Objectively measured physical activity and fat mass in children: a bias-adjusted meta-analysis of prospective studies

Association between physical activity, smartphone usage, and obesity risk among Korean adolescents: A cross-sectional study based on 2021 Korean adolescent health behavior survey

BACKGROUND

With adolescent obesity rates steadily rising, it has become crucial to identify modifiable risk factors to develop effective interventions. This study explores the associations between physical activity (PA) levels, smartphone usage, and obesity risk among Korean adolescents, aiming to inform the design of targeted health promotion programs to mitigate obesity rates in this demographic.

METHODS

This cross-sectional analysis used data from 50,407 Korean adolescents who participated in the 2021 Adolescent Health Behavior Online Survey. Descriptive statistics and chi-square tests compared PA patterns, sedentary behavior, and smartphone usage between adolescents with obesity and those without obesity. To examine the impact of key exposure factors-including PA, muscle strengthening exercises (MSE), sedentary behavior, and smartphone usage-on obesity risk, binary logistic regression models were used, adjusting for grade level, economic status, and other potential confounders.

RESULTS

Male adolescents exercising "3-4 times/week" had a significantly higher obesity risk compared to those with no PA (OR = 1.144, 95 % CI: 1.032-1.267, p < 0.01). Similarly, females exercising "3-4 times/week" (OR = 1.208, 95 % CI: 1.048-1.393, p < 0.01) or "≥ 5 times/week" (OR = 1.333, 95 % CI: 1.087-1.636, p < 0.01) also showed increased risk. Both males and females participating in high-intensity PA (HIPA) "1-2 times/week" were at higher risk (males: OR = 1.110, 95 % CI: 1.011-1.219, p < 0.01; females: OR = 1.427, 95 % CI: 1.283-1.587, p < 0.001). Conversely, MSE was linked to a significant reduction in obesity risk across most frequency groups, especially in males (OR = 0.450, 95 % CI: 0.399-0.508, p < 0.001). For sedentary behavior, females with ≥6 h of weekday non-learning sedentary time (SWD-N) had increased obesity risk (OR = 1.210, 95 % CI: 1.002-1.462, p < 0.01), as did males with ≥6 h of weekend sedentary time (SWK-N) (OR = 1.334, 95 % CI: 1.154-1.542, p < 0.001) and females with ≥6 h of weekend smartphone usage (SPWK_TM) (OR = 1.567, 95 % CI: 1.066-2.303, p < 0.01).

CONCLUSIONS

The findings reveal complex relationships between PA, MSE, sedentary behavior, and smartphone usage in the context of adolescent obesity. Certain PA levels, particularly 3-4 times/week and ≥ 5 times/week for females, and HIPA frequency were associated with increased obesity risk. In contrast, MSE significantly reduced obesity risk across genders, with the most substantial effects observed in males engaging in MSE ≥ 5 times/week. Only associations meeting the p < 0.01 threshold were interpreted in this study to ensure robust conclusions. These results emphasize the importance of promoting MSE and balanced sedentary behavior patterns to reduce adolescent obesity risk, suggesting health policies should address these factors with a focus on gender-specific and age-specific strategies. However, limitations such as the lack of nutrition data, unassessed PA intensity, and HIPA duration should be addressed in future research.

Physical Activity Predicts Better Lung Function in Children and Adolescents

PURPOSE

To investigate (1) whether physical activity is associated with lung function in children and adolescents, (2) whether this association is modified by the subjects' weight status, and (3) whether this association is mediated by the body mass index.

METHODS

This is a cross-sectional study including 460 participants aged 7-17 years, randomly selected from 13 public schools in southern Brazil. Collected data included anthropometric measures, physical activity, screen time, and spirometric measures expressed as percent predicted values. Data were analyzed using multiple linear regression and 2-way analysis of variance.

RESULTS

There were positive associations between physical activity and forced vital capacity (β = 3.897, P = .001) and forced expiratory volume in the first second (β = 2.931, P = .021). The effect modification by weight status was not statistically significant (forced vital capacity: Pinteraction = .296 and forced expiratory volume in the first second: Pinteraction = .057). Body mass index did not mediate the association between physical activity and spirometric outcomes (P > .05).

CONCLUSION

Regular physical activity was associated with higher forced vital capacity and forced expiratory volume in the first second in children and adolescents. The observed associations were not modified by weight status nor mediated by body mass index. Our results reinforce the importance of regular physical activity for the development of lung function during childhood and adolescence.

Physical Activity, Sedentary Behaviour, Weight Status, and Body Composition among South African Primary Schoolchildren

Background: Over the past decades, childhood overweight has increased in many African countries. We examined the relationship between sedentary behaviour, moderate-to-vigorous physical activity (MVPA), and body composition in South African primary schoolchildren living in peri-urban settings. Methods: MVPA was measured via 7-day accelerometry and body composition via bioelectrical impedance analysis in 1090 learners (49.2% girls, M_age = 8.3 ± 1.4 years). The relationships between MVPA and sedentary behaviour with the various body composition indicators (body fat and fat-free mass [total, truncal, arms, and legs], bone mass, muscle mass, and body water) were tested with mixed linear regressions. Results: The prevalence of overweight and obesity was 9.8% and 6.6%, respectively; 77.1% of the children engaged in ≥60 min of MVPA/day. Girls were more likely to be overweight/obese, to accumulate less than 60 min of MVPA/day, and had significantly higher relative body fat than boys (ps < 0.001). Lower MVPA was associated with a higher likelihood of being overweight/obese, higher relative body fat, and lower relative fat-free mass, bone mass, muscle mass, and body water (ps < 0.001). For lower sedentary behaviour, the associations with body composition pointed in the opposite direction. Conclusions: In this South African setting, girls are a particularly relevant target group for future physical activity interventions to prevent overweight/obesity-related non-communicable diseases in later life.

Physical activity and childhood asthma control: Mediation and moderation role of body mass index

BACKGROUND

Physical activity (PA) may be associated with asthma management. Whether PA is associated with childhood asthma control is not well studied, and the role of body mass index (BMI) in this association remains unclarified. This study aimed to evaluate the association between PA and childhood asthma control and investigate the potential mediating and modifying role of BMI in the association.

METHODS

This cross-sectional study involved 303 asthmatic children aged 5-14 years. Information on PA was collected from children. Asthma control was assessed using a valid questionnaire by children and their parents. Height and weight were objectively measured and BMI was calculated and classified. Multiple linear regression, mediation, and moderation analyses were performed.

RESULTS

There was a positive association between PA and childhood asthma control with adjustment for variates (B = 0.144, p = .012). Mediation analysis indicated that BMI status negatively mediated the association (estimate = -0.656, 95% credit interval: -1.645, -0.006), and such indirect effect is lower than the direct effect (indirect effect/direct effect = 58.3%). No evidence of effect modification by BMI was observed (P_interaction = 0.516). Stratified analyses showed that the significant association was only observed in children with overweight/obesity (normal weight: B = 0.863, p = .189; overweight/obese: B = 1.494, p = .044).

CONCLUSIONS

Increased PA is associated with improved childhood asthma control, especially for children with higher BMI. BMI exhibited a negative effect but not effect modification in this association. PA should be encouraged to improve asthma control for asthmatic children. Besides, mechanisms other than weight loss may explain the association.

