How does maturity adjustment influence the estimates of overweight prevalence in adolescents from different countries using an international reference?

Association between precocious puberty and obesity risk in children: a systematic review and meta-analysis

Objectives

The aim of this study was to evaluate the potential association between early onset puberty and the risk of different forms of obesity in children.

Methods

The databases PubMed, EMBASE, Web of Science and Cochrane Library were systematically searched for relevant studies. The odds ratio (OR) and 95% confidence interval (CI) of obesity in precocious puberty were calculated using Stata software 14.0. A fixed-effects model was used if P > 0.1 and I2 ≤ 50%. Otherwise, a random-effects model was used. Publication bias was assessed using funnel plots and Egger's test.

Result

The pooling analysis showed that precocious puberty in girls was associated with a higher risk of obesity (OR = 1.98; 95% CI: 1.76-2.24; I2 = 0.00%, P < 0.001). Girls with a history of precocious puberty were found to have an increased risk of general obesity (OR = 2.03; 95% CI: 1.62-2.55; I2 = 22.2%, P < 0.001), central obesity (OR = 1.96; 95% CI: 1.70-2.26; I2 = 0.00%, P < 0.001), and overweight (OR = 2.03; 95% CI: 1.68-2.46; I2 = 5.1%, P < 0.001). The pooled analysis showed that precocious puberty in boys was not associated with an increased risk of obesity (OR = 1.14; 95% CI: 0.86-1.51; I2 = 50.6%, P = 0.369). In boys, the occurrence of precocious puberty was not associated with an elevated risk of general obesity (OR = 0.96; 95% CI: 0.40-2.27; I2 = 79.6%, P = 0.922), central obesity (OR = 1.17; 95% CI: 0.96-1.43; I2 = 0.00%, P = 0.125), or overweight (OR = 1.03; 95% CI: 0.56-1.88; I2 = 74.4%, P = 0.930).

Conclusion

This meta-analysis suggests that the onset of puberty at an early age in girls is associated with an increased risk of obesity, however precocious puberty in boy was not associated with an increased risk of obesity. These findings highlight that precocious puberty should be considered an independent risk factor for obesity in girls.

Systematic Review Registration

CRD42023404479.

Adjusting for Pubertal Status Reduces Overweight and Obesity Prevalence in the United States

OBJECTIVE

To compare pediatric overweight and obesity prevalence among non-Hispanic white, Mexican American, and non-Hispanic black US youths before and after adjusting body mass index (BMI) for pubertal status, as assessed by Tanner stage.

STUDY DESIGN

We analyzed cross-sectional anthropometric and pubertal data from non-Hispanic white, Mexican American, and non-Hispanic black youths in the National Health and Nutrition Examination Survey (NHANES) III. We developed specialized Tanner stage and chronological age-adjusted models to establish Tanner-stage adjusted BMI z-scores, which were then used to determine adjusted overweight/obesity prevalence. We compared pediatric overweight/obesity prevalence before and after pubertal status adjustment.

RESULTS

Among 3206 youths aged 8-18 years (50% male; 26% non-Hispanic white, 35% Mexican American, 39% non-Hispanic black), adjusting BMI for Tanner stage significantly reduced overweight (males, from 29% to 21%; females, from 29% to 17%) and obesity (males, from 14% to 7%; females, from 11% to 5%) prevalence across all races/ethnicities. The obesity prevalence reduction was more pronounced in Mexican Americans (males, 11% reduction; females, 9% reduction) and non-Hispanic blacks (males and females, 10% reduction) compared with non-Hispanic whites (males, 6% reduction; females, 5% reduction). Similar patterns were seen in overweight prevalence.

CONCLUSIONS

Adjusting for pubertal status reduced the prevalence of overweight/obesity in non-Hispanic white, Mexican American, and non-Hispanic black youth. This suggests that adjusting for puberty incorporates changes otherwise not captured when only considering the age of a child. Adjusting BMI for pubertal status may be important when interpreting a youth's weight status and consideration for obesity management, as well as when interpreting pediatric overweight/obesity prevalence data.

