over another, this review shows that combined behavioural lifestyle interventions compared to standard care or self-help can produce a significant and clinically meaningful reduction in overweight in children and adolescents. In obese adolescents, consideration should be given to the use of either orlistat or sibutramine, as an adjunct to lifestyle interventions, although this approach needs to be carefully weighed up against the potential for adverse effects. Furthermore, high quality research that considers psychosocial determinants for behaviour change, strategies to improve clinician-family interaction, and cost-effective programs for primary and community care is required.

Frequency and duration of vigorous physical activity bouts are associated with adolescent boys' bone mineral status: A cross-sectional study

PURPOSE

Vigorous physical activity (VPA) has been proven to promote osteogenesis in adolescents; however the specifics of the optimal pattern of frequency and duration of VPA are unknown. The main goal of the present study was to analyze the associations of different length of VPA bouts with bone health.

METHODS

180 healthy male adolescents (11-13 years) had their bone mineral content and density assessed by dual-energy X-ray absorptiometry scans at the whole body, femoral neck (FN) and lumbar spine and their physical activity measured by an accelerometer during one week.

RESULTS

VPA was the intensity with the strongest associations with bone mineral parameters especially at the FN. Subjects whose longest VPA bout was 5 min or above had higher FN bone mineral density (BMD) than those who did not complete any 5-min bout and these differences were greater with participants who reached 15 consecutive minutes of VPA (>15': 0.977 ± 0.020 g/cm2; 5'-15': 0.907 ± 0.009 g/cm2; <5': 0.876 ± 0.009 g/cm2; all p < 0.05). When comparing the relevance of VPA bouts and volume of physical activity, the group with low volume and having a VPA bout had better FN BMD compared to the group with high volume but no VPA bout. Additionally, the group with both high volume and VPA bout showed better FN BMD than the rest of the groups.

CONCLUSIONS

VPA may be the most effective activity intensity to improve bone mineral density and content of adolescent boys, with greater benefits if VPA periods either long or frequent.

Exercise and adiposity in overweight and obese children and adolescents: protocol for a systematic review and network meta-analysis of randomised trials

INTRODUCTION

Overweight and obesity is a worldwide public health problem among children and adolescents. However, the magnitude of effect, as well as hierarchy of exercise interventions (aerobic, strength training or both), on selected measures of adiposity is not well established despite numerous trials on this issue. The primary purposes of this study are to use the network meta-analytical approach to determine the effects and hierarchy of exercise interventions on selected measures of adiposity in overweight and obese children and adolescents.

METHODS AND ANALYSIS

Randomised exercise intervention trials >4 weeks, available in any language up to 31 August 2017 and which include direct and/or indirect evidence, will be included. Studies will be located by searching seven electronic databases, cross-referencing and expert review. Dual selection and abstraction of data will occur. The primary outcomes will be changes in body mass index (in kg/m²), fat mass and percent body fat. Risk of bias will be assessed using the Cochrane Risk of Bias assessment instrument while confidence in the cumulative evidence will be assessed using the Grading of Recommendations Assessment, Development and Evaluation instrument for network meta-analysis. Network meta-analysis will be performed using multivariate random-effects meta-regression models. The surface under the cumulative ranking curve will be used to provide a hierarchy of exercise treatments (aerobic, strength or both).

ETHICS AND DISSEMINATION

This study does not require ethics approval. Findings will be presented at a professional conference and published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD 42017073103 .

Diet, physical activity and behavioural interventions for the treatment of overweight or obese children from the age of 6 to 11 years

BACKGROUND

Child and adolescent overweight and obesity has increased globally, and can be associated with significant short- and long-term health consequences. This is an update of a Cochrane review published first in 2003, and updated previously in 2009. However, the update has now been split into six reviews addressing different childhood obesity treatments at different ages.

OBJECTIVES

To assess the effects of diet, physical activity and behavioural interventions (behaviour-changing interventions) for the treatment of overweight or obese children aged 6 to 11 years.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL, LILACS as well as trial registers ClinicalTrials.gov and ICTRP Search Portal. We checked references of studies and systematic reviews. We did not apply any language restrictions. The date of the last search was July 2016 for all databases.

SELECTION CRITERIA

We selected randomised controlled trials (RCTs) of diet, physical activity, and behavioural interventions (behaviour-changing interventions) for treating overweight or obese children aged 6 to 11 years, with a minimum of six months' follow-up. We excluded interventions that specifically dealt with the treatment of eating disorders or type 2 diabetes, or included participants with a secondary or syndromic cause of obesity.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened references, extracted data, assessed risk of bias, and evaluated the quality of the evidence using the GRADE instrument. We contacted study authors for additional information. We carried out meta-analyses according to the statistical guidelines in the Cochrane Handbook for Systematic Reviews of Interventions.

MAIN RESULTS

We included 70 RCTs with a total of 8461 participants randomised to either the intervention or control groups. The number of participants per trial ranged from 16 to 686. Fifty-five trials compared a behaviour-changing intervention with no treatment/usual care control and 15 evaluated the effectiveness of adding an additional component to a behaviour-changing intervention. Sixty-four trials were parallel RCTs, and four were cluster RCTs. Sixty-four trials were multicomponent, two were diet only and four were physical activity only interventions. Ten trials had more than two arms. The overall quality of the evidence was low or very low and 62 trials had a high risk of bias for at least one criterion. Total duration of trials ranged from six months to three years. The median age of participants was 10 years old and the median BMI z score was 2.2.Primary analyses demonstrated that behaviour-changing interventions compared to no treatment/usual care control at longest follow-up reduced BMI, BMI z score and weight. Mean difference (MD) in BMI was -0.53 kg/m2 (95% confidence interval (CI) -0.82 to -0.24); P < 0.00001; 24 trials; 2785 participants; low-quality evidence. MD in BMI z score was -0.06 units (95% CI -0.10 to -0.02); P = 0.001; 37 trials; 4019 participants; low-quality evidence and MD in weight was -1.45 kg (95% CI -1.88 to -1.02); P < 0.00001; 17 trials; 1774 participants; low-quality evidence.Thirty-one trials reported on serious adverse events, with 29 trials reporting zero occurrences RR 0.57 (95% CI 0.17 to 1.93); P = 0.37; 4/2105 participants in the behaviour-changing intervention groups compared with 7/1991 participants in the comparator groups). Few trials reported health-related quality of life or behaviour change outcomes, and none of the analyses demonstrated a substantial difference in these outcomes between intervention and control. In two trials reporting on minutes per day of TV viewing, a small reduction of 6.6 minutes per day (95% CI -12.88 to -0.31), P = 0.04; 2 trials; 55 participants) was found in favour of the intervention. No trials reported on all-cause mortality, morbidity or socioeconomic effects, and few trials reported on participant views; none of which could be meta-analysed.As the meta-analyses revealed substantial heterogeneity, we conducted subgroup analyses to examine the impact of type of comparator, type of intervention, risk of attrition bias, setting, duration of post-intervention follow-up period, parental involvement and baseline BMI z score. No subgroup effects were shown for any of the subgroups on any of the outcomes. Some data indicated that a reduction in BMI immediately post-intervention was no longer evident at follow-up at less than six months, which has to be investigated in further trials.

AUTHORS' CONCLUSIONS

Multi-component behaviour-changing interventions that incorporate diet, physical activity and behaviour change may be beneficial in achieving small, short-term reductions in BMI, BMI z score and weight in children aged 6 to 11 years. The evidence suggests a very low occurrence of adverse events. The quality of the evidence was low or very low. The heterogeneity observed across all outcomes was not explained by subgrouping. Further research is required of behaviour-changing interventions in lower income countries and in children from different ethnic groups; also on the impact of behaviour-changing interventions on health-related quality of life and comorbidities. The sustainability of reduction in BMI/BMI z score and weight is a key consideration and there is a need for longer-term follow-up and further research on the most appropriate forms of post-intervention maintenance in order to ensure intervention benefits are sustained over the longer term.

