Does a Mediterranean diet help reduce belly fat?
A Mediterranean diet demonstrably helps reduce belly fat, and a polyphenol-rich variant with green tea and walnuts appears to more than double that effect compared with the standard diet.
A polyphenol-rich Mediterranean diet, supplemented with green tea, walnuts and an aquatic plant (Wolffia globosa) and with less red meat, reduced visceral fat around the organs by 14.1% over 18 months. The standard Mediterranean diet achieved 6.0%, compared with 4.2% for ordinary healthy eating guidelines. This difference held up after researchers corrected for weight loss, so the extra polyphenol effect does not appear to work solely through the scales.
For waist circumference, a broader measure of abdominal size, the evidence is even stronger. A review of 57 controlled studies involving nearly 37,000 participants found that the Mediterranean diet reduced waist circumference significantly more than control diets or usual care. Weight and BMI also improved.
Combining the Mediterranean diet with calorie restriction, physical activity and behavioural support can achieve even more. In the PREDIMED-Plus study of people aged 55 to 75 with overweight and metabolic syndrome, the intervention group lost an average of 3.2 kg in twelve months, compared with 0.7 kg in the control group. More than a twentieth of body weight was lost by 33.7% of the intervention group, versus 11.9% in the control group. Waist circumference, blood sugar and blood lipids also improved.
The additional benefit for visceral fat therefore appears to come specifically from polyphenols, on top of what the base diet already achieves. If you try the Mediterranean diet, daily green tea and a handful of walnuts are the two most practically applicable additions to emerge from the research.
This answer draws on one large study in which participants were randomly assigned to one of three diet groups (DIRECT-PLUS, 294 participants, 18 months), one analysis of 57 controlled studies involving nearly 37,000 participants on waist circumference and weight, and the PREDIMED-Plus study (626 participants) on a combined lifestyle intervention. The findings for waist circumference are broadly supported; the specific figures for visceral belly fat come from one study and need to be confirmed in further research.