Risk factors for childhood overweight: shift of the mean body mass index and shift of the upper percentiles: results from a cross-sectional study

Tracking the Prevalence of Obesity in Portuguese School-Aged Children: What Future to Expect?

BACKGROUND

Childhood obesity presents a significant public health concern globally, with implications for cardiovascular health and metabolic syndrome. In Portugal, approximately 31.6% of children are affected, highlighting the urgency for intervention strategies. This study aimed to assess the prevalence of overweight and obesity in Portuguese school-aged children, with a focus on sex and age differences.

METHODS

Anthropometric measurements were conducted on 1564 children aged 6-10 years, including weight, height, and skinfold thickness. Body Mass Index (BMI) and the percentage of body fat were calculated using established methods.

RESULTS

The results revealed significant differences in BMI (≤0.001) and body fat percentage (≤0.001) among different BMI categories, with a notable prevalence of overweight and obesity, particularly among boys. A total of 37% of the studied population is overweight or obese, among which 40.1% and 33.9% are boys and girls, respectively.

CONCLUSIONS

This study highlights statistically significant differences in BMI and body fat percentage for both sexes in different BMI categories. A large proportion of the population is overweight or obese, with a greater prevalence in boys. In short, childhood obesity has a negative impact on body composition and is associated with significant differences in anthropometric parameters, emphasizing the importance of preventative and intervention strategies to address this health problem.

Infant Milk Formula with Large, Milk Phospholipid-coated Lipid Droplets Enriched in Dairy Lipids Affects Body Mass Index Trajectories and Blood Pressure at School Age: Follow-up of a Randomized Controlled Trial

BACKGROUND

Human milk comprises large fat globules enveloped by a native phospholipid membrane, whereas infant formulas contain small, protein-coated lipid droplets. Previous experimental studies indicated that mimicking the architecture of human milk lipid droplets in infant milk formula (IMF) alters lipid metabolism with lasting beneficial impact on later metabolic health.

OBJECTIVES

To evaluate in a follow-up (FU) study of a randomized, controlled trial whether a Concept IMF with large, milk phospholipid-coated lipid droplets enriched with dairy lipids beneficially impacts long-term body mass index (BMI in kg/m2) trajectories and blood pressure at school age.

METHODS

Fully formula-fed infants were randomly assigned to Concept IMF (n = 115) or Control IMF with conventional, small lipid droplets containing vegetable oils (n = 108) for the first 4 mo of age. A group of 88 breastfed infants served as a reference. During FU, anthropometrics were collected at 1, 3, 4, and 5 y of age, and blood pressure only at the last visit.

RESULTS

Compared to Control, Concept group children had consistently lower mean BMI values during FU, with the most marked difference at 1 y of age (difference in means -0.71 kg/m2, 95% confidence interval (CI): -1.13, -0.29; P = 0.001); mean values were close to the breastfed group (P > 0.05). Contrary, the mean BMI values of the Control group were higher compared with the breastfed group during FU from 1 to 5 y of age (differences in means from 0.59 to 0.96 kg/m2, respectively; P < 0.02). At 5 y of age, the Concept group had a lower mean diastolic and arterial blood pressure compared with the Control group; -4.3mm Hg (95% CI: -7.3, -1.3; P = 0.005) and -3.7 mm Hg (95% CI: -6.5, -0.9; P = 0.01), respectively.

CONCLUSIONS

Early life feeding of an innovative IMF with large, milk phospholipid-coated lipid droplets enriched with dairy lipids results in a BMI trajectory closer to breastfed infants and a lower blood pressure at school age. This trial was registered at the Dutch Trial Register as NTR3683 and NTR5538.

Having siblings promotes a more healthy weight status—Whereas only children are at greater risk for higher BMI in later childhood

Background

Birth order and having at least one sibling are known to be associated with an increased risk for development of overweight. However, there are no studies assessing pre- and postnatal factors for developing overweight within families. Therefore, the present study aimed to analyse the association of the mother’s weight gain during pregnancy, prepregnancy BMI, mother’s age at birth, breastfeeding, age gap between siblings, and physical activity together with sibling-related characteristics on the development of overweight in children and adolescents.

Methods

Data were obtained from the longitudinal LIFE Child cohort. The study sample included n = 1932 children, stratified into first-born (n = 578), second-born (n = 608), third-or-later-born single-born siblings (n = 162), only children (n = 526), and twin children (n = 58). Children with chronic or syndromic diseases, born prematurely or from mothers with gestational diabetes were excluded. Data were adjusted for multiple children per family using mixed models. Pregnancy weight gain, prepregnancy BMI and mother’s age were considered prenatal co-variates. Postnatal factors included the duration of breastfeeding and the children’s physical activity level.

Results

Particularly until the onset of puberty, the BMI-SDS differed between single-born siblings, only children and twins, and increased with birth order. Compared to children with siblings, only children exhibited a strong increase in BMI-SDS starting at age nine. A higher age gap between siblings was associated with a higher BMI-SDS in second- and third-or-later-born children. Single-born siblings had the highest rate and duration of breastfeeding. Physical activity was highest in twins and third-or-later-born children and lowest in only children. In a multivariate model, being an only child showed a highly significant association with BMI-SDS.

Conclusion

The present study demonstrated that siblings had a lower BMI-SDS than only children did. For single-born siblings, the association between birth order and increased BMI-SDS seemed to persist only up to 11 years of age.

Measurement of screen time among young children aged 0-6 years: A systematic review

The impact of screen-based devices on children's health and development cannot be properly understood without valid and reliable tools that measure screen time within the evolving digital landscape. This review aimed to summarize characteristics of measurement tools used to assess screen time in young children; evaluate reporting of psychometric properties; and examine time trends related to measurement and reporting of screen time. A systematic review of articles published in English across three databases from January 2009 to April 2020 was undertaken using PROSPERO protocol (registration: CRD42019132599) and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Included articles measured screen time as outcome, exposure, or confounder in children 0-6 years. The search identified 35,868 records, 1035 full-text articles were screened for eligibility, and 622 met inclusion criteria. Most measures (60%) consisted of one to three items and assessed duration of screen time on a usual day. Few measures assessed content (11%) or coviewing (7%). Only 40% of articles provided a citation for the measure, and only 69 (11%) reported psychometric properties-reliability n = 58, validity n = 19, reliability and validity n = 8. Between 2009 and 2019, the number of published articles increased from 28 to 71. From 2015, there was a notable increase in the proportion of articles published each year that assessed exposure to mobile devices in addition to television. The increasing number of published articles reflects increasing interest in screen time exposure among young children. Measures of screen time have generally evolved to reflect children's contemporary digital landscape; however, the psychometric properties of measurement tools are rarely reported. There is a need for improved measures and reporting to capture the complexity of children's screen time exposures.

Determinants of the population health distribution: an illustration examining body mass index

Most epidemiological studies examine how risk factors relate to average difference in outcomes (linear regression) or odds of a binary outcome (logistic regression); they do not explicitly examine whether risk factors are associated differentially across the distribution of the health outcome investigated. This paper documents a phenomenon found repeatedly in the minority of epidemiological studies which do this (via quantile regression): associations between a range of established risk factors and body mass index (BMI) are progressively stronger in the upper ends of the BMI distribution. In this paper, we document this finding and provide illustrative evidence of it in the 1958 British birth cohort study. Associations of low childhood socio-economic position, high maternal weight, low childhood general cognition and adult physical inactivity with higher BMI are larger at the upper end of the BMI distribution, on both absolute and relative scales. For example, effect estimates for socio-economic position and childhood cognition were around three times larger at the 90th compared with 10th quantile, while effect estimates for physical inactivity were increasingly larger from the 50th to 90th quantiles, yet null at lower quantiles. We provide potential explanations for these findings and discuss implications. Risk factors may have larger causal effects among those in worse health, and these effects may not be discovered when health is only examined in average terms. In such scenarios, population-based approaches to intervention may have larger benefits than anticipated when assuming equivalent benefit across the population. Further research is needed to understand why effect estimates differ across the BMI outcome distribution and to investigate whether differential effects exist for other physical and mental health outcomes.

