The notion of watching what you eat takes on a whole new meaning when you’re Dr. Barbara Rolls CW’66, author of Volumetrics Weight-Control Plan and more recently, The Volumetrics Eating Plan. As the Guthrie Chair of Nutritional Sciences at Pennsylvania State University, Rolls, 60, oversees a revolving staff of more than 20 undergrads, grad students, and researchers, who spend their days at the university’s Laboratory for the Study of Ingestive Behavior literally watching and weighing what people eat—and what they leave behind on their plates.

Test subjects dish out their own portions from hot buffet stations and bring their bounty back to one of the cubicles set up for optimal chewing-viewing. Behind the booths’ blue curtains, small cameras broadcast images to screens in the kitchen and in the researchers’ offices. These images feed Dr. Rolls’ and her colleagues’ growing repertoire of studies that catalog the way humans eat.

Rolls has been researching eating and drinking behavior for 30 years—her interest in the field dates back to her days as a premed biology major at Penn. After graduation she deferred enrollment to medical school to study at the University of Cambridge on a Thouron scholarship, and stayed in the U.K. to earn a Ph.D. in experimental psychology before returning to the U.S. in 1984. She began studying satiety in the 1980s, when she was among the first to make the observation that humans will eat more if they’re presented with a variety of foods. After a stint at Johns Hopkins as an associate professor of psychology, she moved to Penn State in 1991.

At first Rolls and her colleagues went along with the tide of the dieting-industrial complex, which was focused on low-fat, high-carb, and high-protein diets. But Rolls noticed something else going on—that people seemed to eat for volume or for weight of food rather than for calories. Give them unlimited access to food, and they’ll eat the same volume over a day or two. “Once you start seeing that happening,” she says, “it means you need to figure out ways to help people eat a satisfying volume of food while they’re consuming fewer calories.”

She nosed around in the annals of food-behavior studies and found an article written by researchers at the University of Alabama in 1983. Their subjects felt full on half the calories when they were eating low-energy-density foods, or foods that are packed with water. In light of her findings on volume, the study made sense. What increases volume without increasing calories? Water. “We were so focused on proportions of fats, carbs, and proteins in foods,” Rolls recalls, “that we had overlooked water content and yet, as it turns out, water has the biggest impact on the amount of food.” She started to take a closer look at the effects of water-packed foods on satiety.

One of her first studies involved “preloading” test subjects with milkshakes that came in different volumes, but that contained the same number of calories. Some subjects were given 600-milliliter milkshakes to drink 15 to 20 minutes before sitting down to eat a meal. Others were given 300-milliliter milkshakes that had half the water content but the same number of calories. Those who drank the water-drenched milkshakes ended up consuming 100 fewer calories. Volumetrics was born. Well, the theory was born. Its name came much later, after Rolls played with hundreds of tentative titles. “When you’re doing a diet book,” she points out, “you need something a little different because there are so darn many books out there.”

Her Volumetrics Eating Plan, the sequel to her 2000 book, was published last March. It’s a practical guide to eating the Volumetrics way—lots of water-rich fruits and vegetables, broth-based soups, whole grains, and legumes.

Rolls and her colleagues recently conducted the first yearlong clinical trial to assess the effectiveness of the program. Half of a group of 97 obese women followed a Volumetrics plan and the other half was given more traditional dieting strategies that restricted fat and portion sizes. The first group ate a greater volume of food, but lost more weight—an average of 20 pounds. They also ate a more nutrient-rich diet, full of fruits and vegetables. The second group lost an average of 15 pounds. Of course, as Rolls says, “The tricky part is keeping it off.”

In 2004, Rolls was the first scientist called in to testify before the federal government’s Dietary Guidelines Advisory Committee; the 2005 guidelines reflect her findings in their recommendations to restrict portions of high-energy dense foods. In May she traveled to Italy to attend a meeting on the Mediterranean diet, and the health professionals there were talking about energy-density as a way of managing body weight. She’s even spotted the term volumetrics, with a lowercase v in several scientific journals. “It’s pretty exciting,” Rolls admits.

Still, there’s a long way to go. The rest of the world has energy density—listed as number of grams per 100 calories—on their nutrition fact labels, and Rolls hopes that America will adopt this practice. This information would allow a consumer to pick up two bags of potato chips and determine immediately which one will give you the most amount of food for the least amount of calories—kind of like supersizing for good, not for evil. —Caroline Tiger

©2005 The Pennsylvania Gazette
Last modified 08/25/05

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By Caroline Tiger