Systematic review of the relationships between objectively measured physical activity and health indicators in school-aged children and youth

Moderate-to-vigorous physical activity (MVPA) is essential for disease prevention and health promotion. Emerging evidence suggests other intensities of physical activity (PA), including light-intensity activity (LPA), may also be important, but there has been no rigorous evaluation of the evidence. The purpose of this systematic review was to examine the relationships between objectively measured PA (total and all intensities) and health indicators in school-aged children and youth. Online databases were searched for peer-reviewed studies that met the a priori inclusion criteria: population (apparently healthy, aged 5-17 years), intervention/exposure/comparator (volumes, durations, frequencies, intensities, and patterns of objectively measured PA), and outcome (body composition, cardiometabolic biomarkers, physical fitness, behavioural conduct/pro-social behaviour, cognition/academic achievement, quality of life/well-being, harms, bone health, motor skill development, psychological distress, self-esteem). Heterogeneity among studies precluded meta-analyses; narrative synthesis was conducted. A total of 162 studies were included (204 171 participants from 31 countries). Overall, total PA was favourably associated with physical, psychological/social, and cognitive health indicators. Relationships were more consistent and robust for higher (e.g., MVPA) versus lower (e.g., LPA) intensity PA. All patterns of activity (sporadic, bouts, continuous) provided benefit. LPA was favourably associated with cardiometabolic biomarkers; data were scarce for other outcomes. These findings continue to support the importance of at least 60 min/day of MVPA for disease prevention and health promotion in children and youth, but also highlight the potential benefits of LPA and total PA. All intensities of PA should be considered in future work aimed at better elucidating the health benefits of PA in children and youth.

An After-School Physical Activity Program for Obesity Prevention in Children

This article describes the process of setting up a 3-year, school-based after-school physical activity intervention in elementary schools. The primary aim of the study is to determine whether adiposity and fitness will improve in children who are exposed to a fitogenic versus an obesogenic environment. Eighteen schools were randomized to the control (obesogenic) or intervention (fitogenic) group. The study design, program components, and evaluation of the intervention are described in detail. The intervention consists of (a) academic enrichment, (b) a healthy snack, and (c) physical activity in a mastery-oriented environment. Successful implementation would show the feasibility of schools’ being able to provide a fitogenic environment. Significant differences between the groups would provide evidence that a fitogenic environment after school has positive health benefits. If feasibility and efficacy are demonstrated, implementing an after-school program like this one in elementary schools could play a major role in preventing and reducing childhood obesity.

Exercise and BMI in Overweight and Obese Children and Adolescents: A Systematic Review and Trial Sequential Meta-Analysis

OBJECTIVE

Determine the effects of exercise on body mass index (BMI in kg · m(-2)) among overweight and obese children and adolescents.

METHODS

Trial sequential meta-analysis of randomized controlled exercise intervention trials ≥ 4 weeks and published up to November 11, 2014.

RESULTS

Of the 5,436 citations screened, 20 studies representing 971 boys and girls were included. Average length, frequency, and duration of training were 13 weeks, 3 times per week, for 46 minutes per session. Overall, random-effects models showed that exercise decreased BMI by 3.6% (mean: -1.08; 95% CI: -0.52 to -1.64; Q = 231.4; p < 0.001; I (2) = 90.9%; 95% CI: 87.6% to 93.4%; D (2) = 91.5%). Trial sequential meta-analysis showed that changes in BMI crossed the monitoring boundary for a type 1 error in 2010, remaining stable thereafter. The number needed to treat was 5 while the percentile improvement was 26.9. It was estimated that approximately 2.5 million overweight and obese children in the US and 22.0 million overweight and obese children worldwide could reduce their BMI by participating in a regular exercise program. Overall quality of evidence was rated as moderate.

CONCLUSIONS

Exercise is associated with improvements in BMI among overweight and obese children and adolescents. This trial is registered with PROSPERO Trial Registration #CRD42015017586.

Fat gain with physical detraining is correlated with increased glucose transport and oxidation in periepididymal white adipose tissue in rats

As it is a common observation that obesity tends to occur after discontinuation of exercise, we investigated how white adipocytes isolated from the periepididymal fat of animals with interrupted physical training transport and oxidize glucose, and whether these adaptations support the weight regain seen after 4 weeks of physical detraining. Male Wistar rats (45 days old, weighing 200 g) were divided into two groups (n=10): group D (detrained), trained for 8 weeks and detrained for 4 weeks; and group S (sedentary). The physical exercise was carried out on a treadmill for 60 min/day, 5 days/week for 8 weeks, at 50-60% of the maximum running capacity. After the training protocol, adipocytes isolated from the periepididymal adipose tissue were submitted to glucose uptake and oxidation tests. Adipocytes from detrained animals increased their glucose uptake capacity by 18.5% compared with those from sedentary animals (P<0.05). The same cells also showed a greater glucose oxidation capacity in response to insulin stimulation (34.55%) compared with those from the S group (P<0.05). We hypothesize that, owing to the more intense glucose entrance into adipose cells from detrained rats, more substrate became available for triacylglycerol synthesis. Furthermore, this increased glucose oxidation rate allowed an increase in energy supply for triacylglycerol synthesis. Thus, physical detraining might play a role as a possible obesogenic factor for increasing glucose uptake and oxidation by adipocytes.

Cessation of physical exercise changes metabolism and modifies the adipocyte cellularity of the periepididymal white adipose tissue in rats

All of the adaptations acquired through physical training are reversible with inactivity. Although significant reductions in maximal oxygen uptake (Vo2max) can be observed within 2 to 4 wk of detraining, the consequences of detraining on the physiology of adipose tissue are poorly known. Our aim was therefore to investigate the effects of discontinuing training (physical detraining) on the metabolism and adipocyte cellularity of rat periepididymal (PE) adipose tissue. Male Wistar rats, aged 6 wk, were divided into three groups and studied for 12 wk under the following conditions: 1) trained (T) throughout the period; 2) detrained (D), trained during the first 8 wk and detrained during the remaining 4 wk; and 3) age-matched sedentary (S). Training consisted of treadmill running sessions (1 h/day, 5 days/wk, 50-60% Vo2max). The PE adipocyte size analysis revealed significant differences between the groups. The adipocyte cross-sectional area (in μm(2)) was significantly larger in D than in the T and S groups (3,474 ± 68.8; 1,945.7 ± 45.6; 2,492.4 ± 49.08, respectively, P < 0.05). Compared with T, the isolated adipose cells (of the D rats) showed a 48% increase in the ability to perform lipogenesis (both basal and maximally insulin-stimulated) and isoproterenol-stimulated lipolysis. No changes were observed with respect to unstimulated lipolysis. A 15% reduction in the proportion of apoptotic adipocytes was observed in groups T and D compared with group S. The gene expression levels of adiponectin and PPAR-gamma were upregulated by factors of 3 and 2 in D vs. S, respectively. PREF-1 gene expression was 3-fold higher in T vs. S. From these results, we hypothesize that adipogenesis was stimulated in group D and accompanied by significant adipocyte hypertrophy and an increase in the lipogenic capacity of the adipocytes. The occurrence of apoptotic nuclei in PE fat cells was reduced in the D and T rats; these results raise the possibility that the adipose tissue changes after detraining are obesogenic.