Family and Lifestyle Factors Mediate the Relationship between Socioeconomic Status and Fat Mass in Children and Adolescents

Socioeconomic status (SES) is strongly associated with childhood overweight. The underlying mechanism and the role of family and lifestyle factors as potential mediators of this relationship remain, however, unclear. Cross-sectional data of 4,772 girls and boys aged 5-16 years from the Kiel Obesity Prevention Study were considered in mediation analyses. Fat mass (FM) was assessed by bioelectrical impedance analysis and converted into a percent FM SD score (FM%-SDS). SES was defined by the parental educational level, classified as low, middle, or high. Characteristics of family and lifestyle factors were obtained via validated questionnaires and considered as mediators. In 3 different age groups, the product-of-coefficients method was used to examine age-specific mediator effects on the relationship between SES and FM%-SDS (c = total effects) and their ratio to total effects, adjusted for age, sex, puberty, and nationality. The prevalence of overweight was 6.9%. In all age groups, SES was inversely associated with FM%-SDS as follows: 5-7 years, c1 = -0.11 (95% CI -0.19 to -0.03); 9-11 years, c2 = -0.21 (95% CI -0.27 to -0.14); and 13-16 years, c3 = -0.23 (95% CI -0.28 to -0.17). The relationship between SES and FM%-SDS was fully (5-7 and 9-11 years) and partly (13-16 years) mediated by similar and age-specific mediators, including parental BMI, parental smoking habits, media consumption, physical activity, and shared meals. Overall, these variables resulted in a total mediating effect of 77.8% (5-7 years), 82.4% (9-11 years), and 70.6% (13-16 years). Consistent for both sexes, the relationship between SES and FM%-SDS was therefore mediated by parental weight status, risk-related behavior within families, and children's and adolescents' lifestyle factors. Strategies for obesity prevention, which are predominantly targeted at socially disadvantaged groups, should therefore address the family environment and lifestyle factors.

Cardiovascular morbidity, diabetes and cancer risk among children and adolescents with severe obesity

Severe obesity among children and adolescents is a significant global public health concern. The prevalence has markedly increased over the last decades, becoming common in many countries. Overwhelming rates of obesity among youth have prompted efforts to identify an evidence-based immediate- and long-term cardiometabolic risk factor profile in childhood-onset severe obesity, and to highlight gaps that require further investigation. The PubMed database was systematically searched in accordance with PRISMA guidelines. The search yielded 831 results, of which 60 fulfilled stringent criteria and were summarized in this review. The definition of severe obesity was variable, with only one half the publications using the definition BMI > 120% of the 95th percentile. Point estimates of the prevalence of at least one cardiometabolic risk factor in children with severe obesity reportedly range from 67 to 86%. Cross-sectional studies indicate that children and adolescents with severe obesity are at greater risk than those with mild obesity for type 2 diabetes, hypertension, fatty liver disease and dyslipidemia, already at childhood and adolescence. Robust epidemiological data on the long-term risk and actual point estimates in adulthood are lacking for these diseases as well as for other diseases (coronary heart disease, stroke, chronic kidney disease and cancer). Recent longitudinal studies indicate an increased risk for cardiomyopathy, heart failure, cardiovascular mortality and all-cause mortality in adulthood for adolescents with severe obesity compared to those with mild obesity. Given the alarming increase in the prevalence of severe obesity, the persistence of adiposity from childhood to adulthood and the precarious course of young adults with chronic comorbidities, the economic and clinical services burden on the healthcare system is expected to rise.

Prevalence and Trends of Overweight and Obesity in European Children From 1999 to 2016: A Systematic Review and Meta-analysis

IMPORTANCE

Studies of trends in excess weight among European children throughout the last few decades have rendered mixed results. Additionally, some studies were outdated, were based on self-reported weight and height, or included only a few European countries.

OBJECTIVE

To assess prevalence trends in measured overweight and obesity among children across Europe from 1999 to 2016 using a systematic methodology.

DATA SOURCES

MEDLINE, Embase, CINAHL, and Web of Science were searched from their inception until May 2018. Moreover, searches were conducted on health institutions' websites to identify studies not published in scientific journals.

STUDY SELECTION

The inclusion criteria were: (1) studies reporting the population-based prevalence of excess weight (overweight plus obesity) or obesity according to body mass index cutoffs proposed by the International Obesity Task Force; (2) cross-sectional or follow-up studies; and (3) studies including populations aged 2 to 13 years.

DATA EXTRACTION AND SYNTHESIS

Literature review and data extraction followed established guidelines. The Mantel-Haenszel method was used to compute the pooled prevalence estimates and their 95% CI whenever there was no evidence of heterogeneity (I2 < 50%); otherwise, the DerSimonian and Laird random-effects method was used. Subgroup analyses by study year, country, or European region (Atlantic, Iberian, Central, and Mediterranean) were conducted. Prevalence estimates were calculated as an aggregate mean, weighted by the sample size and the number of individuals in each study.

RESULTS

A total of 103 studies (477 620 children aged 2 to 13 years) with data from 28 countries were included. The combined prevalence of overweight and obesity in the Iberian region tended to decrease from 30.3% (95% CI, 28.3%-32.3%) to 25.6% (95% CI, 19.7%-31.4%) but tended to increase in the Mediterranean region from 22.9% (95% CI, 17.9%-27.9%) to 25.0% (95% CI, 14.5%-35.5%). No substantial changes were observed in Atlantic Europe or Central Europe, where the overweight and obesity prevalence changed from 18.3% (95% CI, 14.0%-23.9%) to 19.3% (95% CI, 17.7%-20.9%) and from 15.8% (95% CI, 13.4%-18.5%) to 15.3% (95% CI, 11.6%-20.3%), respectively.

CONCLUSIONS AND RELEVANCE

The prevalence of childhood overweight and obesity is very high, but trends have stabilized in most European countries. There are substantial between-country differences in the current levels and trends of overweight and obesity. The rising prevalence in some Mediterranean countries is worrisome.

TRIAL REGISTRATION

PROSPERO identifier: CRD42017056924.

Distribution of body mass index in children with different parental risk: Findings of a family-based cohort study in a West-Asian population

Using quantile regression analysis, the current study, conducted within the framework of the Tehran Lipid and Glucose Study (TLGS) aimed to assess the effects of parental risk clusters on different percentiles of Body Mass Index (BMI) distribution in children. Participants included 2296 school-aged children who had participated in the baseline assessment of the TLGS and were followed for an approximate duration of fifteen years. Parental socio-demographic, behavioral and clinical characteristics were considered to determine risk clusters. Comparing of the high- to the low-risk parental clusters showed that after adjusting for age in boys, BMI was significantly higher at the 75^th (1.82, p = 03), 85^th (1.78, p = 0.007) and 95^th (1.66, p = 0.03) percentiles; and in girls it was significantly higher at the 25^th (1.45, p = 0.003), 50^th (1.05, p = 0.015), 95^th (2.31, p = 0.018) and 97^th (2.44, p = 0.006) percentiles in the high risk cluster. Our data indicate that during a long-term follow up, children with a high-risk family are more likely to have higher BMI, compared to their counterparts in low-risk families, a difference observed mainly at the upper percentiles of BMI distribution for both genders and at all ages, findings that should be considered for strategies aimed at preventing childhood obesity and its consequences.

Body Mass Index Is a Better Indicator of Body Composition than Weight-for-Length at Age 1 Month

OBJECTIVE

To assess whether body mass index (BMI) provides a better assessment of measured adiposity at age 1 month compared with weight-for-length (WFL).

STUDY DESIGN

Participants were healthy term-born infants in the Infant Growth and Microbiome (n = 146) and the Baby Peas (n = 147) studies. Length, weight, and body composition by air displacement plethysmography were measured at 1 month. World Health Organization-based WFL and BMI z-scores were calculated. Within-cohort z-scores of percent fat-Z, fat mass-Z, fat mass/length2-Z, fat mass/length3-Z, fat-free mass-Z, and fat-free mass/length2-Z were calculated. Correlation and multiple linear regression (adjusted for birth weight) analyses tested the associations between body composition outcomes and BMI-Z vs WFL-Z. Quantile regression was used to test the stability of these associations across the distribution of body compositions.

RESULTS

The sample was 52% female and 56% African American. Accounting for birth weight, both BMI-Z and WFL-Z were strongly associated with fat mass-Z (coefficients 0.56 and 0.35, respectively), FM/L2-Z (0.73 and 0.51), and FM/L3-Z (0.79 and 0.58), with stronger associations for BMI-Z compared with WFL-Z (P < .05). Even after accounting statistically for birth weight, BMI-Z was persistently more strongly associated than WFL-Z with body composition outcomes across the distribution of body composition outcomes.

CONCLUSIONS

We demonstrate in 2 distinct cohorts that BMI is a better indicator of adiposity in early infancy compared with WFL. Our findings support the preferred use of BMI for growth and nutritional status assessment in infancy.

