In this study, the investigators aimed at evaluating the role of motilin in the regulation of food intake. Motilin, a gastrointestinal hormone, is a hunger signal in healthy volunteers and is significantly increased in obese patients. Its role in food intake regulation might contribute to the pathogenesis of obesity.

Inclusion Criteria:

• BMI < 30 kg/m² for lean volunteers
• BMI > 30 kg/m² for obese volunteers
• Subject is capable and willing to give informed consent
• Female volunteers of child bearing potential must use oral, injected or implanted hormonal methods of contraception

Exclusion Criteria:

• Female volunteer is pregnant or breastfeeding
• GI diseases, major abdominal surgery
• Major psychiatric illnesses
• Volunteers that use drugs affecting the GI tract or the central nervous system
• Volunteers suffering from endocrine diseases such as diabetes, Cushing's disease, Addison's disease, hypothalamic tumor
• Volunteers that have undergone surgical procedure for weight loss