Change and Stability in Sibling Resemblance in Obesity Markers: The Portuguese Sibling Study on Growth, Fitness, Lifestyle, and Health

BACKGROUND/OBJECTIVES

Obesity markers evolve over time and these changes are shared within the family orbit and governed by individual and environmental characteristics. Available reports often lack an integrated approach, in contrast to a multilevel framework that considers their concurrent influence. Hence, this study aims to (1) describe mean changes in obesity markers (body fat (%BF), body mass index (BMI), and waist circumference (WC)) across sib-ships; (2) analyze tracking of individuals within their sib-ship in these markers during 2 years of follow-up; (3) probe consistency in sibling resemblance in these markers; and (4) analyze the joint influence of individual and familial characteristics in these markers.

SUBJECTS/METHODS

The sample comprises 168 biological Portuguese siblings (brother-brother (BB), sister-sister (SS), and brother-sister (BS)) aged 9-17 years. %BF, BMI, and WC were measured using standardized protocols, and biological maturation was assessed. Physical activity, diet, screen time, and familial characteristics were obtained by questionnaires. Multilevel models were used to analyze the clustered longitudinal data. Sibling resemblance was estimated with the intraclass correlation.

RESULTS

On average, all sib types increased in BMI and WC over 2 years of follow-up, and SS pairs increased in %BF. Individuals within sib-ships track high in all obesity markers across time. Consistency in siblings' resemblance was also noted, except for BB pairs in %BF which decreased at follow-up. More maturing siblings tend to have higher values in all markers. Greater screen time was associated with higher %BF, whereas those consuming more sugary drinks had lower %BF and BMI values. Siblings whose mothers had less qualified occupations tended to have lower BMI values.

CONCLUSIONS

Longitudinal individual tracking and sibling resemblance for obesity markers were found. Yet, different trajectories were also identified depending on the marker and sib type. Individual and familial characteristics exert different influences on each obesity marker.

Effect of Adjusting for Tanner Stage Age on Prevalence of Short and Tall Stature of Youths in the United States

OBJECTIVE

To evaluate the extent to which pubertal timing alters the classification of extremes of attained stature across race-ethnicity groups of youths in the US.

STUDY DESIGN

We performed analyses of height and Tanner staging data of 3206 cross-sectional national sample of youths ages 8-18 years (53% male, n = 1606), 72% of whom were non-Hispanic white, 9% Mexican American, and 19% non-Hispanic black . Specialized growth models were used to derive Tanner-stage-age-adjusted z scores (TSA_HAZ). The prevalence of shortness (<-1SD) and tallness (≥+1SD) status was quantified using TSA_HAZ.

RESULTS

Highly variable patterns of prevalence of shortness and tallness via chronologic age height z score (CA_HAZ) were observed in results stratified by race-ethnicity and sex. Tallness CA_HAZ prevalence was high among non-Hispanic white and non-Hispanic black male youths relative to Mexican American (40.0%-43.3% vs 20.5%) with a similar pattern in female youths. In both sexes, this pattern was eliminated with TSA_HAZ, with Mexican American youth becoming statistically not different from their non-Hispanic white and non-Hispanic black peers.

CONCLUSIONS

Differences in timing of puberty between race-ethnicity groups affects estimated prevalence of shortness and tallness of attained height that remains uncaptured with CA_HAZ. Adjustment for pubertal development might help isolate crucial determinants of attained stature and other aspects of body composition that may be most responsive to intervention programs in populations. The curves developed by adjusting for pubertal status may help the clinician avoid misclassification of children with early and late pubertal development.

Prevalence and characteristics of overweight and obesity among Chinese youth aged 12-18 years: a multistage nationwide survey

OBJECTIVE

The aims of the current study were to assess the prevalence of overweight and obesity by four different references and to explore the characteristics of adolescent overweight and obesity in Chinese secondary school students aged 12-18 years.

STUDY DESIGN

A cross-sectional study was conducted in this study.

METHODS

Using stratified random cluster sampling, 8999 secondary school students were enrolled. The references developed by Must and Dallal and Dietz, the Childhood Obesity Working Group of the International Obesity Task Force, the US Centers for Disease Control and Prevention, and the Group of China Obesity Task Force (GCOTF reference) were used to identify overweight and obese students.

