I am unable to verify your claim. What I've seen is that Japan has about the same rate of overweight, obesity, morbid obesity and type 2 diabetes. Is it possible that you compared a figure that combines multiple categories to a figure that just looks at a single figure? For example combining type 1 and type 2 diabetes would be misleading, as type 1 diabetes is caused by fundamentally different factors than type 2 diabetes. Also did you ensure that you are comparing data for the same or similar year?