In this study, the investigators aimed at evaluating the role of bitter taste receptors in the gastrointestinal tract (GIT). Intragastric or intraduodenal administration of denatonium benzoate (DB) or quinine hydrochloride were compared with placebo administration for their effects on lingual sensitivity, gastrointestinal motility (both in the fasted and fed state), gut hormone release (motilin, ghrelin, glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK)) and food intake. Differences between lean and obese subjects will be evaluated.