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Body mass index reference curves for Tunisian children
Abstract
Body mass index (BMI) reference curves are used to assess children's health. The aim of this work is to construct BMI reference curves for Tunisian children and adolescents and compare them with local and international references. The BMI reference curves were constructed using the LMS method using data from 4358 Tunisian children (2182 girls and 2176 boys) aged 0–18 years. The result of this study presents the smoothed percentile curves of BMI on the basis of age and sex of Tunisian children. The reference curves of Tunisian children demonstrated some variations in comparison with the median percentiles with the references of the International Obesity Task Force (IOTF), the World Health Organization (WHO), and with local references from Algeria and Turkey. The prevalence study indicated that the rate of overweight has increased mainly in adolescent children. Conclusion: the new BMI reference curves could help pediatricians and fitness specialists to assess the nutritional status of Tunisian children and to reduce disease and obesity risks.
... The method and recruitment of the subjects in this crosssectional study have been presented previously [14]. In summary, the anthropometric data were collected between November 2012 and May 2013. ...
... Weight and length (for children under 2 years who are unable to stand independently) or height (for children over 2 years and adolescents) were measured by the specialists in pediatrics. These measurements have been described in detail in the previous studies [14,15]. Regarding the measurement of SH in infants, the legs are placed in the vertical plane forming a right angle with the trunk and the cursor (mobile part) of the horizontal height rod is fixed at the level of the buttocks during the measurement (Fig. 1). ...
A growth chart is a powerful graphical tool displaying children's growth patterns. The aim of this study was to develop growth reference curves appropriate for Tunisian children. The collection of data from this cross-sectional study was conducted on 4358 healthy subjects (2182 girls and 2176 boys) in three pediatric centers and 15 schools. Smoothed growth curves were estimated using the LMS method. The smoothed percentile curves for height, weight, sitting height (SH), and leg length (LL) increase rapidly during the 1st years of life and then progress slowly until 18 years. However, the sitting height-to-height ratio (SHTHR) curves decrease sharply before the age of 4 and then stabilize in both sexes. In addition, the comparison between boys and girls indicated that the values are very similar at most ages. Except during puberty, the values in boys increase (P<0.0001) for the weight, height, SH, and LL parameters and decline (P<0.0001) in the SHTHR compared to the values in girls. The growth rate curves presented two remarkable velocity peaks: the first appears during the 1st years of life and the second at puberty. Height gains at the last stage of growth (puberty) are around 15.45% of final height for boys and 15.52% for girls. This study showed a number of discrepancies for certain age groups when comparing the median weight and height values with those of the World Health Organization, the National Center for Health Statistics, and Algerian references in both sexes. Conclusion: The smoothed percentile curves for weight and height will be useful to access the general growth of Tunisian children. Furthermore, the SH, LL, and SHTHR curves can be used to monitor body proportions during childhood.
... Of note, a meta-analysis revealed that physical inactivity, increased screen time, and higher socio-economic status were risk factors for childhood obesity in the Middle East and North Africa (MENA) (Farrag et al., 2017). Therefore, obesity is characterized as a global epidemic that affects all ages (Ghouili et al., 2018) with childhood and adolescence being crucial periods for prevention and intervention efforts (Monteiro et al., 2015). Moreover, it is often coupled with impairments in cardiovascular fitness, muscle strength, physical function, and the capacity to perform daily activities (Pazzianotto-Forti et al., 2020). ...
The prevalence of obesity in the pediatric population has become a major public health issue. Indeed, the dramatic increase of this epidemic causes multiple and harmful consequences, Physical activity, particularly physical exercise, remains to be the cornerstone of interventions against childhood obesity. Given the conflicting findings with reference to the relevant literature addressing the effects of exercise on adiposity and physical fitness outcomes in obese children and adolescents, the effect of duration-matched concurrent training (CT) [50% resistance (RT) and 50% high-intensity-interval-training (HIIT)] on body composition and physical fitness in obese youth remains to be elucidated. Thus, the purpose of this study was to examine the effects of 9-weeks of CT compared to RT or HIIT alone, on body composition and selected physical fitness components in healthy sedentary obese youth. Out of 73 participants, only 37; [14 males and 23 females; age 13.4 ± 0.9 years; body-mass-index (BMI): 31.2 ± 4.8 kg·m-2] were eligible and randomized into three groups: HIIT (n = 12): 3-4 sets×12 runs at 80–110% peak velocity, with 10-s passive recovery between bouts; RT (n = 12): 6 exercises; 3–4 sets × 10 repetition maximum (RM) and CT (n = 13): 50% serial completion of RT and HIIT. CT promoted significant greater gains compared to HIIT and RT on body composition (p < 0.01, d = large), 6-min-walking test distance (6 MWT-distance) and on 6 MWT-VO2max (p < 0.03, d = large). In addition, CT showed substantially greater improvements than HIIT in the medicine ball throw test (20.2 vs. 13.6%, p < 0.04, d = large). On the other hand, RT exhibited significantly greater gains in relative hand grip strength (p < 0.03, d = large) and CMJ (p < 0.01, d = large) than HIIT and CT. CT promoted greater benefits for fat, body mass loss and cardiorespiratory fitness than HIIT or RT modalities. This study provides important information for practitioners and therapists on the application of effective exercise regimes with obese youth to induce significant and beneficial body composition changes. The applied CT program and the respective programming parameters in terms of exercise intensity and volume can be used by practitioners as an effective exercise treatment to fight the pandemic overweight and obesity in youth.
