16 people in Seattle participated in a study where they had blood samples extracted every 20 minutes for 6 hours, after drinking beverages composed primarily of carbohydrate, fats, or protein. "The carbohydrate beverage was composed primarily of glucose, the protein
beverage of whey and egg white, and the lipid beverage of whipping cream. For each
participant, the total caloric content, volume, and energy density of all beverages remained
constant. Thus, test meals differed only in macronutrient distribution."
article From the Journal of Clinical Endocrinology & Metabolism, Jan 15 2008
"One gastrointestinal (GI) peptide that bridges the regulation of long-term energy
homeostasis and short-term food intake is ghrelin, the only known appetite-stimulating
hormone. Ghrelin is implicated in short-term mealtime hunger and meal preparation and/or
initiation, in part because circulating levels rise before meals and are suppressed by food intake"
The researchers were most interested in tracking the gherlin response to carbohydrate intake, but found that "The D-AUC of ghrelin, which best reflects the overall magnitude of postprandial
suppression, was greatest after protein ingestion.." The figures graph glucose, insulin, triglycerides, leptin, acyl ghrelin, and total ghrelin responses to each beverage over the 6 hour period.