University Park, Pa. --- Being able to enjoy your favorite foods, feel full after meals -- and still lose weight -- sounds like having your cake and eating it too.
But "feeling full on fewer calories" is exactly what is promised by a new approach to eating based on research conducted by Dr. Barbara Rolls, who holds Penn State's Guthrie Chair of Nutrition in the College of Health and Human Development.
The eating plan is detailed in a new book, "Volumetrics: Feel Full on Fewer Calories," to be published in January by HarperCollins. The authors are Rolls and nutrition writer Robert A. Barnett.
The basic strategy of "Volumetrics" -- eat a satisfying volume of food while controlling calories and meeting nutrient requirements -- is based on a series of studies conducted by Rolls in Penn State's Laboratory for the Study of Human Ingestive Behavior over the last seven years.
These studies show that eating your usual amount but selecting low-energy density meals, which have fewer calories per ounce and contain lots of fruits and vegetables, offers a way to cut back on calories and still leave the table feeling full and satisfied.
"When we first started these studies, we thought that fat played an important role in satiety," Rolls says. "We found that, when you keep the calories and volume of food that a person eats fairly constant, you don't see any special effects for fat in terms of reducing hunger."
The Rolls research team also investigated the effects of drinking water before or during meals. The results showed that the energy density of food mattered most in producing satiety, the feeling of leaving the table well satisfied.
Rolls explains that her group's research has shown that feeling full depends on eating a satisfying amount of food. Tiny portions just don't do it. The energy density of food, or the ratio of calories to the weight of food, is what matters most in order to feel full while controlling calories. Foods with a high energy density have lots of calories in a small serving and are typically lower in water content. For example, a 100-calorie serving of raisins, a high-energy density food, is only one-quarter cup. A 100-calorie serving of grapes, a food low in energy density and high in water content, is one and two thirds cups.
In one Penn State study, women who had a low energy density soup as a first course, ate fewer calories overall during lunch. However, soup is not the only water-rich food that can help decrease calorie intake, says Rolls. She says her group's research has shown that by consuming other water-rich foods, too, dieters don't have to limit portion size to less than what they normally consume.
Following your usual eating habits but modifying some favorite recipes to reduce the energy density is a sensible way of applying these research findings in a home kitchen, Rolls says.
For example you could reduce the energy density of chili by adding leaner meat, celery, extra tomatoes and mushrooms to increase bulk but not calorie content. Pasta salad bulked up with zucchini, carrots and other veggies, which have a high water content, can provide a portion double the size for the same calories as a pasta salad made with few veggies. Sprouts, lettuce and tomato can round out the satisfaction that a sandwich provides without increasing calories.
"People on diets often substitute pretzels for high-fat, high-calorie snacks. But pretzels have a low-water content and don't fill you up, so you eat more of them. A snack with higher water and fiber content, for example, an apple, would be a better choice," says the Penn State researcher.
Rolls' new book provides more information about the energy density of specific foods along with menus, recipes, and tips for modifying favorite dishes. A Food Guide contains a list of more than 600 foods divided into four categories to help you select a satisfying lower-calorie diet. A menu planning section not only offers 50 recipes but also includes illustrated, step-by-step demonstrations on how to modify favorite dishes.
A section on the Active Life offers advice on becoming more physically active to help you burn more calories. The chapter on the Satiety Lifestyle shows you how much you eat depends on environmental factors from the size of the package you buy at the supermarket to whether you're watching TV while you eat.
Rolls' research shows that your body's natural satiety sensors probably won't even notice if you reduce the amount of calories and fat in meals by adding more water and fiber -- and you can eat larger portions for the same calories. Her new book, "Volumetrics," shows you how.
EDITORS: Dr. Rolls is at (814) 863-8482 or bjr4@psu.edu by email.