... Of note, a meta-analysis revealed that physical inactivity, increased screen time, and higher socio-economic status were risk factors for childhood obesity in the Middle East and North Africa (MENA) (Farrag et al., 2017). Therefore, obesity is characterized as a global epidemic that affects all ages (Ghouili et al., 2018) with childhood and adolescence being crucial periods for prevention and intervention efforts (Monteiro et al., 2015). Moreover, it is often coupled with impairments in cardiovascular fitness, muscle strength, physical function, and the capacity to perform daily activities (Pazzianotto-Forti et al., 2020). ...
The prevalence of obesity in the pediatric population has become a major public health issue. Indeed, the dramatic increase of this epidemic causes multiple and harmful consequences, Physical activity, particularly physical exercise, remains to be the cornerstone of interventions against childhood obesity. Given the conflicting findings with reference to the relevant literature addressing the effects of exercise on adiposity and physical fitness outcomes in obese children and adolescents, the effect of duration-matched concurrent training (CT) [50% resistance (RT) and 50% high-intensity-interval-training (HIIT)] on body composition and physical fitness in obese youth remains to be elucidated. Thus, the purpose of this study was to examine the effects of 9-weeks of CT compared to RT or HIIT alone, on body composition and selected physical fitness components in healthy sedentary obese youth. Out of 73 participants, only 37; [14 males and 23 females; age 13.4 ± 0.9 years; body-mass-index (BMI): 31.2 ± 4.8 kg·m-2] were eligible and randomized into three groups: HIIT (n = 12): 3-4 sets×12 runs at 80-110% peak velocity, with 10-s passive recovery between bouts; RT (n = 12): 6 exercises; 3-4 sets × 10 repetition maximum (RM) and CT (n = 13): 50% serial completion of RT and HIIT. CT promoted significant greater gains compared to HIIT and RT on body composition (p < 0.01, d = large), 6-min-walking test distance (6 MWT-distance) and on 6 MWT-VO 2max (p < 0.03, d = large). In addition, CT showed substantially greater improvements than HIIT in the medicine ball throw test (20.2 vs. 13.6%, p < 0.04, d = large). On the other hand, RT exhibited significantly greater gains in relative hand grip strength (p < 0.03, d = large) and CMJ (p < 0.01, d = large) than HIIT and CT. CT promoted greater benefits for fat, body mass loss and cardiorespiratory fitness than HIIT or RT Hassane Zouhal Hassane.zouhal@univ-rennes2.fr † ORCID: Urs Granacher orcid.org/0000-0002-7095-813X Hassane Zouhal oorcid.org/0000-0001-6743-6464 ‡ These authors have contributed equally to this work Specialty section: This article was submitted to Exercise Physiology, a section of the journal Frontiers in Physiology modalities. This study provides important information for practitioners and therapists on the application of effective exercise regimes with obese youth to induce significant and beneficial body composition changes. The applied CT program and the respective programming parameters in terms of exercise intensity and volume can be used by practitioners as an effective exercise treatment to fight the pandemic overweight and obesity in youth.
... Hence, these national standards were considered as an important tool for investigators and pediatricians in monitoring the overweight/obesity changes over time and for comparing different regions. [3,4] In the Kingdom of Saudi Arabia, L, M, and S parameters as well as Z scores were calculated for weight, height, and BMI for school-aged children and adolescents [5] and they were launched in 2016 for more precise assessment of growth and nutrition in research institutions and clinical fields. Towards this, the conduction of a large-scale study employing the national BMI percentile standards could better estimate the actual prevalence of overweight/obesity among Saudi school children and adolescents. ...
... In our previous study, we found overall prevalences of 13.9% overweight/3.3% obesity in boys and 13.8% overweight/ 2.8% obesity in girls aged 2-18 years [25]. ...
Abdominal obesity for children:
Waist circumference (WC) and waist-to-height ratio (WTHR) reference curves are used to assess the risk of cardiovascular disease in children. The aim of this study was to develop age- and sex-smoothed WC and WTHR reference curves for Tunisian children. Data were collected during the period 2014-2015 in a cross-sectional study including 2308 children aged 6-18 years. The percentiles of WC and WTHR were developed using the LMS method. The optimal percentiles, which are associated with the body mass index (BMI) according to International Obesity Task Force (IOTF) criteria to identify overweight/obesity and with the 0.5 boundary value of WTHR to estimate cardiovascular risk, were identified by ROC curves and the Youden index (j). The results show the smoothed percentiles of WC and WTHR reference curves for Tunisian children. A comparison of the 50th percentiles with other references showed different trends in WC values. The 75th percentiles of WC and WTHR are the optimal percentiles that correspond to both PBMI25 (the percentile linked to BMI≥25) and the 0.5 boundary value. However, the 90th percentiles correspond to PBMI30 (the percentile linked to BMI≥30) in boys and girls.
Conclusion:
The new WC and WTHR reference curves can be added to clinical tools to help specialists in pediatric and physical health to reduce cardiovascular risk in Tunisian children.
... In our previous study, we found overall prevalences of 13.9% overweight/3.3% obesity in boys and 13.8% overweight/ 2.8% obesity in girls aged 2-18 years [25]. ...
