My wife, age 50, had a severe problem with weight gain. Her abdomen was growing enormous, stretching daily. One physician diagnosed gluten intolerance, an inability to digest wheat and particularly rye grain. She cut back on wheat and resumed taking Fen-Phen. Her condition stabilized, but she is still much heavier than before.
Gluten intolerance is thought to be a genetic disorder.
There are several HLA serotypes which are common in this disorder leading to the genetic theory. The reason that people have trouble with gluten digestion is not clear. However, biopsy of the small intestine shows a characteristic lesion. However, these are not specific. Diagnosis depends on a biopsy as well as using a gluten free diet-demonstrating improvement.