High Prevalence of Insulin Resistance and Metabolic Syndrome in Overweight/Obese Preadolescent Hong Kong Chinese Children Aged 9–12 Years

During the past decade, the rising prevalence of childhood obesity has been accompanied by a rapid increase in young-onset type 2 diabetes (1). The associations among obesity, insulin resistance, hypertension, and dyslipidemia are not well defined in preadolescent children. Furthermore, the impact of family history of diabetes, low birth weight, and non–breast-feeding on the clustering of features of insulin resistance syndrome in children remained to be determined. In a cross-sectional study of 271 primary school children between 9 and 12 years of age, we compared the effects of family history of diabetes, breast-feeding, and extremes of birth weight on obesity, insulin resistance, and cardiovascular risk factors between an obese/overweight (n = 129) and a nonobese group (n = 142). Anthropometric indexes, blood pressure, fasting plasma lipids, glucose, and insulin were measured. Family history of diabetes, birth weight, and feeding mode in the first 3 months of life were obtained from parents.

Overweight/obese children were taller and had higher systolic blood pressure, fasting triglycerides, fasting serum insulin, and insulin resistance index (homeostasis model assessment) but lower HDL cholesterol level than nonobese children (Table 1). The odds ratios for a family history of diabetes and formula feeding in overweight/obese children were 4.37- (95% CI 2.25–8.52, P < 0.001) and 2.20-fold (1.29–3.76, P = 0.004). Overweight/obese children had increased risk of high blood pressure (3.21 [1.60–6.45], P = 0.001), dyslipidemia (2.72 [1.58–4.66], P < 0.001), and hyperinsulinemia (defined as insulin level above the age- and sex-specific 85th percentile; 14.1 [7.75–25.48], P < 0.001). Nearly 50% of overweight/obese children had at least two of the three cardiovascular risk factors of dyslipidemia, high blood pressure, and hyperinsulinemia, and 8% had all three risk factors. Seventy-seven percent of overweight/obese children had insulin resistance, which was best predicted by waist circumference (β = 0.52, P < 0.001) and HDL cholesterol level (β = −0.19, P = 0.001) on multivariate analysis.

Clustering of cardiovascular risk factors is common in overweight/obese preadolescent children in Hong Kong. Overweight/obese children are more likely to have a positive family history of diabetes and formula milk-feeding in infancy. Our findings support the notion that breast-feeding may be associated with a reduction in childhood obesity risk (2). In agreement with the recent report by Sinha et al. (3), >77% of overweight/obese children in the present study had hyperinsulinemia. Given the predictive value of insulin resistance on future development of type 2 diabetes and coronary heart disease (4,5), the high prevalence of insulin resistance in these preadolescent children is an important public health issue.