Plasma levels of Ghrelin: will be sampled every 2 hours for 36 hours. An intravenous catheter will be placed on the subject's arm 30 minutes prior to the first blood sampling. Blood samples will be collected with chilled Vacutainer EDTA tubes and immediately centrifuged. Plasma Ghrelin will be measured using commercial radioimmunoassay (RIA- Phoenix Pharmaceuticals).