Insulin resistance in obese pre-pubertal children: Relation to body composition

Abdominal obesity is a strong determinant of obesity related metabolic complications. Data about pre-pubertal children are scarce. The aim of this study is to assess the presence of insulin resistance using different insulin sensitivity indices and investigate its relationship with abdominal fat distribution by Dual energy X-ray absorptiometry scan (DXA). Secondary outcome is to determine the frequency of the metabolic syndrome components. Twenty-three pre-pubertal obese children were recruited (14 females, 9 males). Height, weight, body mass index (BMI), waist and hip circumferences, waist to hip ratio, and blood pressure were measured. Fasting blood samples were withdrawn for glucose, insulin, lipid profile, thyroid and liver functions. Patients underwent oral glucose tolerance testing (OGTT) and DXA scan for body composition. Insulin sensitivity was determined using homeostasis model assessment for insulin resistance (HOMA-IR), fasting glucose to insulin ratio, Matsuda, and Cederholm indices. All patients had BMI, waist circumference, and DXA trunk fat more than 2 SDS. Mean fasting glucose, insulin, fasting glucose to insulin ratio, 120min glucose and HOMA-IR were within normal limits, but mean Matsuda and Cederholm indices exceeded cut off limits. Dyslipidaemia was detected in 13 patients (56.5%), disturbed glucose homeostasis in 8 patients (34.8%), and systolic hypertension in 1 patient (4.3%). Metabolic syndrome diagnosis was established in three patients (13%). More insulin resistant patients were detected by Matsuda index. Trunk fat SDS correlated with Matsuda and Cederholm indices only. Dysglycaemia and dyslipidaemia are common among pre-pubertal obese children. Insulin sensitivity indices based on OGTT are superior to fasting indices in identifying at risk children. OGTT should be included in assessing obese children with BMI>2 SDS. DXA scanning has limited value for this purpose in clinical settings.