Crohn’s disease (CD) and ulcerative colitis (UC) are chronic, relapsing, inflammatory disorders of the digestive tract that characteristically develop in adolescence and early adulthood. The reported prevalence of malnutrition in inflammatory bowel disease (IBD) patients ranges between 20% and 85%. Several factors, including reduced oral food intake, malabsorption, chronic blood and proteins loss, and intestinal bacterial overgrowth, contribute to malnutrition in IBD patients. Poor nutritional status, as well as selective malnutrition or sarcopenia, is associated with poor clinical outcomes, response to therapy and, therefore, quality of life. The nutritional assessment should include a dietetic evaluation with the assessment of daily caloric intake and energy expenditure, radiological assessment, and measurement of functional capacity.

In recent years, research has focused on the use of dietary fibers and prebiotics, since many of these polysaccharides can be metabolized by intestinal microbiota, leading to the production of short-chain fatty acids. The metabolites of prebiotic fermentation also show anti-inflammatory and immunomodulatory capabilities, suggesting an interesting role in the treatment of several pathological conditions. Galacto-oligosaccharide and short- and long-chain fructans (Fructo-oligosaccharides and inulin) are the most studied prebiotics, even if other dietary compounds seem to show the same features. There is an increasing interest in dietary strategies to modulate microbiota. The aim of this review is to explore the mechanisms of action of prebiotics and their effects on the principal gastro-intestinal disorders in adults, with a special focus on Galacto-oligosaccharides, Fructo-oligosaccharides, lactulose and new emerging substances which currently have evidence of prebiotics effects, such as xilooligosaccharides, soybean oligosaccharides, isomaltooligosaccharides, lactobionic acid, resistant starch and polyphenols.

The prevalence of obesity is increasing worldwide, leading to a severe impairment of overall health. Actually, obesity has been associated with several pathological conditions, causing an excess overall mortality. In particular, overweight and obesity are well known risk factors for a variety of gastrointestinal (GI) disorders i.e., functional GI disorders as well as, inflammatory bowel disease (IBD), pancreatitis, and GI cancer. The aim of the present review is to summarize the potential role of overweight and obesity in GI disease with particular focus on plausible biological mechanisms that could explain the association between obesity and GI disease based on the most recent evidence in the literature.