The association between a low magnesium (Mg) status, insulin resistance and metabolic syndrome has been shown repeatedly in adults, and higher Mg intakes have been shown to have a protective role. Magnesium is a cofactor in many enzymes involved in Carbohydrate metabolism. Thus its deficiency can theoretically explain abnormality of carbohydrate metabolism, Glucose intolerance and Insulin resistance. The base of obesity is laid down very much since childhood, further tracking into adulthood. It would be interesting to find out whether Magnesium deficiency also starts since childhood, so that we can ascertain etiological and therapeutic role of Magnesium in childhood Obesity, which can further prevent adulthood obesity and other metabolic syndromes. The objectives of the study were to determine whether serum Magnesium and dietary intake of Magnesium were lower in overweight children compared to normal weight children and to assess the correlation of serum magnesium with parameters of metabolic syndrome. The study was planned in Department of Biochemistry, Patna Medical College, Patna with the help of Department of Pediatrics, PMCH, Patna. Children were divided in 2 groups. Group 1 had 25 overweight children (BMI >85th centile for age and gender as per Agarwal’s growth charts for Indian children) and group 2 had 25 normal weight children. The age group of the patients were from 5 years to 14 years. Serum Magnesium was found to be significantly lower in overweight children in comparison to normal children. Hence from the above findings it can be concluded that presence of lower serum magnesium levels in children with higher BMI, systolic and diastolic BP, Waist Circumference and serum insulin level in our study suggests that the origin of the association of insulin resistant state with low serum magnesium starts in childhood itself.