The federation defines severe obesity as those with a BMI greater than 35 and overweight with a BMI greater than 25.
By 2025 there are expected to 177 million adults globally deemed severely obese and in need of treatment.
This has led the World Obesity Federation to urge governments to take immediate action over the "unsustainable" health epidemic.It is calling for restrictions on advertising food to children and the introduction of taxes on sugar-laden food and drink.
"The obesity epidemic has reached virtually every country worldwide and overweight and obesity levels are set to continue to rise," said federation president Professor Walmir Coutinho.
University of Auckland population health expert Professor Boyd Swinburn said the prognosis was grim for many young New Zealanders, with the rate of childhood obesity continuing to climb.
"For New Zealand, the situation is bad. We are leaving our next generation of kids with a terrible legacy."
Professor Swinburn blamed the rise in obesity on a combination of factors including environments leading to weight gain and Government inaction.
"Every single authoritative report on this says we need to have comprehensive policies and action aimed at im-proving food environments, introducing taxes on sugar, restricting junk food marketing to kids and adopting healthy food policies in schools," he said.