Development of Growth Charts of Pakistani Children Aged 4-15 Years Using Quantile Regression: A Cross-sectional Study

Background

Growth charts are essential tools used by pediatricians as well as public health researchers in assessing and monitoring the well-being of pediatric populations. Development of these growth charts, especially for children above five years of age, is challenging and requires current anthropometric data and advanced statistical analysis. These growth charts are generally presented as a series of smooth centile curves. A number of modeling approaches are available for generating growth charts and applying these on national datasets is important for generating country-specific reference growth charts.

Objective

To demonstrate that quantile regression (QR) as a viable statistical approach to construct growth reference charts and to assess the applicability of the World Health Organization (WHO) 2007 growth standards to a large Pakistani population of school-going children.

Methodology

This is a secondary data analysis using anthropometric data of 9,515 students from a Pakistani survey conducted between 2007 and 2014 in four cities of Pakistan. Growth reference charts were created using QR as well as the LMS (Box-Cox transformation (L), the median (M), and the generalized coefficient of variation (S)) method and then compared with WHO 2007 growth standards.

Results

Centile values estimated by the LMS method and QR procedure had few differences. The centile values attained from QR procedure of BMI-for-age, weight-for-age, and height-for-age of Pakistani children were lower than the standard WHO 2007 centile.

Conclusion

QR should be considered as an alternative method to develop growth charts for its simplicity and lack of necessity to transform data. WHO 2007 standards are not suitable for Pakistani children.

Relations of Demographic and Clinical Factors With Cardiovascular Autonomic Function in a Population-Based Study: An Assessment By Quantile Regression

BACKGROUND

The relationships of many factors with cardiovascular autonomic function (CVAF) outcome parameters may not be uniform across the entire distribution of the outcome. We examined how demographic and clinical factors varied with different subgroups of CVAF parameters.

METHODS

Quantile regression was applied to a cross-sectional analysis of 4,167 adults (56% male; age range, 50-84 years) from 4 ethnic groups (3,419 New Zealand European, 303 Pacific, 227 Maori, and 218 South Asian) and without diagnosed cardiac arrhythmia. Pulse rate variability (root mean square of successive differences (RMSSD) and SD of pulse intervals) and baroreflex sensitivity were response variables. Independent variables were age, sex, ethnicity, brachial and aortic blood pressure (BP) variables, body mass index (BMI), and diabetes.

RESULTS

Ordinary linear regression showed that age, sex, Pacific and Maori ethnicity, BP variables, BMI, and diabetes were associated with CVAF parameters. But quantile regression revealed that, across CVAF percentiles, the slopes for these relationships: (i) varied by more than 10-fold in several cases and sometimes changed direction and (ii) noticeably differed in magnitude often (by >3-fold in several cases) compared to ordinary linear regression coefficients. For instance, age was inversely associated with RMSSD at the 10th percentile of this parameter (β = -0.12 ms/year, 95% confidence interval = -0.18 to -0.09 ms/year) but had a positive relationship at the 90th percentile (β = 3.17 ms/year, 95% confidence interval = 2.50 to 4.04 ms/year).

CONCLUSIONS

The relationships of demographic and clinical factors with CVAF parameters are, in many cases, not uniform. Quantile regression provides an improved assessment of these associations.

Intake of Energy and Protein is Associated with Overweight Risk at Age 5.5 Years: Results from the Prospective TEDDY Study

OBJECTIVE

The associations of energy, protein, carbohydrate, and fat intake with weight status up to the age of 5.5 years were prospectively assessed in The Environmental Determinants of Diabetes in the Young (TEDDY) study.

METHODS

Food record data (over 3 days) and BMI measurements between 0.25 and 5.5 years were available from 5,563 children with an increased genetic risk for type 1 diabetes followed from shortly after birth. Odds ratios (ORs) were calculated for overweight and obesity by previous intake of energy, protein, carbohydrate, and fat with adjustment for potential confounders.

RESULTS

Having overweight or obesity at the age of 5.5 years was positively associated with mean energy intake in previous age intervals (e.g., adjusted OR [95% CI] for overweight: 1.06 [1.04-1.09] per 100 kcal intake at the age of 4.5-5.0 years) and with protein intake after the age of 3.5 and 4.5 years, respectively (e.g., adjusted OR for overweight: 1.06 [1.03-1.09] per 1% of energy intake at the age of 4.5-5.0 years). The respective associations with carbohydrate and fat intake were less consistent.

CONCLUSIONS

These findings indicate that energy and protein intake are positively associated with increased risk for overweight in childhood but yield no evidence for potential programming effects of protein intake in infancy.

The Weight of Inequality: Socioeconomic Status and Adolescent Body Mass in Brazil

The high rate of obesity among adolescents is a global public health problem that has recently expanded to affect middle- and low-income countries. Brazil, which is undergoing a relatively rapid nutrition transition and has inadequate health systems, is currently experiencing the consequences of increasing rates of overweight and obesity concomitantly with the consequences of generations of malnourishment. Given this scenario, Brazil is an ideal context for examining the relationship between family socioeconomic status (SES) and adolescent body mass, as well as how this relationship varies across very different regions within the same country and across the body mass index (BMI) continuum. Guided by a framework that integrates nutrition transition and fundamental cause theories, we use unique nationally representative data with measured height and weight for all household members to conduct quantile regression models. The results suggest that family socioeconomic conditions are important theoretical factors associated with adolescent BMI, but that the way in which family SES impinges on adolescent BMI varies across regions characterized by different locations in the nutrition transition and varying levels of economic development. We also find that family socioeconomic disadvantages operate very differently according to BMI status. The results show that the socioeconomic gradient of adolescent BMI varies by stages of the nutrition transition and economic development and across BMI percentiles.

Physical Activity and Pediatric Obesity: A Quantile Regression Analysis

PURPOSE

We aimed to determine whether moderate to vigorous physical activity (MVPA) and sedentary behavior (SB) were independently associated with body mass index (BMI) and waist circumference (WC) in children and adolescents.

METHODS

Data from the International Children's Accelerometry Database were used to address our objectives (N = 11,115; 6-18 yr; 51% female). We calculated age- and gender-specific BMI and WC z-scores and used accelerometry to estimate MVPA and total SB. Self-reported television viewing was used as a measure of leisure time SB. Quantile regression was used to analyze the data.

RESULTS

MVPA and total SB were associated with lower and higher BMI and WC z-scores, respectively. These associations were strongest at the higher percentiles of the z-score distributions. After including MVPA and total SB in the same model, the MVPA associations remained, but the SB associations were no longer present. For example, each additional hour per day of MVPA was not associated with BMI z-score at the 10th percentile (b = -0.02, P = 0.170) but was associated with lower BMI z-score at the 50th (b = -0.19, P < 0.001) and 90th percentiles (b = -0.41, P < 0.001). More television viewing was associated with higher BMI and WC, and the associations were strongest at the higher percentiles of the z-score distributions, with adjustment for MVPA and total SB.

CONCLUSIONS

Our observation of stronger associations at the higher percentiles indicates that increasing MVPA and decreasing television viewing at the population-level could shift the upper tails of the BMI and WC frequency distributions to lower values, thereby lowering the number of children and adolescents classified as obese.

Parent-related mechanisms underlying the social gradient of childhood overweight and obesity: a systematic review

BACKGROUND

Low socio-economic status (SES) is a significant risk factor for childhood overweight and obesity (COWOB) in high-income countries. Parents to young children buffer and accentuate social and cultural influences, and are central to the development of this disease. An understanding of the parent-related mechanisms that underlie the SES-COWOB relationship is needed to improve the efficacy of prevention and intervention efforts.

OBJECTIVE

A systematic review of relevant literature was conducted to investigate the mechanisms by which levels of SES (low, middle and high) are associated to COWOB, by exploring mediation and interaction effects.

METHOD

Six electronic databases were searched yielding 5155 initial records, once duplicates were removed. Studies were included if they investigated COWOB, SES, parent-related factors and the multivariate relationship between these factors. Thirty studies were included. Factors found to be mediating the SES-COWOB relationship or interacting with SES to influence COWOB were categorized according to an ecological systems framework, at child, parent, household and social system level factors.

RESULTS

High parent body mass index, ethnicity, child-care attendance, high TV time (mother and child), breastfeeding (early weaning), food intake behaviours and birthweight potentially mediate the relationship between SES and COWOB. Different risk factors for COWOB in different SES groups were found. For low SES families, parental obesity and maternal depressive symptoms were strong risk factors for COWOB, whereas long maternal working hours and a permissive parenting style were risk factors for higher SES families. None of the studies investigated parental psychological attributes such as attitudes, beliefs, self-esteem and so on as potential mechanisms/risk factors.

