Eating a Mediterranean-style diet, which is abundant in polyphenol-rich fruits, vegetables, olive oil, legumes, and nuts, helps reduce abdominal fat, a 2022 study found. People who followed a Mediterranean-style diet supplemented with a polyphenol-rich shake for 18 months lost twice as much abdominal fat as those who consumed a lower-polyphenol diet.

Researchers assigned nearly 300 people to follow one of three diets plus exercise: a Mediterranean-style diet that included walnuts; a Mediterranean-style diet that included walnuts, green tea, and a shake that contained duckweed (a polyphenol-rich aquatic plant native to Asia); and a diet that adhered to conventional healthy dietary guidelines. They measured the participants' body weight and waist circumference and conducted magnetic resonance imaging (MRI) studies to assess their abdominal fat at the beginning and end of the intervention.

They found that participants who followed the two variations of the Mediterranean/walnut diets lost body weight and their waist circumferences decreased, compared to those who followed the healthy dietary guidelines. However, MRIs revealed that while those who followed the Mediterranean/walnut diet lost 6.0 percent of their abdominal fat, those who followed the Mediterranean/walnut diet that included tea and duckweed lost 14.1 percent of their abdominal fat – more than twice as much.

Walnuts are rich in the polyphenolic compound ellagic acid. Bacteria in the human gut break down ellagic acid to produce urolithins. Scientists have identified about 20 urolithins, but the most studied of these is urolithin A, which exerts potent anti-obesity effects.

Duckweed is rich in polyphenols, carotenoids, omega-3 fatty acids, fiber, and many micronutrients, including iron and vitamin B12. The polyphenols in duckweed exert robust antioxidant activity and support healthy blood glucose levels – critical elements in maintaining healthy body weight and waist circumference.

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