A weird story of how colonial exploitation caused rampant obesity. Nauruans participating in a walk against diabetes (2007), photo by Lorrie Graham, CC BY 2.0 via Wikimedia Commons No, America is not the fattest country in the world. That title belongs to the small island nation of Nauru. Found in the Pacific, itâs famous for two things â phosphate deposits and wide waistlines. According to the World Health Organization, it is estimated that over 70% of the island nation's population is obese. So it comes as no surprise that the island is plagued by high rates of heart disease, stroke, and diabetes. One study even notes that over 40% of the countryâs population suffers from type 2 diabetes.