Objective: The objective of the present study is to compare the prevalence of childhood and adolescent obesity in West Delhi and South Delhi using the body mass index. Methods: A cross sectional study design was devised in which anthropometric data was collected. A data of 1000 children and adolescents [6-15years] have been collected crosssectionally from West and South Delhi Public Schools in an Indian Council Medical Research funded research, in order to study the prevalence of obesity in these parts of Delhi. Body Mass Index is a height weight system of measurement that applies to both the sexes, has been used to assess obesity. Results: Among West Delhi males, there is a high prevalence of obesity from ages 6-11 years and there is a drop in obesity level during the adolescent spurt. The prevalence of obesity is 14.2% in West Delhi,33.4% in South Delhi.The overall prevalence of obesity and over weight is 23.8% and 24% respectively. More than 1 in 5 children now are overweight or at risk for obesity. So, this problem needs to be addressed urgently. Conclusion: The study highlights the increasing prevalence of obesity in childhood and adolescents. This original research article serves as a model for public health policy makers, in identifying children at risk for cardiovascular diseases in future.