Introduction The prevalence of childhood obesity has contributed to an increased incidence of metabolic syndrome.

Objective To determine the prevalence of metabolic syndrome and its related components in obese children.

Methods This study was performed from 2004 to 2006. Subjects were 235 children aged 4–18 years with a body mass index (BMI) >85th. After physical examination, plasma glucose and lipid profiles were measured after 12-h fasting. The subjects were classified according to CDC 2000 data of BMI: (1) At risk for overweight (95% > BMI >85%). (2) Overweight (97% > BMI ⩾95%). (3) Very overweight (BMI ⩾97%). We defined obesity on the basis of BMI Z-score  =  2 or more, adjusted for age and sex. Metabolic syndrome was diagnosed when three of five risk factors were present: blood pressure >95%, high-density lipoprotein (HDL) cholestrol <5%, triglycerides >95%, BMI Z-score ⩾2 (all adjusted for age and sex) and fasting glycaemia >100 mg/dl.

Results The overall prevalence of the metabolic syndrome was 31.9%; 39.7% of males and 26.3% of females (p = 0.028). The syndrome was present in 40.8% of very overweight compared with 17.6% of at-risk for overweight children and adolescents (p<0.0005). 9.8% of the children had no components and 30.6% had at least two components. Overall, high serum triglycerides was the most common component of the metabolic syndrome (53.2%). Fasting hyperglycaemia (BS >100 mg/dl) was in 29.4% of subjects, 24.% had low HDL-cholesterol and 20.4% had hypertension. There was a significant correlation between impaired fasting glucose and the severity of obesity (p<0.05).

Discussion The prevalence of the metabolic syndrome is high among obese children and increases significantly with the severity of obesity. Triglycerides is the most common component. This study indicates the necessity of early prevention through constant education of correct nutrition and physical activity.