Even in summer Principles of Nutrition draws a crowd. On an early June day hot enough to steam carrots, about two dozen students are packed elbow-to-elbow in a small room in Wilson Hall listening to Flynn talk about protein. The petite, energetic professor fills the blackboard with notes on how proteins help regulate blood pressure, contribute to immunity, and make glucose. Protein is necessary stuff, she says, and it’s good for you — except that in the United States, most people get 60 percent of their dietary protein from meat. That’s not good, because meat, especially seared meat, is associated with heart disease and cancer. "That’s why high-protein, high-fat, no-carbohydrate diets like the Atkins diet aren’t healthy," Flynn tells the students.
Her comments are greeted with rumbles of dissent. Finally one student challenges the professor. "But if the person loses weight, isn’t that healthier than staying fat?" the student asks. "Isn’t that worth it?"
Sure, weight loss is healthy, Flynn agrees, but contrary to popular mythology and best-seller lists, there’s no scientific evidence that fad diets like the Atkins actually work. People lose weight because they’ve restricted the kinds of food they eat, and that means they’re consuming fewer calories. Period.
"Weight loss always comes down to calories," Flynn tells her students. "It doesn’t matter what kinds of food you’re eating. If you eat less, you’ll lose weight."
Busting fad diets is something the food lover in Flynn enjoys. A year ago, she took her fad busting public, publishing, along with Clinical Associate Professor of Medicine Kevin Vigilante, Low-Fat Lies: High-Fat Frauds and the Healthiest Diet in the World. In their book, Flynn and Vigilante take on not only the Atkins diet but the extreme low-fat diet championed by Dr. Dean Ornish as well. The reason? Simply put, neither diet has proven to be effective in the long term, and both can deprive people of nutrients that are essential to good health. When fad dieters give up their regimens, the authors contend, their weight tends to rebound and then some, leaving them heavier and less healthy than they were to begin with.
If the high-fat and high-protein Atkins diet errs by exposing people to too many dangerous carcinogens, then some low-fat diets make the mistake of, well, not containing enough fat. It is a little-known metabolic fact, she says, that the body cannot absorb vegetable nutrients without the assistance of fats. Reduced-fat salad dressings, for example, can actually negate the healthful effects of eating salad. "If you have low-fat salad dressing in your refrigerator," Flynn says, "throw it out."
A more subtle and pernicious danger associated with the low-fat myth is the way people tend to overeat foods billed as "low-fat." In comparing calorie counts of several popular processed food items and their low-fat counterparts, Flynn and Vigilante found their caloric differences were negligible. Reduced-fat Jif peanut butter, for example, has the same number of calories per serving as regular peanut butter, and reduced-fat Triscuits have just ten fewer calories per serving than regular Triscuits. Dieters who think it’s safe to pig out on low-fat foods, Flynn notes, are likely to get a big surprise when they step on the scale.
Flynn and Vigilante argue in Low-Fat Lies that fats do at least two important things: they make foods taste good, and they make people feel full. People who attempt low-fat diets remain perpetually hungry and unsatisfied — a clear recipe for dieting failure. In fact, Flynn says, there’s no evidence that dietary fat has a relationship with weight problems at all. When she conducted a study that placed two groups of people on low-fat and high-fat diets containing the same number of calories, she found no difference in weight loss. Only when her subjects were randomly assigned to low- and high-calorie diets was there any difference.
So how do we translate all the mixed signals in the supermarket aisles and bookstore shelves? How do we eat enough to give our body the nutrients it needs while keeping the love handles in check? Flynn’s answer is a combination of new science and some very old traditions: she favors a Mediterranean-style diet that includes lots of olive oil, vegetables, beans, and fish (as long as it isn’t seared); a moderate amount of red wine; and occasional, small servings of meat. "When I cook for myself, I use extra-virgin olive oil, sauté garlic in it, then add vegetables and clams, fish, or beans, and put it over pasta," she says. "I add fruit if possible. I eat that a lot because it’s quick and easy to prepare."
Flynn discovered the strengths of the Mediterranean diet when her coauthor, Vigilante, returned from a trip to Italy. He was concerned about putting on weight during the several weeks he was in a country where every meal is doused in olive oil. "When he came back," Flynn says, "he had lost five pounds. He walked into my office and said, ‘We have to write a book about this.’ " The two began researching the Mediterranean diet and learned that wine and olive oil, two popular ingredients of the traditional Italian diet, are loaded with healthy substances called phytochemicals that help to prevent heart disease. Phytochemicals also help the body metabolize nutrients found in other foods, especially vegetables, which is why it’s a great idea to put olive-oil dressings on salads.
If much of Flynn’s message surprises you, you’re probably not alone. Most Americans, including many physicians, do not understand nutritional guidelines, she says. One reason is language. "Nutritionists talk about nutrients instead of foods," she says. "People hear the message, but they can’t make sense of it."
The problem is exacerbated by Capitol Hill politics. The governmental agency that issues nutritional guidelines, the
U.S. Department of Agriculture (USDA), has conflicting duties:to make dietary recommendations and to promote all types of agriculture. As a result, the USDA designs its dietary suggestions under intense pressure from powerful lobbyists, and Americans are advised to "eat less fat" rather than to "eat less meat." The dairy industry, meanwhile, has managed to keep calcium recommendations higher than they need to be, Flynn notes. "People are told they need 1,000 milligrams of calcium a day, and that’s ridiculous," she says. "No one can consume that much." Instead, Flynn advises women who are worried about osteoporosis to strengthen their bones by lifting free weights.
Flynn brings her pragmatic approach into the classroom, too. While Principles of Nutrition is heavy on the science, it’s also heavy on the practical. Beginning with the basics on energy-yielding nutrients, Flynn covers metabolism, vitamins and minerals, and weight management. "I want my students to be able to use the information later," she says.
Thanks to Principles of Nutrition, Denise Suh, a senior PLME concentrator, has changed her behavior at the supermarket. These days she’s eschewing red meats in favor of olive oil, vegetables, and fruit. "It’s probably," she says, "the most useful class I’ve ever taken at Brown."