Development and Content Validity of the Physical Activity Questionnaire-Young Children (PAQ-YC) to Assess Physical Activity in Children between 5 and 7 Years

Childhood is a critical period in the development and consolidation of healthy habits, such as the practice of physical activity (PA). It is essential to have valid instruments to measure PA from an early age. The aim of this study was to design and evaluate the content validity of the Physical Activity Questionnaire-Young Children (PAQ-YC) to measure the PA level in children aged 5-7 years. The first version of the questionnaire was tested by a 2-round Delphi study. It was established as a consensus criterion that the relative interquartile range (RIR) and/or the coefficient of variation (CV) were ≤20%. The most significant discrepancies in the Delphi survey (n = 11-13) were observed for items about hours of Physical Education or similar activities at school (item 7: RIR = 20, CV = 38.73) and for items about participation in Physical Education (item 8: RIR = 25, CV = 15.45). The cognitive interviews (n = 5) confirmed the version agreed by the experts. The results show that the PAQ-YC presents adequate content validity in terms of relevance, comprehensiveness and comprehensibility.

Clinic- and Community-Based National Diabetes Prevention Programs in Los Angeles

Clinics and community-based organizations (CBOs) are priority settings for implementing the evidence-based National Diabetes Prevention Program (DPP). Both program settings present theoretical advantages and disadvantages for engaging and helping populations most at risk for diabetes achieve lifestyle change goals. To date, few studies have compared implementation across them. The present study describes participant characteristics and lifestyle change outcomes across a sample of clinic- and community-based National DPPs which delivered services in Los Angeles during 2015 to 2018 (two clinics, two CBOs, combined n = 265 participants). Analyses examined participant gender, age, race/ethnicity, baseline body mass index, and program attributes such as screening method and language of instruction. Negative binomial regression models tested for differences in program attendance, mean weekly physical activity, and percent change in body weight by setting. Overall, participants were largely Hispanic/Latinx (81.51%) and female (90.19%). Programs operated by CBOs engaged other race/ethnic groups including Black participants more frequently than those operated by clinics (20.56% vs. 0%); the latter engaged more men (15.29% vs. 7.22%). Few participants in any setting met the National DPP's weight loss goal (clinic: 15.29%, CBO: 20.00%). Participating in a community-based program was initially associated with higher attendance and mean weekly physical activity, but associations were not significant after adjusting for covariates. Study results have practice implications for National DPP implementation and can help inform future efforts to scale and spread the program in Los Angeles and nationally.

Associations of Physical Activity and Sedentary Behaviour Assessed by Accelerometer with Body Composition among Children and Adolescents: A Scoping Review

The possible adverse health effects of reduced physical activity (PA) on children and adolescents have been extensively documented as a result of the global obesity epidemic. However, the research has sometimes led to controversial results, due to the different methods used for the assessment of PA. The main aim of this review was to evaluate the association between PA and body composition parameters based on quantitative PA studies using the same equipment (Actigraph accelerometer) and cutoffs (Evenson’s). A literature review was undertaken using PUBMED and Scopus databases. Subjects aged 6–15 were considered separately by sex. Weighted multiple regression analyses were conducted. From the analysis of fourteen selected articles, it emerged that 35.7% did not evaluate the association of sedentary time (ST) and moderate-to-vigorous physical activity (MVPA) with body composition, while the remaining 64.3% found a negative association of MVPA with BMI and fat mass with different trends according to sex. Furthermore, only 7.1% of these studies identified a positive association between ST and fat percentage. Based on the regression analyses conducted on the literature data, ST and MVPA were found to be significant predictors of body composition parameters, in addition to age and sex. Further studies using standardized methodologies to assess PA and body composition are needed. The inclusion of sex-disaggregated data may also be crucial to understand this phenomenon and to provide stronger evidence of the determinants of body composition in order to prevent the risk of obesity.

Trends of low physical activity among Iranian adolescents across urban and rural areas during 2006-2011

It is well documented that physical inactivity is related to weight gain and a whole host of chronic diseases. This study investigated trends of low physical activity among Iranian adolescents in urban and rural areas between 2006-2011. A total of 12,178 adolescents, aged between 15 and 19 years, participated in National Surveys of Risk Factors for Non-Communicable Diseases. Data on physical activity was obtained using the global physical activity questionnaire. A complex sample survey and multinomial logistic regression were used to model physical activity levels. The percentage of adolescents who had low levels of physical activity increased from 2006 to 2011 in both urban and rural areas. Low and moderate levels of physical activity were lower in rural girls as compared with urban girls, with a prevalence ratio of 0.59 (95% CI 0.47-0.74) and 0.59 (95% CI 0.47-0.74), respectively. The corresponding values for boys residing in rural areas compared with boys in urban areas were 0.56 (95% CI 0.43-0.75) and 0.60 (95% CI 0.48-0.74), respectively. The adolescents' lifestyles showed an increasing trend for physical inactivity in both genders; however, in rural areas, only girls had a rising affinity for a sedentary lifestyle throughout the 2006-2011 years.

Organised physical activity during leisure time is associated with more objectively measured physical activity among Swedish adolescents

AIM

The aim of this study was to investigate associations between participation in organised physical activity (PA), such as sport and exercise during leisure time, and objectively measured PA and sedentary time in a large representative sample of Swedish adolescents.

METHODS

This study was part of the school-based cross-sectional Swedish national dietary survey Riksmaten Adolescents 2016-17. Data from 3477 adolescents aged 11-12, 14-15 and 17-18 years were used in the analyses. Participation in organised PA and parental education were reported in questionnaires. PA and sedentary time were objectively measured through accelerometry during seven consecutive days.

RESULTS

Adolescents who participated in organised PA had significantly higher total PA (14%, P < .001), more time spent on moderate-to-vigorous PA (MVPA) (8 minutes, P < .001) and had less sedentary time (15 minutes, P < .001). Those who participated in organised PA were more likely to reach recommended PA levels. Total PA and MVPA did not differ by parental education among those who participated in organised PA.

CONCLUSION

Adolescents who participated in organised PA were more physically active, less sedentary and more likely to reach PA recommendations than those who did not.

Maternal and child factors associated with child body fatness in a Ghanaian cohort

OBJECTIVE

We aimed to identify factors (child diet, physical activity; maternal BMI) associated with body composition of Ghanaian pre-school children.

DESIGN

Longitudinal analysis of the International Lipid-Based Nutrient Supplements (iLiNS)-DYAD-Ghana randomized trial, which enrolled 1320 pregnant women at ≤20 weeks' gestation and followed them and their infants until 6 and 18 months postpartum, respectively. At follow-up, child age 4-6 years, we collected data on body composition (by 2H dilution), physical activity and diet, extracted dietary patterns using factor analysis, and examined the association of children's percentage body fat with maternal and child factors by regression analysis.

SETTING

Eastern Region, Ghana.

PARTICIPANTS

Children 4-6 years of age.

RESULTS

The analysis included 889 children with percentage body fat and dietary data at follow-up. We identified two major dietary patterns, a snacking and a cooked foods pattern. Percentage body fat was positively associated (standardized β (se)) with maternal BMI at follow-up (0·10 (0·03); P = 0·003) and negatively associated with physical activity (-0·15 (0·05); P = 0·003, unadjusted for child gender), but not associated with the snacking (0·06 (0·03); P = 0·103) or cooked foods (-0·05 (0·07); P = 0·474) pattern. Boys were more active than girls (1470 v. 1314 mean vector magnitude counts/min; P < 0·0001) and had lower percentage body fat (13·8 v. 16·9 %; P < 0·0001).

