Your friend's diet doesn't sound all that bad really, almost sounds like south beach type foods and many on lc maintenance can eat many of those in correct portions.

I have some very thin friends and family who eat whatever they want and stay slim. It's frustrating to see, but my father in law was never overweight and died from complications from heart disease and diabetes. He was only 59, so like the other poster mentioned, being skinny isn't the whole story.