CONCLUSIONS

Families from different SES groups have different risk and protective factors for COWOB. Prevention and intervention efforts may have improved efficacy if they are tailored to address specific risk factors within SES.

Stabilization of Overweight and Obesity in Slovenian Adolescents and Increased Risk in Those Entering Non-Grammar Secondary Schools

BACKGROUND/AIM

To estimate overweight and obesity prevalence trends in Slovenian adolescents entering secondary schools in the years 2004, 2009 and 2014 and differences in the prevalence between different types of secondary schools.

METHODS

Data from 17,538 adolescents entering secondary schools (mean age ± standard deviation 15.4 ± 0.5 years) collected during obligatory medical examination in years 2004, 2009 and 2014 was analyzed. Overweight and obesity were defined using International Obesity Task Force criteria.

RESULTS

In 2004-2009 overweight and obesity prevalence increased, especially in males and stabilized thereafter (2009-2014) in both genders. It was significantly higher (p < 0.0001) in those attending secondary vocational and technical/professional versus grammar schools (2009; 28.7 vs. 16.8% overweight females and 31.6 vs. 22.3% overweight males; 2014: 29.7 vs. 17.9% overweight females and 33.6 vs. 20.4% overweight males).

CONCLUSIONS

Overweight and obesity prevalence in Slovenian adolescents entering secondary schools stabilized recently. Adolescents attending secondary vocational and technical/professional schools are at an increased risk of overweight and obesity.

Association of early and late maternal smoking during pregnancy with offspring body mass index at 4 to 5 years of age

The objective was to investigate the association between early and late maternal smoking during pregnancy on offspring body mass index (BMI). We undertook a retrospective cohort study using linked records from the Women’s and Children’s Health Network in South Australia. Among a cohort of women delivering a singleton, live-born infants between January 2000 and December 2005 (n=7658), 5961 reported not smoking during pregnancy, 297 reported quitting smoking during the first trimester of pregnancy, and 1400 reported continued smoking throughout pregnancy. Trained nurses measured the height and weight of the children at preschool visits in a state-wide surveillance programme. The main outcome measure was age- and sex-specific BMI z-score. At 4 to 5 years, mean (s.d.) BMI z-score was 0.40 (1.05), 0.60 (1.07) and 0.65 (1.18) in children of mothers who reported never smoking, quitting smoking and continued smoking during pregnancy, respectively. Compared with the group of non-smokers, both quitting smoking and continued smoking were associated with an increase in child BMI z-score of 0.15 (95% confidence interval: 0.01–0.29) and 0.21 (0.13–0.29), respectively. A significant dose–response relationship was also observed between the number of cigarettes smoked per day on average during the second half of pregnancy and the increase in offspring BMI z-score (P<0.001). In conclusion, any maternal smoking in pregnancy, even if mothers quit, is associated with an increase in offspring BMI at 4 to 5 years of age.

Quantile Mediation Models: A Comparison of Methods for Assessing Mediation Across the Outcome Distribution

Recent introduction of quantile regression methods to analysis of epidemiologic data suggests that traditional mean regression approaches may not suffice for some health outcomes such as Body Mass Index (BMI). In the same vein, the traditional mean-based approach to mediation modeling may not be sufficient to capture the potentially different mediating effects of behavioral interventions across the outcome distribution. By combining methods for estimating conditional quantiles with traditional mediation modeling techniques, mediation effects can be estimated for any quantile of the outcome distribution (so-called quantile mediation effects). Estimation and inference techniques for quantile mediation effects are compared through simulation studies, and recommendations are given. The quantile mediation methods are further compared with the traditional mean-based regression approaches to mediation analysis through analysis of data from Healthy Places, a trial that is examining the effects of the community-built environment on resident obesity risk. We found the magnitudes of indirect (mediating) effects of walkability on BMI and waist circumference were substantially larger for the upper quantiles compared with the median or mean. Results suggest that restricting the examination of mediation to the mean of the outcome distribution provides an incomplete picture of proposed mediating mechanisms and in some cases may miss important mediational relationships to outcomes.

Association of pre- and post-natal parental smoking with offspring body mass index: an 8-year follow-up of a birth cohort

BACKGROUND

Although many epidemiological studies have shown an association between maternal smoking during pregnancy and offspring overweight, it is still under debate whether intrauterine tobacco smoke exposure directly affects offspring obesity or if the association is rather due to confounding by lifestyle factors.

OBJECTIVES

The association of parental smoking habits at pre- and post-natal periods with offspring body mass index (BMI) was investigated, whereas maternal smoking during pregnancy was validated by cord serum cotinine measurements.

METHODS

Multivariable linear regression analysis, based on the German Ulm Birth Cohort Study of 1045 children born in 2000 with annual/biennial follow-up until the age of 8 years (n = 609), was conducted.

RESULTS

BMI of offspring from mothers who smoked during pregnancy and non-smoking mothers differed significantly at 8 years. Maternal smoking during pregnancy was associated with an increase in BMI of 0.73 kg m(-2) [95% confidence interval: 0.21-1.25] in 8-year-old children after adjustment for multiple potential confounding variables. Both pre- and post-natal smoking of fathers (0.34 [0.01-0.66]/0.45 [0.08-0.81]) and of both parents (1.03 [0.43-1.63]/0.56 [0.14-0.98]) were likewise significantly associated with offspring BMI.

CONCLUSIONS

The observed patterns suggest that residual confounding by living conditions in smoking families rather than specific intrauterine exposure to tobacco smoke may account for the increased risk of offspring overweight.

Classification tree analyses reveal limited potential for early targeted prevention against childhood overweight

OBJECTIVE

Whether specific combinations of risk factors in very early life might allow identification of high-risk target groups for overweight prevention programs was examined.

DESIGN AND METHODS

Data of n = 8981 children from the German KiGGS study were analyzed. Using a classification tree approach, predictive risk factor combinations were assessed for overweight in 3-6, 7-10, and 11-17-year-old children.

RESULTS

In preschool children, the subgroup with the highest overweight risk were migrant children with at least one obese parent, with a prevalence of 36.6 (95% confidence interval or CI: 22.9, 50.4)%, compared to an overall prevalence of 10.0 (8.9, 11.2)%. The prevalence of overweight increased from 18.3 (16.8, 19.8)% to 57.9 (46.6, 69.3)% in 7-10-year-old children, if at least one parent was obese and the child had been born large-for-gestational-age. In 11-17-year-olds, the overweight risk increased from 20.1 (18.9, 21.3)% to 63.0 (46.4, 79.7)% in the highest risk group. However, high prevalence ratios were found only in small subgroups, containing <10% of all overweight cases in the respective age group.

CONCLUSIONS

Our results indicate only a limited potential for early targeted preventions against overweight in children and adolescents.

Maternal smoking during pregnancy and childhood overweight and fat distribution: the KOALA Birth Cohort Study

What is already known about this subject There is an association between maternal smoking during pregnancy and higher body mass index (BMI) and overweight in childhood. What this study adds The association between maternal smoking during pregnancy and childhood overweight develops with age, starting with a lower birth weight, followed by weight catch-up in the first year after birth, finally leading to overweight at school age. Children of mothers who had smoked during pregnancy had a higher risk of exceeding the 85th percentile of BMI, waist circumference and total skinfold thickness at school age.

BACKGROUND

Maternal smoking during pregnancy is associated with childhood overweight, but the association with fat distribution is not clear.

OBJECTIVE

To explore the longitudinal association between smoking during pregnancy and childhood overweight and fat distribution.

METHODS

In the KOALA Birth Cohort Study, repeated questionnaires were administered to 2698 mother-child pairs, including questions on smoking at 14 and 34 weeks of pregnancy. Main outcomes were birth weight, weight gain in the first year, body mass index (BMI) z-scores and overweight (BMI ≥85th percentile) at 1, 2, 4-5 and 6-7 years (n = 1730) and waist circumference and four skinfold thicknesses measured at home visits at age 6-7 years in a subgroup (n = 418). We used multivariable linear and logistic regression, with generalized estimating equations (GEE) for repeated measurements.

RESULTS

Maternal smoking was associated with lower birth weight, higher weight gain in the first year and increasing overweight after infancy (change with age P = 0.02 in the GEE). Maternal smoking vs. non-smoking during pregnancy was associated with a higher risk of the child exceeding the 85th percentile of BMI (adjusted odds ratio [aOR] 3.72; 95% CI 1.33-10.4), waist circumference (aOR 2.65; 95% CI 1.06-6.59) and sum of skinfold thicknesses (aOR 4.45; 95% CI 1.63-12.2) at the age of 6-7 years.