CONCLUSIONS

In this population, maternal overweight and child physical activity, especially among girls, may be key factors for addressing child overweight/obesity. We did not demonstrate a relationship between the dietary patterns and body fatness, which may be related to limitations of the dietary data available.

Levels of Physical Activity, Obesity and Related Factors in Young Adults Aged 18-30 during 2009-2017

The objective of this study was to analyze the temporal trend of physical activity and body mass index in young adults aged 18–30 in Spain and to ascertain their relationship with sociodemographic and psychosocial variables in the period of 2009–2017. Methods: A descriptive study with a sample of 10,061 young adults aged 18–30 years was performed. The data were obtained from the European Health Survey in Spain in 2009 and 2014 and the National Health Survey in 2011/2012 and 2017. The chi-square test was used for qualitative variables, and multiple linear regression analysis was performed for physical activity. Results: Sedentary levels had decreased in 2017 as compared to 2011/2012 (p < 0.001); smokers were more sedentary than non-smokers (p < 0.001); men were more active than women (p < 0.001); and the year with the highest physical activity was 2014. Body mass index in the total sample increased from 2009 to 2017 (p < 0.01), showing a significant increase in obesity in women (p < 0.05) and no difference in men (p ≥ 0.05). Conclusions: In the period 2011/2012–2017, the sedentary lifestyle of young adults was reduced and physical activity was increased, with men being more active than women.

Prevention and treatment of childhood and adolescent obesity: a systematic review of meta-analyses

BACKGROUND

The goal of this systematic review is to synthesize the published meta-analyses assessing the role of nutritional, behavioral and physical activity factors/interventions on the prevention or treatment of pediatric and adolescent obesity.

METHODS

An online search was conducted in PubMed (end-of-search: September 30, 2015); English-language meta-analyses pooling observational and/or interventional studies examining weight-related indices on children and adolescents were included.

RESULTS

Sixty-six meta-analyses corresponding to more than 900,000 children and adolescents were retrieved. The majority of meta-analyses included interventional studies most of which referred to mixed or combined interventions, including components such as diet, physical activity and sedentary behavior reduction. Discrepancies between meta-analyses on observational and interventional studies were noted. Combined interventions including physical activity and nutritional modifications seemed to represent the most effective means for tackling childhood obesity.

CONCLUSIONS

Synthesis of interventional or observational evidence may yield discrepant results. The combination of enhanced physical activity and improved nutrition emerged as a promising intervention in the fight against childhood/adolescent obesity. However, further research is needed about the most effective multidimensional prevention strategy.

Longitudinal analysis of physical activity, sedentary behaviour and anthropometric measures from ages 6 to 11 years

BACKGROUND/OBJECTIVES

The aim of this study was to examine the effect of physical activity (PA) and sedentary behaviour (SB) on body mass index (BMI) and fat mass index (FMI) in children over the course of five years and identify potential bi-directional associations.

SUBJECTS/METHODS

Data were drawn from the EU Childhood Obesity Project (CHOP). PA and SB were measured with the SenseWear Armband 2 at the ages of 6 (T1), 8 (T2) and 11 (T3) years. Height and weight were measured and BMI was calculated at each time point, resulting in 1254 complete observations from 600 children. Bio impedance analysis was used to measure body fat mass and eventually calculate FMI. To examine the longitudinal association between PA/SB and BMI/FMI as well as to account for repeated measure on these children, mixed model analysis was employed.

RESULTS

Higher levels of total PA and moderate-to-vigorous PA (MVPA) were associated with lower BMI and FMI and higher SB with higher BMI and FMI over the five year period. When looking at the age dependent effects, negative associations of MVPA (β_{MVPA x age}: - 0.05, 95% confidence interval (CI): - 0.09 - -0.01, p = 0.007) and positive associations of SB (β_{SB x age}: 0.04, 95% CI: 0.02-0.06, p < 0.001) increased with each year of age. In a model combining these two effects, only SB x age interaction remained significant (β_{SB x age}: 0.04, 95% CI: 0.03-0.06, p = 0.01). No significant interaction between MVPA and SB could be discerned. Light Physical activity showed no significant associations with BMI or FMI. When reversing outcome and predictor; higher BMI or FMI showed a negative association with MVPA and a positive association with SB, but no age dependency.

CONCLUSIONS

More time per day in SB was associated with a higher BMI over the course of five years, whereas higher MVPA had an inverse effect. In a combined model, only effects of higher SB remained significant, emphasizing the importance of SB in obesity prevention. Present bidirectional associations, where lower body size was associated with higher PA and lower SB, indicated the need for an integrated approach of activity and weight control for obesity prevention.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00338689 . Registered: June 19, 2006 (retrospectively registered).

Social Status and Adolescent Physical Activity: Expanding the Insurance Hypothesis to Incorporate Energy Expenditure

Low social status (SS) is a determinant of poor health status and is associated with increased disease burden. Obesity affects 20.6% of American adolescents, most of whom are from low-SS families. Contributors to the development of obesity among adolescents include sedentary behavior and low levels of physical activity. Environmental determinants-infrastructure, policy, and social relationships-influence engagement in physical activity and are affected by SS. Significant declines in physical activity have been documented during adolescence, and adolescents of low SS engage in significantly less physical activity per week than those with high SS. This article briefly reviews the literature on the relationship between SS and physical activity in adolescents and introduces a proposed biological mechanism that may explain that relationship. Characterizing the effects that SS can have on physical activity may help tailor clinical interventions and public health campaigns seeking to improve adolescent physical activity and weight management, thus increasing their effectiveness. This may be particularly beneficial for underserved populations.

Cross-sectional and prospective associations of meeting 24-h movement guidelines with overweight and obesity in preschool children

BACKGROUND

Cross-sectional studies report that meeting the newly developed 24-h movement guidelines (≥60 min moderate to vigorous physical activity (MVPA), ≤120 min screen time and 9-11 h sleep duration) are associated with lower adiposity indicators in children. However, prospective data are absent.

METHODS

The study sample consisted of 830 children from the PRIMROSE study with GT3X+ accelerometer measured physical activity and parent reported screen time and sleep duration at age 4 years and objectively measured anthropometrics at age 4 and 5 years. The main outcome variables were weight status, body mass index (BMI) and BMI z-score at ages 4 and 5 years. Exposure variables were defined as meeting vs. not meeting the 24-h movement guidelines and combinations of these recommendations.

RESULTS

On average, 18.4% of the total study sample met the combination of MVPA, sleep duration and screen time recommendations. In isolation, the MVPA, screen time and sleep guidelines were met by 31%, 63% and 98% of the total study sample, respectively. Adherence to any single recommendation, or any combination of recommendations at age 4 years, was not associated with being overweight or obese nor with BMI and BMI z-score at age 4 or 5 years.

CONCLUSIONS

In contrast to previous cross-sectional studies, neither individual movement behaviours nor combinations of behaviours at age 4 years was associated with overweight or obesity, BMI or BMI z-score at age 4 or 5 years. More prospective data are needed before effects on weight status from meeting the 24-h movement guidelines are elucidated.

