Query: Coeliac disease is treated by maintaining a fat-free diet.

Relevant passages:
Coeliac disease <=SEP=> Coeliac disease , also spelled celiac disease , is a long term autoimmune disorder primarily affecting the small intestine that occurs in people who are genetically predisposed . Classic symptoms include gastrointestinal problems such as chronic diarrhoea , abdominal distention , malabsorption , loss of appetite , and among children failure to grow normally . This often begins between six months and two years of age . Non-classic symptoms are more common , especially in people older than two years . There may be mild or absent gastrointestinal symptoms , a wide number of symptoms involving any part of the body , or no obvious symptoms . Coeliac disease was first described in childhood ; however , it may develop at any age . It is associated with other autoimmune diseases , such as diabetes mellitus type 1 and thyroiditis , among others .   Coeliac disease is caused by a reaction to gluten , which are various proteins found in wheat and in other grains such as barley , and rye . Moderate quantities of oats , free of contamination with other gluten-containing grains , are usually tolerated . The occurrence of problems may depend on the variety of oat . Upon exposure to gluten , an abnormal immune response may lead to the production of several different autoantibodies that can affect a number of different organs . In the small-bowel this causes an inflammatory reaction and may produce shortening of the villi lining the small intestine ( villous atrophy ) . This affects the absorption of nutrients , frequently leading to anaemia .   Diagnosis is typically made by a combination of blood antibody tests and intestinal biopsies , helped by specific genetic testing . Making the diagnosis is not always straightforward . Frequently , the autoantibodies in the blood are negative and many people have only minor intestinal changes with normal villi . People may have severe symptoms and be investigated for years before a diagnosis is achieved . Increasingly , the diagnosis is being made in people without symptoms as a result of screening . Evidence regarding the effects of screening , however , is not sufficient to determine its usefulness . While the disease is caused by a permanent intolerance to wheat proteins , it is not a form of wheat allergy .   The only known effective treatment is a strict lifelong gluten-free diet , which leads to recovery of the intestinal mucosa , improves symptoms , and reduces risk of developing complications in most people . If untreated , it may result in cancers such as intestinal lymphoma and a slight increased risk of early death . Rates vary between different regions of the world , from as few as 1 in 300 to as many as 1 in 40 , with an average of between 1 in 100 and 1 in 170 people . In developed countries , it is estimated that five out of six cases ( 83 % ) remain undiagnosed , usually because of non-classic , minimal , or absent complaints . Coeliac disease is slightly more common in women than in men . The term `` coeliac '' is from the Greek κοιλιακός ( koiliakós , `` abdominal '' ) and was introduced in the 19th century in a translation of what is generally regarded as an ancient Greek description of the disease by Aretaeus of Cappadocia .