This study investigated the physiological responses and time structure of kickboxing styles (full contact, light contact, and point fighting). Blood lactate [La] before and after combats, mean heart rate (HRmean), percentage of time spent in HR zones, and rating of perceived exertion were assessed. Time spent in high-intensity activities (HIAs), low-intensity activities (LIAs), and referee pauses (P) were recorded according to rounds (R) and kickboxing styles. [La] increased statistically significant after kickboxing combats (p < 0.001) and was higher after light contact compared with point fighting (p = 0.029). HRmean did not differ between kickboxing specialties (p = 0.200). However, more time was spent on HR zones 4 and 5 (Z4: 80–90% and Z5: 90–100% HRmax) than in other zones (all p < 0.001). Rating of perceived exertion scores were higher after light and full contact combats compared with point fighting (p = 0.007 and 0.093, respectively). High-intensity activities, LIAs, and pauses did not statistically differ across rounds (p > 0.05). Moreover, HIA values were lower than LIA (all p < 0.001), and HIA and LIA were higher than pause for all rounds and styles (all p < 0.001). Full contact elicited higher HIA compared with point fighting (p = 0.003, 0.001, and 0.002 for round 1, 2, and 3, respectively). Coaches and strength and conditioning professionals should emphasize anaerobic and muscle power development for all disciplines, especially for full and light contact and maximal aerobic power enhancement by targeting specific HR zones. Moreover, training regimen may include high-intensity interval training to mimic these sports' specificity using the effort-pause ratios according to different kickboxing sports.
The identification of somatic growth, through reference curves, can be used to create strategies and public policies to reduce public health problems such as malnutrition and obesity and to identify underweight, overweight and obesity. The purpose of this systematic review was to identify studies providing reference growth curves for weight status in children and adolescents. A systematic search was conducted in eight databases and in gray literature (Google scholar). To assess the risk of bias/methodological quality of studies, the National Institutes of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-sectional Studies (NHLBI) was used. Overall, 86 studies that met the inclusion criteria were included. Through the values of reference growth curves for the identification of underweight, overweight and obesity, it was possible to verify that there is great variability among percentiles for the identification of underweight, overweight and obesity. The most prevalent percentiles for underweight were P3 and P5; for overweight, the most prevalent was P85 and the most prevalent percentiles for obesity were P95 and P97. The most prevalent anthropometric indicators were Body Mass Index (BMI), Waist Circumference (WC), Body Mass (BM) for age and height for age. Conclusion: Such data can demonstrate that the optimal growth must be reached, through the standard growth curves, but that the reference curves demonstrate a cut of the population growth, raising possible variables that can influence the optimal growth, such as an increase in the practice of physical activities and an awareness of proper nutrition.
BACKGROUND: Inadequate nutrient intakes in adolescents may negatively affect their future health. The identification of inadequate micronutrient intakes by dietary study provides essential information to guide educational strategies for promoting healthy eating habits. OBJECTIVE: To assess the daily micronutrient intake and the prevalence of inadequacy in a sample of middle and high-school pupils in the Rif region of Morocco. METHODS: A cross-sectional study collected dietary information from food records over three non-consecutive days in a sample (n = 302) of Moroccan Riffian adolescents (12–18 years). The DIAL software, adapted for commonly eaten Moroccan foods, was used to estimate micronutrient intakes. The proportion of individuals with intakes below the Estimated Average Requirement (EAR) or the Adequate Intake (AI) level and the probability approach were used to estimate the prevalence of inadequacy. RESULTS: Regardless of gender and age group, our subjects were found to be particularly at risk of inadequate intakes of vitamins E and D, calcium and potassium. Older adolescents (14–18 years) also showed a risk of inadequate intake of folate, biotin, magnesium, iodine and zinc (among boys). CONCLUSION: For many nutrients, the daily diets of our Riffian adolescents do not meet the recommended intake levels. We emphasize the need for monitoring the dietary habits of adolescents and the development of nutrition education programs. Further studies which include the clinical and biological assessment of nutritional status, as well as the regular collection of quality and nationally representative micronutrient data, are recommended.
Objective:
This study aimed to integrate the existing updated reference standards for the growth of Turkish infants and children and to compare these values with World Health Organization (WHO) reference data, data from some European countries, and also with previous local data. Weight, height, and head circumference measurements were obtained on 2,391 boys and 2,102 girls who were regular attenders of a well child clinic and on 1,100 boys and 1,020 girls attending schools in relatively well-off districts in İstanbul. Mean number of measurements per child was 8.2±3.6 in the age group 0-5 years and 5.5±3.3 in the age group 6-18 years. All children were from well-to-do families and all were healthy. All measurements with the exception of measurements at birth, which were based on reported values, were done by trained personnel.
Methods:
The LMS method was used in the analyses and in the construction of the percentile charts. There is an increase in weight for age and body mass index values for age starting in prepubertal ages, indicating an increasing trend for obesity.
Results:
Compared to WHO reference data, weight and height values in Turkish children were slightly higher in infants and in children younger than 5 years, while they showed similarity to those reported for children from Norway and Belgium. Head circumference values, which were slightly higher than the WHO references in the first 5 years, were comparable to the data on Belgian and Norwegian children in the first 9 years of life. At older ages, Turkish children showed higher values for head circumference.
Conclusion:
The relatively larger head circumference values were interpreted to reflect a genetic characteristic.
Obese children are at higher risk of being obese as adults, and adult obesity is associated with an increased risk of morbidity. This systematic review and meta-analysis investigates the ability of childhood body mass index (BMI) to predict obesity-related morbidities in adulthood. Thirty-seven studies were included. High childhood BMI was associated with an increased incidence of adult diabetes (OR 1.70; 95% CI 1.30-2.22), coronary heart disease (CHD) (OR 1.20; 95% CI 1.10-1.31) and a range of cancers, but not stroke or breast cancer. The accuracy of childhood BMI when predicting any adult morbidity was low. Only 31% of future diabetes and 22% of future hypertension and CHD occurred in children aged 12 or over classified as being overweight or obese. Only 20% of all adult cancers occurred in children classified as being overweight or obese. Childhood obesity is associated with moderately increased risks of adult obesity-related morbidity, but the increase in risk is not large enough for childhood BMI to be a good predictor of the incidence of adult morbidities. This is because the majority of adult obesity-related morbidity occurs in adults who were of healthy weight in childhood. Therefore, targeting obesity reduction solely at obese or overweight children may not substantially reduce the overall burden of obesity-related disease in adulthood.
