Obesity has been described as the greatest current threat to human health. In order to design drugs to target obesity, it is essential to understand its physiology and pathophysiology. Several peptides synthesised in the gastrointestinal tract which affect food intake have been identified including ghrelin, cholecystokinin (CCK), glucagon-like peptide-1 (7-36) amide (GLP-1), oxyntomodulin, peptide YY (PYY) and pancreatic polypeptide (PP). These peptides represent potential targets for the design of anti-obesity drugs. In this article we review recent advances in our understanding of food intake by these gastrointestinal hormones.