But first, a diagnosis. Or two. Can one diagnosis explain sacroilliitis, weight loss and symptoms aggravated by "carbohydrates?"
"[i]1: Dig Dis Sci. 1995 Sep;40(9):1906-8.
Adult celiac disease is frequently associated with sacroiliitis.
Usai P, Boi MF, Piga M, Cacace E, Lai MA, Beccaris A, Piras E, La Nasa G, Mulargia M, Balestrieri A.
Istituto di Medicina Interna, University of Cagliari, Italy.
No data are available on the presence and frequency of peripheral or central joint disease, routinely determined by bone scintigraphy with 740 MBq of [99mTc]MDP, in adult celiac disease.
Bone scintigraphy was carried out to detect early acute inflammatory lesions in 22 adult celiac patients (15 females and seven males; mean age 36.72 years, range 17-63). Bone scintigraphy was positive for sacroiliitis in 14 cases (63.6%).
Except in the case of one patient suffering from rheumatoid arthritis, laboratory data were normal. Our data suggest that as in other chronic intestinal diseases, celiac disease in adults, is frequently associated with central joint disease.
This high incidence of sacroiliitis, the joint disease most frequently found in our patients, has not been previously reported in other series. We believe, therefore, this difference could be explained by the different methodology used for the screening of joint disease."[/i]
This might be specious; there are few follow-up citations in confirmation. In any case, carbohydrates do not typically aggravate inflammatory bowel disease (UC and Crohn); but gluten most assuredly aggravates gut and extraintestinal symptoms of celiac disease.
The algorithm for your friend is straightforward: antimysial and antiTGT antibodies, endoscopy to distinguish among celiac, Crohn and UC, or whatever technique is used in Britain.
Withdraw gluten, if appropriate, or treat for UC/Crohns, but blindly adding anabolics will not work until the gut inflammation is addressed specifically (and no, fish oil does not work).
And it is possible to have more than one thing: e.g., UC and AS; or UC and celiac disease can co-exist. This is why they pay spine radiologists; the classic findings of AS occur late. (B27 testing is not good enough for the question posed.)
Best of luck...