Physical activity in depressed and non-depressed patients with obesity

PURPOSE

Obesity and depression have both been shown to be associated with reduced physical activity (PA). However, most studies have not applied objective measures to determine PA in patients. Moreover, to our knowledge, no studies are available comparing depressed and non-depressed patients with regard to PA.

METHODS

We investigated PA in 47 patients with both obesity and depression, 70 non-depressed patients with obesity, and 71 non-depressed and non-obese healthy control participants using the SenseWear™ Armband (SWA) with walked steps per day and metabolic equivalents (MET) as parameters for PA.

RESULTS

Depressed as well as non-depressed patients with obesity showed a significantly reduced PA as reflected by walked steps as well as reduced METs. Healthy controls walked a mean of 11,586 ± 3731 (SD) steps per day, whereas non-depressed patients with obesity accumulated 7283 ± 3547 and patients with both obesity and depression recorded only 6177 ± 3291 steps per day. However, the difference between depressed and non-depressed patients with obesity did not reach statistical significance either in terms of walked steps or with regard to METs.

CONCLUSIONS

Obesity seems to be associated with a substantial reduction of PA and energy expenditure, whereas the effect of an additional depressive disorder was comparably small. Even though depression did not have any statistically significant effect on steps and METs per day in this study with obese patients, it could be clinically relevant for an individual patient.

Determinants of body mass index by gender in the Dikgale Health and Demographic Surveillance System site, South Africa

BACKGROUND

The study was conducted in the Dikgale Health and Demographic Surveillance System (DHDSS) site where we have observed increasing obesity levels, particularly in women, despite evidence of high physical activity (PA) and a relatively low daily energy intake.

OBJECTIVE

This study aimed to assess the socio-demographic, behavioural and biological determinants of body mass index (BMI) in adult residents permanently residing in the DHDSS.

METHODS

A cross-sectional study was conducted in which socio-demographic, behavioural and biological characteristics from 1143 participants (aged 40-60 years) were collected using a paper questionnaire and standard anthropometric measures. Human immunodeficiency virus (HIV) testing was performed on all participants except those who indicated that they had tested positive. Chi-square and Mann-Whitney tests were used to analyze categorical and continuous variables, respectively, while hierarchical multivariate regression was used to analyze predictors of BMI.

RESULTS

The median age of women and men was 51 (46-56) and 50 (45-55) years, respectively. The prevalence of overweight-obesity was 76% in women and 21% in men. A significant negative association of BMI with HIV and smoking and a significant positive association with socio-economic status (SES) was observed in both sexes. In women, BMI was negatively associated with sleep duration (p = 0.015) and age (p = 0.012), but positively associated with sugar-sweetened beverages (SSBs) (p = 0.08). In men, BMI was negatively associated with alcohol use (p = 0.016) and positively associated with being married (p < 0.001). PA was not associated with BMI in either sexes. Full models explained 9.2% and 20% of the variance in BMI in women and men, respectively.

CONCLUSION

BMI in DHDSS adults is not associated with physical inactivity but is associated wealth, marital status, sleep, smoking, alcohol use, and HIV status. Future studies should explore the contribution of nutrition, stunting, psycho-social and genetic factors to overweight and obesity in DHDSS.

A systematic review of methods to measure family co-participation in physical activity

The family environment is key in influencing children's health behaviours. Encouraging family co-participation in physical activity may therefore be an effective approach to increasing children's physical activity levels. Yet, little is known about how to best assess family co-participation in physical activity. This review summarizes methods to measure family co-participation in physical activity, which was defined as joint physical activities including at least one healthy child (0-18 years) and one other family member. Methods were identified through a systematic literature search, cross-referencing pre-selected reviews and contacting research groups. Thirty-seven measurement methods were included. Questionnaires were the most common method used, with the majority assessing frequency of co-participation and few also assessing duration and type. Reliability and internal consistency of scales were often reported, but rarely specified for the item(s) relevant to co-participation. Other methods of measuring co-participation included diaries, event history calendars, direct observations and accelerometry combined with diary, ecological momentary assessment or global positioning systems (GPS). Whilst a large number of measurement methods of family co-participation in physical activity exist, few are comprehensive and/or report acceptable psychometric properties. Future work should focus on reaching consensus in defining family co-participation in physical activity, and subsequently developing reliable and valid measures.

Knowledge, attitude and practice towards eating and physical activity among primary school children in Brunei: a cross-sectional study

Background Childhood obesity has become a global public health crisis. Many studies have been conducted to explore the knowledge, attitude and practices towards eating and physical activity amongst parents and healthcare workers. However, very little is known amongst children. It is imperative to understand these factors as they have been associated with obesity among children. Objective This study aimed to assess the knowledge, attitude and practices of Bruneian children towards eating and physical activity, in order to identify the factors that influence the development of obesity. Methods The study involved 353 children from four primary schools in Brunei. The data collection tool used was modified validated questionnaires with sections on demographic characteristic, knowledge about obesity, eating habits and physical activity. Results The majority of children (>60%) had good knowledge of obesity and intake of healthy food, but, 84.2% lacked knowledge on the required daily servings of fruits and vegetables. 68.8% purchased food and beverages from their school canteen. 93.8% were aware about the health benefits of physical activity and 70.2% spent only 1-2 h of screen time per day, however, 46.9% did not meet the recommended amount of physical activity although they reported to have performed enough. This suggested that a comprehensive education on food intake requirements and physical activity are necessary in order to better educate children. Conclusion Health educators and public health professionals may find our findings useful in order to plan and develop tailored interventions for children, as well as better promotion of a healthy lifestyle to children and their families.

Does adiposity mediate the relationship between physical activity and biological risk factors in youth?: a cross-sectional study from the International Children's Accelerometry Database (ICAD)

BACKGROUND/OBJECTIVES

To model the association between accumulating 60 daily minutes of moderate-to-vigorous physical activity and a composite score of biological risk factors into a direct and an indirect effect, using abdominal obesity as the mediator.

SUBJECTS/METHODS

Cross-sectional data from the International Children's Accelerometry Database (ICAD) including 6-18-year-old children and adolescents (N=3412) from 4 countries providing at least 3 days of accelerometry-assessed physical activity. A standardized composite risk score was calculated from systolic blood pressure and fasting blood samples of insulin, glucose, triacylglycerol and inverse HDL-cholesterol. Abdominal obesity was assessed by the waist-circumference:height ratio. Two-stage regression analysis, allowing for exposure-mediator interaction, was used for the effect decomposition.

RESULTS

Participants achieving 60 daily minutes of moderate-to-vigorous physical activity had a 0.31 (95% CI: -0.39, -0.23) standard deviations lower composite risk score than those achieving less than 60 min. Modelling the associations suggested that 0.24 standard deviations (95% CI: -0.32, -0.16) was attributed to the direct effect and -0.07 (95% CI: -0.11, -0.02) to the indirect effect indicating that 22% of the total effect was mediated by central adiposity. Modelling 30 and 90 min of moderate-to-vigorous physical activity per day resulted in changes in the direct but not the indirect effect.

CONCLUSIONS

One hour of daily moderate-to-vigorous physical activity was associated with clinically relevant differences in metabolic control compared to engagement in less than this minimally recommended amount. The majority of the difference was explained by the direct effect of physical activity.International Journal of Obesity advance online publication, 31 October 2017; doi:10.1038/ijo.2017.241.

