The Mediterranean diet may have met its match — at least on the scale.
Going Greek has long been praised as one of the healthiest ways to eat, boosting longevity and helping fend off chronic disease.
But if shedding pounds is the goal, new research suggests another diet may deliver bigger results, even if it includes some so-called “unhealthy” foods.
In the study, 62 overweight adults were randomly assigned to follow one of two diets for 16 weeks without calorie limits.
Half ate a Mediterranean diet featuring fruits, vegetables, legumes, fish, low-fat dairy and extra-virgin olive oil. The other half stuck to a low-fat vegan diet consisting of fruits, vegetables, grains and beans.
Afterward, participants took a four-week break and returned to their usual diets before switching to the opposite eating style for another 16 weeks.
By the end of the study, researchers found that the vegan diet was more effective for weight loss than the Mediterranean approach.
It also led to better outcomes for insulin sensitivity and cholesterol levels, as well as more favorable changes in body composition.
That’s a big deal: nearly 3 in 4 US adults are overweight or obese, putting them at a higher risk for a wide range of health problems, including heart disease, stroke and certain cancers.
Around 1 in 3 Americans also have insulin resistance — an early warning sign for prediabetes and Type 2 diabetes that many people don’t realize they have.
In a secondary analysis of the results, researchers reviewed participants’ food records to see how different types of plant-based eating were associated with weight loss.
To do this, they used the plant-based diet index (PDI), which has three scoring systems:
- PDI: Measures overall adherence to plant-based eating, with higher scores reflecting greater consumption of plant foods
- hPDI: Assesses intake of “healthful” plant foods, with higher scores indicating a greater proportion of nutritious options and fewer “unhealthful” foods
- uPDI: Gauges intake of “unhealthful” plant foods, with higher scores signifying a greater consumption of these items and fewer “healthful” choices
Foods classified as “healthful” include fruits, vegetables, whole grains, nuts, legumes, oils, coffee and tea.
The “unhealthful” category includes fruit juice, sugar-sweetened beverages, refined grains, potatoes and sweets.
The researchers found that participants’ overall PDI scores rose significantly on the vegan diet, but remained largely unchanged on the Mediterranean diet.
Interestingly, uPDI scores decreased on the Mediterranean diet but increased on the vegan diet — even though participants lost more weight following the vegan plan.
Meanwhile, hPDI scores increased on both diets, but these changes were not linked to weight loss.
“Our research shows that even when a low-fat vegan diet includes so-called unhealthy plant-based foods-as defined by the plant-based diet index-like refined grains and potatoes, it’s better than the Mediterranean diet for weight loss,” Dr. Hana Kahleova, director of clinical research at the Physicians Committee for Responsible Medicine and lead author of the study, said in a statement.
The researchers noted that most of the increases in plant-based scores came from avoiding animal products.
On the vegan diet, participants consumed fewer nuts and oils — considered “healthful” — than on the Mediterranean plan, but ate more refined grains and potatoes, which are classified as “unhealthful.”
This pattern, the researchers said, explains the rise in the vegan diet’s uPDI scores.
“These findings suggest that replacing animal products with plant-based foods and reducing the consumption of oil and nuts may be successful strategies for weight loss,” the study authors wrote.
Many plant-based foods, they explained, are high in fiber and have a low energy density — meaning they contain fewer calories per gram. This allows you to eat larger, more satisfying portions without consuming excess calories, which can support weight loss.
For example, most vegetables are very low in calories, so you can enjoy a big plate and still stay within your calorie goals. In contrast, nuts, while rich in healthy fats, protein and other nutrients, have a high energy density, meaning even small portions contain many calories and can make it easier to overeat.
The researchers also reported that many foods in the vegan diet can stimulate the body’s production of glucagon-like peptide-1.
Also known as GLP-1, this hormone triggers insulin release from the pancreas, slows digestion and signals to the brain that you are full.
Sound familiar? GLP-1 is the same hormone that weight-loss drugs like Ozempic and Wegovy mimic to help people manage their blood sugar and lose weight by making them feel full sooner and stay full longer.
