Metabolically obese normal weight and phenotypically obese metabolically normal youths: the CASPIAN Study

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.

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.

Obesity type was considered the independent variable, cardiovascular risk factors and the metabolic syndrome were dependent variables. Prevalence of risk factors in different types of obesity was compared by multivariate analysis of variance and post-hoc tests. Logistic regression analysis was used to examine the associations between obesity type and the metabolic syndrome.

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).

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.