INTRODUCTION: Worldwide, the rates of childhood obesity have risen dramatically in recent decades. Obesity may cause serious sequelae during childhood and throughout adulthood. Insulin resistance is prevalent metabolic abnormality in pediatric obesity. The Pediatric Obesity Clinic was established in 2011 at the Children's Medical Center, Landspítali University Hospital. This study aimed to observe metabolic abnormalities and insulin resistance in blood values of children receiving obesity treatment. METHODS: The study included all children (n = 180) who received obesity treatment at The Pediatric Obesity Clinic between 2016 and 2020 and had at least eight out of the nine following serum values analyzed while fasting: HbA1c, glucose, insulin, ALAT, total cholesterol, HDL-cholesterol, triglycerides, TSH and free T4. HOMA-IR value was calculated from insulin and glucose values. Decreased insulin sensitivity was defined as HOMA-IR > 3.42. RESULTS: 84% of the children had at least one abnormality in their tested blood values. 50% had abnormal insulin values and 44% had abnormal ALAT values. 78% had decreased insulin sensitivity, and their mean HOMA-IR was 7.3 (± 5.0), surpassing twice the normal value. CONCLUSION: A large majority of the children undergoing obesity treatment already exhibited signs of metabolic sequelae during their treatment. The prevalence of affected children has increased compared to a similar study conducted in 2013. Of particular concern is the growing number of children with decreased insulin sensitivity. Proper measures must be taken to combat this alarming trend.