Exercise dose and diabetes risk in overweight and obese children: a randomized controlled trial

CONTEXT

Pediatric studies have shown that aerobic exercise reduces metabolic risk, but dose-response information is not available.

OBJECTIVES

To test the effect of different doses of aerobic training on insulin resistance, fatness, visceral fat, and fitness in overweight, sedentary children and to test moderation by sex and race.

DESIGN, SETTING, AND PARTICIPANTS

Randomized controlled efficacy trial conducted from 2003 through 2007 in which 222 overweight or obese sedentary children (mean age, 9.4 years; 42% male; 58% black) were recruited from 15 public schools in the Augusta, Georgia, area.

INTERVENTION

Children were randomly assigned to low-dose (20 min/d; n = 71) or high-dose (40 min/d; n = 73) aerobic training (5 d/wk; mean duration, 13 [SD, 1.6] weeks) or a control condition (usual physical activity; n = 78).

MAIN OUTCOME MEASURES

The prespecified primary outcomes were postintervention type 2 diabetes risk assessed by insulin area under the curve (AUC) from an oral glucose tolerance test, aerobic fitness (peak oxygen consumption [VO2]), percent body fat via dual-energy x-ray absorptiometry, and visceral fat via magnetic resonance, analyzed by intention to treat.

RESULTS

The study had 94% retention (n = 209). Most children (85%) were obese. At baseline, mean body mass index was 26 (SD, 4.4). Reductions in insulin AUC were larger in the high-dose group (adjusted mean difference, -3.56 [95% CI, -6.26 to -0.85] × 10(3) μU/mL; P = .01) and the low-dose group (adjusted mean difference, -2.96 [95% CI, -5.69 to -0.22] × 10(3) μU/mL; P = .03) than the control group. Dose-response trends were also observed for body fat (adjusted mean difference, -1.4% [95% CI, -2.2% to -0.7%]; P < .001 and -0.8% [95% CI, -1.6% to -0.07%]; P = .03) and visceral fat (adjusted mean difference, -3.9 cm3 [95% CI, -6.0 to -1.7 cm3]; P < .001 and -2.8 cm3 [95% CI, -4.9 to -0.6 cm3]; P = .01) in the high- and low-dose vs control groups, respectively. Effects in the high- and low-dose groups vs control were similar for fitness (adjusted mean difference in peak VO2, 2.4 [95% CI, 0.4-4.5] mL/kg/min; P = .02 and 2.4 [95% CI, 0.3-4.5] mL/kg/min; P = .03, respectively). High- vs low-dose group effects were similar for these outcomes. There was no moderation by sex or race.

CONCLUSION

In this trial, after 13 weeks, 20 or 40 min/d of aerobic training improved fitness and demonstrated dose-response benefits for insulin resistance and general and visceral adiposity in sedentary overweight or obese children, regardless of sex or race.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00108901.

Comparison of Hologic QDR-1000/W and 4500W DXA Scanners in 13- to 18-Year Olds

OBJECTIVE

Body composition measurements made using Hologic QDR-1000/W pencil-beam and QDR-4500W fan-beam scanners (Bedford, MA) were compared in a sample of 13- to 18-year-old white and black youth (n = 219).

RESEARCH METHODS AND PROCEDURES

Total fat (FAT), fat-free soft tissue (FFST), bone mineral content (BMC), bone mineral density (BMD), and percent body fat (%BF) were compared between repeated measurements using the QDR-4500 and between the two scanners using mixed model ANOVA. Intraclass correlation coefficients and Bland-Altman limits of agreement were used to evaluate inter- and intrascanner reliability.

RESULTS

Intraclass correlation coefficients for repeated measurements using the QDR-4500 ranged from 0.997 to 0.999 for FAT, %BF, FFST, and BMC and 0.987 for BMD. Mean measurements made using the two scanners differed significantly for FAT, %BF, BMC, and BMD (p < 0.0001), and scan by sex interactions were significant (all p < 0.0005). There were no significant differences in mean measurements between repeat scans using the QDR-4500 (all p > 0.19). Limits of agreement for measurements of FAT, FFST, and %BF made using the two scanners were approximately three times as wide as those for two measurements using the QDR-4500. For lower values of FAT and %BF, the QDR-4500 gave higher measurements than the QDR-1000, whereas at higher values, this relationship was reversed. The QDR-1000 tended to give higher BMC measurements, with larger differences for higher values.

DISCUSSION

Using different models of DXA scanners within a study may reduce precision of body composition measurement. This issue needs to be considered in the design of longitudinal studies.

Electronic Games and Environmental Factors Associated with Childhood Obesity in Switzerland

OBJECTIVE

Environmental factors and behaviors associated with obesity have not been well described in children living in Europe. Although television watching has been repeatedly associated with obesity, it is unclear whether other sedentary activities, such as use of electronic games, are independently associated with obesity in children. The hypothesis was that various types of sedentary activities are associated with obesity in children living in Switzerland.

RESEARCH METHODS AND PROCEDURES

This was a cross-sectional study of children (grades one to three) from four communities in the Greater Zurich Area (Switzerland). Obesity was defined as a combination of overweight (BMI) and overfat (skinfold thicknesses). Environmental factors were assessed by questionnaire. The children's physical activity was estimated by their teacher (scale 0 to 10).

RESULTS

Of 922 eligible subjects, 872 (94.6%) took part in the study. Use of electronic games [odds ratio (OR) = 2.03 per hour per day, 95% confidence interval (CI): 1.57 to 2.61, p < 0.001], television (OR = 2.83 per hour per day, 95% CI: 2.08 to 3.86, p < 0.001), physical activity (OR = 0.80 per unit, 95% CI: 0.72 to 0.88, p < 0.001), maternal work (OR = 1.93, 95% CI: 1.13 to 3.29, p = 0.02), and paternal smoking (OR = 1.78, 95% CI: 1.07 to 2.96, p = 0.03) were independently associated with obesity. Further adjustment for socioeconomic status, when available, did not change these results.

DISCUSSION

In this sample of children living in Switzerland, the use of electronic games was significantly associated with obesity, independently of confounding factors. The association of obesity with television use and lack of physical activity confirms results from other populations and points to potential strategies for obesity prevention.

External validity reporting in behavioral treatment of childhood obesity: a systematic review

CONTEXT

To aid translation of childhood obesity interventions evidence into practice, research studies must report results in a way that better supports pragmatic decision making. The current review evaluated the extent to which information on key external validity dimensions, participants, settings, interventions, outcomes, and maintenance of effects, was included in research studies on behavioral treatments for childhood obesity.

EVIDENCE ACQUISITION

Peer-reviewed studies of behavioral childhood obesity treatments published between 1980 and 2008 were identified from (1) electronic searches of social science and medical databases; (2) research reviews of childhood obesity interventions; and (3) reference lists cited in these reviews. Included studies reported on a controlled obesity intervention trial, targeted overweight or obese children aged 2-18 years, included a primary or secondary anthropometric outcome, and targeted change in dietary intake or physical activity behaviors.

EVIDENCE SYNTHESIS

1071 publications were identified and 77 met selection criteria. Studies were coded on established review criteria for external validity elements. All studies lacked full reporting of generalizability elements. Across criteria, the average reporting was 23.9% (range=0%-100%). Infrequently reported were setting-level selection criteria and representativeness, characteristics regarding intervention staff, implementation of the intervention content, costs, and program sustainability.

CONCLUSIONS

Enhanced reporting of relevant and pragmatic information in behavioral investigations of childhood obesity interventions is needed to improve the ability to evaluate the applicability of results to practice implementation. Such evidence would improve translation of research to practice, provide additional explanation for variability in intervention outcomes, and provide insights into successful adaptations of interventions to local conditions.

