according to a new analysis of the 18-month Dietary Intervention Randomized Controlled Trial Polyphenols Unprocessed (DIRECT-PLUS) trial.
The new results indicate that the green Mediterranean diet lowered visceral fat by twice as much as the standard Mediterranean diet (14% vs. 7%), reported Iris Shai, PhD, of Ben-Gurion University of the Negev in Be’er Sheva, Israel, and colleagues.
“This study may suggest an improved dietary protocol for treating visceral adiposity,” the authors wrote in their article, published recently in BMC Medicine.
“A healthy lifestyle is a strong basis for any weight-loss program. We learned from the results of our experiment that the quality of food is no less important than the number of calories consumed and the goal today is to understand the mechanisms of various nutrients, for example, positive ones such as the polyphenols, and negative ones such as empty carbohydrates and processed red meat, on the pace of fat cell differentiation and their aggregation in the viscera,” Dr. Shai said in a press release from Ben‐Gurion University.
“A 14% reduction in visceral fat is a dramatic achievement for making simple changes to your diet and lifestyle. Weight loss is an important goal only if it is accompanied by impressive results in reducing adipose tissue,” added coauthor Hila Zelicha, RD, PhD, also of Ben‐Gurion University of the Negev.
Previous randomized controlled trials have shown that dietary changes with a higher polyphenol content tend to produce better cardiometabolic outcomes and appear to mobilize particular ectopic fat depots, the researchers noted.
The main results of the DIRECT-PLUS trial were published in 2020 in Heart. Almost 300 participants with abdominal obesity/dyslipidemia were randomized to one of three diet groups (all accompanied by physical activity): standard healthy dietary guidelines (HDG), standard Mediterranean diet, and the so-called green Mediterranean diet. The mean age of participants was 51 years, and men comprised 88% of the study cohort.
Participants in both Mediterranean diet groups ate 28 grams/day of walnuts, which accounted for about 440 mg/day of polyphenols. Participants in the green Mediterranean group also ate 100 grams/day of frozen cubes of a Wolffia globosa (duckweed strain) plant green shake, and three to four cups/day of green tea, which contributed to consumption of 800 mg/day of polyphenols, and decreased red meat consumption.
Both the green and standard Mediterranean diet groups achieved similar weight loss (–6.2 kg and –5.4 kg) compared with the HDG group (–1.5 kg; P < .001). However, the green Mediterranean diet group had a greater reduction in waist circumference (–8.6 cm) than the standard Mediterranean diet group (–6.8 cm; P = .033) and HDG group (–4.3 cm; P < .001). Stratification by gender showed these differences were significant only among men.
Explaining the rationale for the study, the researchers noted that visceral adipose tissue accumulation is a key factor that differentiates metabolic healthy and unhealthy obese individuals, is closely related to the development of multiple cardiovascular risk factors, including hypertension, dyslipidemia, and type 2 diabetes, and is an independent marker of mortality.
Now, their latest data show the green Mediterranean diet group lost approximately twice as much visceral adipose tissue compared with the standard Mediterranean diet and HDG groups (−14.1%, −6.0%, and − 4.2%; P < .05 independent of weight loss, sex, waist circumference, or age).
Lower red meat consumption, greater dietary consumption of walnuts, Wolffia globosa, and green tea, increased urine urolithin A polyphenol, and elevated total plasma polyphenols were significantly associated with greater visceral adipose tissue loss (P < .05, multivariate models).
“A green Mediterranean diet enriched with polyphenols and decreased red meat consumption might serve as an improved version of the Mediterranean diet for targeted VAT reduction. Future studies are needed to explore the exact mechanisms of specific polyphenol-rich foods on visceral adiposity,” the study authors concluded.
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