The effect of high-polyphenol Mediterranean diet on visceral adiposity: the DIRECT PLUS randomized controlled trial.

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• The positive health effects of the traditional MED diet, moderately high in PUFAs and MUFAs and low in red meat, are well-established
• Higher levels of total plasma polyphenol and serum folate may reflect higher consumption of “green” dietary components, which were significantly associated with greater VAT loss
• The green-MED diet, richer in dietary polyphenols and green plant-based proteins and lower in red meat, might be a more effective strategy for VAT loss than the traditional healthy MED diet, achieving more than twice the degree of VAT reduction, despite similar weight loss.
• VAT loss was specifically related to lower red meat intake and increased walnuts, green tea, Wolffia globosa, and dietary fibre and was reflected by higher plasma polyphenol and serum folate levels.

A mediterranean (MED) diet is a rich source of polyphenols, which benefit adiposity by several mechanisms. Visceral adipose tissue (VAT) accumulation is one of the main factors that differentiate between metabolic healthy and unhealthy obese individuals. In this Dietary Intervention Randomised Controlled Trial PoLyphenols UnproceSsed (DIRECT‐ PLUS) weight‐loss trial, 294 participants were randomised to: (A) healthy dietary guidelines (HDG), (B) MED, or (C) green‐MED diets, all combined with physical activity. The study duration was 18‐months. This study explored the effect of the green‐MED diet, twice fortified in dietary polyphenols and lower in red/processed meat, on visceral adipose tissue (VAT) and used magnetic resonance imaging (MRI) to quantify the abdominal adipose tissues. Both isocaloric (with the same calorific value) MED groups consumed 28 g/day of walnuts (+ 440 mg/day polyphenols). The green‐MED group further consumed green tea (3–4 cups/day) and Wolffia globosa (duckweed strain) plant green shake (100 g frozen cubes/day) (+ 800mg/day polyphenols) and reduced red meat intake. The mean weight loss (HDG: −0.4% (5.0), MED: −2.7% (5.6), green-MED: −3.9% (6.5)) and WC loss (HDG: −3.6% (5.1), MED: −4.7% (5.0), green-MED: −5.7%(5.7)) after 18 months were similar between the two MED diets (p > 0.05 for all) and higher as compared to the HDG (weight: HDG vs. MED: p = 0.02; HDG vs. green+MED: p < 0.001; WC: HDG vs. MED: p = 0.33, HDG vs. green+MED: p = 0.02). All three abdominal fat depots decreased over 18 months of intervention (p < 0.05 vs. baseline for all). The green-MED group achieved a greater reduction in VAT than the other intervention groups (HDG: −4.2% (22.5), MED: −6.0%(31.3), green-MED: −14.1%(27.7); p < 0.05 green-MED vs. MED or vs. HDG groups). These differences in VAT loss across the groups remained significant after adjusting for age, sex, and 18-month WC change (green-MED vs. MED p = 0.023; green-MED vs. HDG p = 0.002) (Fig. 1) Limitations of the study included a low proportion of women, and different VAT proportions at baseline across groups limit the generalisability of findings to women. The authors of the study did not identify the exact components responsible for the dietary effects when they compared dietary regimens and not specific nutrients. Adherence was by a validated, self-reported dietary intake assessment tool, which the authors acknowledge is subject to error Strengths of the study included the relatively large sample size, high retention rate, and use of 3-T MRI measurements (considered one of the gold standards tools for the quantification of specific fat depots

• This trial shows that, when combined with a Mediterranean diet, higher dietary consumption of green tea, walnuts, and dietary fibre and reduced red meat consumption were significantly associated with greater %VAT loss
• The authors observed a significant synergistic interaction effect between decreased red meat consumption and increased serum folate on VAT loss
• A reduction in VAT accumulation, known as a key risk factor in CVD development, may reduce metabolic complications, improve the lipid profile, and decrease cardiometabolic risk.

• Future studies are needed to explore the exact mechanisms of specific polyphenol-rich foods on visceral adiposity.
• Future studies could explore whether the results are replicable in both male and female participants, as this sample was largely male.