The Middlesteins by Jami Attenberg. Here is the Amazon blurb-
"Edie and Richard have been married for over thirty years, living in the Chicago suburbs. Everyone who knew them - even their own children Robin and Benny - agreed that Edie was a tough woman to love, but no one expected Richard to walk out on her, especially not in her condition. Edie is fifty-nine years old, she weighs 300 pounds, and her doctors have told her she'll die if she doesn't stop eating.As Richard is shut out by the family and seeks solace in the world of internet dating, Robin is dragged back from the city and forced to rebuild a relationship with her mother. Meanwhile Benny and his neurotic wife Rachelle try to take control of the situation. But have any of them stopped to think about whether Edie really wants to be saved?Written with sly humour, warmth and great insight, The Middlesteins is a novel about what it means to be part of a family"
I also enjoyed 'Ada's Rules' by Alice Randall-
"Ada Howard, the wife of the preacher at Nashville's Full Love Baptist Tabernacle, has a whole lot of people to take care of. There's her husband, of course, and the flock that comes with him, plus the kids at the day care centre where she works, two grown daughters, and two ailing, wayward parents. It's no wonder she can't find time to take care of herself. And her husband's been so busy lately she's suspicious some other woman may be taking care of him...
Then it comes: the announcement of her twenty-five-year college reunion in twelve months' time, signed with a wink by her old campus flame. It sets Ada thinking about the thrills of young love lost, and the hundred or so pounds gained since her college days, and she decides it's high time to change her body, and her life. So she starts laying down some rules. The first rule is: Don't Keep Doing What You've Always Been Doing. And so begins her unforgettable journey on the way to less weight and more love...For anyone who has ever found themselves at a crossroads, with one hand in their pocket and the other in the cookie jar, Ada's Rules is a warm, funny and soulfully wise novel about falling back in love with the life you have.
Then there is 'Bed' by David Whitehouse' about a larger than life kid and Sue Townsend's 'The Woman Who Went To Bed For A Year'