RESULTS

The prevalence of adolescent overweight and obesity vary substantially based on the four references. The prevalence of adolescent overweight and obesity based on GCOTF reference are 8.4% and 4.1%, respectively, which is significantly lower than the prevalence of overweight and obesity in their peers in 2000 (χ² = 24.03, P < 0.01). The prevalence of overweight and obesity in boys are 12.0% and 5.7%, which are higher than those in girls, 4.6% and 5.7% (χ² = 240.68, P < 0.01). The prevalence of overweight and obesity in singletons are higher than those in non-singletons (χ² = 40.25, P < 0.01). The prevalence of overweight and obesity in students with lower school community ladder of subjective social status are higher than those from higher ones (χ² = 21.61, P < 0.01).

CONCLUSION

The GCOTF reference is more suitable for screening overweight and obesity in Chinese adolescents. The current prevalence rates of adolescent overweight and obesity decreased, and girls made a tremendous contribution to this decreasing trend. Singletons and adolescents in lower school community ladder of subjective socio-economic status may be at higher risk of getting overweight and obesity. More effective strategies with full consideration to the characteristics above should be developed to control and prevent adolescent overweight and obesity.

Associations of pubertal stage and body mass index with cardiometabolic risk in Hong Kong Chinese children: A cross-sectional study

BACKGROUND

Puberty is associated with a clustering of cardiometabolic risk factors (CMRFs) during adolescence that are manifested in later life. Although anthropometric variables such as body mass index (BMI) can predict cardiometabolic risk in children and adolescents, it is not clear whether there is an interaction between pubertal stage and BMI associated with cardiometabolic risk in this age group. This paper examines the association of pubertal stage and BMI with CMRFs in Hong Kong Chinese children.

METHODS

A cross-sectional school-based study was conducted among 1985 (95.1%) students aged 6 to 18 years. Fasting lipid profile and plasma glucose, blood pressure, body weight, body height and waist circumference were measured. A self-reported pubertal stage questionnaire was used to assess pubertal stage of participants. Two cardiometabolic risk scores, alpha and beta, were constructed to quantify cardiometabolic risk. Cardiometabolic risk score alpha refers to the sum of z-scores of sex-specific, age-adjusted waist circumference, height-adjusted systolic and diastolic blood pressure, fasting plasma glucose, triglyceride and low-density lipoprotein cholesterol, and minus z-score of sex-specific age-adjusted high-density lipoprotein cholesterol. Cardiometabolic risk score beta includes all components of risk score alpha except waist circumference.

RESULTS

The interaction of BMI z-score (ZBMI) and pubertal stage demonstrated a further increase in variance explained in both the cardiometabolic risk scores alpha and beta (0.5% and 0.8% respectively) in boys and (0.7% and 0.5% respectively) in girls.

CONCLUSIONS

Pubertal stage has an interaction effect on the association of cardiometabolic risk by BMI in boys and may have a similar but lesser effect in girls.

Body mass index distribution affects discrepancies in weight classifications in children

BACKGROUND

The aim of the present study was to investigate the effect of body mass index (BMI) distribution, ethnicity and age at menarche on the consistency in the prevalence of underweight and overweight defined by the Centers for Disease Control and Prevention (CDC) and the International Obesity Task Force (IOTF) cut-off points in 2-17-year-old Chinese and US children.

METHODS

Data from the China Health and Nutrition Survey (CHNS) 1991 (n= 3895), CHNS 2004 (n= 1902), and the National Health and Nutrition Examination Survey (NHANES) 2003-2004 (n= 3344) were used to define the prevalence of underweight and overweight using the CDC and IOTF BMI cut-off points.

RESULTS

An upward shift in the BMI distribution was observed from the CHNS 1991 to CHNS 2004, and between the CHNS and NHANES 2004. The prevalence of underweight defined by the IOTF cut-off points was higher than that obtained using the CDC cut-off points; absolute differences between IOTF and CDC classifiers were 7%, 5%, and 2% in boys, and 12%, 11%, and 4% in girls in the CHNS 1991, CHNS 2004, and NHANES 2004, respectively. There was a greater consistency in the prevalence of overweight. The consistency of the two classification systems increased with the higher BMI distribution and was not affected significantly by ethnicity or age at menarche.

