Studies will be performed after discontinuation of medications that could affect gastrointestinal motility for at least 48 hours and overnight fast. Endoluminal images were obtained with the Pillcam capsule (Pillcam SB3 video capsule; Medtronic). Images will be obtained at a fixed 2 per second rate and recorded for a total of 8 hours with the subjects lying comfortably on a hospital bed and the trunk raised 30° above horizontal. Forty-five minutes after gastric exit, participants will be instructed to ingest a liquid meal (Ensure HN; Abbott; 300 mL,1 Kcal/mL). Endoluminal images of the small bowel will be analyzed with a computer program specifically developed in our laboratory for the evaluation of intestinal motility. This previously validated program is based on computer vision techniques, which allow the detection and quantification of contractile and non-contractile patterns characterizing small bowel motility.