A Preliminary Investigation of Stimulus Control, Self-Monitoring, and Reinforcement in Lifestyle Interventions for Pediatric Overweight

Objective. The current study examined the use of stimulus control, self-monitoring, and reinforcement by youth, parents, and interventionists as related to weight management in lifestyle intervention programs. Design. Secondary analysis of an existing data set was used to integrate the results of 14 published, randomized treatment–control intervention trials for overweight youth aged 2 to 18 years. Main outcome measure. Between-group differences in weight-related outcomes, including weight, body mass index (BMI), and percentage overweight, measured at the end of treatment, were used to calculate effect sizes for each treatment–control comparison. Additionally, average effect sizes were calculated among sets of comparisons sharing similar approaches to implementing behavioral techniques. Results. Treatment programs that taught youth to use stimulus control, taught youth to self-monitor, and taught parents to use reinforcement, produced significantly larger effect sizes than programs that did not include these components. The beneficial effects of these specific behavioral techniques appeared to be amplified when used with multiple key individuals. Conclusion. This initial study quantitatively demonstrated significant benefits associated with teaching youth stimulus control and self-monitoring, and teaching parents reinforcement to shape health behaviors in lifestyle interventions for pediatric overweight. Furthermore, teaching youth and parents the same techniques may contribute to better weight-related outcomes. These findings and descriptive information on how techniques were described, taught, and delivered may guide future research efforts aimed at identifying and examining the most effective behavioral components to include in brief interventions.

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.

A meta-analysis of obesity interventions among U.S. minority children

PURPOSE

To quantitatively evaluate the efficacy of interventions designed to prevent or treat obesity among U.S. minority children using meta-analytic techniques.

METHODS

A total of 40 intervention trials involving 10,725 children aged 6-19 years were examined.

RESULTS

Interventions with more components showed a higher mean effect size than those with fewer components: among 32 controlled trials, d = .07 for one-component (n = 6); d = .08 for two-component (n = 15); d = .33 for three-component (n = 10); and d = .71 for four-component (n = 1) interventions. Interventions with parental involvement (n = 22, d = .21) and lifestyle interventions (n = 14, d = .34) showed a greater mean effect size than those without parental involvement (n = 10, d = .05) or lifestyle interventions (n = 18, d = .04), despite the fact that their 90% confidence intervals overlapped. Among uncontrolled trials (n = 8), two-component interventions (n = 5) yielded d = .86 and three-component interventions (n = 3) yielded d = .96.

CONCLUSIONS

Evidence indicates that, among U.S. minority children, obesity interventions with three or more components might be more efficacious than those using fewer components. Parental involvement, lifestyle change, culturally-based adaptation, and interactive computer programs seem to show promise in the reduction of obese minority children.

Interventions for treating obesity in children

BACKGROUND

Child and adolescent obesity is increasingly prevalent, and can be associated with significant short- and long-term health consequences.

OBJECTIVES

To assess the efficacy of lifestyle, drug and surgical interventions for treating obesity in childhood.

SEARCH STRATEGY

We searched CENTRAL on The Cochrane Library Issue 2 2008, MEDLINE, EMBASE, CINAHL, PsycINFO, ISI Web of Science, DARE and NHS EED. Searches were undertaken from 1985 to May 2008. References were checked. No language restrictions were applied.

SELECTION CRITERIA

We selected randomised controlled trials (RCTs) of lifestyle (i.e. dietary, physical activity and/or behavioural therapy), drug and surgical interventions for treating obesity in children (mean age under 18 years) with or without the support of family members, with a minimum of six months follow up (three months for actual drug therapy). Interventions that specifically dealt with the treatment of eating disorders or type 2 diabetes, or included participants with a secondary or syndromic cause of obesity were excluded.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data following the Cochrane Handbook. Where necessary authors were contacted for additional information.

MAIN RESULTS

We included 64 RCTs (5230 participants). Lifestyle interventions focused on physical activity and sedentary behaviour in 12 studies, diet in 6 studies, and 36 concentrated on behaviorally orientated treatment programs. Three types of drug interventions (metformin, orlistat and sibutramine) were found in 10 studies. No surgical intervention was eligible for inclusion. The studies included varied greatly in intervention design, outcome measurements and methodological quality.Meta-analyses indicated a reduction in overweight at 6 and 12 months follow up in: i) lifestyle interventions involving children; and ii) lifestyle interventions in adolescents with or without the addition of orlistat or sibutramine. A range of adverse effects was noted in drug RCTs.

AUTHORS' CONCLUSIONS

While there is limited quality data to recommend one treatment program to be favoured over another, this review shows that combined behavioural lifestyle interventions compared to standard care or self-help can produce a significant and clinically meaningful reduction in overweight in children and adolescents. In obese adolescents, consideration should be given to the use of either orlistat or sibutramine, as an adjunct to lifestyle interventions, although this approach needs to be carefully weighed up against the potential for adverse effects. Furthermore, high quality research that considers psychosocial determinants for behaviour change, strategies to improve clinician-family interaction, and cost-effective programs for primary and community care is required.

Ten months of exercise improves general and visceral adiposity, bone, and fitness in black girls

OBJECTIVE

The goal of this study was to evaluate the impact of a 10-month after-school physical activity (PA) program on body composition and cardiovascular (CV) fitness in young black girls.

RESEARCH METHODS AND PROCEDURES

Subjects were 8- to 12-year-olds recruited from elementary schools. Body composition was measured using anthropometrics {waist circumference and BMI, DXA [percentage body fat (%BF)] and bone mineral density (BMD)}, and magnetic resonance imaging [visceral adipose tissue (VAT)]. CV fitness was measured using a graded treadmill test. The intervention consisted of 30 minutes homework/healthy snack time and 80 minutes PA (i.e., 25 minutes skills instruction, 35 minutes aerobic PA, and 20 minutes strengthening/stretching). Analyses were adjusted for age, baseline value of the dependent variable, and sexual maturation (pediatrician observation).

RESULTS

Mean attendance was 54%. Compared with the control group, the intervention group had a relative decrease in %BF (p < 0.0001), BMI (p < 0.01), and VAT (p < 0.01) and a relative increase in BMD (p < 0.0001) and CV fitness (p < 0.05). Higher attendance was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.01) and BMI (p < 0.05). Higher heart rate during PA was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.005).

DISCUSSION

An after-school PA program can lead to beneficial changes in body composition and CV fitness in young black girls. It is noteworthy that the control and intervention groups differed in change in VAT but not waist circumference. This suggests that changes in central adiposity can occur in response to PA, even in young children, but that waist circumference may not be a good indicator of central adiposity.

Correlates of adherence to a physical activity program in young African-American girls

OBJECTIVE

The goal was to identify correlates of adherence to a structured physical activity (PA) program.

RESEARCH METHODS AND PROCEDURES

Subjects were 136 8- to 12-year-old African-American girls. Potential correlates at baseline were: 1) fitness index (FI: % body fat from DXA and cardiovascular fitness from treadmill test), and 2) self-esteem, anxiety, attitude to school and teachers, relationship with parents, and interpersonal relations (Behavioral Assessment System for Children). The 10-month PA program included 80 minutes of PA offered 5 days/wk. Regression tree classification was used to model attendance.

RESULTS

Six splits occurred (34% total variance explained). Less anxious subjects attended more often than highly anxious subjects (3 days/wk vs. 1.5 days/wk) did. Subjects with a healthier FI attended more often than those with a less healthy FI (3 days/wk vs. 0.5 days/wk) did. Younger subjects attended more often than older ones (3 days/wk vs. 2.5 days/wk) did. The next two splits were again with anxiety (3.5 days/wk vs. 3 days/wk) and FI (3 days/wk vs. 2.5 days/wk). Finally, subjects with higher levels of self-esteem attended more often than those with lower levels (3.5 days/wk vs. 2 days/wk) did.

