A study has found that a low-fat vegan diet that replaces animal protein with plant protein may help with weight loss. The findings suggest that the source of protein, as well as the amount, could affect weight management.

Medical News Today (MNT) reported on Nov. 8 that researchers compared the weight-loss effects of a low-fat vegan diet and a Mediterranean diet in 62 overweight adults. The results were published in October in the international journal BMJ Nutrition, Prevention & Health.

Researchers divided participants into two groups and had them follow each diet for 16 weeks. After a four-week break, they switched diets and were observed for another 16 weeks. A total of 52 participants completed the 36-week study.

The low-fat vegan diet centered on fruits and vegetables, grains and legumes. It excluded animal products, added fats and cooking oils, and recommended that 75 percent of calories come from carbohydrates, 15 percent from protein and 10 percent from fat.

Participants who followed the vegan diet lost about 6 kg on average over 16 weeks. Total daily protein intake fell to about 46 grams from about 80 grams. Daily animal protein decreased by 47.7 grams, while plant protein increased by 14.4 grams.

By contrast, those on the Mediterranean diet, which includes vegetables and fruits, fish, nuts and olive oil, showed no statistically significant change in weight or protein intake.

Differences were also found in amino acid intake. Participants who had larger decreases in isoleucine, lysine, methionine and tyrosine tended to lose more weight.

Still, it cannot be concluded that plant protein itself caused the weight loss. Switching to a vegan diet also changed the shares of fat and carbohydrates, as well as the calorie density of foods.

Experts said the results alone should not be used to judge that a vegan diet is better than a Mediterranean diet for everyone. They said older people at risk of muscle loss need to maintain protein intake, and that a Mediterranean diet may be suitable for people with high triglycerides or metabolic syndrome.

Researchers added that further studies are needed to clearly identify the relationship between protein sources and changes in body weight.