The potential benefits from the reduction of excessive weight levels among the general population are of considerable public health importance. Early intervention against selected risk factors is a principle key in the prevention of chronic diseases. In this context, a number of school-based interventions to promote healthy lifestyles have been implemented globally in response to the WHO health promotion initiatives. In Tunisia, most studies have primarily focused on the principal determinants of overweight and obese school children. A number of intervention programs for school children have been implemented in different regions and similarly show that supplemental educative program interventions result in only substantive improvements with regard to knowledge, and behavior intent, in the children intervention group (p < 0.05) with no significant effect on their body composition. Therefore, more elaborate, multidisciplinary interventions (education, diet and endurance programs) are recommended to have a significant effect on the health of Tunisian children.
Background
The aim of this study was to assess the less studied interrelationships and pathways between parental BMI, socioeconomic factors, family structure and childhood overweight.
Methods
The cross-sectional LATE-study was carried out in Finland in 2007–2009. The data for the analyses was classified into four categories: younger boys and girls (ca 3–8 years) (n = 2573) and older boys and girls (ca 11–16 years) (n = 1836). Associations between parental BMI, education, labor market status, self-perceived income sufficiency, family structure and childhood overweight were first examined by logistic regression analyses. As parental BMI and education had the most consistent associations with childhood overweight, the direct and indirect (mediated by parental BMI) associations of maternal and paternal education with childhood overweight were further assessed using a path model.
Results
Parental BMI and education were the strongest determinants of childhood overweight. Children of overweight parents had an increased risk of being overweight. In younger boys, maternal and paternal education had both direct (b-coefficient paternal −0.21, 95% CI −0.34 to −0.09; maternal −0.17, 95% CI −0.28 to −0.07) and indirect (b-coefficient paternal −0.04, 95% CI −0.07 to −0.02; maternal −0.04, 95% CI −0.06 to −0.02) inverse associations with overweight. Among the older boys, paternal education had both direct (b-coefficient −0.12, 95% CI −0.24 to −0.01) and indirect (b-coefficient −0.03, 95% CI −0.06 to −0.01) inverse associations with overweight, but maternal education had only an indirect association (b-coefficient −0.04, 95% CI −0.07 to −0.02). Among older girls, only an indirect association of maternal education with childhood overweight was found (b-coefficient −0.03, 95% CI −0.06 to −0.01). In younger girls, parental education was not associated with childhood overweight.
Conclusion
The observed pathways between parental BMI and education and childhood overweight emphasize a need for evidence-based health promotion interventions tailored for families identified with parental overweight and low level of education.
The primary aim of the International Study of Childhood Obesity, Lifestyle and the Environment (ISCOLE) was to determine the relationships between lifestyle behaviours and obesity in a multi-national study of children, and to investigate the influence of higher-order characteristics such as behavioural settings, and the physical, social and policy environments, on the observed relationships within and between countries.Methods/designThe targeted sample included 6000 10-year old children from 12 countries in five major geographic regions of the world (Europe, Africa, the Americas, South-East Asia, and the Western Pacific). The protocol included procedures to collect data at the individual level (lifestyle, diet and physical activity questionnaires, accelerometry), family and neighborhood level (parental questionnaires), and the school environment (school administrator questionnaire and school audit tool). A standard study protocol was developed for implementation in all regions of the world. A rigorous system of training and certification of study personnel was developed and implemented, including web-based training modules and regional in-person training meetings.
The results of this study will provide a robust examination of the correlates of adiposity and obesity in children, focusing on both sides of the energy balance equation. The results will also provide important new information that will inform the development of lifestyle, environmental, and policy interventions to address and prevent childhood obesity that may be culturally adapted for implementation around the world. ISCOLE represents a multi-national collaboration among all world regions, and represents a global effort to increase research understanding, capacity and infrastructure in childhood obesity.
Objective. The aim of this study was to find out the prevalence of overweight and obesity among adolescents in seven Arab countries using similar reference standard. Methods. A school-based cross-sectional study was carried out in seven cities in Arab countries, namely, Algeria, Jordan, Kuwait, Libya, Palestine, Syria, and United Arab Emirates. A multistage stratified random sampling technique was used. The total sample included was 4698 adolescents aged from 15 to 18 years (2240 males, 2458 females). The International Obesity Task Force (IOTF) reference standard was used to classify the adolescents as nonobese, overweight, and obese. Results. Among males, overweight was highest among Kuwaiti adolescents (25.6%), followed by Jordanian (21.6%), and Syrian (19.7%) adolescents. Among females, the highest prevalence of overweight was reported in Libyan adolescents (26.6%), followed by Kuwaiti (20.8%), and Syrian (19.7%) adolescents. As for obesity, Kuwaiti adolescents showed the highest prevalence of obesity for both males (34.8%) and females (20.6%). Conclusion. There is an urgent need to establish a plan of action to combat obesity in schoolchildren in these countries.
To examine the genetic and environmental influences on variances in weight, height, and BMI, from birth through 19 years of age, in boys and girls from three continents.
Cross-sectional twin study. Data obtained from a total of 23 twin birth-cohorts from four countries: Canada, Sweden, Denmark, and Australia. Participants were Monozygotic (MZ) and dizygotic (DZ) (same- and opposite-sex) twin pairs with data available for both height and weight at a given age, from birth through 19 years of age. Approximately 24,036 children were included in the analyses.