CONCLUSIONS

The BMI distribution of a population can affect the classification of childhood underweight and overweight differentially as defined by the CDC and IOTF cut-off points, and thus should be considered in the interpretation of results in clinical and population settings.

Childhood obesity: are we all speaking the same language?

Terminology and measures used in studies of weight and adiposity in children can be complex and confusing. Differences arise in metrics, terminology, reference values, and reference levels. Most studies depend on body mass index (BMI) calculated from weight and height, rather than on more direct measures of body fatness. Definitions of overweight and obesity are generally statistical rather than risk-based and use a variety of different reference data sets for BMI. As a result, different definitions often do not give the same results. A basic problem is the lack of strong evidence for any one particular definition. Rather than formulate the question as being one of how to define obesity, it might be useful to consider what BMI cut-points best predict future health risks and how efficiently to screen for such risks. The answers may be different for different populations. In addition, rather than depending solely on BMI to make screening decisions, it is likely to be useful to also consider other factors, including not only race-ethnicity, sex and age, but also factors such as family history. Despite their limitations, BMI-based definitions of overweight and obesity provide working practical definitions that are valuable for general public health surveillance and screening.

Trends in blood pressure and hypertension among Chinese children and adolescents: China Health and Nutrition Surveys 1991-2004

OBJECTIVE

To observe the trends in blood pressure (BP) and prevalence of hypertension among Chinese children and adolescents.

METHODS

Data were extracted from the China Health and Nutrition Survey conducted from 1991 to 2004; 8247 children and adolescents aged 6-17 years were selected for this study. Multivariate linear regression analysis and multivariate logistic regression analysis were performed to evaluate the secular trends in BP levels and prevalence of hypertension, respectively.

RESULTS

During the study period, there was an upward trend in BP in Chinese children and adolescents. After adjustment for gender, age and weight status, the prevalence of pre-hypertension and hypertension increased dramatically from 1991 to 2004, with average relative increases of 6.38% and 8.13% in children and adolescents, respectively. Overweight was strongly associated with pre-hypertension and hypertension in comparison with normal weight, with odds ratios (95% confidence intervals) of 2.21 (1.58-3.11) and 4.13 (3.32-5.13), respectively.

CONCLUSION

BP levels and prevalence of hypertension increased dramatically among Chinese children and adolescents from 1991 to 2004.

Association between overweight and early sexual maturation in Portuguese boys and girls

OBJECTIVE

The purpose of this study was to examine the relationship between sexual maturation (SM), and the prevalence of overweight among boys and girls.

SUBJECTS AND METHODS

The sample of this cross-sectional study included 819 children and adolescents (382 boys and 437 girls), aged 10-15 years old randomly selected from 30 schools in the Porto region. Anthropometrical measurements (body height, weight and skinfolds thickness) were determined by standard anthropometrical methods. Body mass index (BMI) was calculated from the ratio weight/height(2) (kg/m(2)). The sum of tricipital and subscapular skinfolds (TriSub) was also used. Physicians collected data on Tanner stages during physical examination. Subjects were grouped using the quartiles of the decimal age adjusted for Tanner stages of SM and gender.

RESULTS

The prevalence of overweight was higher in early maturing boys (30.5%) and early maturing girls (32.7%). The late maturers presented a lower prevalence (p < 0.05) of overweight (20.3% boys and 18.3% girls). Logistic regression analysis illustrates that early maturing is associated with an increased risk for overweight or obesity for boys (OR: 1.87 and 95% CI: 0.99-3.50) and girls (OR: 2.14 and 95% CI: 1.12-4.07), when compared with the boys and girls of the fourth quartile (p < 0.05).

CONCLUSIONS

We conclude that there is an association between early SM and the prevalence of overweight in both genders.

Prevention and treatment of pediatric obesity: an endocrine society clinical practice guideline based on expert opinion

OBJECTIVE

Our objective was to formulate practice guidelines for the treatment and prevention of pediatric obesity.

