Hello - thanks for asking your question.
IBS is a possibility, and with a recent colonoscopy, IBD would not be likely.
One possibility I would inquire about would be tests for malabsorption. This can present with weight loss and loose stools. There are various types of malabsorption, including fat and carbohydrate malabsorption, or celiac disease.
I would suggest testing your stools for fat malabsorption and further tests for carbohydrate malabsorption. There are serum antibody tests for celiac disease that I would also considered.
If those tests are negative, then I would work with your GI doc to optimize treatment for IBS.
Followup with your personal physician is essential.
This answer is not intended as and does not substitute for medical advice - the information presented is for patient education only. Please see your personal physician for further evaluation of your individual case.
Thanks,
Kevin, M.D.