CONCLUSIONS

Maternal smoking during pregnancy is associated with lower birth weight, weight catch-up and development of overweight into childhood.

Breastfeeding shows a protective trend toward adolescents with higher abdominal adiposity

OBJECTIVE

The question of whether breastfeeding has a protective effect against the development of overweight or obesity later in life remains controversial, especially during adolescence. The objective was to assess the relationship between breastfeeding and adolescents' body composition.

METHODS

The HELENA study is a cross-sectional study involving 3,528 adolescents from 10 European cities. The outcome measures were body weight and height, subscapular skinfolds as well as waist circumferences. Breastfeeding, smoking status, and parental socioeconomic status were assessed by self-administered questionnaires. Dietary intake was recorded using two 24-hour recall surveys. Two adjustment approaches were used: i) covariance analysis adjusted for confounding factors (propensity score adjustment) and ii) multivariate quantile regression.

RESULTS

After adjustment, no significant associations were observed between breastfeeding and body composition parameters (BMI Z-score; sum of skinfolds; waist-to-height ratio). An adjusted quantile regression analysis showed a non-significant trend for a protective effect of breastfeeding toward the highest percentiles of adiposity in boys but not in girls. This is of particular interest with respect to the superiority of the waist-to-height ratio over waist circumference and BMI for detecting cardiometabolic risk factors.

CONCLUSION

This first European study, including a large set of factors influencing adolescents' body composition, showed a non-significant trend toward a protective effect of breastfeeding on highest percentiles of adolescent's abdominal adiposity.

Opposing socioeconomic gradients in overweight and obese adults

OBJECTIVE

Investigate the relationship between socioeconomic status (SES) and prevalence of overweight and/or obesity, by sex, using total annual household income as the indicator of SES and the World Health Organization (WHO) recommended ranges of self-reported Body Mass Index (BMI) as the indicator of overweight and/or obesity.

METHODS

Total annual household income and BMI data were obtained from the Victorian Population Health Survey (VPHS), an annual computer-assisted telephone survey of the health and well-being of Victorian adults aged 18 years and older. Statistical analysis was conducted using ordinary least squares linear regression on the logarithms of age-standardised prevalence estimates of overweight (25.0-29.9 kg/m(2)), obesity (≥ 30.0 kg/m(2)), and overweight and obesity combined (≥ 25.0 kg/m(2)), by income category and sex.

RESULTS

Typical SES gradients were observed in obese males and females, where the prevalence of obesity decreased with increasing income. No SES gradient was observed in overweight females, however, a reverse SES gradient was observed in overweight males, where the prevalence of overweight increased with increasing income. Combining the overweight and obesity categories into a single group eliminated the typical SES gradients observed in males and females for obesity, and resulted in a statistically significant reverse SES gradient in males.

CONCLUSIONS

Combining the BMI categories of overweight and obesity into a single category masks important SES differences, while combining the data for males and females masks important sex differences. BMI categories of overweight and obesity should be analysed and reported independently, as should BMI data by sex.

Sedentary Behavior and Health Outcomes in Children and Adolescents

The purpose of this review was to summarize findings from epidemiological studies that determined if sedentary behavior was associated with obesity, metabolic risk factors, and cardiorespiratory fitness in children and adolescents. We noted if studies adjusted for moderate-to-vigorous physical activity (MVPA), dietary intakes, and/or sleep duration. Articles were identified through PubMed using the search terms: (sedentary OR sitting OR television) AND (adiposity OR blood pressure OR body mass index OR cardiometabolic OR metabolic risk OR waist circumference). The search was limited to ages 6 to 18 years, humans, and published between January 1, 2008 and September 26, 2012. Cross-sectional and longitudinal studies observed associations between more sedentary behavior, especially screen-based sedentary behavior, and measures of obesity; and most associations were independent of MVPA and dietary intake. Cross-sectional and longitudinal studies reported associations between screen-based sedentary behavior and lower cardiorespiratory fitness, and most associations were independent of MVPA and obesity. Cross-sectional studies observed associations between more screen-based and objectively measured sedentary behavior and lower insulin sensitivity; and most associations were independent of MVPA and obesity. There was little-to-no evidence that sedentary behavior was associated with increased blood pressure and increased blood lipids.

Interactions of genetic and environmental risk factors with respect to body fat mass in children: results from the ALSPAC study

OBJECTIVE

To evaluate if percentile-specific effects of genetic, environmental and lifestyle obesity risk factors on body mass index (BMI) might reflect gene-environment interactions with respect to the development of overweight.

DESIGN AND METHODS

Retrospective study with data of 2,346 children from the Avon Longitudinal Study of Parents and Children (ALSPAC), using quantile regression with body fat mass index (FMI) for children at the age of 9 years as outcome variable. We assessed interactions of an "obesity-risk-allele-score" with environmental and nutritional factors.

RESULTS

There was no evidence of interactions between the obesity-risk-allele score and the environmental variables except for maternal overweight. However, we found a significant interaction with respect to intake of mono- and polyunsaturated fatty acids at the age of 7. In children with low intake, genetic risk was associated with increasing effect sizes by FMI percentile.

CONCLUSIONS

Our results suggest an interaction between a low dietary content of unsaturated fatty acids and genetic risk factors for overweight on FMI. This effect is likely to be stronger in children with higher FMI.

Moderate-to-vigorous physical activity is associated with decreases in body mass index from ages 9 to 15 years

OBJECTIVE

The purpose of this study is to determine whether time spent in objectively measured physical activity is associated with change in body mass index (BMI) from ages 9 to 15.

DESIGN AND METHODS

The participants were enrolled in the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (n = 938). At ages 9, 11, 12, and 15 the time spent in moderate-to-vigorous physical activity (MVPA) was objectively measured, and BMI was calculated (kg/m(2) ). Longitudinal quantile regression was used to analyze the data. The 10th, 25th, 50th, 75th, and 90th BMI percentiles were modeled as the dependent variables with age and MVPA (h/day) modeled as predictors. Adjustment was also made for gender, race, sleep, healthy eating score, maternal education, and sedentary behavior.

RESULTS

A negative association between MVPA and change in BMI was observed at the 90th BMI percentile (-3.57, 95% CI -5.15 to -1.99 kg/m(2) per hour of MVPA). The negative association between time spent in MVPA and change in BMI was progressively weaker toward the 10th BMI percentile (-0.27, 95% CI -0.62 to 0.07 kg/m(2) per hour of MVPA). The associations remained similar after adjusting for the covariates, and when the analyses were stratified by gender.

CONCLUSION

Time spent in MVPA was negatively associated with change in BMI from age 9 to 15. The association was strongest at the upper tail of the BMI distribution, and increasing time spent in MVPA could help reduce the prevalence of childhood obesity.

Evaluation of the association between maternal smoking, childhood obesity, and metabolic disorders: a national toxicology program workshop review

BACKGROUND

An emerging literature suggests that environmental chemicals may play a role in the development of childhood obesity and metabolic disorders, especially when exposure occurs early in life.

OBJECTIVE

Here we assess the association between these health outcomes and exposure to maternal smoking during pregnancy as part of a broader effort to develop a research agenda to better understand the role of environmental chemicals as potential risk factors for obesity and metabolic disorders.

METHODS

PubMed was searched up to 8 March 2012 for epidemiological and experimental animal studies related to maternal smoking or nicotine exposure during pregnancy and childhood obesity or metabolic disorders at any age. A total of 101 studies-83 in humans and 18 in animals-were identified as the primary literature.

DISCUSSION

Current epidemiological data support a positive association between maternal smoking and increased risk of obesity or overweight in offspring. The data strongly suggest a causal relation, although the possibility that the association is attributable to unmeasured residual confounding cannot be completely ruled out. This conclusion is supported by findings from laboratory animals exposed to nicotine during development. The existing literature on human exposures does not support an association between maternal smoking during pregnancy and type 1 diabetes in offspring. Too few human studies have assessed outcomes related to type 2 diabetes or metabolic syndrome to reach conclusions based on patterns of findings. There may be a number of mechanistic pathways important for the development of aberrant metabolic outcomes following perinatal exposure to cigarette smoke, which remain largely unexplored.

CONCLUSIONS

From a toxicological perspective, the linkages between maternal smoking during pregnancy and childhood overweight/obesity provide proof-of-concept of how early-life exposure to an environmental toxicant can be a risk factor for childhood obesity.