CONCLUSIONS

We recommend defining overweight as body mass index (BMI) in at least the 85th percentile but < the 95th percentile and obesity as BMI in at least the 95th percentile against routine endocrine studies unless the height velocity is attenuated or inappropriate for the family background or stage of puberty; referring patients to a geneticist if there is evidence of a genetic syndrome; evaluating for obesity-associated comorbidities in children with BMI in at least the 85th percentile; and prescribing and supporting intensive lifestyle (dietary, physical activity, and behavioral) modification as the prerequisite for any treatment. We suggest that pharmacotherapy (in combination with lifestyle modification) be considered in: 1) obese children only after failure of a formal program of intensive lifestyle modification; and 2) overweight children only if severe comorbidities persist despite intensive lifestyle modification, particularly in children with a strong family history of type 2 diabetes or premature cardiovascular disease. Pharmacotherapy should be provided only by clinicians who are experienced in the use of antiobesity agents and aware of the potential for adverse reactions. We suggest bariatric surgery for adolescents with BMI above 50 kg/m(2), or BMI above 40 kg/m(2) with severe comorbidities in whom lifestyle modifications and/or pharmacotherapy have failed. Candidates for surgery and their families must be psychologically stable and capable of adhering to lifestyle modifications. Access to experienced surgeons and sophisticated multidisciplinary teams who assess the benefits and risks of surgery is obligatory. We emphasize the prevention of obesity by recommending breast-feeding of infants for at least 6 months and advocating that schools provide for 60 min of moderate to vigorous daily exercise in all grades. We suggest that clinicians educate children and parents through anticipatory guidance about healthy dietary and activity habits, and we advocate for restricting the availability of unhealthy food choices in schools, policies to ban advertising unhealthy food choices to children, and community redesign to maximize opportunities for safe walking and bike riding to school, athletic activities, and neighborhood shopping.

Early sexual maturation, central adiposity and subsequent overweight in late adolescence. a four-year follow-up of 1605 adolescent Norwegian boys and girls: the Young HUNT study

Background

Early sexual maturation has been associated with overweight that may persist after the completion of biological growth and development. We have prospectively examined the influence of early sexual maturation on subsequent overweight in late adolescence and assessed if this association was modified by central adiposity in early adolescence.

Methods

1605 Norwegian adolescents were followed from early (baseline, mean age 14.2 years) to late adolescence (follow-up, mean age 18.2 years). Maturational timing was assessed by self-reports of pubertal status (PDS) in boys and age at menarche (AAM) in girls. Central adiposity was classified according to waist circumference (waist) measured at baseline, using age and gender specific medians as cut off. Overweight was classified according to International Obesity Task Force (IOTF) standards.

Results

At follow-up, early sexual maturation in girls, but not in boys, was associated with overweight. This association, however, was restricted to girls with high waist circumference (> median) at baseline (OR, 2.7, 95% CI 1.5–4.9). Thus, age at menarche was not associated with overweight in girls with low waist (≤ median) at baseline. Central adiposity was, independent of maturational timing, associated with higher BMI at follow-up in both genders, but differences were more pronounced among early matured girls (3.5 kg/m²), than among intermediate (2.7 kg/m²) and late matured girls (1.2 kg/m²).

Conclusion

In girls, the combination of central adiposity and early age at menarche appears to increase the risk of being overweight in late adolescence.

Limitations of the current world health organization growth references for children and adolescents

Since the 1970s, the World Health Organization (WHO) has recommended the use of the growth references developed by the United States National Center for Health Statistics (NCHS) based on national survey data collected in the 1960s and 1970s. These references are known as the WHO or NCHS/WHO growth references. Over the past three decades, the WHO or NCHS/WHO growth references have played an important role internationally in the assessment of child and adolescent growth and nutritional status. However, the references have a number of weaknesses. The limitations of the infant portion of the references were thoroughly assessed in WHO's effort to develop a new international growth reference for infants and preschool children. The present report discusses the limitations of the NCHS/WHO references for school-aged children and adolescents, including a number of conceptual, methodological, and practical problems. The global obesity epidemic poses another challenge that the NCHS/WHO reference cannot appropriately meet. There is a need for a single international reference to assess the nutritional status and growth of school-aged children and adolescents across different countries.