DISCUSSION

Subjects who were self-confident, younger, fitter, and less anxious were more likely to participate regularly. This suggests that children who may be more likely to benefit from a PA program are less likely to participate. To enhance participation in PA programs, especially in older African-American girls: 1) psychological concerns should be identified and addressed before enrollment, and 2) programs should be designed to be appealing to children of all fitness levels.

The Medical College of Georgia Fitkid project: the relations between program attendance and changes in outcomes in year 1

OBJECTIVE

To investigate the relations of attendance of children in an after-school physical activity (PA) program to changes in body composition and cardiovascular fitness (CVF).

DESIGN

Eight-month after-school PA-based intervention.

SUBJECTS

In all, 278 third-grade boys and girls from nine elementary schools (age, 8.7 y (s.d. = 0.6 y), body mass index (BMI) 19.1 kg/m2 (s.d. = 4.4) and percent body fat (%BF) 26.0 (s.d. = 9.0)).

MEASUREMENTS

Body composition (from dual-energy X-ray absorptiometry), BMI (from height and weight), waist circumference (WC) and CVF (from the YMCA submaximal bench-stepping test).

RESULTS

There was a significant negative linear trend between level of attendance in the after-school program and change in %BF and fat mass; there was also a significant positive linear trend between program attendance and change in CVF. There was a marginally significant linear trend between program attendance and fat-free mass. Greater increases in bone mineral density were observed with higher program attendance. Changes in BMI and WC were not influenced by program attendance.

CONCLUSION

Understanding the dose-response effect of PA on health outcomes, particularly body composition, in children is crucial in our effort to prevent overweight and its health consequences. Since there is limited data available to base PA dose recommendations for youths, findings from this study are relevant, and suggest that greater health benefits can be obtained in young children with more frequent participation in PA.

Youth at risk of physical inactivity may benefit more from activity-related support than youth not at risk

Background

This study examines whether associations between activity-related support and adolescents' physical activity differ for adolescents at high versus low risk of physical inactivity.

Methods:

Participants included 202 middle-school-aged girls (N = 92) and boys (N = 110). Physical activity was assessed using three self-report questionnaires. Activity-related support from mothers, fathers, siblings, and peers was assessed using the Activity Support Scale. Perceived sport competence was assessed using the Physical Activity Self Description Questionnaire. Participants' height and weight were measured and used to calculate their age- and sex-adjusted Body Mass Index percentile. Participants were classified as being at high risk for physical inactivity if they fulfilled two of the following three criteria: (1) overweight; (2) female; or (3) having low perceived sport competence.

Results:

Activity-related support from all sources was associated with higher levels of physical activity among adolescents. A stronger association between activity support and physical activity was found for adolescents at high risk for physical inactivity in comparison to adolescents at low risk.

Conclusions:

Findings from this study suggest that the activity-related support from family and friends may be an effective tool in promoting physical activity among youth at risk of physical inactivity.

Efficacy of exercise for treating overweight in children and adolescents: a systematic review

BACKGROUND

Overweight prevalence among children/adolescents is increasing, while adult obesity may potentially cause a decline in life expectancy. More exercise is uniformly recommended, although treatment efficacy remains unclear.

OBJECTIVE

To determine the efficacy of exercise alone for treating overweight in children/adolescents.

DESIGN

A systematic review and meta-analysis of randomized trials published in English were completed following multiple database searches performed on December 10, 2004. Studies of isolated or adjunctive exercise/physical activity treatment in overweight/obese children or adolescents which reported any overweight outcome were included. Literature searches identified 645 papers which were manually searched, of which 45 were considered for inclusion, of which 13 papers which reported 14 studies were included (N=481 overweight boys and girls, aged approximately 12 years). Two reviewers independently identified relevant papers for potential inclusion and assessed methodological quality. Principal measures of effects included the mean difference (MD) (between treatment and control groups), the weighted MD (WMD), and the standardized MD (SMD).

RESULTS

Few studies were of robust design. The pooled SMD was -0.4 (-0.7, -0.1, P=0.006) for percent body fat, and -0.2 (-0.6, 0.1, P=0.07) for central obesity outcomes, whereas the pooled WMD was -2.7 kg (-6.1 kg, 0.8 kg, P=0.07) for body weight, all of which favored exercise. Pooled effects on body weight were significant and larger for studies of higher doses, whereas nonsignificant and smaller effects were seen for studies of lower doses of exercise (155-180 min/weeks vs 120-150 min/weeks).

CONCLUSIONS

Based on the small number of short-term randomized trials currently available, an aerobic exercise prescription of 155-180 min/weeks at moderate-to-high intensity is effective for reducing body fat in overweight children/adolescents, but effects on body weight and central obesity are inconclusive. Recommendations for future study designs are discussed.

An environmental approach to obesity prevention in children: Medical College of Georgia FitKid Project year 1 results

OBJECTIVE

To test the hypothesis that third grade children (mean age = 8.7, SD = 0.5) who attended an 8-month after-school program would exhibit favorable changes in body composition, cardiovascular fitness, blood pressure, total cholesterol, and high-density lipoprotein-cholesterol compared with children in control condition.

RESEARCH METHODS AND PROCEDURES

Subjects were 61% African-American, 31% white, and 8% other racial background from 18 public schools. Sixty-eight percent were eligible for free or reduced price lunch. Percentage body fat and bone mineral density were assessed by DXA, cardiovascular fitness by heart rate response to a step test, resting blood pressure with a Dinamap, and non-fasting total cholesterol and high-density lipoprotein-cholesterol by finger stick. Data pre- and post-intervention were available for 447 children. Children in the nine intervention schools who attended at least 40% of the after-school sessions were compared with control subjects.

RESULTS

Compared with the control subjects and after controlling for race, sex, free/reduced price lunch status, and school-level covariates, youths in the intervention group showed a relative reduction of percentage body fat [-0.76 (95% confidence interval (CI), -1.42, -0.09)], a greater relative gain in bone mineral density [0.008 (95% CI, 0.001, 0.005)], and a greater relative reduction in heart rate response to the step test [-4.4 (95% CI, -8.2, 0.6)]. The other outcome variables showed non-significant trends in favor of the intervention subjects.

DISCUSSION

These results are promising in light of the potential impact on the emerging childhood obesity epidemic. The Medical College of Georgia FitKid Project has the potential to be institutionalized because it is built on the existing infrastructure in most public schools in the U.S.

Heart Rate Variability in Adolescents: Relations to Physical Activity, Fitness, and Adiposity

PURPOSE

We determined the degree to which variation in cardiac autonomic modulation was explained by race, sex, moderate-vigorous physical activity (MVPA), cardiovascular fitness (CVF), percent body fat (%BF), waist girth, subcutaneous abdominal adipose tissue (SAAT), and visceral adipose tissue (VAT).

METHODS

Subjects were 304 adolescents; SAAT and VAT values were available for 168 youths. Cardiac parasympathetic modulation (PM) was the root mean square of successive differences (RMSSD). Sympathetic-parasympathetic balance was the ratio of low- to high-frequency power (LFnu:HFnu). MVPA was measured with accelerometry, CVF with a treadmill, %BF with dual-energy x-ray absorptiometry (DXA), and SAAT and VAT with magnetic resonance imaging (MRI).

