Obesity has reached pandemic proportions, obesity-associated complications are extensive and the current treatment options are limited. These facts demonstrate the need for an improved understanding of the pathogenesis of obesity. The gastrointestinal tract plays a key element in the control of satiation; discrepancies exist, however, for the role of gastric and intestinal parameters in the control of satiation in relation to body mass. To achieve a comprehensive understanding for the reciprocal control between gastric functions and intestinal parameters in the development of satiation in obese people the investigators will compare satiation parameters, gastric emptying and plasma glucagon-like peptide-1 (GLP-1), peptide tyrosine tyrosine (PYY) and ghrelin levels between normal and obese healthy volunteers.