Celiac disease (CD) is a chronic immune-mediated gluten dependent enteropathy induced by ingestion of gluten, characterized by intestinal malabsorption and subtotals or total atrophy of intestinal villi. The predominant consequence of CD in untreated patients, is malnutrition as a result of malabsorption. Moreover, several and increasing extra-intestinal clinical manifestations have been described in the CD patients. Strict adherence to a gluten-free diet (GFD) improves nutritional status, inducing an increase in fat and bone compartments, but does not completely normalize body composition and nutritional deficiencies. An early and accurate evaluation of nutritional status can be of the pivotal step in the clinical management of the adult CD patients. The aim of this review is to present the most important and recent data on nutritional and metabolic features in the CD adult patients, the related implications and the effects of the GFD on these conditions.