For 10th year in a row, the Volumetrics Weight-loss plan developed by Barbara Rolls, professor of nutritional sciences and Helen A. Guthrie Chair in Nutrition at Penn State, ties for the #2 weight-loss plan in this year’s U.S. News & World Report's "Best Diets." Volumetrics, based on the science of satiety or the feeling of fullness you get as you eat, aims to bring healthy eating to a weight-loss journey.