The peripherally circulating peptide hormone ghrelin is purported to stimulate hunger and feeding in humans, and is affected by the energy storage state as reflected in body mass index and body composition, and by macronutrient content of the diet. There have been few studies in humans that have measured both ghrelin, in its various isoforms, and appetite. To address this, Manuscript #1 of this dissertation examined fasting and postprandial ghrelin and ratings of appetite, in addition to anthropometric and fitness measures in 50 college-age student. There were no significant correlations between fasting or postprandial ghrelin and appetite or anthropometric measures in this population of college-age students. The macronutrient content of the diet is purported to influence ghrelin, but there have been few studies of the impact of carbohydrates on ghrelin, and no studies on the impact of state of grain refinement on ghrelin. To address this, Manuscript #2 examined the responses of ghrelin, glucose, insulin, metabolism, and appetite to matched whole and refined grain breakfasts. There was greater satiety following the whole grain breakfast, but no other between-meal differences. The chemical assay typically used to detect ghrelin cannot differentiate among various isoforms of ghrelin. An assay that specifically detects the "active" form of ghrelin was used, and the results were compared to the results of the conventional assay in Manuscript #3. Active ghrelin varied over time differently than the total ghrelin assay, suggesting peripheral conversion in the circulatory system between isoforms of ghrelin.
