Volumetrics may be the most popular diet you've never heard of. But, it's been gaining currency with nutritionists and dieters alike for its simplicity and the fact that it's backed by recent peer-reviewed studies at a time when other diet plans have been losing favor.

Fighting hunger is the goal of Volumetrics, developed by Barbara Rolls, a professor of nutritional sciences the the Pennsylvania State University. Rolls has researched everything from thirst to portion control. Its her study of satiety that is giving her street credit with dieters.

What Rolls found is that feeling full is intrinsically linked to certain foods. The nutritional principle behind those foods is called energy density, or ED. It may sound counter-intuitive, but foods low in energy density make you feel fuller. Think fruits, soups and vegetables, all of which have high water content, "the secret ingredient" to satiety says Rolls. Rolls' research shows that a person eats about the same volume, or weight, of food everyday. The trick is to fill your plate with low-calorie foods that leave you satisfied.

In a one-year study of Volumetrics, 97 obese women were divided into two groups. One group was taught the principles of Volumetrics and ate low-Ed foods. The second group was told to restrict portions sizes and reduce fat. Neither group had to count calories or fat grams. What Rolls discovered is that both groups reduced fat intake and lost weight. But the group of women who had the low-ED foods actually ate a greater quantity of food over a year, but lost more weight, about 20 pounds, compared with 15 pounds for the fat-and portion-reducing group. They also fell in line with the USDA's Food Guide Pyramid (mypyramid.gov) recommendations: five servings of fruits and vegetables a day.

In her latest book, The Volumetrics Eating Plan (volumetricseatingplan.com) Rolls gives detailed recipes, developed in her lab, that increase portion size but lower the Ed of traditional favorites like risotto.

If you want to reduce your calories even more, eat a salad before dinner, according to Rolls' study published in the Journal of the American Dietetic Association in 2004. Folks who were served three cups of salad totaling 100 calories before their pasta lunch ate 12% fewer calories overall, compared with when they were served no salad.

If all this sounds too good to be true, remember, the program is just s few years old, and long term studies have been small. And unlike many commercial weight-loss programs (Rolls is a medical advisor for Jenny Craig and has adapted a cookbook for the program), there is no support group for Volumetrics followers. Research shows that support is a factor for long-term success.