Acyl and total ghrelin are suppressed strongly by ingested proteins, weakly by lipids, and biphasically by carbohydrates.
BACKGROUND
Ghrelin is an orexigenic hormone that can increase body weight. Its circulating levels increase before meals and are suppressed after food ingestion. Understanding the effects of specific types of ingested macronutrients on ghrelin regulation could facilitate the design of weight-reducing diets.


OBJECTIVE
We sought to understand how ingestion of carbohydrates, proteins, or lipids affect acyl (bioactive) and total ghrelin levels among human subjects, hypothesizing that lipids might suppress ghrelin levels less effectively than do either carbohydrates or proteins.


METHODS
This was a randomized, within-subjects cross-over study.


METHODS
The study was conducted at a University Clinical Research Center.


METHODS
There were 16 healthy human subjects included in the study.


METHODS
Isocaloric, isovolemic beverages composed primarily of carbohydrates, proteins, or lipids were provided.


METHODS
The magnitude of postprandial suppression of total and acyl ghrelin levels (measured with a novel acyl-selective, two-site ELISA) was determined.


RESULTS
All beverages suppressed plasma acyl and total ghrelin levels. A significant effect of macronutrient class on decremental area under the curve for both acyl and total ghrelin was observed; the rank order for magnitude of suppression was protein more than carbohydrate more than lipid. Total ghrelin nadir levels were significantly lower after both carbohydrate and protein, compared with lipid beverages. In the first 3 postprandial hours, the rank order for acyl and total ghrelin suppression was carbohydrate more than protein more than lipid. In the subsequent 3 h, there was a marked rebound above preprandial values of acyl 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.
Foster-Schubert
Karen E
KE
University of Washington School of Medicine, Seattle, WA 98195, USA. kfoster@u.washington.edu
Overduin
Joost
J
Prudom
Catherine E
CE
Liu
Jianhua
J
Callahan
Holly S
HS
Gaylinn
Bruce D
BD
Thorner
Michael O
MO
Cummings
David E
DE
D000215:Acylation; D000328:Adult; D000368:Aged; D001066:Appetite; D019540:Area Under Curve; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004041:Dietary Fats / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D005260:Female; D054439:Ghrelin / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D008297:Male; D008875:Middle Aged; D013997:Time Factors
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D054439:Ghrelin; D007328:Insulin; D020738:Leptin