I've been reading the Straight Dope for years (ever since I found it on America Online -- yeah, the mid 1990s!). Cecil Adams, the world's smartest human, has been on a quest to fight ignorance out of the teeming millions since 1973. One of my favorite articles addresses the age-old question, "Can man live by bread alone?"
Well, it depends. Let's assume you are serious about this: nothing but bread. No water. You're going to need to eat about 6 loaves per day just to get enough moisture to keep you alive. And that's assuming you eat low-sodium bread and don't do anything all day but knit (or you'll need more water).
So if you can get past the dehydration death, the next problem will be scurvy. You need to consume vitamin C, and to quote Cecil, "I am not going to sully this discussion by considering wacky, hypothetical 'breads' like lemon-peel loaf." Unfortunately, one of the early signs of scurvy is loss of appetite, so you'll need to really stuff those 6 loaves down.
"If you don't drink water, and consequently try to shove six loaves down your throat day in and day out--and that means consuming about 8,000 calories a day, four times what a 160-pound man needs when he's moderately active (and you won't be)..." Cecil gives you maybe six months.