By Joyce Hendley, M.S.
Better known as “the food lab,” Penn State’s Laboratory for the Study of Human Ingestive Behavior looks like a series of anonymous dressing rooms. In these plain, curtained-off cubicles, where test subjects eat carefully prepared and measured foods, Barbara Rolls has been debunking some of the most enduring beliefs about eating and appetite.
Despite what diet gurus had espoused for decades, Rolls’s lab discovered that drinking water before meals has little effect on reducing hunger. Her work also unraveled the widely recommended advice that eating a variety of foods can help us eat less. In fact, she found, we eat more when we’re given lots of foods to choose from—and less when the range is so narrow that our variety-craving palates, in essence, become bored and we stop eating. This concept explains the short-term success of those diets that have us eating nothing but cabbage soup—and their ultimate failure when our bored palates eventually fight back.
Rolls is widely acknowledged to be the nation’s top authority in the study of satiety, the sense of fullness that signals the body we can stop eating. Her book Volumetrics Weight-Control Plan (HarperCollins, 2000) is one of the rare bestselling weight-loss books to also win widespread kudos from weight-control experts.
The Volumetrics approach sprang from the findings that people tend to help themselves to the same weight of foods from day to day, regardless of calorie content. In the food lab, Rolls experimented with changing the energy density (calorie content) but not the portion size, by pumping up volume and weight with low-calorie vegetables. She found that as long as the portion sizes of the foods remained the same, regardless of calories, people were satisfied by what they ate. Test subjects reported feeling just as full from two cups of vegetable-packed pasta salad as they did from two cups of higher-calorie salad with more pasta and fewer vegetables.
Eat filling, low-energy-dense foods at most meals, recommends Rolls, and you’ll control hunger without feeling like you are on a “diet.” Rolls’s latest book, The Volumetrics Eating Plan (HarperCollins, 2005), expands upon that approach with tips, menus and recipes.
Q: Americans are getting fatter and fatter. Yet you’ve written that it’s not very helpful to tell people to eat less. Why not?
If people just eat less across the board, they’re going to have a small amount of food on their plates. They’ll think, “That’s not enough food.” The message needs to be tailored: Eat more of the low-energy-dense foods and less of the high-energy-dense foods. But overall, achieve a balance that you enjoy.
When you eat low-energy-dense foods, you can have big, satisfying portions. With the very low range of energy density—nonstarchy vegetables and fruits—it’s very hard to overeat calories. You’d have to eat huge volumes. So you can consider those free foods—the ones you should turn to when you get the munchies. But that doesn’t mean you have to give up foods that are higher in energy density… just moderate the portions.
Most of us who manage our weight on a daily basis do this anyway. When I talk with people who’ve been a normal weight most of their lives, they say they eat a pattern that’s pretty high in fruits and vegetables, and lower in fat—and they’re not eating everything in sight. Most of us are using some restraint on a daily basis, because frankly, we’re now confronted with so much food every day that you almost have to be “the weird one” not to become overweight.
Q: But the foods we’re surrounded by are usually high in energy density—like fast foods and sweets. How do we keep from piling them on our plates?
It takes a mindset. You have to be aware of what you’re eating, and you have to have a plan. Ideally, you should decide where you’re going to eat, choosing where you know you’ll find options that fit with your plan. It’s easier in some places than in others—but if enough of us ask for healthier foods, the food industry is going to give them to us. The success of salads at some fast-food restaurants has already sent a message.
You need to educate yourself by getting nutrition information and learning about what’s in your food—but once you understand what you’re looking for, it’s pretty easy. If a food is glistening, it’s probably high in fat. If the vegetables are barely visible on your plate, it’s a clue that it’s a fairly energy-dense meal.
When you’re cooking for yourself, think: “How can I tweak this recipe?” Say you’re making a sandwich. You could build it up by adding lots of your favorite vegetables. You could use a lower-fat meat or a lower-fat cheese or a lower-fat spread—or leave the spread off altogether. There are lots of choices, and no strategy that’s right or wrong.
Q: What do you do if you don’t like vegetables?
That’s a problem—I admit it. If you need to add a bit of fat, or even sugar, to your vegetables to make them more palatable, that’s okay. Try tucking vegetables into things where you won’t notice them, like casseroles or pizza. And keep trying new ones. We’ve also got to expose kids to a wider selection of vegetables, so that they get a taste for them early.
Q: If drinking water before or during a meal seems to have no effect on cutting hunger (despite popular belief), why are foods that contain a lot of water, like soup, so filling?
Hunger and thirst are controlled by completely separate mechanisms in the body and the brain. One of the big unresolved questions in our field is, when is a caloric liquid processed as a food and when is it processed as a beverage? We don’t really know yet. Clearly, there’s a huge psychological component to eating behavior, which can often override the biology.
Our work has shown that although drinking water has little effect on energy intake, incorporating water into foods helps increase satiety. Having a big portion of a water-rich low-calorie food at the start of the meal—like a salad or broth-based soup—is a great strategy to reduce overall calorie intake. If the course is large enough and low enough in energy density, it can help fill you up and displace the more energy-dense foods later in the meal.
Q: What role should low-fat or reduced-calorie foods play in a healthy diet?
Lots of people don’t like the idea of foods that have been “tinkered with.” If you have that kind of mindset, you shouldn’t go there. But those products are an easy way to lower energy density and calories. If you’re drinking a 12-ounce soda daily, just switching to diet soda will save you 150 calories a day. If you don’t like a low-fat cheese, try mixing it with regular cheese—or just use less of the regular.
Of course, some people use low-calorie foods as an excuse, like ordering a diet soda to go with their huge burgers and fries in a fast-food restaurant. That’s clearly not going to work. You still need to be mindful of what you’re eating.
Q: Can a person tell the difference between satisfied and stuffed?
I’m not sure that many of us are paying enough attention to know that. I suspect people rarely let themselves feel hungry these days…they’re nibbling, they’re eating on the go. They need to really think as they’re eating.
Q: If we Americans could only make one change in our eating habits, what would do us
the most good?
Eat more produce—for so many reasons. The “5-A-Day” program is recommending 5 cups of fruits and vegetables a day, which is actually 10 servings. Another way of looking at it is to fill half your plate with produce over your day—with some low-fat dairy products on the side. That’s easy to remember.
Rolls’s Daily Menu:
Breakfast: High-fiber cereal with skim milk and fruit. It seems more substantial if I put a bit of nonfat yogurt on it and a sprinkle of sugar. I actually prefer skim milk now, and even put it in my coffee.
Lunch: The food around here is geared to students—big and caloric. I try very hard to bring something with me; usually a sandwich on whole-grain bread—with hummus or lean deli-meat, and plenty of vegetables like lettuce, cucumbers and tomatoes. I’ll also have a piece of fruit, and diet soda or water.
Dinner: My partner is the best cook around—so I don’t have to cook for myself very often. When I do, I’ll make pasta primavera with the veggies I have on hand; sometimes I’ll add lean poultry or fish. I don’t have dessert on a daily basis, but once in a while I’ll finish with a small piece of great chocolate.
100-Calorie Snacks (Volumetric vs. Typical)
• 1 1/2 cups strawberries
• 2 cups fresh vegetables (baby carrots, celery sticks, cucumber slices) with 1 tablespoon
• nonfat Ranch dressing
• 12 ounces fruit smoothie (fruit, nonfat yogurt and crushed ice)
• 1 1/4 cups vegetable soup
• 1 chocolate chip cookie
• 10 potato chips
• 4 ounces strawberry milkshake
• 1/2 medium bagel, dry