By Jon Bonné
msnbc.com
updated 11/15/2004 10:23:11 AM ET 2004-11-15T15:23:11

Appearances can be deceiving -- even in an everyday meal.

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By making small changes to seemingly identical meals, nutritionists were able to get young women to consume 800 fewer calories a day, according to research released Monday.

Women in a Penn State study were served nearly identical portions of food, except that one set of meals included slightly smaller servings and contained fewer calories -- with food that was 30 percent less energy-dense.

The less-dense food accounted for an average 544 fewer calories consumed over three daily meals and an evening snack, and the smaller portions lopped off another 256 calories. Almost none of the subjectes complained about being hungry.

"To save 800 calories a day, that's pretty enormous," said Penn State nutrition sciences professor Barbara Rolls, who led the study.

Women who participated were served the same sets of meals at the university's nutrition lab for two consecutive days each week for four weeks. Breakfasts included a blueberry muffin or coffee cake; lunch consisted of a small pizza or turkey sandwich and dinners were a casserole or pasta, with sides. 

The lower-calorie meals were cooked using extra fruits and vegetables and some reduced-calorie commercial foods, and high-fat ingredients in baked goods were often replaced with items like applesauce. For equal-sized portions, the actual weight of the food -- about 5.5 pounds per day -- didn't vary much, though the calorie content varied by nearly 1,000 calories.

While both energy density and portion size have been studied independently as factors in getting people to eat fewer calories, Rolls and other researchers wanted to consider how both could work in tandem. Their work was being presented at a meeting of the North American Association for the Study of Obesity.

More food, fewer calories
Rolls has focused recently on the importance of less-dense foods as a key method for helping people lose weight, making it the core of her Volumetrics diet plan, which recommends low-density foods: those thare are big in volume but low in calories, such as vegetables and broth-based soups. She has a new diet book, "The Volumetrics Eating Plan," due next March.

As the nation struggles with an obesity epidemic, other nutritionists have similarly focused on low-density foods as a convenient way to get ever-fatter Americans to slim down without feeling hungry. Some two-thirds of the population is now overweight or obese, according to the Centers for Disease Control.

The 24 women subjects, who ranged from 19 to 35 years years old, reported little difference in how full or satisfied they felt, regardless of the foods' density. They perceived most smaller servings to be closer in size to the larger ones than they actually were.

"That's neat," said New York University nutrition professor Marion Nestle, who frequently studies portion sizes. "The obvious question is: This is a short term study. ... Would it hold up over time? I think yes."

'Subtle changes'
Earlier this year, Rolls released a study showing an inverse effect in portion sizes. The larger the pasta dish or sandwich was served, the more of it people would eat. 

Rolls also unveiled research Monday showing that overweight adults who ate two servings of soup per day, or who did not snack, lost more weight than those who ate two servings of dry snacks. That study was partially funded by the Campbell Soup Company.

The energy-density research is intended to help instruct packaged food manufacturers, Rolls said: "We wanted to send a message to the food industry that you can do this. And even with subtle changes you can have an impact on how people are eating."

Given consumer wariness about being short-changed by food companies, it is not clear how successful such changes could be.

Nestle noted that servings of packaged foods have, if anything, been growing in recent years. In 2002, she documented a steady increase in the number of large-size portions being introduced into the food market. The few exceptions have often been in healthier foods, like yogurt.

A similar problem exists in restaurants. While McDonald's did away with supersize meals this year, the best values on many other menus are often still found in oversized items.

"As long as the price structure favors larger portions, this is going to be a tough sell," Nestle said.

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