A high-polyphenol Mediterranean diet may be a more effective method for reducing visceral adipose tissue (VAT) than the conventional healthy Mediterranean (MED) diet, reaching more than double the degree of VAT reduction while achieving equivalent weight loss, according to an 18-month Dietary Intervention Randomized Controlled Trial PoLyphenols UnproceSsed (DIRECT-PLUS) weight-loss trial. Researchers aimed to assess the effect of a green-MED diet on VAT.

A total of 294 individuals (aged 51 years old; 29% VAT; body mass index = 31.2 kg/m2) were randomly assigned to one of three diets, all of which included physical activity: (1) the healthy dietary guidelines (HDG), (2) MED, or 3) green-MED diets. Both isocaloric MED groups ate 28 g of walnuts per day (+ 440 mg/day polyphenols). The green-MED group also had Wolffia globosa (duckweed strain) plant green shake (100 g frozen cubes every day) (+ 800mg/day polyphenols) and green tea (3 to 4 cups daily), while consuming less red meat. The abdomen adipose tissues were quantified using magnetic resonance imaging (MRI).

Volunteers (79.3%) completed all necessary MRIs with a retention rate of 89.8%. Green-MED dieters doubled the VAT reduction (HDG: -4.2%, MED: -6.0%, green-MED: -14.1%, irrespective of weight loss, circumference of waist, sex, or age), whereas both MED diets achieved comparable moderate waist circumference loss (MED: -4.7%, green-MED: -5.7%) and weight loss (MED: -2.7%, green-MED: -3.9%).

Higher VAT loss (multivariate models) was substantially associated with higher urine urolithin A polyphenol levels, higher total plasma polyphenol levels (majorly hippuric acid), reduced consumption of red meat, and higher dietary intake of Wolffia globosa, walnuts, and green tea. For targeted VAT reduction, a green-MED diet, twice fortified in dietary polyphenols and lower in red/processed meat, may serve as an improved version of the MED diet.