Vegan vs. Mediterranean diets for weight loss – which is better? Original paper

Previous research suggests that vegan diets lead to greater weight loss than Mediterranean diets.^[1] Because the Mediterranean diet includes animal-derived products (which are absent in a vegan diet), differences in gut microbiome composition may partly explain the greater weight loss effect. However, studies with a head-to-head diet comparison are scarce.

This 16-week randomized crossover trial compared the Mediterranean diet and a low-fat vegan diet in 62 adults with overweight (mean age of 57) . The primary outcome was the change in body weight, and the secondary outcome was changes in the gut microbiome.

A low-fat vegan diet decreased body weight (by approximately 6 kg after 16 weeks) more effectively than a Mediterranean diet (no changes in body weight observed).

The changes in body weight were correlated positively with changes in the microbiome. Bacteriodetes and Eubacteria decreased on both diets, Enterobacteria and Ruminococcus increased only in the vegan diet, and Lachnospiraceae and the Firmicutes to Bacteroidetes ratio increased only for the Mediterranean diet.

The daily energy intake in the vegan diet group (1,315 kcal) was significantly lower than for the Mediterranean diet (1,855 kcal). Consequently, the differences in weight loss observed for both diets cannot be explained by changes in the gut microbiome alone. Future studies need to correct for caloric intake to better understand how the microbiome can promote weight loss.