Effects of habitual diet on ethnic differences in serum total ghrelin.

Ghrelin, an orexigenic hormone, may be involved in the etiology of obesity. African Americans (AA) experience higher obesity rates than European Americans (EA), but it is unclear whether ghrelin differs with ethnicity. This study was designed to compare ghrelin concentrations between overweight AA and EA adults in a post absorptive state, in response to a standard meal, and after 8-week habituation to diets of differing macronutrient profiles. Sixty-one overweight men and women (31 EA and 30 AA) were assigned to either a higher-carbohydrate/lower-fat diet (55% CHO, 18% PRO, 27% FAT) or a lower-carbohydrate/higher-fat diet (43% CHO, 18% PRO, 39% FAT) for 8 weeks. At baseline and week 8, participants ingested a standard liquid mixed meal. Blood was sampled before the meal and serially after ingestion to measure total ghrelin and insulin. Hunger was assessed with a visual analog scale. Composite scores for ghrelin, insulin, and hunger were calculated as area under the curve (AUC), and ghrelin suppression was calculated as the change from fasting concentration. Fasting ghrelin and ghrelin AUC were higher among EA at baseline and week 8 (p < 0.001), and these differences were not affected by diet habituation. Despite greater postprandial ghrelin suppression, EA displayed greater hunger immediately following the test meal (p < 0.05). Overweight EA displayed higher circulating ghrelin and greater ghrelin suppression compared to AA. Further study is warranted to explore the physiological basis for these ethnic differences and to determine whether they may relate to higher obesity rates among AA.