Weight is thought to be managed largely by balancing calories eaten with calories burned, so researchers are studying why some people tend to burn calories more easily than others. In an Italian study, researchers recruited 52 adults (half vegetarian, half not) and matched each group by age, BMI, and gender. All of the vegetarians had been following their diet for at least 3 years. After adjusting for age, BMI, exercise, and other lifestyle factors, the scientists found that the vegetarians had a significantly higher resting energy expenditure, meaning that their bodies burned more calories at rest. Of the different dietary components studied, higher intake of vegetable fats (oils, nuts, seeds) were most closely associated with the significantly higher resting energy expenditure seen in vegetarians.
Nutrients. 2015 Jul 17;7(7):5933-47. (Montalcini T et al.)