How do I help my overweight friend?

I am really unsure what to do about my friend. She is overweight, 250+ pounds and very obsessive over food. I have tried to help her eat less and better choices, but she just cant do it. Her family is the type to sit around and eat and put salt on EVERYTHING that is put on the table. Her mother is the only one in the house of five that is not overweight. She picks at my friend for being the biggest out of her three kids and my friend wants to lose it but wont. I was over at her house last weekend and this is what she ate from the time she woke up till I left. Two big bowls of cereal, a plate piled with chips and a big bowl of cheese sauce, three grilled cheese sandwiches, (Not to mention all the soda she drank. I do believe she went through a whole two litter bottle by herself.) and before I left she had a ‘snack’ which consisted of a bowl filled with ice cream and fudge with cookies in it. When I say ‘big’ bowls I mean not the normal size bowls you eat with on a normal basses. Im talking about the bowls you use to mix stuff up in. Its really gross and hard for me to sit there and watch her eat all that when all I had was a handful of chips. Its disturbing to think that she might clog up her insides before too long and end up in a coffin, but unless I do something soon she wont be here very much longer. My question to you is, how do I help her with her weight and control her eating habits? She is the type that is lazy and doesnt want to get up to walk across the room to grab her cigarettes or whatnot. So I cant get her up off the couch to go for a stroll when I am over there. The closest she has to exercise is when she is at work. That’s it. Please help me.