Heritability for body weight, height, and BMI was low at birth (between 6.4 and 8.7% for boys, and between 4.8 and 7.9% for girls) but increased over time, accounting for close to half or more of the variance in body weight and BMI after 5 months of age in both sexes. Common environmental influences on all body measures were high at birth (between 74.1-85.9% in all measures for boys, and between 74.2 and 87.3% in all measures for girls) and markedly reduced over time. For body height, the effect of the common environment remained significant for a longer period during early childhood (up through 12 years of age). Sex-limitation of genetic and shared environmental effects was observed.
Genetics appear to play an increasingly important role in explaining the variation in weight, height, and BMI from early childhood to late adolescence, particularly in boys. Common environmental factors exert their strongest and most independent influence specifically in pre-adolescent years and more significantly in girls. These findings emphasize the need to target family and social environmental interventions in early childhood years, especially for females. As gene-environment correlation and interaction is likely, it is also necessary to identify the genetic variants that may predispose individuals to obesity.
To determine a range of anthropometric measurements including skinfold thickness measurements in four different areas of the body, to construct population growth charts for body mass index (BMI), skinfolds, and to compare these with growth charts from other countries. One aim was also to validate body fat charts derived from skinfold thickness.
A national cross-sectional growth survey of children, 0-18 years old, was conducted using multistage stratified random sampling. The sample size included at least 200 children in each age-sex group. Height, weight, biceps skinfold, triceps skinfold, subscapular skinfold, suprailiac skinfold, and mid-upper-arm circumference were measured in each child. We describe correlation, standard deviation scores relative to the other standards, and calculation of body density in the United Arab Emirates population. We determined whether any of the above is a good indicator of fatness in children.
BMI, upper-arm circumference, sum of four skinfolds, and percentage body fat charts were constructed using the LMS method of smoothing. BMI was very significantly correlated with sum of skinfold thicknesses, and mid-upper-arm circumference. Prevalence of obesity and overweight in ages 13-17 years was respectively 9.94% and 15.16% in females and 6.08% and 14.16% in males. Derived body fat charts were found not to be accurate.
A national BMI, upper-arm circumference, and sum of four skinfolds chart has been constructed that can be used as a reference standard for the United Arab Emirates. Sum of four skinfold thickness charts can be used as crude determinants of adiposity in children, but derived body fat charts were shown to be inaccurate.
The World Health Organization recommended in 1978 that the National Center for Health Statistics/Centers for Disease Control growth reference curves be used as an international growth reference. To permit the expression of growth in terms of standard deviations, CDC developed growth curves from the observed data that approximate normal distributions. Because of significant skewness, standard deviations for weight-for-age and weight-for-height were calculated separately for distributions below and above the median. Standard deviations below the median were calculated from the 5th, 10th, 25th, and 50th observed percentiles while those above the median were based on the 50th, 75th, 90th, and 95th observed percentiles. Height-for-age distributions did not show significant skewness, thus, the standard deviations were calculated based on all six of the above observed percentiles. The normalized reference curves provide a highly useful data base that permits the standardized comparison of anthropometric data from different populations.
Reference curves for stature and weight in British children have been available for the past 30 years, and have recently been updated. However weight by itself is a poor indicator of fatness or obesity, and there has never been a corresponding set of reference curves to assess weight for height. Body mass index (BMI) or weight/height has been popular for assessing obesity in adults for many years, but its use in children has developed only recently. Here centile curves for BMI in British children are presented, from birth to 23 years, based on the same large representative sample as used to update the stature and weight references. The charts were derived using Cole's LMS method, which adjusts the BMI distribution for skewness and allows BMI in individual subjects to be expressed as an exact centile or SD score. Use of the charts in clinical practice is aided by the provision of nine centiles, where the two extremes identify the fattest and thinnest four per 1000 of the population.
To develop an internationally acceptable definition of child overweight and obesity, specifying the measurement, the reference population, and the age and sex specific cut off points.
International survey of six large nationally representative cross sectional growth studies.
Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States.
97 876 males and 94 851 females from birth to 25 years of age.
Body mass index (weight/height(2)).
For each of the surveys, centile curves were drawn that at age 18 years passed through the widely used cut off points of 25 and 30 kg/m(2) for adult overweight and obesity. The resulting curves were averaged to provide age and sex specific cut off points from 2-18 years.
The proposed cut off points, which are less arbitrary and more internationally based than current alternatives, should help to provide internationally comparable prevalence rates of overweight and obesity in children.
To delineate a classification system, comprising reference curves and cutoff points, based on the distribution of body mass index (BMI) across a national reference population and designed for the assessment of the nutritional status of Brazilian children and adolescents.
Data from 13,279 males and 12,823 females aged from 2 to 19 years, extracted from the National Nutrition and Health Survey dataset (1989), were used to construct a reference curve. The LMS method was employed to calculate the BMI curve parameters and polynomial functions were used to model these parameters against age. The cutoff values for classifying nutritional status as underweight, overweight and obese were expressed as centiles and BMI values equivalent to 17.5, 25 and 30 kg/m(2) at 20 years, respectively.
Values for the L, M and S parameters were tabulated at 6-month intervals for each sex. Using these values, a graph was plotted with nine BMI distribution reference centiles. Cutoff values were presented that are equivalent to BMIs of 17.5, 25 and 30 kg/m(2) at the start of adulthood.
The classification system presented here can be used for clinical and epidemiological assessments, it is methodologically similar to the majority of national curves that have been presented to date and, furthermore, it offers a definition of underweight.
To determine cut offs to define thinness in children and adolescents, based on body mass index at age 18 years.
International survey of six large nationally representative cross sectional studies on growth.
