Gut bacteria

In the news recently has been a lot of talk about gut flora. We all have a lot of different kinds of microorganisms living in our intestinal tracts, naturally and normally. Without them, we don't process food like we should. Now, if the populations of one bacteria or another are reduced, they might grow back. But what if every last one of some kind is dead?

What happens if your body gets so out of whack (technical term!) that some of your bacteria populations die out entirely? Like by taking a lot of antibiotics to deal with another problem? Or maybe by a really horrible diet? (Maybe?) Your digestive system would start behaving differently, and those bacteria would never return. Maybe this would explain why it's harder to lose weight than it was to put it on!

Obviously I'm just making stuff up. But it's an interesting concept.