Childhood predictors of adolescent behaviour: The prospective association of familial factors with meeting physical activity guidelines

Little is known about the longitudinal association of familial socio-demographic factors, behaviours, attitudes, or home environment with meeting physical activity guidelines. Our objective was to a) describe 4-year change in the prevalence of meeting guidelines, and characteristics of participants across categories of physical activity maintenance, and b) identify familial factors in childhood that are longitudinally associated with meeting guidelines in adolescence. Data on 17 parent- and child-reported family variables and objectively measured physical activity (ActiGraph GT1M) were available from 406 children (10.3 ± 0.3 years, 53.5% female) participating in the SPEEDY study. Average duration of week- and weekend day moderate-to-vigorous physical activity (MVPA, ≥ 2000 cpm) at baseline and follow-up (14.3 ± 0.3 years) were calculated to determine whether participants met 60 min MVPA/day guidelines at each assessment. Descriptives were calculated across four MVPA change categories. Multi-level logistic regression examined the association of baseline familial factors with meeting guidelines at follow-up, adjusting for sex, baseline physical activity, family socio-economic position, and school clustering. At follow-up, 51.5% and 36.1% of adolescents met guidelines on weekdays and weekend days, respectively (baseline: 68.0%, 67.2%). Girls were less likely than boys to remain sufficiently active, particularly on weekdays. Family social support was positively associated with adolescents meeting guidelines at weekends (OR 1.2; 95% CI 1.0-1.4). The presence of play equipment at home was negatively associated with meeting guidelines on weekdays (OR 0.5; 95% CI 0.3-0.8). Interventions that foster parent's facilitation of physical activity may help to encourage the upkeep of healthy behaviours during the transition from childhood to adolescence.

Fifty states of self-control: A U.S. statewide examination of the initiation and inhibition dimensions of self-regulation

Individual differences in self-control have been shown to reflect two underlying dimensions: initiation and inhibition. We examined the possibility that degrees of self-control might likewise be modeled at a broader social level, similar to other socio-cultural differences that operate at an individual level (e.g., collectivism). To test this notion, we used a variety of mundane behaviors measured at the level of U.S. states to create inhibitory and initiatory indices of self-control at a collective level. We show that statewide levels of initiatory and inhibitory self-control, despite being correlated with one another, exhibit unique patterns of association with a wide range of outcomes, including homicide, suicide, home foreclosures, divorce, and infidelity. This study represents one of the first attempts to model the dimensional structure of self-control at a social level and supports the utility of conceptualizing self-control as an important socio-cultural variable.

Associations between asthma, overweight and physical activity in children: a cross-sectional study

Background

Asthma and obesity are highly prevalent in children, and are interrelated resulting in a difficult-to-treat asthma-obesity phenotype. The exact underlying mechanisms of this phenotype remain unclear, but decreased physical activity (PA) could be an important lifestyle factor. We hypothesize that both asthma and overweight/obesity decrease PA levels and interact on PA levels in asthmatic children with overweight/obesity.

Methods

School-aged children (n = 122) were divided in 4 groups (healthy control, asthma, overweight/obesity and asthma, and overweight/obesity). Children were asked to perform lung function tests and wear an activity monitor for 7 days. PA was determined by: step count, active time, screen time, time spent in organized sports and active transport forms. We used multiple linear regression techniques to investigate whether asthma, body mass index-standard deviation score (BMI-SDS), or the interaction term asthma x BMI-SDS were associated with PA. Additionally, we tested if asthma features (including lung function and medication) were related to PA levels in asthmatic children.

Results

Asthma, BMI-SDS and the interaction between asthma x BMI-SDS were not related to any of the PA variables (p ≥ 0.05). None of the asthma features could predict PA levels (p ≥ 0.05). Less than 1 in 5 children reached the recommended daily step count guidelines of 12,000 steps/day.

Conclusion

We found no significant associations between asthma, overweight and PA levels in school-aged children in this study. However, as PA levels were worryingly low, effective PA promotion in school-aged children is necessary.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3600-1) contains supplementary material, which is available to authorized users.

Role of physical activity and sleep duration in growth and body composition of preschool-aged children

OBJECTIVE

The impact of physical activity patterns and sleep duration on growth and body composition of preschool-aged children remains unresolved. Aims were (1) to delineate cross-sectional associations among physical activity components, sleep, total energy expenditure (TEE), and body size and composition; and (2) to determine whether physical activity components, sleep, and TEE predict 1-year changes in body size and composition in healthy preschool-aged children.

METHODS

Anthropometry, body composition, accelerometry, and TEE by doubly labeled water were measured at baseline; anthropometry and body composition were repeated 1 year later (n = 111).

RESULTS

Cross-sectionally, positive associations between sedentary activity and weight and fat-free mass (FFM) (P = 0.009-0.047), and a negative association between moderate-vigorous physical activity (MVPA) and percent fat mass (FM) (P = 0.015) were observed. TEE and activity energy expenditure (AEE) were positively associated with weight, body mass index (BMI), FFM, and FM (P = 0.0001-0.046). Prospectively, TEE, AEE, physical activity level, and MVPA, but not sedentary activity, were positively associated with changes in BMI (P = 0.0001-0.051) and FFM (P = 0.0001-0.037), but not percent FM. Sleep duration inversely predicted changes in FM (P = 0.005) and percent FM (P = 0.006).

CONCLUSIONS

Prospectively, MVPA, TEE, AEE, and physical activity level promote normal growth and accretion of FFM, whereas sleep duration inversely predicts changes in adiposity in preschool-aged children.

Family-based interventions to increase physical activity in children: a systematic review, meta-analysis and realist synthesis

OBJECTIVE

Family-based interventions represent a potentially valuable route to increasing child physical activity (PA) in children. A dual meta-analysis and realist synthesis approach examined existing interventions to assist those developing programmes to encourage uptake and maintenance of PA in children.

DESIGN

Studies were screened for inclusion based on including participants aged 5-12 years, having a substantive aim of increasing PA by engaging the family and reporting on PA outcome. Duplicate data extraction and quality assessment were conducted. Meta-analysis was conducted in STATA. Realist synthesis included theory development and evidence mapping.

RESULTS

Forty-seven studies were included, of which three received a 'strong' quality rating, 21 'moderate' and 23 'weak'. The meta-analysis (19 studies) demonstrated a significant small effect in favour of the experimental group (standardized mean difference: 0.41; 95%CI 0.15-0.67). Sensitivity analysis, removing one outlier, reduced this to 0.29 (95%CI 0.14-0.45). Realist synthesis (28 studies) provided insight into intervention context (particularly, family constraints, ethnicity and parental motivation), and strategies to change PA (notably, goal-setting and reinforcement combined).

CONCLUSION

This review provides key recommendations to inform policy makers and other practitioners in developing evidence-based interventions aimed at engaging the family to increase PA in children, and identifies avenues for future research.