Brazil, Great Britain, Hong Kong, the Netherlands, Singapore, and the United States.
97 876 males and 94 851 females from birth to 25 years.
Body mass index (BMI, weight/height(2)).
The World Health Organization defines grade 2 thinness in adults as BMI <17. This same cut off, applied to the six datasets at age 18 years, gave mean BMI close to a z score of -2 and 80% of the median. Thus it matches existing criteria for wasting in children based on weight for height. For each dataset, centile curves were drawn to pass through the cut off of BMI 17 at 18 years. The resulting curves were averaged to provide age and sex specific cut-off points from 2-18 years. Similar cut offs were derived based on BMI 16 and 18.5 at 18 years, together providing definitions of thinness grades 1, 2, and 3 in children and adolescents consistent with the WHO adult definitions.
The proposed cut-off points should help to provide internationally comparable prevalence rates of thinness in children and adolescents.
Acquired resistance to the action of insulin to stimulate glucose transport in skeletal muscle is associated with obesity and promotes the development of type 2 diabetes. In skeletal muscle, insulin resistance can result from high levels of circulating fatty acids that disrupt insulin signalling pathways. However, the severity of insulin resistance varies greatly among obese people. Here we postulate that this variability might reflect differences in levels of lipid-droplet proteins that promote the sequestration of fatty acids within adipocytes in the form of triglycerides, thereby lowering exposure of skeletal muscle to the inhibitory effects of fatty acids.
The body mass index (BMI) is widely accepted as a measure of overweight and obesity in children. There are no BMI reference charts for Algerian children and adolescents. The purpose of this study was to construct BMI percentile curves appropriate for children aged 6-18 years in Algeria. The weight and height of 7772 (54.9% girls) healthy schoolchildren from Constantine (eastern Algeria) were measured in 2008/2009. Weight and height for age curves based on the same sample were published previously. The BMI for age percentile curves were estimated in girls and boys separately using the LMS smoothing method. In both sexes, the median BMI increased with age. Girls had lower BMI values than boys before the age of 10 years but they were higher after this age until 18 years of age. Within the study population, the prevalence of overweight (including obesity) and obesity in girls and boys together was 13.7% and 3.0%, respectively, according to the International Obesity Task Force (IOTF) and 16.9% and 4.9% according to the World Health Organization (WHO) (2007). The median BMI curves of Algerian girls and boys were generally lower than those observed in other Arab countries. Compared with other references, the median BMI values of girls were lower than those of a Belgian Flemish population and WHO 2007 until 14 years of age and higher than the French reference between 7 and 18 years of age. The BMI values of Algerian boys were close to the Belgian (Flemish population), French and WHO 2007 references between 6 and 9 years of age and generally lower thereafter. These BMI curves are complementary to the height and weight charts published previously for the assessment of growth in children and adolescents. They were developed according to international guidelines and could serve as a national reference. They could be used as a complement to the 0- to 5-year-old WHO 2006 standards.
Copyright © 2017 Elsevier Masson SAS. All rights reserved.
Aim: To describe the methods used to construct the WHO Child Growth Standards based on length/height, weight and age, and to present resulting growth charts. Methods: The WHO Child Growth Standards were derived from an international sample of healthy breastfed infants and young children raised in environments that do not constrain growth. Rigorous methods of data collection and standardized procedures across study sites yielded very high-quality data. The generation of the standards followed methodical, state-of-the-art statistical methodologies. The Box-Cox power exponential (BCPE) method, with curve smoothing by cubic splines, was used to construct the curves. The BCPE accommodates various kinds of distributions, from normal to skewed or kurtotic, as necessary. A set of diagnostic tools was used to detect possible biases in estimated percentiles or z-score curves. Results: There was wide variability in the degrees of freedom required for the cubic splines to achieve the best model. Except for length/height-for-age, which followed a normal distribution, all other standards needed to model skewness but not kurtosis. Length-for-age and height-for-age standards were constructed by fitting a unique model that reflected the 0.7-cm average difference between these two measurements. The concordance between smoothed percentile curves and empirical percentiles was excellent and free of bias. Percentiles and z-score curves for boys and girls aged 0-60 mo were generated for weight-for-age, length/height-for-age, weight-for-length/h eight (45 to 110 cm and 65 to 120 cm, respectively) and body mass index-for-age. Conclusion: The WHO Child Growth Standards depict normal growth under optimal environmental conditions and can be used to assess children everywhere, regardless of ethnicity, socio-economic status and type of feeding.
The combination of obesity and hypertension is associated with high morbidity and mortality because it leads to cardiovascular and kidney disease. Potential mechanisms linking obesity to hypertension include dietary factors, metabolic, endothelial and vascular dysfunction, neuroendocrine imbalances, sodium retention, glomerular hyperfiltration, proteinuria, and maladaptive immune and inflammatory responses. Visceral adipose tissue also becomes resistant to insulin and leptin and is the site of altered secretion of molecules and hormones such as adiponectin, leptin, resistin, TNF and IL-6, which exacerbate obesity-associated cardiovascular disease. Accumulating evidence also suggests that the gut microbiome is important for modulating these mechanisms. Uric acid and altered incretin or dipeptidyl peptidase 4 activity further contribute to the development of hypertension in obesity. The pathophysiology of obesity-related hypertension is especially relevant to premenopausal women with obesity and type 2 diabetes mellitus who are at high risk of developing arterial stiffness and endothelial dysfunction. In this Review we discuss the relationship between obesity and hypertension with special emphasis on potential mechanisms and therapeutic targeting that might be used in a clinical setting.
