Study finds vegan diet outperforms Mediterranean for weight loss, even with carbs - Video

You don't have to eat perfectly to lose weight-just ditch the animal products. A new analysis published in Frontiers in Nutrition suggests that a low-fat vegan diet promotes more weight loss than the Mediterranean diet, even when it includes refined grains and starchy foods like potatoes often considered “unhealthy.” The findings come from researchers at the Physicians Committee for Responsible Medicine, who found that swapping animal foods for plant foods-regardless of quality-had the greatest impact on body weight and metabolism.

The research builds on a previous randomized clinical trial that directly compared a low-fat vegan diet to a Mediterranean diet in 62 overweight adults over 16 weeks. Both diets featured fruits, vegetables, legumes, and grains, but the vegan plan excluded all animal products and added oils, while the Mediterranean plan emphasized fish, low-fat dairy, and olive oil. Participants switched between the two diets across two 16 week phases, separated by a short break, allowing each person to serve as their own control.

In the original trial, the vegan diet led to greater weight loss, improved body composition, and enhanced insulin sensitivity—and this new study reveals why. Using the plant-based diet index (PDI)—a tool that classifies foods by how “healthy” their plant origins are—scientists analyzed participants’ food logs and linked specific dietary patterns to weight changes. The index distinguishes between healthful foods (whole grains, fruits, and nuts) and unhealthful ones (refined grains, sweets, and potatoes).

Interestingly, those on the vegan plan saw the greatest rise not only in overall PDI scores but also in unhealthful plant-based diet index (uPDI) scores—because refined grains and potatoes replaced meat and dairy. This boost in plant-based eating, even from less than perfect foods, was the strongest predictor of weight loss. In contrast, participants on the Mediterranean diet showed no significant weight change despite “healthier” PDI scores.

Lead author Dr. Hana Kahleova explains, “Even when it includes less ideal plant foods, a vegan diet still outperforms other diets for weight management, simply because it eliminates animal fats and added oils.”

The takeaway? You don’t need to obsess over superfoods—just focus on shifting from animal to plant-based meals. Cutting out meat and dairy, even with some pasta or potatoes on your plate, can tip the scale toward better health and lasting weight loss.

REFERENCE: Hana Kahleova, Reagan Smith, Ilana Fischer, Haley Brennan, Tatiana Znayenko-Miller, Richard Holubkov, Neal D. Barnard. Plant-based dietary index on the Mediterranean and a vegan diet: a secondary analysis of a randomized, cross-over trial. Frontiers in Nutrition, 2025; 12 DOI: 10.3389/fnut.2025.1666807