FYI, Ultrase is just a brand name for the digestive enzymes needed to break down the nutrients for foods.
Some patients may use Creon, some may use Pancrease, or even Viokase. (all of them have a difference of balance to the active ingredients)
As I was growing up, I had Viokase in powder form (YUCK!!), and then went from Pancrease in capsule, to Cotazym-S.
The enzymes have 3 basic active ingredients: Lipase, Amylase, and Protease.
the Lipase is used to digest fats, and there are three types, one type produced in the mouth, one in the liver, and the one we more than likely need, is the one produced in the pancrease.
Amylase is used to change complex sugars (and starches) into simple sugars for the body to digest. Two kinds, one produced through the salivary glands, and the other, also one we are more than likely in need; is produced by the pancreas into the small intestine.
Last of the active ingredients, Protease, is an enyme, used in the aid of digestion of proteins, basically.
(disclaimer-this is what I resarched, so anyone correct me if I'm wrong, ok)
Basically, due to the mucus blockage in the pancrease, the enzymes needed are not being supplied. The result was to give enzymes to make up for what was not being produced by ourselves.
I was using other forms of "digestive aids" in Japan, but was shocked to find out what it really was! (Boy, did my ex stiff me!) When I realized that it WASN'T the same, I looked at it like this; In order to get the nutrients I needed, I had to eat twice the amount of food, but nearly 3/4 of it would just pass through my body (sometimes painfully), and that would be just to keep up on nutrients, etc.
With eating a normal amount without enzymes, anytime I ate, the nutrients wouldn't be sufficient, and my body would begin to break down, and I'd always be hungry.
Probably, in my case, I was both mis-absorbing nutrients, and anytime I had something high in saturated fats (animal, or vegetable), I'd have to run to the bathroom every hour, (And, sometimes say, "What the heck did I eat wrong, this time!!") because my body didn't absorb it.
My weight went down from about 175 to 160 my first year here, but leveled off from then. If I ate enough, and was carefull, I could gain, but it would burn off after I went back to my daily routine. Up until a few years ago, I was pretty active, including having to walk quite a bit (No car for me). Though I'm still perplexed as to how I could gain so fast in a few months. I wonder if it could be bloating has started.
Now, I found some "over-the-counter" enzymes, and they help me, maybe too much 'cause I don't wanna be the fattest CF'r in the world! (good for some, but not for me!)
Anyway, long answer, but I hope it was very helpful as to answer why weightloss (and stomache aches) occurs when not taking enzymes.
(P.S. Lilith--good idea about the medicine section! My wife doesn't have a place for my meds, so the table is full of medicine bottles--You'd think it was a pharmacy! But I rarely forget with that method)