Objectively measured sedentary time, physical activity and markers of body fat in preschool children

The purpose of this study was to examine the associations between sedentary behavior and moderate to vigorous physical activity (MVPA), measured by accelerometry, with body mass index (BMI) and waist circumference in 357 preschool children. Linear mixed models were used adjusting for race/ethnicity, parental education, and preschool. Follow-up analyses were performed using quantile regression. Among boys, MVPA was positively associated with BMI z-score (b = 0.080, p = .04) but not with waist circumference; quantile regression showed that MVPA was positively associated with BMI z-score at the 50th percentile (b = 0.097, p < .05). Among girls, no associations were observed between sedentary behavior and MVPA in relation to mean BMI z-score and mean waist circumference. Quantile regression indicated that, among girls at the 90th waist circumference percentile, a positive association was found with sedentary behavior (b = 0.441, p < .05), and a negative association was observed with MVPA (b = -0.599, p < .05); no associations were found with BMI z-score. In conclusion, MVPA was positively associated with BMI z-score among boys, and MVPA was negatively associated and sedentary behavior was positively associated with waist circumference among girls at the 90th percentile.

Changes in cardiovascular disease risk factors from age 9 to 19 and the influence of television viewing

OBJECTIVE

The purpose of this study was to determine if time spent watching television is associated with changes in cardiovascular disease (CVD) risk factors from age 9 to 19.

DESIGN AND METHODS

Participants were girls enrolled in the NHLBI Growth and Health Study (n = 1,702), and CVD risk factors were measured at ages 10, 12, 14, 16, and 19. Longitudinal quantile regression was used to determine if television viewing was associated with changes in CVD risk factors over time at the 10th, 25th, 50th, 75th, and 90th percentiles of the CVD risk factors.

RESULTS

In black girls, television viewing (h/wk) was positively associated with sum of skinfolds (mm) at the 75th (0.22, 99% CI, 0.06-0.38) and 90th percentiles (0.21, 99% CI, 0.05-0.36), but not at the 10th, 25th, or 50th percentiles. In white girls, television viewing (h/wk) was positively associated with sum of skinfolds (mm) with the strength of the associations progressively stronger toward the upper tail of the skinfold distribution, adjusting for physical activity and other covariates (10th percentile: 0.08, 99% CI, 0.03-0.13; 90th percentile: 0.42, 99% CI, 0.24-0.59). All associations were adjusted for physical activity, dietary factors, sleep, and maturation. No associations were observed between television viewing and changes in systolic blood pressure, triglycerides, or cholesterol levels in black or white girls.

CONCLUSION

Girls who spent more time watching television had greater increases in sum of skinfolds from age 9 to 19, independent of physical activity levels and other covariates. The associations observed were stronger at the upper tail of the skinfold distribution.

Organized sports, overweight, and physical fitness in primary school children in Germany

Physical inactivity is associated with poor physical fitness and increased body weight. This study examined the relationship between participation in organized sports and overweight as well as physical fitness in primary school children in southern Germany. Height, weight, and various components of physical fitness were measured in 995 children (7.6 ± 0.4 years). Sports participation and confounding variables such as migration background, parental education, parental body weight, and parental sports participation were assessed via parent questionnaire. Multiple logistic regression as well as multivariate analysis of covariance (MANCOVA) was used to determine associations between physical fitness, participation in organized sports, and body weight. Participation in organized sports less than once a week was prevalent in 29.2%, once or twice in 60.2%, and more often in 10.6% of the children. Overweight was found in 12.4% of the children. Children participating in organized sports more than once per week displayed higher physical fitness and were less likely to be overweight (OR  =  0.52, P < 0.01). Even though causality cannot be established, the facilitation of participation in organized sports may be a crucial aspect in public health efforts addressing the growing problems associated with overweight and obesity.

Parental, fetal, and infant risk factors for preschool overweight: the Generation R Study

BACKGROUND

Overweight has its origins largely in early life. We aimed to identify the most important parental, fetal, and infant risk factors of preschool overweight.

METHODS

In a prospective cohort study, among 3,610 Caucasian preschool children, we assessed the associations of 34 putative parental, fetal, and infant factors with overweight risk.

RESULTS

Higher maternal BMI, paternal BMI, and birth weight were associated with higher risk of preschool overweight (odds ratio (OR): 1.23, 95% confidence interval (CI): 1.10, 1.39; OR: 1.35, 95% CI: 1.19, 1.53; and OR: 2.71, 95% CI: 2.27, 3.25, respectively, per SD increase). The same model identified low household income (OR: 1.74, 95% CI: 1.24, 2.45), being female (OR: 1.55, 95% CI: 1.20, 2.01), and experiencing third-trimester accelerated growth (OR: 1.73, 95% CI: 1.24, 2.40) or postnatal accelerated growth (OR: 6.39, 95% CI: 4.54, 8.99) as risk factors for preschool overweight. Higher polyunsaturated fat intake at 14 mo was associated with a lower risk of preschool overweight (OR: 0.77, 95% CI: 0.62, 0.96 per SD).

CONCLUSION

Parental anthropometrics and household income, fetal and infant accelerated growth, and infant dietary fat intake are the major risk factors for the development of preschool overweight. Further studies need to explore whether these risk factors could be potential targets for preventive interventions.

Body fat mass of exclusively breastfed infants born to overweight mothers

BACKGROUND

Although there is evidence that maternal prepregnancy obesity (body mass index [BMI; calculated as kg/m(2)] ≥30) results in elevated risk of obesity in the offspring later in life, maternal prepregnancy overweight (BMI 25 to 29.9) has not been clearly demonstrated as a risk factor for the future development of obesity in the offspring.

OBJECTIVE

Our objective was to determine if body composition differs between infants born to lean or overweight breastfeeding women.

DESIGN

Body composition (PeaPod, COSMED USA, Inc) and anthropometric outcomes were measured in 65 infants born to lean mothers (n=46) (BMI 18.5 to 24.9) or overweight mothers (n=19) (BMI 25 to 29.9) between 2006 and 2007. Maternal body composition (BodPod, COSMED USA, Inc) was also measured.

RESULTS

Body fat mass was higher in infants born to overweight mothers compared with infants born to lean mothers at age 2 weeks and 3 months (11.9% vs 15.3% and 24.1% vs 26.8%, respectively; P<0.05). After adjusting for gestational weight gain and birth weight, body fat mass was significantly greater only at age 2 weeks.

CONCLUSIONS

Infants of overweight mothers have greater body fat mass in the neonatal period compared with infants of lean mothers, suggesting that maternal overweight may predispose fetal metabolism to favor fat storage. Although our data suggest that this effect is short lived, future studies are needed to investigate children beyond the infancy period to test if body composition is greater in offspring of overweight women.

Assortative marriages by body mass index have increased simultaneously with the obesity epidemic

BACKGROUND

The genetic predisposition to obesity may have contributed to the obesity epidemic through assortative mating. We investigated whether spouses were positively assorted by body mass index (BMI; = kg/m(2)) in late childhood, and whether changes in assorted marriage by upper BMI-percentiles occurred during the obesity epidemic.

METHODS

In the Copenhagen School Health Records Register (CSHRR) boys and girls with measures of BMI at age 13 years later became 37,792 spousal-pairs who married between 1945 and 2010. Trends in the spousal BMI correlations using sex-, age-, and birth cohort-specific BMI z-scores across time were investigated. Odds ratios (ORs) of marriage among spouses both with BMI z-scores >90th or >95th percentile compared with marriage among spouses ≤90th percentile were analyzed for marriages entered during the years prior to (1945-1970), and during the obesity epidemic (1971-2010).

FINDINGS

Spousal BMI correlations were around 0.05 and stayed similar across time. ORs of marriage among spouses with BMIs >90th percentile at age 13 were 1.21, 1.05-1.39, in 1945-1970, and increased to 1.63, 1.40-1.91, in 1971-2010 (p = 0.006). ORs of marriage among spouses both >95th BMI percentile were higher and increased more; from 1.39, 1.10-1.81, to 2.39, 1.85-3.09 (p = 0.004).

INTERPRETATION

Spousal correlations by pre-marital BMIs were small and stable during the past 65 years. Yet, there were assorted marriages between spouses with high BMI at age 13 years and the tendency increased alongside with the obesity epidemic which may increase the offsprings' predisposition to obesity.

