The objectives of this study were to estimate the prevalence and distribution of cardiovascular risk factors and the metabolic syndrome in children with generalized, central, or combined types of obesity and to possibly discover if a phenotypically obese metabolically normal and a metabolically obese normal weight phenotype could be identified in children and adolescents.
Design
This cross-sectional study is the baseline survey of a national longitudinal study.
Subject/setting
Overall 4,811 nationally representative children, aged 6 to 18 years, were recruited from the community through randomly selected schools within six provinces in Iran. In addition to physical examination, fasting glucose and lipid profile were assessed.
Varying with age and sex groups, 6% to 9% of children were categorized into the isolated central obesity group, 7.5% to 11% into the isolated generalized obesity, and 14% to 16.5% into the combined type group. The prevalence of dyslipidemia, high blood pressure, and metabolic syndrome was higher in those children with combined obesity than in those with the other two types of obesity, as well as in the central than in the generalized obesity groups. Phenotypically obese metabolically normal subjects were more prevalent in the generalized obesity group. The likelihood of metabolic syndrome was highest in those with combined obesity (odds ratio 3.7, 95% confidence interval 3.1 to 4), and lowest in generalized obesity group (odds ratio 2.1, 95% confidence interval 1.8 to 2.5).
Conclusions
This study complements recent research about the adverse health hazards of abdominal obesity in children. The finding of metabolically obese normal weight children suggests that additional investigation for cardiovascular risk factors may be warranted in normal-weight children with an ethnic predisposition to chronic diseases.
Section snippets
Methods
The study subjects were school children who participated in the baseline survey of the national CASPIAN study. This undergoing multicentric longitudinal study is a joint collaboration of the World Health Organization and the Iranian National Ministries of Health and Education (17, 18). Overall, 4,811 school students (91% participation rate), aged 6 to 18 years, were selected by multistage random cluster sampling from urban and rural areas of six provinces located in diverse parts of the country.
Results
Participants of this multicenter study were 2,248 boys and 2,563 girls, with a mean age of 12.07±3.2 years without significant difference between boys and girls.
The subjects’ characteristics are presented in Table 1, which shows that boys had higher mean levels of weight, height, BMI, waist circumference, SBP, and DBP than girls; other variables were not significantly different in terms of sex. The age group×sex difference was significant for waist circumference and SBP. Other than HDL
Discussion
In this study we found that the prevalence of CVD risk factors and metabolic syndrome was significantly higher in those children with combined obesity than in those with isolated types of obesity. In addition, phenotypically obese metabolically normal subjects were more prevalent in the generalized obesity group. These findings complement some recent observations on adverse health hazards of abnormal central body fat deposition even in childhood. Asian populations are facing an epidemic of
R. Kelishadi is an associate professor of pediatrics and head of the Preventive Pediatric Cardiology Department, and M. A. Ramezani is a community physician, Isfahan University of Medical Sciences, Isfahan, Iran.
The normal-weight BMI range (18.5–24.9 kg/m2) includes adults with body shape and cardiometabolic disease risk features of excess adiposity, although a distinct phenotype developed on a large and diverse sample is lacking.
To identify demographic, behavioral, body composition, and health-risk biomarker characteristics of people in the normal-weight BMI range who are at increased risk of developing cardiovascular and metabolic diseases based on body shape.
Six nationally representative waist circumference index (WCI, weight/height0.5) prediction formulas, with BMI and age as covariates, were developed using data from 17,359 non-Hispanic (NH) white, NH black, and Mexican-American NHANES 1999–2006 participants. These equations were then used to predict WCI in 5594 NHANES participants whose BMI was within the normal weight range. Men and women in each race/Hispanic-origin group were then separated into high, medium, and low tertiles based on the difference (residual) between measured and predicted WCI. Characteristics were compared across tertiles; P values for significance were adjusted for multiple comparisons.
Men and women in the high WCI residual tertile, relative to their BMI and age-equivalent counterparts in the low tertile, had significantly lower activity levels; higher percent trunk and total body fat (e.g. NH white men, X ± SE, 25.3 ± 0.2% compared with 20.4 ± 0.2%); lower percent appendicular lean mass (skeletal muscle) and bone mineral content; and higher plasma insulin and triglycerides, higher homeostatic model assessment of insulin resistance (e.g. NH white men, 1.45 ± 0.07 compared with 1.08 ± 0.06), and lower plasma HDL cholesterol. Percent leg fat was also significantly higher in men but lower in women. Similar patterns of variable statistical significance were present within sex and race/ethnic groups.
Cardiometabolic disease risk related to body shape in people who are normal weight according to BMI is characterized by a distinct phenotype that includes potentially modifiable behavioral health risk factors.
The number of urine samples collected per month in each season is presented in Table S1. Trained physicians and healthcare providers conducted the physical examination according to standard protocols, and using calibrated equipments (Kelishadi et al., 2008). Weight was recorded in light clothing to the nearest 0.1 kg by a SECA digital weighing scale (SECA 803, Germany) and height was measured without shoes to the nearest 0.1 cm (SECA 216, Germany).
A limited body of evidence exists on the association of exposure to polycyclic aromatic hydrocarbons (PAHs) with cardiometabolic risk factors and obesity in children. No study has evaluated these associations in subgroups of children with and without excess weight, and those with and without cardiometabolic risk factors. We aimed to investigate the association between PAH exposure and cardiometabolic risk factors in children independent of their weight status. The secondary aim was to evaluate the obesogen properties of PAHs in children independent of their cardiometabolic risk factors. This study was based on a representative sample of 186 children (aged 6–18 years) living in Isfahan, Iran (2014–2016). We enrolled four groups of participants with and without excess weight and with and without cardiometabolic risk factor. Urinary levels of monohydroxy PAHs (OH-PAHs) were measured twice, six months apart. Logistic regression models were developed to estimate the associations of tertiles of urinary OH-PAH concentrations with cardiometabolic risk factors and excess weight, adjusted for the relevant covariates. The findings in all participants combined showed that increased risk of cardiometabolic risk factors and excess weight was associated with exposure to most of evaluated PAHs. Exposure to 1-hydroxypyrene was associated with higher risk of cardiometabolic risk factors in participants with excess weight. Exposure to 2-Naphtol was also associated with higher risk of cardiometabolic risk factors in both groups, but the associations were not significant (p < 0.1). For participants without cardiometabolic risk factors, exposure to 2-naphtol, 9-phenanthrol, and ∑ OH-PAH was associated with increased risk of obesity. For participants with cardiometabolic risk factors, we observed similar pattern of associations for 2-naphtol and ∑ OH-PAH, but the associations were not statistically significant (p < 0.1). We found that exposure to PAHs could possibly explain, in part, the cardiometabolic risk factors in children with excess weight as well as obesity in children with normal cardiometabolic profile.
R. Kelishadi is an associate professor of pediatrics and head of the Preventive Pediatric Cardiology Department, and M. A. Ramezani is a community physician, Isfahan University of Medical Sciences, Isfahan, Iran.
S. R. Cook is an assistant professor of pediatrics, Department of Pediatrics, University of Rochester Medical Center, Rochester, NY.
R. Majdzadeh is an associate professor of epidemiology, School of Public Health and Institute of Public Health Research, Tehran University of Medical Sciences, Tehran, Iran.
M. E. Motlagh is an associate professor of pediatrics and director, Bureau of Family Health, M. M. Gouya is an internist and director, Center for Disease Control, and G. Ardalan is a pediatrician and director, School Health Office, Ministry of Health and Medical Education, Tehran, Iran.
M. Motaghian is deputy, Bureau of Health, Ministry of Education and Training, Tehran, Iran.
