I'm somewhat skeptical about that number. There is no source, only thing what I could find about it was xml file on that site (img). In another pdf on that same oecd site they are using different data about Finland. (self reported like many others used on that graph) That shows that Finland's number is about the same as other nordic countries. I googled about this in finnish and found an article (in finnish) written by the Finnish national institute for health and welfare. There it states that obesity in Finland is just above EU average: men 20% and women 19%. Data was collected via medical checkups and was not self reported. But if someone knows more about that number used in this thread's picture I would gladly know more about it!