Socio-demographic and lifestyle determinants of 'Western-like' and 'Health conscious' dietary patterns in toddlers

Determinants of a child's diet shortly after weaning and lactation have been relatively understudied. The aim of the present study was hence to identify common dietary patterns in toddlers and to explore parental and child indicators of these dietary patterns. The study was a population-based, prospective birth-cohort study in Rotterdam, the Netherlands. Food consumption data of 2420 children aged 14 months were used. A 'Health conscious' dietary pattern characterised by pasta, fruits, vegetables, oils, legumes and fish, and a 'Western-like' dietary pattern characterised by snacks, animal fats, confectionery and sugar-containing beverages were extracted using principal component analysis. Low paternal education, low household income, parental smoking, multiparity, maternal BMI, maternal carbohydrate intake and television-watching of child were determinants of a 'Western-like' diet, whereas parental age, dietary fibre intake during pregnancy, introduction of solids after 6 months and female sex were inversely associated with a 'Western-like' diet of the child. Maternal co-morbidity, alcohol consumption during pregnancy and female sex were inversely associated with a 'Health conscious' dietary pattern of the child, while single parenthood, folic acid use and dietary fibre intake during pregnancy were positively associated. All aforementioned associations were statistically significant. In conclusion, both 'Western-like' and 'Health conscious' diets can already be identified in toddlers. Particularly, adherence to a 'Western-like' diet is associated with unfavourable lifestyle factors of the parents and child, and low socio-economic background. These findings can form a basis for future epidemiological studies regarding dietary patterns and health outcomes in young children.

Gestational weight gain and body mass index in children: results from three german cohort studies

Introduction

Previous studies suggested potential priming effects of gestational weight gain (GWG) on offspring’s body composition in later life. However, consistency of these effects in normal weight, overweight and obese mothers is less clear.

Methods

We combined the individual data of three German cohorts and assessed associations of total and excessive GWG (as defined by criteria of the Institute of Medicine) with offspring’s mean body mass index (BMI) standard deviation scores (SDS) and overweight at the age of 5–6 years (total: n = 6,254). Quantile regression was used to examine potentially different effects on different parts of the BMI SDS distribution. All models were adjusted for birth weight, maternal age and maternal smoking during pregnancy and stratified by maternal pre-pregnancy weight status.

Results

In adjusted models, positive associations of total and excessive GWG with mean BMI SDS and overweight were observed only in children of non- overweight mothers. For example, excessive GWG was associated with a mean increase of 0.08 (95% CI: 0.01, 0.15) units of BMI SDS (0.13 (0.02, 0.24) kg/m² of ‘real’ BMI) in children of normal-weight mothers. The effects of total and excessive GWG on BMI SDS increased for higher- BMI children of normal-weight mothers.

Discussion

Increased GWG is likely to be associated with overweight in offspring of non-overweight mothers.

Time spent in sedentary behavior and changes in childhood BMI: a longitudinal study from ages 9 to 15 years

OBJECTIVE

To determine if time spent in objectively measured sedentary behavior is associated with a change in body mass index (BMI) between ages 9 and 15 years, adjusting for moderate-to-vigorous physical activity (MVPA).

DESIGN

Prospective observational study of children at ages 9 (2000), 11 (2002), 12 (2003) and 15 years (2006). Longitudinal quantile regression was used to model the influence of predictors on changes at the 10th, 25th, 50th, 75th and 90th BMI percentiles over time.

SUBJECTS

Participants were enrolled in the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development and include both boys and girls (n=789).

MEASUREMENTS

Objectively measured BMI (kg m(-2)) was the outcome variable and objectively measured sedentary behavior was the main predictor. Adjustment was also made for MVPA, gender, race, maternal education, hours of sleep and healthy eating index.

RESULTS

Increases in BMI were observed at all percentiles, with the greatest increase observed at the 90th BMI percentile. Spending more time in sedentary behavior (h per day) was associated with additional increases in BMI at the 90th, 75th and 50th BMI percentiles, independent of MVPA and the other covariates (90th percentile=0.59, 95% confidence interval (95% CI): 0.19-0.98 kg m(-2); 75th percentile=0.48, 95% CI: 0.25-0.72 kg m(-2); and 50th percentile=0.19, 95% CI: 0.05-0.33 kg m(-2)). No associations were observed between sedentary behavior and changes at the 25th and 10th BMI percentiles.

CONCLUSION

Sedentary behavior was associated with greater increases in BMI at the 90th, 75th and 50th BMI percentiles between ages 9 and 15 years, independent of MVPA. Preventing an increase in sedentary behavior from childhood to adolescence may contribute to reducing the number of children classified as obese.

Prediction intervals for future BMI values of individual children: a non-parametric approach by quantile boosting

Background

The construction of prediction intervals (PIs) for future body mass index (BMI) values of individual children based on a recent German birth cohort study with n = 2007 children is problematic for standard parametric approaches, as the BMI distribution in childhood is typically skewed depending on age.

Methods

We avoid distributional assumptions by directly modelling the borders of PIs by additive quantile regression, estimated by boosting. We point out the concept of conditional coverage to prove the accuracy of PIs. As conditional coverage can hardly be evaluated in practical applications, we conduct a simulation study before fitting child- and covariate-specific PIs for future BMI values and BMI patterns for the present data.

Results

The results of our simulation study suggest that PIs fitted by quantile boosting cover future observations with the predefined coverage probability and outperform the benchmark approach. For the prediction of future BMI values, quantile boosting automatically selects informative covariates and adapts to the age-specific skewness of the BMI distribution. The lengths of the estimated PIs are child-specific and increase, as expected, with the age of the child.

Conclusions

Quantile boosting is a promising approach to construct PIs with correct conditional coverage in a non-parametric way. It is in particular suitable for the prediction of BMI patterns depending on covariates, since it provides an interpretable predictor structure, inherent variable selection properties and can even account for longitudinal data structures.

Impact of maternal physical activity and infant feeding practices on infant weight gain and adiposity

Increasing evidence supports the contribution of intrauterine environmental exposures on obesity risk in offspring. Few studies have included maternal and infant lifestyle factors. Our objective was to study the impact of maternal physical activity, infant feeding, and screen time on offspring weight gain and adiposity. In a prospective cohort study, 246 mothers underwent testing during pregnancy to assess glucose tolerance status and insulin sensitivity. Anthropometry and questionnaires on physical activity, infant feeding, and screen time were completed. Multiple-linear regression was performed to examine the impact of maternal and infant factors on infant weight gain and weight-for-length z-score at 1 year. Infant weight outcomes were negatively predicted by maternal pregravid vigorous/sport index and exclusive breastfeeding duration. After adjustment, each unit increase in maternal pregravid vigorous/sport index decreased infant weight gain by 218.6 g (t = 2.44, P = 0.016) and weight-for-length z-score by 0.20 (t = 2.17, P = 0.031). Each month of exclusive breastfeeding reduced infant weight gain by 116.4 g (t = 3.97, P < 0.001) and weight-for-length z-score by 0.08 (t = 2.59, P = 0.01). Maternal pregravid physical activity and exclusive breastfeeding duration are associated with weight gain and adiposity as early as 1 year of age.

Tobacco smoke exposure before, during, and after pregnancy and risk of overweight at age 6

Maternal smoking during pregnancy has been associated with overweight and obesity in childhood and is strongly correlated with children's tobacco smoke exposure before and after pregnancy. We investigated the independent association of tobacco smoke exposure at various pre- and postnatal periods and overweight at age 6. A total of 1,954 children attending the 2001-2002 school entrance health examination in the city of Aachen, Germany, were included into this study. Height and weight were measured, BMI was calculated. Tobacco smoke exposure at various periods, other lifestyle and sociodemographic factors were ascertained by questionnaire. Multiple logistic regression models were used to assess the association between tobacco smoke exposure and overweight. Prevalence of overweight was 8.9%. Significant positive associations were found with maternal smoking before and during pregnancy and during the first and sixth year of life. When all smoking periods were included into one logistic model simultaneously, secondhand smoke exposure after birth remained positively associated with overweight at age 6 at either one of the two time periods (first year only: odds ratio (OR) (95% confidence interval (CI)): 2.94 (1.30-6.67), sixth year only: 2.57 (1.64-4.04), respectively) or at both (4.43 (2.24-8.76)). Exposure to tobacco smoke during the first years of life appears to be a key risk factor for development of childhood overweight.

Evidence that obesity risk factor potencies are weight dependent, a phenomenon that may explain accelerated weight gain in western societies

BACKGROUND

We have shown that individuals at the highest percentiles of the body mass index (BMI) distribution (i.e., most overweight) experience greater increases in body weight from sedentary lifestyle than those from the lowest percentiles. The purpose of the current analyses was to assess whether recent, accelerated increases in obesity could potentially be due to increased vulnerability to obesity risk factors as the population has become more overweight.