RESULTS

Root mean square of successive differences was higher, and LFnu:HFnu was lower, in blacks than in whites. The final regression model revealed positive relations with CVF and MVPA, and a %BF by race by sex interaction, such that higher %BF was associated with lower RMSSD in black females and higher RMSSD in white females. Higher RMSSD was associated with lower VAT; for SAAT, the relationship was negative for blacks and positive for whites. For LFnu:Hfnu, a negative relationship was seen with MVPA and higher waist girth was associated with a higher ratio in blacks, but not in whites. Both higher VAT and SAAT were related to higher LFnu:HFnu.

CONCLUSIONS

Black youths had a more favorable HRV profile than white youths. After controlling for age, race, and sex, more favorable HRV profiles were associated with more MVPA, better CVF, and less visceral and subcutaneous adiposity. The deleterious impact of higher adiposity was greater in blacks, especially females, than in whites. Enhancement of cardiac autonomic modulation may be a pathway through which physical activity, fitness, and leanness contribute to cardiovascular health early in life.

A Review of Childhood and Adolescent Obesity Interventions

Obesity is one of the largest health problems facing Americans. Figures produced by the National Center for Health Statistics show that in 1999-2002, 15.8% of 6-11-year-olds were overweight as were 16.1% of adolescents aged 12-19. Some have proposed that interventions in childhood may be the best place to focus efforts to reduce the growing obesity epidemic. This paper examines several of the popular intervention strategies that have been proposed for youth and assesses the potential of these interventions for meaningful public health impacts. Findings show that most childhood obesity interventions completed to date produced only meager results, creating need for more well-designed studies that are tailored to the needs of specific age, ethnic and economic groups.

Links between parents' and girls' television viewing behaviors: a longitudinal examination

OBJECTIVE

This longitudinal study examines links between parents' television (TV)-related parenting practices and their daughter's daily TV viewing hours.

STUDY DESIGN

Participants included 173 non-Hispanic white girls and their parents who were examined when girls were age 9 and 11 years. Girls' daily TV viewing hours, mothers' and fathers' daily TV viewing hours, parents' use of TV as a recreational activity, family TV co-viewing, and parents' restriction of girls' access to TV were assessed.

RESULTS

Approximately 40% of girls exceeded the TV-viewing recommendations (ie, < or =2 hours/day). Girls watched significantly more TV when their parents were high-volume TV viewers, relied heavily on TV as a recreational activity, watched TV with them, and failed to limit their access to TV. A parenting risk score was calculated by collapsing information across all parenting variables. In comparison with girls exposed to 1 or fewer parenting risk factors at age 9, girls exposed to 2 or more parenting risk factors were 5 to 10 times more likely to exceed TV viewing recommendations at age 9 and 11.

CONCLUSIONS

Efforts to reduce TV viewing among children should encourage parents to limit their own TV viewing, reduce family TV viewing time, and limit their children's access to TV.

Bone outcomes and technical measurement issues of bone health among children and adolescents: considerations for nutrition and physical activity intervention trials

Weight-bearing physical activity and calcium intake are two important behavioral influences for bone health. Physical-activity and calcium-intake intervention trials with youth have been implemented to evaluate their efficacy and effectiveness to decrease the risk for subsequent osteoporosis and fractures. Technical aspects of bone measurement have not been routinely reported in published trials of youth, even though they can have an impact on study findings and interpretation. This paper provides an overview of the outcome variables reported, and technical issues--such as software and bone detection, growth, and movement--that affect bone mass measurements among children and adolescents. It describes the implications of these issues for the interpretation of intervention effects observed in intervention trials, and provides recommendations for future research.

Influence of an interpersonal laboratory stressor on youths' choice to be physically active

OBJECTIVE

To determine whether interpersonal stress reduces youths' motivation to exercise in a laboratory setting.

RESEARCH METHODS AND PROCEDURES

Physical activity and sedentary behavior were measured in boys and girls across a control day, after reading children's magazines, and on a stress day, after giving a videotaped speech. For one analysis, children were divided into low (n = 12) and high (n = 13) heart-rate reactivity groups based on changes in heart rate to stress. In a second analysis, children were divided into low and high perceived level of stress based on changes in perceived stress. To determine differences in choice of exercise or sedentary behavior across the control and stress conditions, subjects chose either to exercise for progressively longer periods to earn a monetary reinforcer or to engage in a high-rated sedentary behavior.

RESULTS

The choice to exercise was influenced by stress reactivity differently in the stress and control conditions. Low heart-rate reactive children participated in similar (p > 0.50) amounts of exercise on the stress and control days, but high heart-rate reactive children participated in less (p < 0.01) exercise (22.0 +/- 2.5 vs. 26.3 +/- 2.2 minutes) on the stress than control days. When grouped by change in perceived stress, there were no group differences, but subjects exercised longer (p < 0.01) on the control day than the stress day.

DISCUSSION

Interpersonal stress decreased exercise in children susceptible to interpersonal stress. Stress-induced alterations in health behaviors may lead to weight gain in children.

Interventions for treating obesity in children

BACKGROUND

The prevalence of overweight and obesity is increasing in child populations throughout the world. Obesity in children has significant short and long term health consequences.

OBJECTIVES

To assess the effects of a range of lifestyle interventions designed to treat obesity in childhood.

SEARCH STRATEGY

We searched CCTR, MEDLINE, EMBASE, CINAHL, PsychLIT, Science Citation Index, Social Science Citation Index. Each database was searched from 1985 to July 2001. We also contacted experts in child obesity treatment.

SELECTION CRITERIA

We selected randomised controlled trials of lifestyle interventions for treating obesity in children with a minimum of six months duration. Examples of lifestyle interventions include dietary, physical activity and/or behavioural therapy interventions, with or without the support of associated family members. Interventions from any setting and delivered by any professional were considered. However, interventions that specifically dealt with the treatment of eating disorders were excluded.

DATA COLLECTION AND ANALYSIS

Two of our research team independently assessed trial quality and extracted data. Authors of the included studies were contacted for additional information where this was appropriate.

MAIN RESULTS

We included 18 randomised controlled trials with 975 participants. Many studies were run from a specialist obesity clinic within a hospital setting. Five studies (n=245 participants) investigated changes in physical activity and sedentary behaviour. Two studies (n=107 participants) compared problem-solving with usual care or behavioural therapy. Nine studies (n=399 participants) compared behavioural therapy at varying degrees of family involvement with no treatment or usual care or mastery criteria and contingent reinforcement. Two studies (n=224 participants) compared cognitive behavioural therapy with relaxation.Most of the studies included in this review were too small to have the power to detect the effects of the treatment. We did not conduct a meta-analysis since so few of the trials included the same comparisons and outcomes. Therefore, we synthesised the results in a narrative format.

REVIEWER'S CONCLUSIONS

Although 18 research studies were found, most of these were very small studies drawn from homogenous, motivated groups in hospital settings and so generalisable evidence from them is limited. In conclusion, there is a limited amount of quality data on the components of programs to treat childhood obesity that favour one program over another. Further research that considers psychosocial determinants for behaviour change, strategies to improve clinician-family interaction, and cost-effective programs for primary and community care is required. We conclude that no direct conclusions can be drawn from this review with confidence.

Physical training improves insulin resistance syndrome markers in obese adolescents

INTRODUCTION

The purpose of this study was to test the hypothesis that physical training (PT), especially high-intensity PT, would have a favorable effect on components of the insulin resistance syndrome (IRS) in obese adolescents.

METHODS

Obese 13- to 16-yr-olds (N = 80) were randomly assigned to one of the following 8-month interventions; 1) lifestyle education (LSE)-alone every 2 wk, 2) LSE+moderate-intensity PT, and 3) LSE+high-intensity PT. PT was offered 5 d x wk(-1). Plasma triacylglycerol (TAG), total cholesterol (TC), high-density lipoprotein cholesterol (HDLC), very low-density lipoprotein cholesterol (VLDLC), low-density lipoprotein cholesterol (LDLC), low-density lipoprotein (low density lipoprotein (LDL)) particle size, apolipoproteins AI and B, glucose, insulin, and blood pressure were measured with standardized methods.

