<<Disclaimer:  Verify this information before applying it to your situation.>>

Continued weight loss or new weight loss in an adult celiac may be due to
the diet being lower in calories than before. However the absorption of
food should be better resulting in a greater availability of nutrition to
the individual.  Failure to gain weight in a malnourished patient should
suggest non-compliance with the GFD, a complication of celiac disease or
the possibility nor an alternative diagnosis either with celiac disease
or instead of it.
These problems are not simple and require careful nutritional and GI
review to address the problem.
Not Medical advice
Joe Murray
University of Iowa