A new Harvard study has found that specific elements of plant-based diets — found in foods such as flax and sesame seeds — help prevent or slow weight gain.

The study, published in the American Journal of Epidemiology, found that women who consumed high levels of these compounds, called lignans, tended to weigh less and gain less weight over time than women who didn't, LiveScience reports.

The findings are preliminary, but they "support the notion that increased lignan consumption might potentially lead to less weight gain," said the researchers, from Harvard School of Public Health.

Because the study involved women who were mainly of European ancestry, future research should test the results in men and people of other ethnicities, the researchers said.