RESULTS

The intent-to-treat analyses for all subjects who completed pre- and post-tests regardless of their adherence to the interventions showed that the LSE+high-intensity PT group had more favorable changes than the LSE-alone group in TAG level (P = 0.012), TC/HDLC (P = 0.013), and diastolic blood pressure (P = 0.031). For efficacy analyses, all PT subjects who attended at least 2 d x wk(-1) (40%) were combined into one group (LSE+PT) and compared with the LSE-alone group. These two-group analyses showed significant interactions (P < 0.001) between baseline values and group membership for deltaTAG, deltaVLDLC, and deltaTC/HDLC, such that subjects who had the least favorable baseline values showed the most beneficial impact of the PT. Of particular interest was a favorable effect of the PT on LDL particle size.

CONCLUSION

PT, especially high-intensity PT, had a favorable effect on several IRS markers in obese adolescents.

Relations of adiposity and effects of training on the left ventricle in obese youths

PURPOSE

1) To determine the relations of left ventricular (LV) structure and function to total body composition, visceral adipose tissue (VAT), and hemodynamics in obese children; 2) to determine the effects of 4-month of physical training (PT) on LV structure and function and hemodynamics; and 3) to explore determinants of individual variability in response to PT.

METHODS

Measurements included LV structure/function with echocardiography, total body composition with dual-energy x-ray absorptiometry, VAT with magnetic resonance imaging (MRI), and resting and exercising hemodynamics with a Dinamap monitor and Doppler-echocardiography. Youths were randomly assigned to engage in PT for the first or second 4-month periods of the 8-month intervention period.

RESULTS

Correlation and regression at baseline showed that elevated LV mass was associated with excess general and visceral adiposity, and elevated cardiac output. Although the PT had favorable effects on percent body fat and VAT, no significant changes were found in LV or hemodynamic variables. Over the 4-month period of the PT intervention, those who increased the most in VAT tended to increase the most in LV mass.

CONCLUSION

General and visceral adiposity were associated with elevated LV mass. However, no evidence was provided that 4 months of PT had a significant effect on LV or hemodynamic variables.

Effects of exercise intensity on cardiovascular fitness, total body composition, and visceral adiposity of obese adolescents

BACKGROUND

Little is known about how the intensity of exercise influences cardiovascular fitness and body composition, especially in obese adolescents.

OBJECTIVE

Our goal was to determine the effects of physical training intensity on the cardiovascular fitness, percentage of body fat (%BF), and visceral adipose tissue (VAT) of obese adolescents.

DESIGN

Obese 13-16-y-olds (n = 80) were assigned to 1) biweekly lifestyle education (LSE), 2) LSE + moderate-intensity physical training, or 3) LSE + high-intensity physical training. The intervention lasted 8 mo. Physical training was offered 5 d/wk, and the target energy expenditure for all subjects in physical training groups was 1047 kJ (250 kcal)/session. Cardiovascular fitness was measured with a multistage treadmill test, %BF with dual-energy X-ray absorptiometry, and VAT with magnetic resonance imaging.

RESULTS

The increase in cardiovascular fitness in the high-intensity physical training group, but not in the moderate-intensity group, was significantly greater than that in the LSE alone group (P = 0.009); no other comparisons of the 3 groups were significant. Compared with the LSE alone group, a group composed of subjects in both physical training groups combined who attended training sessions >or=2 d/wk showed favorable changes in cardiovascular fitness (P < 0.001), %BF (P = 0.001), and VAT (P = 0.029). We found no evidence that the high-intensity physical training was more effective than the moderate-intensity physical training in enhancing body composition.

CONCLUSIONS

The cardiovascular fitness of obese adolescents was significantly improved by physical training, especially high-intensity physical training. The physical training also reduced both visceral and total-body adiposity, but there was no clear effect of the intensity of physical training.

Association of lean tissue and fat mass with bone mineral content in children and adolescents

OBJECTIVES

There has been uncertainty in the adult body composition literature about whether fat mass (FM) or fat free mass is a better predictor of bone mineral content and bone mineral density. This issue has recently also been raised in the pediatric literature. Based on suggested skeletal muscle-bone relationships, this study tested the hypothesis that in children and adolescents lean tissue mass (LTM) is a better predictor of total bone mineral content (TBMC) than is FM.

RESEARCH METHODS AND PROCEDURES

Subjects were 133 Italian children and adolescents, 5 to 17 years of age, undergoing a routine medical screen. FM (kilograms), LTM (kilograms), and TBMC (kilograms) were measured by DXA. Multiple regression analyses tested the independent association of FM and LTM with bone mineral content.

RESULTS

Regression analyses, adjusting for pubertal status and other covariates, showed that FM and LTM were independently associated with TBMC. These associations were similar for boys and girls. TBMC was more strongly associated with LTM than FM.

DISCUSSION

These observations support the hypothesis that in children and adolescents a close association exists between LTM, a measure of skeletal muscle, and skeletal characteristics.

Child and parent characteristics as predictors of change in girls' body mass index

OBJECTIVE

This study assessed predictors of change in girls' body mass index (BMI) between ages 5 and 7 y and familial aggregation of risk factors associated with childhood overweight.

METHOD

Participants included 197 5-y-old girls and their parents, of whom 192 were reassessed when girls were 7-y-old. Three classes of predictors of girls' change in BMI were assessed including girls' and parents' weight status, dietary intake and physical activity. Girls' and parents' BMI and change in BMI were calculated based on height and weight measurements. Girls' dietary intake was assessed using three 24 h recalls; parents' intake was assessed using a food frequency questionnaire. Girls and mothers provided reports of girls' physical activity; parents' frequency and enjoyment of activity were assessed using a self-administered questionnaire.

RESULTS

The most effective model predicting girls' change in BMI between ages 5 and 7 included both child and parent characteristics, specifically girls' BMI at age 5, mothers' change in BMI, fathers' energy intake, fathers' enjoyment of activity, and girls' percentage of energy from fat. In addition, results showed substantial intra-familial associations in weight status and dietary intake and to a lesser extent physical activity, and the presence of multiple risk factors within families. Associations were also noted between girls' and parents' change in BMI.

CONCLUSIONS

Results from this study highlight the centrality of the family in the etiology of childhood overweight and the necessity of incorporating parents in the treatment of childhood overweight.

Energy expenditure, physical activity, and obesity in children

Although there are physiologic and genetic influences on the various components of energy metabolism and body weight regulation, and a major portion of individual differences in body weight can be explained by genetic differences, it seems unlikely that the increased global prevalence of obesity has been driven by a dramatic change in the gene pool. It is more likely and more reasonable that acute changes in behavior and environment have contributed to the rapid increase in obesity and that genetic factors may be important in the deferring individual susceptibilities to these changes. The most striking behavioral changes that have occurred have been an increased reliance on high-fat and energy-dense "fast foods," with larger portion sizes, coupled with an ever-increasing sedentary lifestyle. The more sedentary lifestyle is caused by an increased reliance on technology and labor-saving devices, which has reduced the need for physical exertion for everyday activities. Examples of energy-saving devices that have resulted in a secular decline in physical activity include: Increased use of automated transport rather than walking or biking Central heating and use of automated equipment, such as washing machines, in the household. Reduction in physical activity in the workplace because of computers, automated equipment, and electronic mail. Increased use of television and computers for entertainment and leisure activities. Use of elevators and escalators rather than stairs. Increased concern for crime, which has reduced the likelihood of outdoor playing. Poor urban planning that does not provide adequate biking paths or even sidewalks in some communities. Thus, the increasing prevalence, numerous health risks, and astounding economic costs of obesity clearly justify widespread efforts toward prevention efforts. These prevention efforts should begin in childhood because the behaviors are learned and continue through the lifetime.

