Still, that 40% doesn't really mean anything until we know what percentage of "normal" (not fat) people consider suicide. Plenty of people kill themselves who aren't fat. In fact, I betcha of the people who kill themselves--a lesser percentage are fat.
Many of us have found a more insidious way to deal with the pain of life by killing ourselves--slowly--with food. It's not a big leap to say that anyone who has died as a result of an obesity related illness has committed suicide.
It is all in the way one looks at it.