Fibre exerts these anti-obesity effects by acting in the gastrointestinal tract through different mechanisms such as increasing gastric distension, delaying gastric emptying, digestion and absorption of nutrients, increasing insulin and glycemic responses, affecting gut hormones secretion such as GLP-1, peptide YY and neurotensin, reducing the absorption of fat and increasing the fecal energy excretion (for review see [51]). The gene discussed is PYY; the disease is obesity due to melanocortin 4 receptor deficiency.