For women facing breast cancer, battling the disease is just the beginning. Surgery, radiation, and chemotherapy are difficult enough, but many patients must endure hair loss, nausea, bone-deep exhaustion, and depression. To make matters even worse, the American Cancer Society reports that more than half of post-menopausal breast cancer patients put on excess weight during treatment, and doctors now realize that this can interfere with recovery.

Although the cause of this weight gain is not clearly understood—the suspects include medication side effects, hormones, fatigue, and food cravings due to nausea—its effect on the disease is becoming clearer. Researchers believe that the estrogen produced in body fat promotes the proliferation of breast cancer cells. Some recent studies have even shown that extreme weight gain during treatment dramatically increases a woman's chance of death.

The more weight gained, the greater the risk. A Kaiser Permanente study presented at the annual meeting of the American Association for Cancer Research in April found no ill effect from moderate weight gain, but concluded that women who added 10 percent or more to their pre-diagnosis weight had a higher risk of recurrence and were 25 percent more likely to die of the disease. A 2007 Johns Hopkins study found that every eleven pounds of excess weight increases a woman's risk of death by 14 percent and that patients who put on more than twenty-two pounds after their diagnosis had an 80 percent higher risk of death. Overall, obese women were twice as likely to die as women of normal weight.

Several years ago, Assistant Professor of Medical Science Mary Flynn, a nutrition researcher at Providence's Miriam Hospital and the Warren Alpert Medical School, decided to take on this issue. Flynn, a nutritionist who studies the relationship between diet and disease, believes strongly that most physicians are poorly equipped to give their patients nutritional advice or to help them lose weight. At the time Flynn became interested in breast cancer patients, the National Cancer Institute (NCI) was recommending that overweight patients follow a fairly standard low-fat diet. Flynn, however, had just completed a study in which she had reduced the weight of cardiac patients and improved their cardiovascular health by putting them on a Mediterranean diet relatively high in fat: participants, in fact, were required to consume at least three tablespoons of olive oil daily.

Flynn wondered if she could help breast cancer patients with this same diet. Aided by $250,000 from the Susan G. Komen Foundation, she found 151 women over the age of fifty willing to participate. All but one had become overweight during cancer treatment. Flynn screened the group and admitted forty-four to the study. The participants had all been diagnosed with invasive breast cancer after age fifty and had completed treatment within the past four years. Their body mass index, or BMI, which is a measure of body fat, was between twenty-five and thirty-five. (A BMI of twenty-five or higher is considered overweight, and over thirty indicates obesity.)

The women were randomly assigned to one of two diets.Those placed on the low-fat NCI diet for the first eight weeks switched to Flynn's Mediterranean regimen for the next eight weeks, and vice versa. By the end of the sixteen-week study, all the women in the study had lost an average of sixteen pounds.

The weight loss, however, was twice as great while the women were on Flynn's diet. When, after sixteen weeks, the women were asked to choose a diet for the next six months, all but one chose Flynn's diet.

And there's more. Not only did the women lose more weight on Flynn's diet, but they became healthier. After each eight-week diet and then after six months of follow-up, the women received extensive blood work. On the olive oil diet, the women actually improved their breast cancer biomarkers, achieving lower levels of triglycerides. Their levels of HDL, the so-called good cholesterol, went up.

The results of Flynn's study were published in the Journal of Women's Health last year, and in September Flynn published The Pink Ribbon Diet: A Revolutionary New Weight Loss Plan to Lower Your Breast Cancer Risk, which she coauthored with Nancy Verde Barr, a James Beard Award–winning cooking teacher and author. The book is part health and nutrition class, part diet plan, and part cookbook. Its 150 recipes include hearty salads, soups, sandwiches, pastas, and rice dishes. The book even includes muffins and desserts—all made with olive oil. About the lack of austerity in her book's recommendations, Flynn says, "After the roller-coaster of cancer treatment, the last thing anyone wants to do is deprive herself of food."

Mary Flynn has been fascinated by the potential health benefits of olive oil and a general Mediterranean diet since the 1980s, when she read the landmark Seven Countries Study, a fifty-year study of almost 13,000 men from four regions of the world that was the first to analyze the effects of diet and lifestyle on coronary heart disease and stroke. Men living on the island of Crete demonstrated the lowest incidence of heart disease in the study. These men consumed 40 percent of their daily calories in the form of fat—mostly olive oil used to cook and complement grains and vegetables. Their dairy intake was primarily from yogurt and cheese, and the men ate fish and poultry but little meat. Even with all that fat, their heart disease rate was 90 percent lower than that of the Americans in the study.

Despite widespread knowledge of this and later studies with similar findings, by the late 1990s the buzzword in the U.S. diet world was low-fat. As the country faced a public health crisis in obesity, all fats were demonized. Manufacturers raced to bring low-fat products to grocery store shelves. In 1999, Flynn teamed up with Kevin Vigilante, who was then an associate professor in the Brown medical school, to publish Low Fat Lies: High Fat Frauds and the Healthiest Diet in the World. The book attacked a number of high-visibility diets, including the high-protein Atkins diet and the extreme low-fat Dean Ornish plan. Flynn and Vigilante argued in favor of the traditional Mediterranean diet and put forth the argument that remains a cornerstone of Flynn's thinking: not all fats are bad, and good olive oil is actually good for you.

