More than four billion people will be affected, with rates rising fastest among children, its report says.
BBC reports low or middle-income countries in Africa and Asia are expected to see the greatest rises.
The report predicts the cost of obesity will amount to more than US$4 trillion (NZ$6.5t) annually by 2035.
Federation president Prof Louise Baur described the report's findings as a clear warning to countries to act now or risk repercussions in the future.
