I will give you a link to the Florida Bar Association website that should guide your sister in the process.  It sounds as if you consider him unable to care for his well being given his weight and you would like to step in.  That may in fact be a good enough reason but he can object so be aware that she may be in for a fight.  Good luck.http://www.floridabar.org/tfb/TFBConsum.nsf/48e76203493b82ad852567090070c9b9/e8fd739d221b11c085256b2f006c5a4e