Diet pumps up the volume, not calories

Calories are back. Again.

With the release in January of the newly revised Dietary Guidelines for Americans and the recent cooling of demand for carb-light foods and, presumably, for low-carb diets, we are forced once more to face up to a simple truth: If you don’t burn off what you eat, you wear it.

The report lays out the number of calories to be consumed, from 1,000 to 3,200 daily, based on age and levels of physical activity. And it notes that many Americans consume more calories than they need, but still fall short of nutritional recommendations.

The cold truth of calories never really left, said Barbara Rolls, a professor of nutritional sciences at Pennsylvania State University and author of “The Volumetrics Eating Plan.” But there is a way to satisfy hunger without overdosing on calories, Rolls says. It’s an approach she calls ‘volumetrics.’ Her current book is a more user-friendly, recipe-filled version of her more scholarly book published in 2000.

The logic of volumetrics is this: Individuals eat about the same weight of food each day -- an amount that satisfies their hunger. But ounce for ounce, some foods have more calories than others. Fresh fruits and vegetables, for example, are loaded with water, which adds weight but no calories. There are 100 calories in a quarter-cup of raisins, for example, and the same 100 calories in two cups of grapes. Fiber, found in fruits, vegetables, beans and whole grains, also adds weight without adding too many calories -- only 2 calories per gram.

On the other side of the spectrum is fat, the most calorie-dense food component, at 9 calories per gram. Cut down on fat and you automatically cut calories -- often without affecting the volume of the food. One can easily compute the calorie density of foods by dividing the calories in a given serving of food by the size, in grams, of that serving.

If the calories are less than the number of grams, the energy density is less than one, and this food can be eaten in what Rolls calls “satisfying portions.” But as the energy density approaches and exceeds 1, conscientious diners need to watch portion sizes or limit their intake of these foods. Broccoli has an energy density of 0.28, for example, while bacon weighs in at 5.

Starting off a meal with a low-density item such as salad, it turns out, can reduce the total amount eaten at that meal.

In 2004 Rolls published a study that showed that diners who began lunch with a 100-calorie, three-cup portion of salad ate less of the pasta course that followed than those who ate the pasta alone. Adding the salad resulted in fewer calories eaten overall, even when the calories in the salad were added to the total.

“Soup works the same way,” Rolls said.

The idea is to favor and fill up on the less-dense stuff, watch portion size, include some low-fat protein such as lean poultry, seafood or tofu (this helps trigger the feeling of being satisfied) and become more physically active.

Not accidentally, the less-energy-dense foods are also the most healthful.

“Basically, the fundamentals of the way I’m trying to show people how to eat are the fundaments of solid nutrition,” Rolls says.

Nancy Rodriguez, associate professor of nutritional sciences at the University of Connecticut in Storrs, says Rolls’ approach has something in common with various weight-loss surgical procedures that are used to shrink the stomach.

“She is physically filling up the stomach,” Rodriguez says. “You can only eat so much. It does seem sensible to me.”

Rolls acknowledged that some people have less access to high-quality fresh fruits and vegetables, but that canned and frozen vegetables and canned soups are also good choices.