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Ghrelin is a stomach-derived hormone that stimulates appetite. Ghrelin levels rise during overnight fasting when a person is sleeping. The levels fall after an individual eats a meal.

The 18m clinical trial study found that dieting induces elevation in fasting levels of ghrelin and that elevation of fasting ghrelin is associated with abdominal visceral fat loss and improving insulin sensitivity. This suggests individuals who have higher levels of fasting ghrelin following weight loss face decreased risk of developing diabetes or other metabolic diseases.

Individuals who followed the green-Mediterranean diet that included a leafy vegetable called Mankai and green tea and omitted red meat had two-fold greater elevation in fasting ghrelin levels compared with of participants who followed a more traditional Mediterranean diet or a healthy balanced diet, which suggests this approach may have additional cardiometabolic benefits.

“The findings suggest fasting ghrelin levels may serve as a valuable indicator of cardiometabolic health following weight loss,” said the study’s senior author, Iris Shai of Ben-Gurion University of the Negev in Beer-Sheva, Israel, and the Harvard T.H. Chan School of Public Health in Boston, Mass.

Shai and her colleagues recently suggested the green-MED diet as an improved version of the healthy MED diet in the DIRECT PLUS trial. This clinical trial study examined fasting ghrelin levels in 294 participants over 18 months. During the clinical trial, participants with either abdominal obesity or dyslipidemia — a condition with abnormally elevated cholesterol or fats in the blood — were randomized to one of three diets: following healthy dietary guidelines, the Mediterranean diet or a green version of the Mediterranean diet that was protein plant-based and free of red meat. All the participants, who were selected from an isolated workplace, provided with monitored lunches, instructed to exercise and given gym memberships.

Individuals following the green Mediterranean diet, which included daily consumption of green tea and a green leafy vegetable called Mankai, had fasting ghrelin levels that were twice as high as those who followed a traditional Mediterranean diet, despite similar caloric restriction and weight loss.

“The elevation in fasting ghrelin levels might help to explain why the green Mediterranean diet optimized the microbiome, reduced liver fat and improved cardiometabolic health more than the other diets in our study,” Shai said.

“The results of our study suggest that fasting ghrelin is an essential hormonal factor in the diet-associated recovery of sensitivity to insulin and visceral adiposity regression, or reduction in belly fat,” said the first author of the paper, Gal Tsaban, a researcher and cardiologist of Ben-Gurion University of the Negev and Soroka University Medical Center, both in Beer-Sheva, Israel. “The differential, diet-specific response in fasting ghrelin levels elevation might suggest another mechanism in which distinct dietary regimens, such as the green-Mediterranean diet, reduce cardiometabolic risk.”

Other authors of the study include: Anat Yaskolka Meir, Hila Zelicha, Ehud Rinott, Alon Kaplan, and Amos Katz of Ben-Gurion University of the Negev; Aryeh Shalev of Soroka University Medical Center; Dov Brikner of the Nuclear Research Center Negev in Dimona, Israel; Matthias Blüher, Uta Ceglarek and Michael Stumvoll of the University of Leipzig in Leipzig, Germany; and Meir J. Stampfer of the Harvard T.H. Chan School of Public Health, Harvard Medical School and Brigham and Women’s Hospital in Boston, Mass.

The research was supported by Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), the Israel Ministry of Health, Israel Ministry of Science and Technology and the California Walnuts Commission.

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Materials provided by The Endocrine Society. Note: Content may be edited for style and length.