The independent prospective associations of activity intensity and dietary energy density with adiposity in young adolescents

There is limited evidence on the prospective association of time spent in activity intensity (sedentary (SED), moderate (MPA) or vigorous (VPA) physical activity) and dietary intake with adiposity indicators in young people. This study aimed to assess associations between (1) baseline objectively measured activity intensity, dietary energy density (DED) and 4-year change in adiposity and (2) 4-year change in activity intensity/DED and adiposity at follow-up. We conducted cohort analyses including 367 participants (10 years at baseline, 14 years at follow-up) with valid data for objectively measured activity (Actigraph), DED (4-d food diary), anthropometry (waist circumference (WC), %body fat (%BF), fat mass index (FMI), weight status) and covariates. Linear and logistic regression models were fit, including adjustment for DED and moderate-to-vigorous physical activity. Results showed that baseline DED was associated with change in WC (β for 1kJ/g difference: 0·71; 95% CI 0·26, 1·17), particularly in boys (1·26; 95% CI 0·41, 2·16 v. girls: 0·26; 95% CI −0·34, 0·87), but not with %BF, FMI or weight status. In contrast, baseline SED, MPA or VPA were not associated with any of the outcomes. Change in DED was negatively associated with FMI (β for 1kJ/g increase: −0·86; 95% CI −1·59, −0·12) and %BF (−0·86; 95% CI −1·25, −0·11) but not WC (−0·27; 95% CI −1·02, 0·48). Change in SED, MPA and VPA did not predict adiposity at follow-up. In conclusion, activity intensity was not prospectively associated with adiposity, whereas the directions of associations with DED were inconsistent. To inform public health efforts, future studies should continue to analyse longitudinal data to further understand the independent role of different energy-balance behaviours in changes in adiposity in early adolescence.

Active lifestyle in childhood and adolescence prevents obesity development in young adulthood

OBJECTIVE

To test the hypothesis that individuals who are active but who decrease physical activity (PA) over time have a higher risk of becoming obese in young adulthood, when compared to individuals who are consistently active throughout childhood and adolescence.

METHODS

Iowa Bone Development Study cohort members (242 males and 251 females) participated in accelerometry assessments, dual-energy X-ray absorptiometry scans, and dietary questionnaire surveys at ages 5, 8, 11, 13, 15, 17, and 19 years. Group-based trajectory analyses identified distinct trajectory patterns of moderate- to vigorous-intensity PA (MVPA), percentage of body fat, and energy intake. A multivariable logistic regression model was fit to estimate the odds of "becoming obese" based on the MVPA trajectories, adjusted for mother's education, somatic maturation, and energy intake.

RESULTS

Among males, 74.7% had a "normal" body fat pattern, 14.6% had a "becoming obese" pattern, and 10.7% had a "consistently obese" pattern, while among females, the percentages were 58.6%, 28.6%, and 12.8%, respectively. Participants who were active (≥45 min MVPA) as children but decreased MVPA with age were more likely to become obese, compared to consistently active participants (adjusted OR = 2.77; 95% CI = 1.16, 6.58).

CONCLUSIONS

An active lifestyle throughout childhood and adolescence could prevent obesity development in young adulthood.

"Couch-potatoeism" and childhood obesity: The inverse causality hypothesis

The bulk of cross-sectional studies suggests that lower levels of physical activity are associated with childhood obesity. Although this has led to the general understanding that "couch-potatoes" are fat on account of their inactive lifestyles, cross-sectional studies do not imply causality. On the contrary, the contribution of physical activity to obesity during childhood is currently unclear, and lately, studies have suggested that "couch-potatoeism" could be the result of obesity rather than its cause. Coupled with evidence suggesting that interventions have had little effect on children's physical activity levels as well as on obesity, this inverse causality challenges the role of physical activity in childhood obesity prevention strategies.

Sedentary behaviors, physical activity behaviors, and body fat in 6-year-old children: the generation R study

Background

Childhood overweight and obesity is a major public health concern. Knowledge on modifiable risk factors is needed to design effective intervention programs. This study aimed to assess associations of children’s sedentary behaviors (television viewing and computer game use) and physical activity behaviors (sports participation, outdoor play, and active transport to/from school) with three indicators of body fat, i.e., percent fat mass, body mass index (BMI) standard deviation scores, and weight status (normal weight, overweight).

Methods

Cross-sectional data from 5913 6-year-old ethnically diverse children were analyzed. Children’s weight and height were objectively measured and converted to BMI. Weight status was defined according to age- and sex-specific cut-off points of the International Obesity Task Force. BMI standard deviation scores were created, based on Dutch reference growth curves. Fat mass was measured my dual-energy X-ray absorptiometry (DXA). Sedentary and physical activity behaviors were assessed by parent-reported questionnaires. Series of logistic and linear regression analyses were performed, controlling for confounders (i.e., socio-demographic factors, family lifestyle factors, and other sedentary behaviors and physical activity behaviors).

Results

Sports participation was inversely associated with fat mass (p < 0.001), even after adjustment for socio-demographic factors, family lifestyle factors, and other sedentary behaviors and physical activity behaviors. No other independent associations were observed.

Conclusions

The results of this study indicate that sports participation is inversely associated with percent body fat among ethnically diverse 6-year-old children. More research in varied populations including objective measurements and longitudinal designs are needed to confirm these current results.

Sedentary behaviors, physical activity behaviors, and body fat in 6-year-old children: the generation R study

BACKGROUND

Childhood overweight and obesity is a major public health concern. Knowledge on modifiable risk factors is needed to design effective intervention programs. This study aimed to assess associations of children's sedentary behaviors (television viewing and computer game use) and physical activity behaviors (sports participation, outdoor play, and active transport to/from school) with three indicators of body fat, i.e., percent fat mass, body mass index (BMI) standard deviation scores, and weight status (normal weight, overweight).

METHODS

Cross-sectional data from 5913 6-year-old ethnically diverse children were analyzed. Children's weight and height were objectively measured and converted to BMI. Weight status was defined according to age- and sex-specific cut-off points of the International Obesity Task Force. BMI standard deviation scores were created, based on Dutch reference growth curves. Fat mass was measured my dual-energy X-ray absorptiometry (DXA). Sedentary and physical activity behaviors were assessed by parent-reported questionnaires. Series of logistic and linear regression analyses were performed, controlling for confounders (i.e., socio-demographic factors, family lifestyle factors, and other sedentary behaviors and physical activity behaviors).

RESULTS

Sports participation was inversely associated with fat mass (p < 0.001), even after adjustment for socio-demographic factors, family lifestyle factors, and other sedentary behaviors and physical activity behaviors. No other independent associations were observed.

CONCLUSIONS

The results of this study indicate that sports participation is inversely associated with percent body fat among ethnically diverse 6-year-old children. More research in varied populations including objective measurements and longitudinal designs are needed to confirm these current results.

Family-based interventions to increase physical activity in children: a meta-analysis and realist synthesis protocol

INTRODUCTION

Despite the established relationship between physical activity and health, data suggest that many children are insufficiently active, and that levels decline into adolescence. Engaging the family in interventions may increase and maintain children's physical activity levels at the critical juncture before secondary school. Synthesis of existing evidence will inform future studies, but the heterogeneity in target populations recruited, behaviour change techniques and intervention strategies employed, and measurement conducted, may require a multifaceted review method. The primary objective of this work will therefore be to synthesis evidence from intervention studies that explicitly engage the family unit to increase children's physical activity using an innovative dual meta-analysis and realist approach.

METHODS AND ANALYSIS

Peer-reviewed studies will be independently screened by two authors for inclusion based on (1) including 'healthy' participants aged 5-12 years; (2) having a substantive intervention aim of increasing physical activity, by engaging the family and (3) reporting on physical activity. Duplicate data extraction and quality assessment will be conducted using a specially designed proforma and the Effective Public Health Practice Project Quality Assessment Tool respectively. STATA software will be used to compute effect sizes for meta-analyses, with subgroup analyses conducted to identify moderating characteristics. Realist syntheses will be conducted according to RAMESES quality and publication guidelines, including development of a programme theory and evidence mapping.

