Acyl and Total Ghrelin Are Suppressed Strongly by Ingested Proteins, Weakly by Lipids, and Biphasically by Carbohydrates
University of Washington School of Medicine (K.E.FS., J.O., H.S.C., D.E.C.) Seattle,
Washington 98195;
Veterans Affairs Puget Sound Health Care System (K.E.FS., J.O., D.E.C) Seattle,
Washington 98108;
University of Virginia Schools of Medicine (J.L., B.D.G., M.O.T.) and
Arts and Sciences (Chemistry) (C.E.P.)
Charlottesville, Virginia 22903
Context
Ghrelin is an orexigenic hormone that can increase bodyweight. Its circulating levels rise before meals and are suppressed following food ingestion. Understanding the effects of specifictypes of ingested macronutrients on ghrelin regulation could facilitate design of weight-reducing diets.
Objective
We sought to understand how ingestion of carbohydrates, proteins, or lipidsaffect acyl (bioactive) and total ghrelin levels among humansubjects, hypothesizing that lipids might suppress ghrelin levelsless effectively than do either carbohydrates or proteins.
Design
Randomized, within-subjects cross-over study
Setting
University Clinical Research Center
Participants
16 healthy human subjects
Interventions
Administration of isocaloric, isovolemic beverages composed primarily of carbohydrates, proteins, or lipids
Main OutcomeMeasures
Magnitude of postprandial suppression of total andacyl ghrelin levels (measured with a novel acyl-selective, two-siteELISA)
Results
All beverages suppressed plasma acyl and totalghrelin levels. A significant effect of macronutrient classon decremental area-under-the-curve for both acyl and total ghrelin was observed; the rank order for magnitude of suppressionwas protein > carbohydrate > lipid. Total ghrelin nadirlevels were significantly lower following both carbohydrate and protein, compared to lipid beverages. In the first 3 postpra ndialhours, the rank order for acyl and total ghrelin suppressionwas carbohydrate > protein > lipid. In the subsequent3 h, there was a marked rebound above preprandial values ofacyl and total ghrelin after carbohydrate ingestion alone.
Conclusions
These findings suggest possible mechanisms contributing to the effects of high-protein/low-carbohydrate diets to promote weight loss, and high-fat diets to promote weight gain.