Vegan diet with “unhealthy” foods beats Mediterranean diet for weight loss

The Physicians Committee for Responsible Medicine has found that vegan diets with greater “unhealthy” plant-based foods have a greater weight loss effect than the Mediterranean diet. They saw that the vegan diet had better results for weight, body composition, insulin sensitivity, and cholesterol levels.

The publication in Frontiers in Nutrition reveals that consuming refined grains and potatoes over animal-sourced foods leads 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 — it’s better than the Mediterranean diet for weight loss, because it avoids animal products and added oils,” says lead author Hana Kahleova, M.D., Ph.D., director of clinical research at the Physicians Committee for Responsible Medicine.

Randomized control trial 

The researchers carried out a randomized controlled trial with 62 overweight adults who were placed on a low-fat vegan diet. They have better weight outcomes than those placed on a Mediterranean diet over 16 weeks.

The vegan diet consisted of fruits, vegetables, grains, and beans, and the Mediterranean diet included fruits, vegetables, legumes, fish, low-fat dairy, and extra-virgin olive oil. The two groups had no calorie limit.

The participants went back to their baseline diets for four weeks for a washout period before they switched to the opposite group for 16 more weeks.

Indexes reveal weight loss strategies

The researchers noted the participants’ dietary records to assess plant-based diet index (PDI), healthful PDI (hPDI), and unhealthful PDI (uPDI) with weight loss.

According to the PDI system, hPDI includes fruits, vegetables, whole grains, nuts, legumes, oils, coffee, and tea. The PDI score was noted to increase with vegan diets but not with the Mediterranean diet.

Food and drink classified as uPDI include fruit juice, sugar-sweetened beverages, refined grains, potatoes, and sweets. In the analysis, researchers observed this increase in the vegan diet, especially after reducing nut and oil consumption. Meanwhile, uPDI decreased on the Mediterranean diet.

Researchers have linked these higher PDI scores in the vegan diet to weight loss.

In other recent research on vegan diets, the Physicians Committee for Responsible Medicine found that a low-fat vegan diet significantly decreases dietary acid load compared to a Mediterranean diet. The randomized crossover trial also confirmed that this diet — comprising leafy greens, berries, and legumes — promotes weight loss and a healthy gut microbiome.

Another study found that vegan diets do not impact muscle building during weight training. It concluded that following plant- or animal-based diets made no difference in muscle protein synthesis.

However, a different research warned that New Zealand vegans do not meet the daily requirements for essential amino acids lysine and leucine, even though three in four eat sufficient protein.