DISSEMINATION

This review will be the first to use the framework of a traditional review to conduct a dual meta-analysis and realist synthesis, examining interventions that engage the family to increase physical activity in children. The results will be disseminated through peer-reviewed publications, conferences, formal presentations to policy makers and practitioners and informal meetings. Evidence generated from this synthesis will also be used to inform the development of theory-driven, evidence-based interventions aimed at engaging the family to increase physical activity levels in children.

PROTOCOL REGISTRATION

International Prospective Register for Systematic Reviews (PROSPERO): number CRD42013005780.

Improving physical activity in daycare interventions

BACKGROUND

The aim of the study was to objectively determine whether the Nutrition and Physical Activity Self-Assessment for Child Care (NAP SACC) program improved physical activity levels during the school day.

METHODS

The study compared the physical activity levels of subjects from 26 daycare centers, randomized into treatment (N=13) and control (N=13) groups. The subjects were 3 to 5 year olds (N=209, 104 males and 105 females; age [years]=3.85±0.8 [mean±standard deviation]), and accelerometry was used to determine the subjects' physical activity levels. Accelerometers were attached to each subject for 2 days before and immediately after a 6-month intervention. Height, mass, and waist were also measured.

RESULTS

Regression analyses indicated that the treatment group demonstrated significant increases in moderate and vigorous physical activity, as compared to the control group (F(1, 207)=6.3, p<0.05, Cohen's d=0.30; F(1, 207)=4.7, p<0.05, Cohen's d=0.25, respectively). The treatment group also showed significant increases in total physical activity (F(1, 218)=12.4; p<0.05) from pre- to post-test with significant increases in moderate and vigorous intensity physical activity (F(1, 218)=18.6, p<0.05; F(1, 218)=23.3, p<0.05, respectively). Regression analyses revealed significant increases in height for both groups from pre- to post-tests, but no differences were noted between groups.

CONCLUSIONS

Implementation of the NAP SACC program in treatment daycare facilities resulted in significant increases in objectively measured physical activity levels, compared to the control group, demonstrating physical activity improvement in the treatment daycare centers.

Physical activity, screen time and obesity status in a nationally representative sample of Maltese youth with international comparisons

Background

There is some evidence that physical activity (PA), sedentary time and screen time (ST) are associated with childhood obesity, but research is inconclusive and studies are mainly based on self-reported data. The literature is dominated by data from North American countries and there is a shortage of objective data from Malta which has one of the highest prevalences of childhood obesity in the world. The aims of this study were to assess the PA levels and ST patterns of Maltese boys and girls and how they compared with children in other countries while also examining differences in PA and ST by weight status.

Methods

A nationally representative sample of 1126 Maltese boys and girls aged 10–11 years, of which 811 provided complete data. Physical activity was assessed using accelerometry, and ST by questionnaire. Body mass index (BMI) was computed from measured height and weight.

Results

Only 39% of boys and 10% of girls met the recommendation of one hour of daily MVPA. Comparison with international data indicated that mean MVPA (58.1 min for boys; 41.7 min for girls) was higher than in North America and Australia, but lower than in England. Girls were less active than boys at all measured times and spent less time in ST. A quarter of the children exceeded guidelines of two hours of TV on weekends, and double the amount on weekdays. Obese children were less active than normal weight children on weekdays and on weekends, reaching significance during the period after school, and they spent more time in ST than their normal weight counterparts.

Conclusions

A low percentage of Maltese 10–11 year olds, particularly girls, reached the recommended levels of daily MVPA and spent large amounts of time engaged in screen time. Obese children were less active than non-obese children. As children spend most of their waking time at school and that activity during this time is less than one third of the daily requirements, aiming to increase MVPA at school for all Maltese children is likely to be an important strategy to promote MVPA. Targeting less active and obese children is important.

Assessing causality in the association between child adiposity and physical activity levels: a Mendelian randomization analysis

BACKGROUND

Cross-sectional studies have shown that objectively measured physical activity is associated with childhood adiposity, and a strong inverse dose-response association with body mass index (BMI) has been found. However, few studies have explored the extent to which this association reflects reverse causation. We aimed to determine whether childhood adiposity causally influences levels of physical activity using genetic variants reliably associated with adiposity to estimate causal effects.

METHODS AND FINDINGS

The Avon Longitudinal Study of Parents and Children collected data on objectively assessed activity levels of 4,296 children at age 11 y with recorded BMI and genotypic data. We used 32 established genetic correlates of BMI combined in a weighted allelic score as an instrumental variable for adiposity to estimate the causal effect of adiposity on activity. In observational analysis, a 3.3 kg/m² (one standard deviation) higher BMI was associated with 22.3 (95% CI, 17.0, 27.6) movement counts/min less total physical activity (p = 1.6×10⁻¹⁶), 2.6 (2.1, 3.1) min/d less moderate-to-vigorous-intensity activity (p = 3.7×10⁻²⁹), and 3.5 (1.5, 5.5) min/d more sedentary time (p = 5.0×10⁻⁴). In Mendelian randomization analyses, the same difference in BMI was associated with 32.4 (0.9, 63.9) movement counts/min less total physical activity (p = 0.04) (∼5.3% of the mean counts/minute), 2.8 (0.1, 5.5) min/d less moderate-to-vigorous-intensity activity (p = 0.04), and 13.2 (1.3, 25.2) min/d more sedentary time (p = 0.03). There was no strong evidence for a difference between variable estimates from observational estimates. Similar results were obtained using fat mass index. Low power and poor instrumentation of activity limited causal analysis of the influence of physical activity on BMI.

CONCLUSIONS

Our results suggest that increased adiposity causes a reduction in physical activity in children and support research into the targeting of BMI in efforts to increase childhood activity levels. Importantly, this does not exclude lower physical activity also leading to increased adiposity, i.e., bidirectional causation.

Methods for the bias adjustment of meta-analyses of published observational studies

BACKGROUND

A unique challenge in meta-analysis of observational studies is bias adjustment. Two different approaches have been proposed for doing this - using summary scores versus component scores. The prevailing view on this matter is that summary quality scores are inaccurate because information from its components can cancel each other out.

METHODS

A head-to-head comparison of the component score adjustment with our method using summary scores is undertaken, using data reported by the authors of the component method.

RESULTS

It is demonstrated that the consideration of components or of aggregate scores does indeed lead to the same conclusions. Yet, the latter does not require imputation of the direction and magnitude of changes to effect sizes.

CONCLUSIONS

The summary quality score used for bias adjustment within the context of an appropriate model may be most expedient. Implications for the bias adjustment of meta-analyses of observational studies are discussed.

Physical activity and 3-year BMI change in overweight and obese children

OBJECTIVES

Targeting physical activity (PA) is a mainstay in obesity treatment, but its BMI benefits are poorly quantified. We studied long-term predictive PA-BMI relationships in overweight/obese children presenting to primary care.

METHODS

Three-year follow-up of 182 overweight/obese 5- to 10-year-olds recruited from 45 Melbourne general practices.

PREDICTOR

7-day accelerometry (counts per minute, cpm).

OUTCOMES

change in BMI z score, BMI category, and clinically significant BMI improvement (z score change ≥0.5).

ANALYSIS

Linear and logistic regression.