Objective:
The age of adiposity rebound (AR) is defined as the time at which BMI starts to rise after infancy and is thought to be a marker of later obesity. To determine whether this age is related to future occurrence of metabolic syndrome, we investigated the relationship of the timing of AR with metabolic consequences at 12 years of age.
Methods:
A total of 271 children (147 boys and 124 girls) born in 1995 and 1996 were enrolled in the study. Serial measurements of BMI were conducted at the ages of 4 and 8 months and 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12 years, based on which age of AR was calculated. Plasma lipids and blood pressure were measured at 12 years of age.
Results:
An earlier AR (<4 years of age) was associated with a higher BMI (≥ 20) and a lipoprotein phenotype representative of insulin resistance. This phenotype consists of elevated triglycerides, apolipoprotein B, and atherogenic index and decreased high-density lipoprotein cholesterol in boys and elevated apolipoprotein B in girls at 12 years of age. The earlier AR was also related to elevated blood pressure in boys.
Conclusions:
This longitudinal population-based study indicates that children who exhibit AR at a younger age are predisposed to future development of metabolic syndrome. Therefore, monitoring of AR may be an effective method for the early identification of children at risk for metabolic syndrome.
Body mass index (BMI) curves are very useful tools to supervise corpulence during growth and to detect children at risk of overweight and obesity early. In 2009, the French National Nutrition Health Program decided to update the BMI curves used in France. A working group was then created, coordinated by the committee on nutrition of the société française de pédiatrie and by the association pour la prevention de l’obésité en pédiatrie. This article discusses the criteria adopted in elaborating the new curves among the existing references and curves (French references, the International Obesity Task Force [IOTF], the World Health Organization [WHO] standards). It presents recommendations for using the new curves and the BMI values used to define weight insufficiency, overweight, and obesity according to the references utilized.
A general method is described for fitting smooth centile curves to reference data, based on the power transformation family of Box and Cox. The data are defined by values or ranges of values of the independent variable t, and best fitting powers $\hat\lambda_i$ assuming normality are estimated for each group i. Corresponding estimates for the generalized mean and coefficient of variation $\hat\mu_i$ and $\hat\sigma_i$ are also obtained. The $\hat\lambda_i, \hat\mu_i$ and $\hat\sigma_i$ plotted against ti are fitted by smooth curves L(t), M(t) and S(t) respectively, which together define a smooth curve for the 100αth centile given by C100α(t) = M(t)[ 1 + L(t)S(t)zα]1/L(t), where zα is the normal equivalent deviate for tail area α. The method is validated by comparison with published growth standards and illustrated on weight and height data in children. A section describing the practical details of the method is also included.
Context:
De Montbeillard produced the first growth chart in the late 18(th) century. Since then, growth assessment has developed to become an essential component of child health practice.
Objective:
To provide a brief history of (i) anthropometry, i.e. growth measurements; (ii) growth references, the statistical summary of anthropometry and (iii) growth charts, the visual representation of growth references for clinical use.
Methods:
The major contributors in the three categories over the past 200 years were identified and their historical contributions put in context with more recent developments.
Results:
Anthropometry was originally collected for administrative or public health purposes, its medical role emerging at the end of the 19(th) century. Growth reference data were collected in earnest from the 19(th) century, during which time the familiar statistical summary statistics-mean, SD, centiles-were developed. More advanced statistical methods emerged much later. Growth charts first appeared in the late 19(th) century and Tanner and Whitehouse later popularized the concepts of velocity and conditional references for growth in puberty. An important recent reference is the WHO growth standard, which documents optimal growth and has been adopted by many countries including the UK. Arising from it, the UK-WHO charts have pioneered many design features to improve usability and accuracy.
Conclusion:
Growth charts have developed considerably in 200 years and they represent an impressive synthesis of anthropometry, statistical summary and chart design.
We performed a systematic review and meta-analysis of studies that assessed the performance of body mass index (BMI) to detect body adiposity.
Data sources were MEDLINE, EMBASE, Cochrane, Database of Systematic Reviews, Cochrane CENTRAL, Web of Science, and SCOPUS. To be included, studies must have assessed the performance of BMI to measure body adiposity, provided standard values of diagnostic performance, and used a body composition technique as the reference standard for body fat percent (BF%) measurement. We obtained pooled summary statistics for sensitivity, specificity, positive and negative likelihood ratios (LRs), and diagnostic odds ratio (DOR). The inconsistency statistic (I2) assessed potential heterogeneity.
The search strategy yielded 3341 potentially relevant abstracts, and 25 articles met our predefined inclusion criteria. These studies evaluated 32 different samples totaling 31 968 patients. Commonly used BMI cutoffs to diagnose obesity showed a pooled sensitivity to detect high adiposity of 0.50 (95% confidence interval (CI): 0.43-0.57) and a pooled specificity of 0.90 (CI: 0.86-0.94). Positive LR was 5.88 (CI: 4.24-8.15), I (2)=97.8%; the negative LR was 0.43 (CI: 0.37-0.50), I (2)=98.5%; and the DOR was 17.91 (CI: 12.56-25.53), I (2)=91.7%. Analysis of studies that used BMI cutoffs >or=30 had a pooled sensitivity of 0.42 (CI: 0.31-0.43) and a pooled specificity of 0.97 (CI: 0.96-0.97). Cutoff values and regional origin of the studies can only partially explain the heterogeneity seen in pooled DOR estimates.
Commonly used BMI cutoff values to diagnose obesity have high specificity, but low sensitivity to identify adiposity, as they fail to identify half of the people with excess BF%.
We determined the prevalence by age and sex and associated factors of overweight and obesity in French adolescents.
