Coeliac disease (a.k.a. celiac disease or celiac sprue) is characterised by malabsorption, diarrhoea and weight loss and is caused by an immunological reaction to gluten in the diet.
Those affected with coeliac disease have shortened intestinal villi which are less useful for nutrient absorption, leading to their malnutrition.
The only cure is a gluten-free diet.
look up http://www.celiac.com/