RESULTS

Mean (SD) baseline and 3-year BMI z scores were 1.8 (0.6) and 1.8 (0.7), and mean (SD) activity scores 334 (111) and 284 (104) cpm, respectively. Baseline activity did not predict BMI change. However, for every 100 cpm increase in change in activity over 3 years, BMI z score fell by 0.11 (95% confidence interval [CI] 0.03-0.20; P = .006). There were also trends toward greater odds of staying in the same, versus moving to a higher, BMI category (odds ratio 1.85, 95% CI 0.99-3.46) and clinically significant BMI improvement (odds ratio 1.96, 95% CI 0.90-4.27; P = .09). Change in percentage time spent in moderate-vigorous (P = .01), but not sedentary (P = .39) or light (P = .59), activity predicted reduced BMI z score.

CONCLUSIONS

Sustained increase in moderate-vigorous PA predicts reducing BMI z score over 3 years in overweight/obese children presenting to primary care. However, the small BMI change associated with even the largest activity changes may explain disappointing BMI outcomes of brief primary care interventions targeting PA.

Correlates of weight status among Norwegian 11-year-olds: The HEIA study

Background

The underlying mechanisms of overweight and obesity in adolescents are still not fully understood. The aim of this study was to investigate modifiable and non-modifiable correlates of weight status among 1103 Norwegian 11-year-old adolescents in the HEalth in Adolescents (HEIA) study, including demographic factors such as gender and parental education, and behavioral factors such as intake of sugar-sweetened beverages, snacks and breakfast consumption, watching TV and playing computer games, physical activity and sedentary time.

Methods

Weight and height were measured objectively, body mass index (BMI) was calculated and International Obesity Task Force cut-offs were used to define weight status. Physical activity and sedentary time were measured by accelerometers. Other behavioral correlates and pubertal status were self-reported by questionnaires. Parental education was reported by the parents on the consent form for their child. Associations were investigated using logistic regressions.

Results

There were gender differences in behavioral correlates of weight status but not for weight status itself. Adolescents with parents in the highest education category had a 46% reduced odds of being overweight compared to adolescents with parents in the lowest education category. Adolescents with parents with medium education had 42% lower odds of being overweight than adolescents with parents with the lowest education category. Level of parental education, breakfast consumption and moderate to vigorous physical activity were positively associated with being normal weight, and time watching TV was positively associated with being overweight for the total sample. Gender differences were detected; boys had a doubled risk of being overweight for every additional hour of watching TV per week, while for girls there was no association.

Conclusions

The present study showed a social gradient in weight status in 11-year-olds. Both breakfast consumption and moderate to vigorous physical activity were inversely associated with weight status. No associations were found between intake of sugar-sweetened beverages and snacks, playing computer games and weight status. Watching TV was positively associated with weight status for boys but not for girls. Interventions are needed to gain more insight into the correlates of change in weight status.

Physical activity and fat mass gain in Mexican school-age children: a cohort study

BACKGROUND

In México, the prevalence of unhealthy weight increased from 24% at 6 y to 33% at 12 y of age, opening a window of opportunity to better understand the pathogenesis of obesity. The objective of this study was to explore the association between time spent on medium, vigorous physical activity (MVPA) and concurrent gains in BMI, fat mass (FM) and fat-free mass (FFM), alternately, in a cohort of Mexican children followed from kindergarten (baseline) to 2nd grade elementary school (endline).

METHODS

The MVPA (5-d accelerometry), BMI, FM and FFM (air displacement plethysmography) were measured at baseline and endline. Associations between gains in BMI, FM and FFM and changes in MVPA were examined using lagged and dynamic regression models, controlling for energy intake and demographic variables.

RESULTS

A total of 205 children were analyzed. Gender affected the effect of MVPA on FM gain. In girls, a high baseline MVPA predicted a lower FM gain (-0.96 kg, p=0.025) compared to low/medium MVPA. Increasing, decreasing or having a persistently high MVPA predicted a lower FM gain (range -1.6 to -1.03 kg, p<0.05) compared to persistently low MVPA. In boys, increases in MVPA were associated with higher gains in BMI (+0.76 kg/m2, p=0.04) and FFM (+1.1 kg, p=0.01) compared to persistently low MVPA.

CONCLUSION

These results support a protective role of MVPA on FM gain in girls, suggesting that it may play a crucial role in the development of obesity. Further research on the gender effect of MVPA is warranted to better understand its role in the prevention and control of overweight and obesity.

A proposed method of bias adjustment for meta-analyses of published observational studies

OBJECTIVE

Interpretation of meta-analyses of published observational studies is problematic because of numerous sources of bias. We develop bias assessment, elicitation and adjustment methods, and apply them to a systematic review of longitudinal observational studies of the relationship between objectively measured physical activity and subsequent change in adiposity in children.

METHODS

We separated internal biases that reflect study quality from external biases that reflect generalizability to a target setting. Since published results were presented in different formats, these were all converted to correlation coefficients. Biases were considered as additive or proportional on the correlation scale. Opinions about the extent of each bias in each study, together with its uncertainty, were elicited in a formal process from quantitatively trained assessors for the internal biases and subject-matter specialists for the external biases. Bias-adjusted results for each study were combined across assessors using median pooling, and results combined across studies by random-effects meta-analysis.

RESULTS

Before adjusting for bias, the pooled correlation is difficult to interpret because the studies varied substantially in quality and design, and there was considerable heterogeneity. After adjusting for both the internal and external biases, the pooled correlation provides a meaningful quantitative summary of all available evidence, and the confidence interval incorporates the elicited uncertainties about the extent of the biases. In the adjusted meta-analysis, there was no apparent heterogeneity.

CONCLUSION

This approach provides a viable method of bias adjustment for meta-analyses of observational studies, allowing the quantitative synthesis of evidence from otherwise incompatible studies. From the meta-analysis of longitudinal observational studies, we conclude that there is no evidence that physical activity is associated with gain in body fat.

Dietary energy density and adiposity: employing bias adjustments in a meta-analysis of prospective studies

BACKGROUND

Dietary studies differ in design and quality making it difficult to compare results. This study quantifies the prospective association between dietary energy density (DED) and adiposity in children using a meta-analysis method that adjusts for differences in design and quality through eliciting and incorporating expert opinion on the biases and their uncertainty.

METHOD

Six prospective studies identified by a previous systematic literature search were included. Differences in study quality and design were considered respectively as internal and external biases and captured in bias checklists. Study results were converted to correlation coefficients; biases were considered either additive or proportional on this scale. The extent and uncertainty of the internal and external biases in each study were elicited in a formal process by five quantitatively-trained assessors and five subject-matter specialists. Biases for each study were combined across assessors using median pooling and results combined across studies by random-effects meta-analysis.

RESULTS

The unadjusted combined correlation between DED and adiposity change was 0.06 (95%CI 0.01, 0.11; p = 0.013), but with considerable heterogeneity (I² = 52%). After bias-adjustment the pooled correlation was 0.17 (95%CI - 0.11, 0.45; p = 0.24), and the studies were apparently compatible (I² = 0%).

CONCLUSIONS

This method allowed quantitative synthesis of the prospective association between DED and adiposity change in children, which is important for the development of evidence-informed policy. Bias adjustment increased the magnitude of the positive association but the widening confidence interval reflects the uncertainty of the assessed biases and implies that higher quality studies are required.