‘Green’ Mediterranean diet may boost fasting ghrelin, cardiometabolic health
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Men assigned a “green” Mediterranean diet saw a twofold increase in fasting ghrelin level compared with a traditional Mediterranean diet, as well as an improvement in insulin sensitivity and visceral adipose tissue regression, data show.
Ghrelin, known as the “hunger hormone,” increases during fasting and decreases shortly after eating; lower fasting ghrelin levels are associated with obesity and metabolic syndrome, Gal Tsaban, MD, MPH, a researcher and cardiologist at Ben-Gurion University and Negev and Soroka University Medical Center in Beer-Sheva, Israel, and colleagues wrote in the study background. Weight loss is associated with an increased fasting ghrelin level and improved insulin sensitivity; however, the underlying mechanism between change in fasting ghrelin level and insulin sensitivity due to dietary intervention is unclear. “The findings of this study suggest that fasting ghrelin levels may serve as a valuable indicator of cardiometabolic health following weight loss,” Tsaban told Healio. “We also found that individuals who followed the green-Mediterranean diet that included green tea [and] an aquatic duckweed plant named mankai and omitted red meat had a twofold greater elevation in fasting ghrelin levels compared with participants who followed a regular Mediterranean diet or a healthy balanced diet. This suggests the green Mediterranean diet may have additional cardiometabolic benefits.”
In a secondary analysis of the 18-month DIRECT-PLUS trial initiated in May 2017 to assess effects of dietary interventions on weight and adiposity, Tsaban and colleagues analyzed data from 294 adults with abdominal obesity and/or dyslipidemia (mean BMI, 31.3 kg/m2; 88% men; 37% with prediabetes; 11% with type 2 diabetes). Participants were randomly assigned to one of three diets: healthy dietary guidance (n = 98; 86 men), Mediterranean diet (n = 98; 86 men) or a green Mediterranean diet (n = 98; 87 men), all combined with physical activity. Both Mediterranean diets were similarly hypocaloric and included 28 g walnuts daily. The green Mediterranean group also consumed three to four cups of green tea daily and a Wolffia-globosa (mankai) plant shake. Researchers measured fasting ghrelin levels (mean baseline fasting ghrelin level, 504 pg/mL) and quantified body fat depots via MRI at baseline and 18 months.
Retention rate was 98.3% at 6 months and 89.8% at 18 months. Researchers observed similar, moderate weight loss in the two calorie-restricted Mediterranean diet groups (mean, –2.9% for Mediterranean and –3.9% for green Mediterranean) vs. the healthy diet group (mean, –0.6%).
Researchers found that lower fasting ghrelin levels were associated with unfavorable cardiometabolic parameters, such as higher visceral-adipose-tissue (VAT), intra-hepatic fat, leptin and blood pressure (P < .05 for all). Change in fasting ghrelin level at 18 months differed for men (mean increase, 7.3 pg/mL; 26.6%) and women (mean decrease, –9.2 pg/nL; 21.3%; P = .001).
At 18-months, fasting ghrelin level increased by a mean of 1.3%, 5.4% and 10.5% in the healthy diet group, Mediterranean group and green Mediterranean group, respectively (P = .03 for green Mediterranean vs. healthy diet group). Sex-stratified analysis revealed similar changes for men only.
Among men, fasting ghrelin level at 18 months was associated with favorable changes in insulin resistance profile as assessed by homeostatic model of insulin resistance (HOMA-IR; r = –0.154) and VAT regression (r = –0.221) after adjusting for relative weight loss (P < .05 for both).
In residual regression analyses, insulin resistance and VAT remained inversely related with fasting ghrelin level elevation, beyond what was explained by weight-loss (P < .05), according to the researchers.
“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,” Tsaban told Healio. “The differential, diet-specific response in fasting ghrelin levels elevation might suggest another mechanism in which distinct dietary regimens reduce cardiometabolic risk, such as the green Mediterranean diet.”
For more information:
Gal Tsaban, MD, MPH, can be reached at gtsaban@gmail.com; Twitter: @GalTsaban.
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