My favourite thing about having cystic fibrosis is the fact that my digestive system is faulty in just such a way that I could, if I wanted/could afford to, eat KFC five times a day for a year and maintain a healthy weight. I mean, I'd have terrible teeth and skin, but I'd only be about 70 kilos which, I have to say, is a marked improvement on my current weight.
The reason I can do this is because the cells in my pancreas that produce the enzymes essential to digesting my food are permanently on strike, I am therefore prescribed pancreatin capsules which contain a mixture of said enzymes. However, solely relying on pancreatin to digest everything I eat means my digestion of essential nutrients is less effective than it would otherwise be were I not terminally ill. When my chemical structure was being made my genes decided to not do the thing that would allow my body to effectively absorb salt and fats, which sounds brilliant and yes, I am very thin as a result, but salt and fats are things that your body needs in order to be not dead, so without pancreatin I do run a risk of being malnourished while still stuffing my face because it'll come out at more or less the same rate it goes in.
If I become malnourished (and that is not a big 'if'), my lung function collapses, which takes my already shite immune system with it, opening me right up to all kinds of delightful infections which make me actually properly ill, cause me to lose my appetite (which is serious), and then I quite literally start wasting away. Because that's called 'decomposition' and it's what happens after you die, which is what would happen to me in this, the very worst case scenario. It's worth mentioning at this point that it would take time for that scenario to progress, although I don't actually know how much time so it may well be less time than I think. Thankfully, neither I, my mother, nor any of the medical professionals closely associated with my well-being have never, and hopefully will never, let it get quite that bad. Although I have been in hospital several times over the last fifteen years as a result of my own negligence, but I'll gloss over that.