Obesity is defined as Body Mass Index (BMI) of more than 95th percentile for age and sex. It is on rise and affecting not only people in developed countries but also those in developing and modernizing countries. Obesogenic environment has resulted in major healthcare problem of obesity, but there is also substantial evidence for the heritability of obesity, and research in both rare and common forms of obesity has identified genes with significant roles in its etiology. However, many genes and variations do not fully explain the heritability of obesity, epigenetic markers may also be playing important role. Advances in genetic technology and application of clinical epidemiology will have a huge impact making the picture clearer. Though not exhaustive, this review will focus on our current knowledge and Understanding of the role of genetic factors in obesity.