Fibromyalgia, a chronic pain disorder, is characterized by generalized chronic musculoskeletal pain that is usually accompanied by several other clinical manifestations that contribute to a diminished quality of life, such as sleep disturbances, chronic fatigue, mood disorders, and cognitive difficulties. Many patients with fibromyalgia suffer from gastrointestinal and extra-intestinal symptoms that are similar to those experienced by adult celiac disease patients such as abdominal pain, dyspepsia, nausea, diarrhea, constipation, fatigue, pain and mood changes. This raises the possibility that some patients with fibromyalgia may also suffer from oligosymptomatic celiac disease or non-celiac gluten intolerance. On the other hand, the emerging evidence linking obesity with fibromyalgia and the high prevalence of overweight among fibromyalgia patients suggest a potential benefit for weight loss among these patients. Thus, the main objective of this study is to compare the efficacy of a gluten-free diet (GFD) with a hypocaloric diet (HCD) in patients with fibromyalgia that also experience celiac-type symptoms.