Study: Vegan Diet Promotes Greater Weight Loss Than Mediterranean Diet

The analysis suggests that the inclusion of foods such as potatoes and refined grains, categorized as "unhealthy" by the plant-based diet index, still contributes to better weight loss outcomes than the Mediterranean diet, which emphasizes fish, low-fat dairy, and olive oil. Hana Kahleova, MD, PhD, director of clinical research at the Physicians Committee and lead author, noted that the vegan diet's avoidance of animal products and added oils plays a crucial role in its effectiveness for weight loss.

This analysis builds on a prior study involving 62 overweight adults, who were assigned to either a low-fat vegan diet or a Mediterranean diet for 16 weeks without calorie restrictions. Following a return to their baseline diets for four weeks, participants switched diets for an additional 16 weeks. Results indicated that the vegan diet was superior in promoting weight loss and improving metrics such as body composition, insulin sensitivity, and cholesterol levels.

The secondary analysis utilized participants' dietary records to evaluate the relationship between different plant-based diet indices—overall plant-based diet index (PDI), healthful plant-based diet index (hPDI), and unhealthful plant-based diet index (uPDI)—with weight loss outcomes on both diets. The study found that the PDI score significantly increased on the vegan diet, while remaining unchanged on the Mediterranean diet. Both diets saw an increase in hPDI, but there was a rise in uPDI only on the vegan diet.

Notably, the increases in PDI and uPDI scores observed with the vegan diet were linked to weight loss, while changes in hPDI did not correlate with changes in body weight. The findings point towards the benefits of substituting animal-based foods with plant-based options, alongside reducing the intake of oils and nuts, as effective strategies for weight loss.