METHODOLOGY/PRINCIPAL FINDINGS

Quantile regression was used to compare BMI population percentiles to obesity risk factors (lower education, diets characterized by high-meat/low-fruit content, parental adiposity) in two independent samples of men (N(1) = 3,513, N(2) = 11,365) and women (N(1) = 15,809, N(2) = 10,159). The samples were subsets of the National Walkers' (Study 1) and Runners' (Study 2) Health Studies whose physical activities fell short of nationally recommended activity levels. The data were adjusted for age, race, and any residual effects of physical activity. The regression slopes for BMI vs. education, diet, and family history became progressively stronger from the lowest (e.g., 5(th), 6(th)…) to the highest (e.g., …, 94(th), 95(th)) BMI percentiles. Compared to the 10(th) BMI percentile, their effects on the 90(th) BMI percentile were: 1) 2.7- to 8.6-fold greater in women and 2.0- to 2.4-fold greater in men for education; 2) 3.6- to 4.8-fold greater in women and 1.7- to 2.7-fold greater in men for diet; and 3) 2.0- to 2.6-fold greater in women and 1.7-fold greater in men for family history.

CONCLUSIONS/SIGNIFICANCE

Thus we propose risk factors that produce little weight gain in lean individuals may become more potent with increasing adiposity. This leads us to hypothesize that an individual's obesity is itself a major component of their obesogenic environment, and that, the cycle of weight gain and increased sensitivity to obesity risk factors may partly explain recent increases in obesity in western societies.

Increasing genetic variance of body mass index during the Swedish obesity epidemic

BACKGROUND AND OBJECTIVES

There is no doubt that the dramatic worldwide increase in obesity prevalence is due to changes in environmental factors. However, twin and family studies suggest that genetic differences are responsible for the major part of the variation in adiposity within populations. Recent studies show that the genetic effects on body mass index (BMI) may be stronger when combined with presumed risk factors for obesity. We tested the hypothesis that the genetic variance of BMI has increased during the obesity epidemic.

METHODS

The data comprised height and weight measurements of 1,474,065 Swedish conscripts at age 18-19 y born between 1951 and 1983. The data were linked to the Swedish Multi-Generation Register and the Swedish Twin Register from which 264,796 full-brother pairs, 1,736 monozygotic (MZ) and 1,961 dizygotic (DZ) twin pairs were identified. The twin pairs were analysed to identify the most parsimonious model for the genetic and environmental contribution to BMI variance. The full-brother pairs were subsequently divided into subgroups by year of birth to investigate trends in the genetic variance of BMI.

RESULTS

The twin analysis showed that BMI variation could be explained by additive genetic and environmental factors not shared by co-twins. On the basis of the analyses of the full-siblings, the additive genetic variance of BMI increased from 4.3 [95% CI 4.04-4.53] to 7.9 [95% CI 7.28-8.54] within the study period, as did the unique environmental variance, which increased from 1.4 [95% CI 1.32-1.48] to 2.0 [95% CI 1.89-2.22]. The BMI heritability increased from 75% to 78.8%.

CONCLUSION

The results confirm the hypothesis that the additive genetic variance of BMI has increased strongly during the obesity epidemic. This suggests that the obesogenic environment has enhanced the influence of adiposity related genes.

Body size and growth in 0- to 4-year-old children and the relation to body size in primary school age

Excess weight in early life is believed to increase susceptibility to obesity, and in support of such theory, excess weight and fast weight gain in early childhood have been related to overweight later in life. The aim of this study was to review the literature on body size and growth in 0- to 4-year-old children and the association with body size at age 5-13 years. In total, 43 observational studies on body size and/or growth were included, of which 24 studies had been published in 2005 or later. Twenty-one studies considered body size at baseline, and 31 studies considered growth which all included assessment of weight gain. Eight (38%) studies on body size, and 15 (48%) on weight gain were evaluated as high-quality studies. Our results support conclusions in previous reviews of a positive association between body size and weight gain in early childhood, and subsequent body size. Body size at 5-6 months of age and later and weight gain at 0-2 years of age were consistently positively associated with high subsequent body size. Results in this review were mainly based on studies from developed Western countries, but seven studies from developing countries showed similar results to those from developed countries.

Genetic markers of obesity risk: stronger associations with body composition in overweight compared to normal-weight children

Background

Genetic factors are important determinants of overweight. We examined whether there are differential effect sizes depending on children's body composition.

Methods

We analysed data of n = 4,837 children recorded in the Avon Longitudinal Study of Parents and Children (ALSPAC), applying quantile regression with sex- and age-specific standard deviation scores (SDS) of body mass index (BMI) or with body fat mass index and fat-free mass index at 9 years as outcome variables and an “obesity-risk-allele score” based on eight genetic variants known to be associated with childhood BMI as the explanatory variable.

Results

The quantile regression coefficients increased with increasing child's BMI-SDS and fat mass index percentiles, indicating larger effects of the genetic factors at higher percentiles. While the associations with BMI-SDS were of similar size in medium and high BMI quantiles (40th percentile and above), effect sizes with fat mass index increased over the whole fat mass index distribution. For example, the fat mass index of a normal-weight (50th percentile) child was increased by 0.13 kg/m² (95% confidence interval (CI): 0.09, 0.16) per additional allele, compared to 0.24 kg/m² per allele (95% CI: 0.15, 0.32) in children at the 90th percentile. The genetic associations with fat-free mass index were weaker and the quantile regression effects less pronounced than those on fat mass index.

Conclusions

Genetic risk factors for childhood overweight appear to have greater effects on fatter children. Interaction of known genetic factors with environmental or unknown genetic factors might provide a potential explanation of these findings.

Is low birth weight in the causal pathway of the association between maternal smoking in pregnancy and higher BMI in the offspring?

A number of cross-sectional and prospective studies suggested a priming effect of maternal smoking in pregnancy on offspring's obesity. It has been hypothesized that this association might be explained by low birth weight and subsequent catch-up growth in the causal pathway. We therefore examined the role of birth weight in children exposed versus not exposed to cigarette smoking in utero on later body mass index (BMI). Using data of 12,383 children and adolescents (3-17 years of age) recorded in a German population-based survey (KiGGS), we assessed mean body mass index standard deviation scores (BMI-SDS) in different birth weight SDS categories, stratified for children with smoking and non-smoking mothers. We calculated spline regression models with BMI-SDS as outcome variable, cubic splines of birth weight SDS, and potential confounding factors. Children whose mothers had been smoking during pregnancy had lower birth weight SDS and higher BMI-SDS at interview compared to children of non-smoking mothers. However, we observed a linear association between birth weight SDS and BMI-SDS in crude analyses for both groups. Similarly, almost linear effects were observed in adjusted spline regression analyses, except for children with very low birth weight. The respective 95% confidence bands did not preclude a linear effect for the whole birth weight SDS distribution. Our findings suggest that low birth weight is unlikely to be the main cause for the association between intrauterine nicotine exposure and higher BMI in later life. Alternative mechanisms, such as alterations in the noradrenergic system or increased food efficiency, have to be considered.

Risk factors for obesity: further evidence for stronger effects on overweight children and adolescents compared to normal-weight subjects

BACKGROUND

We recently showed that in preschoolers risk factors for overweight show stronger associations with BMI in children with high BMI values. However, it is unclear whether these findings might also pertain to adolescents.

METHODS

We extracted data on 3-10 year-old (n = 7,237) and 11-17 year-old (n = 5,986) children from a representative cross-sectional German health survey (KiGGS) conducted between 2003 and 2006 and calculated quantile regression models for each age group. We used z-scores of children's body mass index (BMI) as outcome variable and maternal BMI, maternal smoking in pregnancy, low parental socioeconomic status, exclusive formula-feeding and high TV viewing time as explanatory variables.

RESULTS

In both age groups, the estimated effects of all risk factors except formula-feeding on BMI z-score were greatest for children with the highest BMI z-score. The median BMI z-score of 11-17 year-old children with high TV viewing time, for example, was 0.11 [95% CI: 0.03, 0.19] units higher than the median BMI z-score of teenage children with low TV viewing time. This risk factor was associated with an average difference of 0.18 [0.06, 0.30] units at the 90(th) percentile of BMI z-score and of 0.20 [0.07, 0.33] units at the 97(th) percentile.

CONCLUSIONS

We confirmed that risk factors for childhood overweight are associated with greater shifts in the upper parts of the children's BMI distribution than in the middle and lower parts. These findings pertain also to teenagers and might possibly help to explain the secular shift in the upper BMI percentiles in children and adolescents.