Childhood overweight: a contextual model and recommendations for future research

The prevalence of overweight among children has doubled within the past two decades. Increases in the rate of childhood overweight are of particular concern due to the negative health and psychological effects noted among overweight children. As shown by previous research, the development of childhood overweight involves a complex set of factors from multiple contexts that interact with each other to place a child at risk of overweight. This multifaceted system can be conceptualized using Ecological Systems Theory (EST). EST highlights the importance of considering the context(s), or ecological niche, in which a person is located in order to understand the emergence of a particular characteristic. In the case of a child, the ecological niche includes the family and the school, which are in turn embedded in larger social contexts including the community and society at large. In this review, EST is used as a framework with which to summarize research assessing predictors of childhood overweight. Specifically, child characteristics that place children at risk of the development of overweight (including dietary intake, physical activity, and sedentary behaviour) will be reviewed while taking into consideration the influence of the familial environment, the school environment, and the community and larger social environments. It is concluded that future research needs to adopt a broader contextual approach in order to understand and intervene against the processes leading to the development of overweight among children and that the use of theories or paradigms such as EST will facilitate developing and testing models of causal processes.

Dose-response of physical activity and low back pain, osteoarthritis, and osteoporosis

PURPOSE

The purpose of this study was to examine the evidence for causal relationships between physical activity (PA) and low back pain (LBP), osteoarthritis (OA), and osteoporosis (OP), and for dose-response relations involved.

METHODS

Computer database searches and personal retrieval systems were used to locate relevant literature.

RESULTS

PA can be effective in preventing LBP (Category A) but prolonged, heavy loading can lead to LBP (Category C). Specific exercises have not been found effective in treatment of acute LBP (Category A), but PA can be effective in chronic LBP (Category B), especially for diminishing the effects of deconditioning. No evidence indicates that PA directly prevents OA. Large amounts of intensive PA involving high impacts or torsional loadings or causing injuries increases risk of OA (Category C). Light or moderate PA does not increase the risk of OA (Category C). PA can be effective in the treatment and rehabilitation of OA (Category B). High-intensity loading is osteogenic and possibly useful in prevention of OP (Category A) at the loaded site, but low to moderate loading is not osteogenic (Category D). Static efforts and slow movements are ineffective or less effective than fast application of force (Category B). The types of PA to attain the effects mentioned above are known except in the case of prevention of LBP, but dose-response relationships are poorly known; at best, semiquantitatively on the basis of just a few studies.

CONCLUSION

Given the shown primary and/or secondary preventative effectiveness of PA regarding LBP, OA, and OP, research to elucidate the inadequately known dose-response relations should be given high priority.

Training, muscle volume, and energy expenditure in nonobese American girls

Little is known about the relationship among training, energy expenditure, muscle volume, and fitness in prepubertal girls. Because physical activity is high in prepubertal children, we hypothesized that there would be no effect of training. Forty pre- and early pubertal (mean age 9.1 +/- 0.1 yr) nonobese girls enrolled in a 5 day/wk summer school program for 5 wk and were randomized to control (n = 20) or training groups (n = 20; 1.5 h/day, endurance-type exercise). Total energy expenditure (TEE) was measured using doubly labeled water, thigh muscle volume using magnetic resonance imaging, and peak O(2) uptake (VO(2 peak)) using cycle ergometry. TEE was significantly greater (17%, P < 0.02) in the training girls. Training increased thigh muscle volume (+4.3 +/- 0.9%, P < 0.005) and VO(2 peak) (+9.5 +/- 6%, P < 0.05), effects surprisingly similar to those observed in adolescent girls using the same protocol (Eliakim A, Barstow TJ, Brasel JA, Ajie H, Lee W-NP, Renslo R, Berman N, and Cooper DM, J Pediatr 129: 537-543, 1996). We further compared these two sample populations: thigh muscle volume per weight was much lower in adolescent compared with prepubertal girls (17.0 +/- 0.3 vs. 27.8 +/- 0.6 ml/kg body mass; P < 0.001), and allometric analysis revealed remarkably low scaling factors relating muscle volume (0.34 +/- 0.05, P < 0.0001), TEE (0.24 +/- 0. 06, P < 0.0004), and VO(2 peak) (0.28 +/- 0.07, P < 0.0001) to body mass in all subjects. Muscle and cardiorespiratory functions were quite responsive to brief training in prepubertal girls. Moreover, a retrospective, cross-sectional analysis suggests that increases in muscle mass and VO(2 peak) may be depressed in nonobese American girls as they mature.

Increasing weight-bearing physical activity and calcium intake for bone mass growth in children and adolescents: a review of intervention trials

OBJECTIVE

The purpose of this review is to evaluate the current state-of-the-science for interventions to increase bone mass gains in children and adolescents using weight-bearing physical activity or calcium supplementation.

METHODS

Studies were located using computerized and manual searches of the empirical literature. Inclusion criteria were: (a) intervention study targeting weight-bearing physical activity or calcium intake; (b) inclusion of a control group; (c) subject age range under 18 years; and (d) outcome measured bone mineral density or bone mineral content.

RESULTS

Weight-bearing physical activity and calcium supplement intervention studies both consistently show positive effects on bone mass gains in children and adolescents. The most consistent findings for both weight-bearing physical activity and calcium were for lumbar spine and total body bone sites. Only weight-bearing physical activity interventions had significant effects on the femoral neck sites. Low power may have contributed to the lack of statistically significant findings in several studies and also prevented proper evaluation of potential interactions between pubertal status and interventions on bone mass gains.

CONCLUSIONS

Increases in weight-bearing physical activity or calcium intake have positive effects on bone mass gains in children and adolescents. Further research is needed to evaluate: (a) the long-term durability of these effects; (b) specific dose-response associations; (c) interactions between weight-bearing physical activity and calcium intake; and (d) interactions between pubertal development and weight-bearing physical activity or calcium intake on bone mass outcomes.

Heart rate variability in obese children: relations to total body and visceral adiposity, and changes with physical training and detraining

OBJECTIVE

Heart rate variability provides non-invasive information about cardiac parasympathetic activity (PSA). We determined in obese children: (1) relations of baseline PSA to body composition and hemodynamics; (2) effects of physical training (PT) and cessation of PT; and (3) which factors explained individual differences in responsivity of PSA to the PT.

RESEARCH METHODS AND PROCEDURES

The root mean square of successive differences (RMSSD) was the index of PSA. Obese children (n = 79) were randomly assigned to groups that participated in PT during the first or second 4-month periods of the study.

RESULTS

Baseline RMSSD was significantly (p<0.05) associated with lower levels of: fat mass, fat-free mass, subcutaneous abdominal adipose tissue, resting heart rate (HR), resting systolic blood pressure, and exercise HR. Stepwise multiple regression produced a final model (R2 = 0.36) that included only resting HR. The analysis of changes over the three time points of the study found a significant (p = 0.026) time by group interaction, such that RMSSD increased during periods of PT and decreased following cessation of PT. Greater individual increases in response to the PT (p<0.05) were seen in those who had lower pre-PT RMSSD levels, showed the greatest decreases in resting HR, and increased most in vigorous physical activity. The final regression model retained only the change in resting HR as a significant predictor of the changes in the RMSSD (R2 = 0.23).

DISCUSSION

Regular exercise that improved fitness and body composition had a favorable effect on PSA in obese children.