Long-term growth and puberty concerns in international adoptees

Growth delay is one of the most common and persistent findings in children who have been adopted from abroad. Although the cause is not clearly understood, it may be related to the observed phenomenon of psychosocial short stature described in children from abusive and neglectful settings in western countries. Fortunately, adopted children generally experience significant improvement in growth after joining their new family, but this may put girls at risk for early and rapidly progressing puberty. This review should help the health care team to understand these issues and work better with the adoptive parents to ensure a child's smooth transition into family life.

Epidemiology of childhood obesity--methodological aspects and guidelines: what is new?

INTRODUCTION

It is still a matter of debate as to how to define obesity in young people, although a growing consensus is to use body mass index (BMI) cutoffs to classify obesity in children and adolescents.

OBJECTIVE

This article provides a brief overview of issues related to the assessment of obesity in children and adolescents.

RESULTS

At present, BMI is probably the best choice among available measures. BMI can be easily assessed at low cost, and has a strong association with body fatness and health risks. However, as an indirect measure of adipose tissue, BMI has a number of limitations. Cole et al published a set of sex- and age-specific BMI cutoffs, which had been developed based on data collected in six countries, and the reference has been recommended for international use. Recently, several researchers have raised concerns regarding this international reference. It has been argued that population-specific standards should be used due to biological differences between populations.

CONCLUSION

BMI is a valid and feasible indirect measure of body fatness, but it suffers from a number of limitations. More efforts are needed to develop valid classifications of childhood obesity.

Early sexual maturation, body composition, and obesity in African-American girls

OBJECTIVE

To describe associations between sexual maturation and body composition in a sample of African-American girls who were participants in phase 1 pilot interventions of the Girls Health Enrichment Multisite Studies.

RESEARCH METHODS AND PROCEDURES

Stature, weight, and waist circumference were measured. Pubic hair and breast development were assessed, and body composition was measured by DXA for 147 African-American girls who were 8 to 10 years of age from three field centers. Participants had BMI > or =25th percentile for age (one site) or BMI > or =50th percentile for age.

RESULTS

Girls Health Enrichment Multisite Studies girls had greater BMI, fat mass, and percentage body fat than national norms and relatively earlier initiation of breast development and pubic hair. Increasing stages of breast development, but not stages of pubic hair, were related to increased stature, waist circumference, BMI, lean mass, fat mass, and percentage of body fat. Pubescent girls (breast stage > or = 2) were greater than six times as likely to be classified as at risk of overweight (BMI > or = 85th percentile) and greater than eight times as likely to be classified as overweight (BMI > or = 95th percentile) as prepubescent counterparts. Adjusted odds ratios for advanced breast development [breast stage > or = 2 (8 years) or > or = 3 (9 and 10 years)] were 3.6 for risk of overweight and for overweight compared to girls with average or less than average breast development.

DISCUSSION

Sexual maturation is important to consider in understanding the classification of overweight and the development of obesity during adolescence. Breast development and pubic hair development should be considered separately for their associations with growth and body composition.

The relationship of ethnicity, socioeconomic factors, and overweight in US adolescents

OBJECTIVE

To examine the extent to which race/ethnic differences in income and education account for sex-specific disparities in overweight prevalence in white, African American, Hispanic, and Asian U.S. teens.

RESEARCH METHODS AND PROCEDURES

We used nationally representative data collected from 13113 U.S. adolescents enrolled in the National Longitudinal Study of Adolescent Health. Logistic regression models were used to examine the relationship of family income and parental education to overweight prevalence (body mass index >or= 85th percentile of age and sex-specific cutoff points from the 2000 Centers for Disease Control and Prevention/National Center for Health Statistics growth charts). In addition, we used coefficients from our logistic regression models to project the effects on overweight prevalence of equalizing the socioeconomic status (SES) differences between race/ethnic groups.

RESULTS

Keeping adolescents in their same environments and changing only family income and parental education had a limited effect on the disparities in overweight prevalence. Ethnicity-SES-overweight differences were greater among females than males. Given that overweight prevalence decreased with increasing SES among white females and remained elevated and even increased among higher SES African-American females, African-American/white disparity in overweight prevalence increased at the highest SES. Conversely, disparity was lessened at the highest SES for white, Hispanic, and Asian females. Among males, disparity was lowest at the average SES level.

