How can I help my friend?

I have a wonderful friend who is literally eating herself to death. She lives alone and orders a great deal of take out food. Oh did I mention that I think she is close to, if not there yet, 500 lbs. At present, she needs a wheelchair to get around. I've watched her go from walking slower and slower to walking with a cane to walking with a walker to only being able to step to her wheelchair. I'm scared that she will take it to the next level of being home bound or worse; bed ridden. What can I do to help her? I love her like my own sister and she has been in my life now for the last forty-six years. I pray that we are around for another forty-six.