Want to Lose Weight? Study Finds a Plant-Based Diet Beats Mediterranean

No doubt you’ve heard the accolades for the Mediterranean diet. This plant-rich diet, which allows some animal products (such as low-fat cheese, fish, and lean protein), has been lauded as the best diet for long-term health. Yet here’s the million-dollar question: How does the Mediterranean diet stack up against a vegan or plant-based diet when it comes to overall health and weight loss?

A new study from the Journal of the American College of Nutrition provides the answer. As it turns out, not all plant-based diets are created equal, and if you want to achieve weight loss and optimal health, eating plant-based foods is the answer.

The Mediterranean diet and vegan diet share many similarities, namely that they’re both rich in fruits and vegetables and high in fiber. Yet there are key differences.

While the vegan or whole-food, plant-based diet eliminates animal products, a Mediterranean diet only limits them, explains Hana Kahleova, M.D., Ph.D., study co-author and director of clinical research for the Physicians Committee for Responsible Medicine. A vegan or whole-food plant-based diet is also low in fats; higher-fat foods like oils, nuts, and seeds are also prevalent in a Mediterranean diet.

So how might these diets impact health markers, like weight, cholesterol, blood pressure, blood lipids, and insulin sensitivity? That's the question that drove researchers, especially given that the Mediterranean diet has been touted not only as being heart healthy but also for its weight loss effects.

Kahleova and her colleagues recruited 62 individuals who were overweight with no history of diabetes and randomly assigned them to a vegan diet or a Mediterranean diet for 16 weeks, neither of which had calorie restrictions. Those on the vegan diet were asked to eliminate all animal products, keep oils and added fats low (limited to 10 percent of daily caloric intake), and base their diet on fruits, vegetables, grains, and legumes. “From there, they were free to eat the foods they enjoyed and eat until they felt satiated without counting calories,” she says.

Meanwhile, the Mediterranean diet group not only ate those foods but also low-fat dairy and extra virgin olive oil. In addition, they limited (to one serving a week or less) or avoided red meat and saturated fats and were asked to limit or eliminate cream, butter, margarine, processed meats, sweetened beverages, pastries, and processed snacks.

After 16 weeks, study participants resumed their former diets for four weeks before switching to the other diet for 16 weeks. The results? Not surprisingly, the vegan diet won on almost every health measure. “We were expecting to see positive results on the low-fat, plant-based (vegan) diet since we know that past studies have found that plant-based (vegan) diets are excellent for improving these health markers,” Kahleova says.

Take weight loss and body fat, for starters. People on the plant-based diet not only lost about 7.5 pounds more fat, but they also lost 13 pounds on average, versus no meaningful change on the Mediterranean diet. Visceral fat, the toxic fat between the organs, also decreased more on the vegan diet. And although there weren’t significant cholesterol changes on the Mediterranean diet, the vegan diet decreased total and LDL (aka bad) cholesterol.

There’s good reason to explain the magnitude of difference between the two diets. “A vegan diet is low in fat and high in fiber, which means you’ll feel satiated on fewer calories,” Kahleova says. On the flip side, more energy-dense foods like fish, chicken, and higher-fat plant foods like oil and nuts won’t fill you up as much. “This, in part, likely led to lower weight loss on the Mediterranean diet.”

Blood pressure, which decreased on both diets, came down slightly more on the Mediterranean diet. Researchers aren’t sure why but say the sodium content of an individual participants’ diet may have played a role as may have olive oil. “It’s been hypothesized that olive oil may help lower blood pressure due to a high content of vitamin E and polyphenols,” Kahleova says. Just don’t take this as a license to indulge in olive oil. “People need to be careful with olive oil because it’s energy-dense and may not promote weight management and other cardiometabolic risk factors as well as a low-fat vegan diet.”

While this study clearly proved that the vegan diet has numerous advantages over the Mediterranean diet, it also showed that the Mediterranean diet isn’t all it’s cracked up to be. “People who really need help – with weight or other health problems – are often misled into believing a Mediterranean diet will be most effective,” Kahleova says, adding that studies on the Mediterranean diet often add exercise or calorie restriction, which could confound the effects of the dietary change.
Kahleova points to the Lyon Diet Heart Study, which found that a Mediterranean diet led to a three-pound weight gain, not weight loss, during that two-year study. In that study, which first popularized the Mediterranean diet back in 2001, all of the participants, 90 percent of whom had excess body weight, followed a Mediterranean diet supplemented with either extra-virgin olive oil or with nuts. During the first three months, weight loss was less than half a pound in the olive oil group and just over half a pound in the nut group. The significant benefits were to overall health and especially cardiovascular health.

Want to shift all the way to a vegan or plant-based diet? Follow what study participants did and test the possibilities of losing weight while eating healthy whole foods. Think about the plant-based based foods you already enjoy–oatmeal for breakfast? black bean chili for dinner?–as well as new dishes you may be excited to try and for three weeks, incorporate them into your daily diet. Because there’s no calorie counting or carb restrictions it's easy to do, and you get to explore new foods and flavors you may be surprised that you love. “People often find it’s much less restrictive [to go plant-based] than they may have imagined,” Kahleova says.

“Within three weeks, many people start losing weight, feel more energized, and improve other health markers, which often encourages them to stick with a plant-based diet longer."