We conducted a cross-sectional study of 2385 adolescents aged 11-18 y (1213 boys and 1172 girls) from middle and high schools in the Aquitaine region (southwest France) in 2004-2005. Weight and height were measured, and adolescents filled in a questionnaire about their characteristics and those of their parents. Overweight and obesity were defined according to the age- and sex-specific body mass index cutoff points of the International Obesity Task force.
Prevalence of overweight (obesity included) was greater in boys and younger children. The odds ratio (OR) for an adolescent being overweight increased with parents' being overweight (at least one parent overweight, OR 1.97, 1.48-2.62, P<0.0001), low paternal socioeconomic status (OR 1.78, 1.22-2.60, P<0.01) and sedentary behavior (22 h/wk, OR 1.33, 1.02-1.74, P<0.05), and decreased with physical activity of parents (at least one parent active, OR 0.67, 0.51-0.89, P=0.01).
Our data support the hypothesis that parental overweight and low socioeconomic status and adolescents' sedentary behavior are strong risk factors for adolescent overweight and obesity, and that parents active lifestyle is associated with a lower risk of overweight in their adolescents.
Here we examine the effect of puberty on components of human body composition, including adiposity (total body fat, percentage body fat and fat distribution), lean body mass and bone mineral content and density. New methods and longitudinal studies have expended our knowledge of these remarkable changes.
Human differences in adiposity, fat free mass and bone mass reflect differences in endocrine status (particularly with respect to estrogens, androgens, growth hormone and IGF-1), genetic factors, ethnicity and the environment. During puberty, males gain greater amounts of fat free mass and skeletal mass, whereas females acquire significantly more fat mass. Both genders reach peak bone accretion during the pubertal years, though males develop a greater skeletal mass. Body proportions and fat distribution change during the pubertal years as well, with males assuming a more android body shape and females assuming a more gynecoid shape. Pubertal body composition may predict adult body composition and affects both pubertal timing and future health.
Sexual dimorphism exists to a small degree at birth, but striking differences develop during the pubertal years. The development of this dimorphism in body composition is largely regulated by endocrine factors, with critical roles played by growth hormone and gonadal steroids. It is important for clinicians and researchers to know the normal changes in order to address pathologic findings in disease states.
At 5 to 6 years of age, body fatness normally declines to a minimum, a point called adiposity rebound (AR), before increasing again into adulthood. We determined whether a younger age at AR was associated with an increased risk of adult obesity and whether this risk was independent of fatness at AR and parent obesity.
A retrospective cohort study using lifelong height and weight measurements recorded in outpatient medical records.
Group Health Cooperative of Puget Sound (GHC), a health maintenance organization based in Seattle, Washington.
All 390 GHC members (and their parents) born at GHC between January 1, 1965, and January 1, 1971, who had at least one recorded adult height and weight measurement plus two visits with recorded height and weight measurements in each of three age intervals: 1.5 to 4, 4 to 8, and 8 to 16 years.
We calculated the mean body mass index (BMI) of each subject during young adulthood (age 21 to 29 years) and the BMI of the parents when each subject was 1.5 years of age. Adult obesity was defined as a BMI >/=27.8 for males and >/=27. 3 for females. Curves were fit to each subject's BMI values between ages 1.5 and 16 years, and the age and BMI at AR were calculated from these curves. Subjects were divided into tertiles of age at AR (early, middle, and late), BMI at AR, and parent BMI (heavy, medium, and lean).
The mean age at AR was 5.5 years, and 15% of the cohort was obese in young adulthood. Adult obesity rates were higher in those with early versus late AR (25% vs 5%), those who were heavy versus lean at AR (24% vs 4%), those with heavy versus lean mothers (25% vs 5%), and those with heavy versus lean fathers (21% vs 5%). After adjusting for parent BMI and BMI at AR, the odds ratio for adult obesity associated with early versus late AR was 6.0 (95% CI, 1.3-26.6).
An early AR is associated with an increased risk of adult obesity independent of parent obesity and the BMI at AR. Future research should examine the biological and behavioral determinants of AR.
Assessing body mass index in children requires cutoffs that are different from those for adults. The aim of this review is to summarize the evidence base, rationale, and practical issues that should inform decisions about the use of national and international reference data for assessing obesity in children. In many countries, decisions are being made without consideration of the existing evidence, and with limited understanding of the practical problems or potential harm that may arise.
The Box–Cox power exponential (BCPE) distribution, developed in this paper, provides a model for a dependent variable Y exhibiting both skewness and kurtosis (leptokurtosis or platykurtosis). The distribution is defined by a power transformation Yν having a shifted and scaled (truncated) standard power exponential distribution with parameter τ. The distribution has four parameters and is denoted BCPE (µ,σ,ν,τ). The parameters, µ, σ, ν and τ, may be interpreted as relating to location (median), scale (approximate coefficient of variation), skewness (transformation to symmetry) and kurtosis (power exponential parameter), respectively.
Smooth centile curves are obtained by modelling each of the four parameters of the distribution as a smooth non-parametric function of an explanatory variable. A Fisher scoring algorithm is used to fit the non-parametric model by maximizing a penalized likelihood. The first and expected second and cross derivatives of the likelihood, with respect to µ, σ, ν and τ, required for the algorithm, are provided. The centiles of the BCPE distribution are easy to calculate, so it is highly suited to centile estimation.
This application of the BCPE distribution to smooth centile estimation provides a generalization of the LMS method of the centile estimation to data exhibiting kurtosis (as well as skewness) different from that of a normal distribution and is named here the LMSP method of centile estimation. The LMSP method of centile estimation is applied to modelling the body mass index of Dutch males against age. Copyright
Development of a WHO growth reference for school-aged children and adolescents
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