Women everywhere can eat more and weigh less, according to three new diet studies conducted at Penn State.

Researchers presented their findings two weeks ago in Las Vegas at the annual conference of the North American Association for the Study of Obesity, proving that a low energy-density diet can result in weight loss while still satisfying hunger.

A low energy-density diet is based on foods lower in fat and, therefore, lower in calories, said Julie Ello-Martin, a doctoral candidate in nutrition.

These foods, including water-rich fruits and vegetables, have fewer calories but are high in volume, she said.

In one study directed by Barbara Rolls, who holds the Guthrie Chair of Nutrition in Penn State's College of Health and Human Development, 24 women ages 19 to 35 ate breakfast, lunch and dinner at the university's Laboratory for the Study of Human Ingestive Behavior.

Participants ate at the lab on two consecutive days of the week for four weeks, consuming meals designed by research technologist Jennifer Meengs.

For breakfast, they ate such foods as blueberry muffins and yogurt; for lunch, vegetable pizza with a salad and chocolate-chip cookie bar; and for dinner, a baked pasta dish.

Researchers served typical restaurant-size portions and then decreased the serving size by 25 percent, Meengs said. Those consuming the smaller portion size experienced a 12 percent reduction in daily caloric intake.

By reducing the energy density by 30 percent for both the reduced and typical portion sizes, participants consumed 23 percent fewer calories daily, she said.

"Whenever they ate smaller portions of the lower energy-density food, they ended up eating 800 calories less" per day, Meengs said.

Despite consuming fewer calories when served low energy-density meals, participants felt just as full, she said.

They were "still receiving enough foods to meet their energy needs," Ello-Martin said.

If the sample had included men, the results would probably have been the same, even though men generally eat more than women, she said.

In another study, postdoctoral fellow in nutritional epidemiology Jenny Ledikwe calculated the daily energy density of 7,500 typical American diets.

The nationally representative sample showed that individuals with lower density diets, richer in vitamins and minerals and lower in fat, are more prone to experience weight loss.

This diet allows people to consume fewer calories despite eating more food.

The results of the study support what researchers expected to see, though Ledikwe said they were glad to see them nonetheless.

"The most exciting thing is it lets people eat a good, healthy diet of nutrients without eliminating food groups," she said, adding that people "don't feel like they're on a diet."

Ello-Martin also conducted a diet study of 101 obese women.

Participants were divided into two dietary counseling groups. One group was instructed to eat low energy-density and water-rich foods, as well as reducing dietary fat intake. A second group ate less fat in a stricter diet with more limitations on portion size.

The participants did not count calories or fat grams but instead, over a six-month period, ate whatever they wanted based on the diet principles taught in their counseling groups.

"We just directed them toward healthy foods," Ello-Martin said. "That was a very critical part of the intervention."

After six months, women in the energy-density group lost 21 pounds while those in the reduced-fat, limited portions group lost 15 pounds.

"It shows that people can have successful weight loss by still having a healthy diet," Ello-Martin said.

She said she didn't anticipate the magnitude of the group's weight loss.

"This was a very encouraging first step," Ello-Martin said.