A study by the Physicians Committee for Responsible Medicine indicates that vegan diets rich in certain “unhealthy” plant-based foods can lead to greater weight loss than the Mediterranean diet. The findings published in Frontiers in Nutrition show that participants on a vegan diet experienced improvements in weight, body composition, insulin sensitivity, and cholesterol levels.
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Lead author Hana Kahleova, M.D., Ph.D., stated that the research shows a low-fat vegan diet, even when including unhealthy plant-based foods, outperformed the Mediterranean diet for weight loss because it eliminates animal products and added oils.
The study involved a randomized controlled trial with 62 overweight adults who followed a low-fat vegan diet for 16 weeks, resulting in better weight outcomes compared to those on a Mediterranean diet. The vegan diet comprised fruits, vegetables, grains, and beans, while the Mediterranean diet included similar foods along with fish, low-fat dairy, and extra-virgin olive oil, with no calorie restrictions for either group.
After a four-week washout period, participants switched diets for another 16 weeks. Researchers evaluated participants’ dietary records to assess their plant-based diet index (PDI), healthful PDI (hPDI), and unhealthful PDI (uPDI). The analysis revealed that hPDI scores increased with the vegan diet but not with the Mediterranean diet.
Foods classified as uPDI, which include fruit juice, sugar-sweetened beverages, and refined grains, showed an increase in the vegan group, especially after reducing nut and oil intake. Conversely, uPDI decreased within the Mediterranean diet. Higher PDI scores in the vegan diet were associated with greater weight loss.
In other research, the Physicians Committee found that a low-fat vegan diet significantly reduces dietary acid load compared to a Mediterranean diet and promotes weight loss and a healthier gut microbiome. Another study confirmed that a vegan diet does not adversely affect muscle building during weight training, demonstrating no significant difference in muscle protein synthesis between plant-based and animal-based diets. However, concerns were raised that New Zealand vegans often do not meet daily requirements for essential amino acids such as lysine and leucine, despite a majority reporting adequate protein intake.