Eating fruits, vegetables and other foods packed with water but fewer calories per portion could help you lose weight while still feeling full and satisfied at meals, says the nutritionist whose diet book was named recently as tops in the country.

Noted author Barbara Rolls, a professor at Penn State University, says slashing your “energy density” – the number of calories per gram – could allow you to eat more food and still lose weight. And your best bet for keeping your energy density as low as possible is feasting on fruits, vegetables, whole grains, low-fat dairy products, and soups. 

Rolls adroitly weaves “energy density” throughout The Volumetrics Eating Plan: Techniques and Recipes for Feeling Full on Fewer Calories, her diet book lauded earlier this week by Consumer Reports as the country’s best diet book backed up by research.

The other top diet book in the Consumer Reports article was The Best Life Diet by fitness expert Bob Greene.

Losing double-digit weight

Rolls bases her findings on energy density on her study of diet and weight loss in nearly 660 adults, whose body mass indexes of 33.6 qualified them as “obese.” Their average age was 50.

One group of participants received only one counseling session on diet, while the other two groups each got 18 sessions. In each session, they were told to either boost their physical activity and reduce energy intake – burning more calories through exercise than they took in via food.

Some also got information on the federal government’s Dietary Approaches to Stop Hypertension, better known as DASH, which places fruits, vegetables and low-fat dairy products above all else.

People who reduced their energy density the most lost nearly 13 pounds in six months, compared to only five pounds to people who cut their density the least, according to the findings.The participants who reduced their energy density the least ate 300 more grams of food, or 10.5 ounces, a day.

Cutting density with soup 

A good way to cut your energy density is to eat a low-calorie soup before you tackle the main course, which will cut your calories and the amount of food you eat, Rolls said.

People in one of Rolls’ studies who ate a first course of soup before diving into their lunches, cut their total calories by 20 percent compared to people who didn’t eat soup.

The findings give credence in the nutrition and dieting world to Rolls being the guru of "Volumetrics," which refers to eating a satisfying volume of food while controlling calories and meeting nutrient requirements. The thinking is based upon studies led by Rolls in Penn State’s Laboratory for the Study of Human Ingestive Behavior.

This spring, the paperback edition of Volumetrics is being published by HarperCollins, according to the university.

Keeping weight off

Other nutritionists, such as Karen Collins with the American Institute for Cancer Research, say that reducing your energy density slashes your calories but also boosts your diet’s nutritional value because you’re eating more vegetables.

“Emphasizing foods that fill you up while limiting calories seems to help not only with losing weight, but with keeping it off, too,” Collins wrote on major Web sites, such as Nubella News and MSNBC.com, earlier this year.

In a study by researchers at the University of Alabama, Birmingham, more than three-fourths of people who lost almost nine pounds in a 12-week program had kept it off two years later because they had eaten more lower-density vegetables, fruits and whole grains, and fewer high-density meats, cheeses, sugars and fat, Collins said.

“For people who are overweight, losing 10 percent of their weight is considered a realistic target with significant health benefits,” Collins said. “Studies suggest that reducing the energy density of our diets alone may not be enough to reach such targets, however.”

Collins noted previous research at Penn State that showed moderately reducing both energy density and portion sizes brings a more substantial drop in calorie consumption than just dropping energy density.

“A three-part strategy to lose weight – reduce energy density, control portions, and get some activity daily – can make weight loss more successful,” Collins said.

Check these out! 

•  Find plenty of foods that are low in energy density among the 6,000-plus healthy-eating recipes
in Nubella’s Recipe Database.

•  Check the nutrients of foods and beverages, try Nubella’s Nutrient Database.