DISCUSSION

One cannot automatically assume that the benefits of increased SES found among white adults will transfer to other gender-age-ethnic groups. Our findings suggest that efforts to reduce overweight disparities between ethnic groups must look beyond income and education and focus on other factors, such as environmental, contextual, biological, and sociocultural factors.

Is obesity associated with early sexual maturation? A comparison of the association in American boys versus girls

BACKGROUND

Increasing evidence suggests a close association between early sexual maturation (SM) and obesity in girls and female adults. Earlier maturing girls are more likely to be obese than nonearly maturers. However, limited research has been conducted in boys.

OBJECTIVE

To examine the influence of early SM on fatness in boys and compare it with girls, and to test the hypothesis that the associations differ by gender because of the differences in growth and SM patterns in boys and girls.

STUDY DESIGN

Cross-sectional study.

SUBJECTS

One thousand five hundred one girls and 1520 boys (aged 8-14 years) who participated in the Third National Health and Nutrition Examination Survey survey (1988-1994) and had complete anthropometry (weight, height, skinfold thickness) and SM data.

METHODS

Based on each individual's age and SM status (Tanner stages: genitalia stages for boys and breast stages for girls), the subjects were classified as: 1) early maturers (those who reached a certain Tanner stage earlier than the median age for that stage), and 2) the others (average and later maturers). Overweight was defined as a body mass index (BMI) > or =85th percentile, and obesity > or =95th percentile. Logistic regression analysis was to test how early maturation affected the risks for overweight and obese. Using multiple linear regression models, the associations between fatness (BMI and skinfold thickness) and SM were systematically examined. Covariates including age, ethnicity, residence, family income, energy intake, and physical activity were adjusted.

RESULTS

Early SM was positively associated with overweight and obesity in girls, but the associations were reverse for boys. The prevalence of overweight in early maturers versus the others was 22.6% versus 31.6% in boys and 34.4% versus 23.2% in girls; the figures for obesity were 6.7% versus 14.8% and 15.6% versus 8.1%, respectively. Odd ratios and 95% confidence intervals for obesity were 0.4 (0.2, 0.8) for boys and 2.0 (1.1, 3.5) for girls, and covariates were adjusted. Most significant differences in overweight and obesity among ethnic groups disappeared after controlling for SM. Fatness (BMI and skinfold thickness) was associated with SM stages and with early maturation in boys and girls, but the associations were in opposite directions. Compared with their counterparts, early maturing boys were thinner, whereas early maturing girls were fatter.

CONCLUSIONS

Obesity is associated with sexual maturation in both boys and girls, but the association differs. There is positive association in girls, but a negative one in boys. Maturation status should be taken into consideration when assessing child and adolescent obesity.

A comparison of international references for the assessment of child and adolescent overweight and obesity in different populations

OBJECTIVE

To compare different references assessing child and adolescent overweight and obesity in different populations.

DESIGN

Comparison cross-sectional study.

SETTING

The United States, Russia, China.

SUBJECTS

A total of 6108 American, 6883 Russian and 3014 Chinese children aged 6-18 y.

INVESTIGATION

Using nationwide survey data from the USA (NHANES III, 1988-1994), Russia (1992), and China (1991), we compared three references: (1) the International Obesity Task Force (IOTF) reference, sex-age-specific body mass index (BMI) cut-offs that correspond to BMIs of 25 for overweight and 30 for obesity at age 18; (2) the World Health Organization (WHO) reference--BMI 85th percentiles for overweight in adolescents (10-19 y) and weight-for-height Z-scores for obesity in children under 10; (3) a USA reference--BMI 85th and 95th percentiles to classify overweight and obesity, respectively.

RESULTS

Using the IOTF reference and 85th BMI percentiles, overweight prevalence was 6.4 and 6.5% in China, 15.7 and 15.0% in Russia, and 25.5 and 24.4% in the USA, respectively. Notable differences existed for several ages. Kappa (=0.84-0.98) indicated an excellent agreement between the two references in general, although they varied by sex-age groupings and countries. Overweight prevalence was twice as high in children (6-9 y) than in adolescents (10-18 y) in China and Russia, but was similar in the USA. Estimates of obesity prevalence using these three references varied substantially.

