I have bile acid malabsorbtion but am hardly a starved waif. I found it made me crave food more as I'd just feel empty with the diarrhea as well, especially certain types of food like salt. I lost some weight when I started on my meds as I found I wasn't craving food so much.
They can do a sample if needs be to check for fat and undigested food etc... (if that is what the photo idea is for) as well to see diarrhea itself.
With mine (there are different kinds of malabsorption though) I get very frequent urgent diarrhea with huge amounts of water in it, often felt it was almost burning but think it's my poor bum getting so sore, I'd also get a lot of pelvic pain (no idea why though). Food would go straight through me. I'd feel drained a lot and have a lot of pain too and had deficiencies show up in tests like Vitamin D abd low iron count. I noticed a big difference in my hair skin, energy levels, all sorts when I started on meds.
I was under a gastro consultant and had a barium scan, cameras up and down and a pill camera (went through my system in under 5 hours) and they found the malabsorption in a Sehcat scan (took a radioactive pill and was scanned a week apart). It was the latter that found the malasorbtion.
They are still looking as Crohns was a suspicion (hoping it's a good sign I'm not skinny enough :)) as I have inflammatory arthritis, stomach ulcers, get fissures, recurrent abcesses and other stuff but no sign so far ("yet" as my gastro put it) but hoping not as I'd have though the scans would have picked something up.
Have you noticed anything in particular which you don't seem to be able to digest?
Hope you feel better soon!