This work attempts to highlight the global magnitude of the obesity and examining the evolutionary perspective with focus on the correlates and temporal trend. It is based on a wide literature survey following PRISMA. The data on country wise prevalence was obtained after systematic review of over 500 articles and websites on the prevalence of obesity. A total of 301 entries/data points were found for 84 countries. Regression analysis was computed for 177 countries based on prediction made by WHO to identify the correlates. To find out the regional variation, data on height and weight of two different national surveys at an interval of 35 years from India were used. The highest prevalence of obesity was found in Tonga (65.5±13.3%) and Cook Island (61.6±5.9%) followed by Middle Eastern countries: Saudi Arabia, United Arab Emirates, Iraq, and countries of American continent, namely Paraguay, Argentina and USA. The lowest prevalence was reported in Vietnam (0.5±0.2%) and African countries of Mali, Ghana, and Tanzania. Out of 7 billion population of the world, about 1.5 billion are already overweight or obese and this number is constantly increasing. The regression analyses indicate that obesity is higher in those countries where HDI and life expectancy are higher. No doubt, obesity is now a pandemic as underdeveloped region are also in the grip of the problem; but positive regression of female obesity and life expectancy (r2=0.040, β=0.275 p>0.009) indicate its evolutionary significance as adaptive strategy of surviving, as long as it is not morbid. Any biological or cultural trait that enhances the ability of survival and reproduction become inheritable. In this view, obesity can also be considered as a measure of biological adaptation to a particular ecological setting. But, its association with multiple chronic disorders is now a great challenge for public health and being designated as global pandemic.