CONCLUSIONS

The references examined produce similar estimates of overall overweight prevalence but different estimates for obesity. One should be cautious when comparing results based on different references.

SPONSORSHIP

University of Illinois and University of North Carolina.

Trends of obesity and underweight in older children and adolescents in the United States, Brazil, China, and Russia

BACKGROUND

Few studies have used the same references across countries to examine the trends of over- and underweight in older children and adolescents.

OBJECTIVE

Using international references, we examined the trends of overweight and underweight in young persons aged 6-18 y from 4 countries.

DESIGN

Nationally representative data from Brazil (1975 and 1997), Russia (1992 and 1998), and the United States (1971-1974 and 1988-1994) and nationwide survey data from China (1991 and 1997) were used. To define overweight, we used the sex- and age-specific body mass index cutoffs recommended by the International Obesity Task Force. The sex- and age-specific body mass index fifth percentile from the first US National Health and Nutrition Examination Survey was used to define underweight.

RESULTS

The prevalence of overweight increased during the study periods in Brazil (from 4.1 to 13.9), China (from 6.4 to 7.7), and the United States (from 15.4 to 25.6); underweight decreased in Brazil (from 14.8 to 8.6), China (from 14.5 to 13.1), and the United States (from 5.1 to 3.3). In Russia, overweight decreased (from 15.6 to 9.0) and underweight increased (from 6.9 to 8.1). The annual rates of increase in the prevalence of overweight were 0.5% (Brazil), 0.2% (China), -1.1% (Russia), and 0.6% (United States).

CONCLUSIONS

The burden of nutritional problems is shifting from energy imbalance deficiency to excess among older children and adolescents in Brazil and China. The variations across countries may relate to changes and differences in key environmental factors.

Cross-national comparison of childhood obesity: the epidemic and the relationship between obesity and socioeconomic status

BACKGROUND

Obesity has become a worldwide epidemic. Recently WHO acknowledged an urgent need to examine child obesity across countries using a standardized international standard. Studies in adults find obesity and socioeconomic factors (SES) factors are correlated, but results are inconsistent for children. Using an international standard, we examined the prevalence of obesity and compared the associations between SES factors and obesity across countries.

METHODS

Data for children aged 6-18 from nationwide surveys in the US (NHANES III, 1988-1994), China (1993), and Russia (1992) were used. We used the recently updated US NCHS body mass index (BMI = wt/ht(2)) reference to define obesity (BMI > or =95th percentile) and overweight (85th< or =BMI<95th percentile). The WHO recommends an early version of the NCHS reference for international use. We conducted logistic analyses to examine the relationship between SES and obesity.

RESULTS

The prevalence of obesity and overweight was 11.1% and 14.3%, respectively, in the US, 6.0% and 10.0% in Russia, and 3.6% and 3.4% in China. The relationship between obesity and SES varied across countries. Higher SES subjects were more likely to be obese in China and Russia, but in the US low-SES groups were at a higher risk. Obesity was more prevalent in urban areas in China but in rural areas in Russia.

CONCLUSIONS

Child obesity is becoming a public health problem worldwide, but the prevalence of obesity varies remarkably across countries with different socioeconomic development levels. Different SES groups are at different risks, and the relationship between obesity and SES varies across countries.

Maturational timing and overweight prevalence in US adolescent girls

OBJECTIVES

This study examined the relation of age at menarche to overweight in US adolescent girls.

METHODS

Effects of age at menarche and race/ethnicity on overweight were estimated via logistic regression, after adjustment for sociodemographic characteristics, in a sample of 6507 Hispanic, Black, White, and Asian American girls who participated in wave 2 of the National Longitudinal Study of Adolescent Health.

RESULTS

Overweight prevalence rates were significantly higher in early maturing adolescents of all racial/ethnic groups but highest (57.5%) among early maturing Black girls. Early maturation nearly doubled the odds of being overweight (body mass index at or above the 85th percentile).

CONCLUSIONS

Greater public health attention should be focused on the high prevalence of overweight, particularly among minority female adolescents.