I just had to do this a week ago for colonoscopy--it is awful. I was starving, too. But then, (my mother suggested) I make some homemade chicken broth, and it did help to fill me up--just put a breast with bones in a pot of water add some large pieces of celery, carrots and onions, and bouillion cubes--after about
an hour, dip some broth out, I kept adding more water, and dipping more out--originally thought I'd make soup for the rest of the family, but ended up using all the broth myself! The day of the test was worse as my test wasn't until 1:30, hopefully yours is earlier. I wasn't allowed anything but sips of water until 2 hrs before the test, then nothing--I told my husband not to aggrevate me, I was having "food rage". Oh well--good luck, hope everything goes well for you.