Out of that thinking, Flynn created what she calls the Plant-Based Olive Oil (PBOO) diet. Like the Cretan diet, it's heavy on foods that come from plants—vegetables, grains, and beans—and light on animal protein. Such an approach is not uncommon among cancer patients. Nutritionists often prescribe a plant-based diet for such patients because meat, especially red meat, is thought to increase inflammation and oxidation, both of which have long been associated with the development of cancers. But Flynn went further than her mainstream colleagues by insisting that participants eat four or five servings of fat a day, including at least three tablespoons of extra virgin olive oil.

One of those colleagues was nutritionist Jeanette Nessett, who was stunned when her own cardiologist told her to add three tablespoons of olive oil to her daily diet. A fit and slender woman who runs health improvement programs at Lifespan, the parent company of several Rhode Island hospitals, Nessett had had a major heart attack at age fifty—the same age at which heart disease killed her father. She'd grown up on a traditional Lebanese diet, with big olive oil cans in the kitchen, and seldom ate meat.

Even though Nessett was familiar with Flynn's cardiac study, she was wary. "I thought, 'Can life be that simple? Could something as easy as adding olive oil to your diet really make a difference?'"

It did. Four weeks later, Nessett discovered that she'd lost five pounds and improved her cholesterol levels. Five years later, she's a convert.

"At conferences, there's always a buzz when Mary speaks," Nessett says. "She's the big one in front of the research."

In 2004, though, when Flynn began the Komen study, the accepted thinking was that fat is bad, and the NCI was recommending a fairly low-fat diet of 1,200 calories a day for women aiming to lose weight. Flynn, however, had already found that women shed pounds just as quickly when consuming 1,500 calories a day. The difference of 300 calories, she argues, can make a significant difference because at 1,200 calories women's metabolism slows down to conserve energy, which actually impedes weight loss. So for the Komen study she allotted women on both diets 1,500 calories a day.

The NCI diet included five or more servings of fruits and vegetables and up to seven ounces of fish or lean meat daily. The study provided canola oil for the NCI diet, which, like olive oil, is low in omega-6 polyunsaturated fats, a type of fat associated with increased breast cancer risk. Dieters were allowed twenty-five to fifty grams of fat a day—between 15 and 30 percent of their calories.

The lower-fat diet felt familiar to the women in the Komen study, some of whom had been on the similar Weight Watchers diet. At first, though, the largely vegetarian PBOO diet seemed daunting, Flynn says. While vegetables were unlimited, fruits were rationed to three servings a day because the literature does not indicate that they have as substantial health benefits as vegetables do, Flynn says. Her diet allowed just six ounces of poultry and eight ounces of seafood a week, and no red meat. For the first two weeks of the diet, she encouraged participants to avoid even fish and chicken. Instead, the diet prescribed a combination of vegetables, legumes and grains, especially whole grains—and those daily three tablespoons of olive oil.

Flynn provided instructions and prepared meal plans and recipes for both diets. She and her assistant met with the women for weigh-ins, and their measurements and blood work were taken at the start and at the end of each eight-week diet. Women who couldn't stick with the diet plans were dropped from the study, as were those who had to change their lipid-reducing medications. Twenty-eight of the original forty-four women completed the sixteen-week study.

The great advantage to Flynn's diet is that it tastes better than many low-fat diets. Most of the women in her study found the olive oil diet more filling and more enjoyable.

"I grew up in a meat-and-potatoes family, and I'm not a great cook," says Ellen Kasle, a Providence real estate agent who remains cancer free five years after the study. At first, Kasle admits, when she made Flynn's recipes for tuna and white bean salad, or whole-wheat pasta with vegetables, she was skeptical. "But," she says, "my husband would try what I'd made and say, 'This is delicious!'" She jokes that she was miffed when he lost weight faster than she did. After eight weeks on the diet, Kasle says, "I loved it. There was no red meat, almost no fat other than olive oil. I started using more whole grains, buying whole-wheat pasta. I felt really good. Then it was time to switch. The [NCI] diet had meat, and more dairy. I really did not enjoy it. I just didn't feel as good on it." After her eight weeks on the NCI diet, Kasle says she went back to the olive oil diet for the remaining six months of the study, and, she says, "I haven't turned back." For her, the olive oil diet has become a way of life.

Flynn's work with cancer patients trying to keep their weight down may help save lives, but she doesn't stop there. A self-described foodie and a rapid-fire talker, she is a zealot on the subject of the medicinal benefits of extra virgin olive oil. Made from the first pressing of the fruit, extra virgin olive oil has the advantage of being pressed without heat or chemicals, which force more juice from the pulp but rob the oil of plant nutrients, or phytonutrients, some of which are thought to fight cancer.

Some of olive oil's components are clearly beneficial. A 2005 Nature study found that one phytonutrient, oleocanthal, mimics the effect of ibuprofen in reducing inflammation, which can decrease the risk of breast cancer and its recurrence. Squalene and lignans are among the other olive oil components being studied for their possible effects on breast cancer.

Olive oil is also rich in antioxidants, especially vitamin E, long thought to minimize cancer risk. Among plant oils, olive oil is the highest in monounsaturated fat, which doesn't oxidize in the body, and it's low in polyunsaturated fat, the kind that does oxidize. While canola oil, too, is high in monounsaturated fat and low in polyunsaturated fat, canola does not prevent oxidation and it does not have health benefits, Flynn says, which is why she urges cancer patients to opt for extra virgin olive oil instead.

Another advantage of olive oil, Flynn says, is that it lowers blood glucose levels and increases insulin sensitivity. The latter is especially critical for overweight patients because it safeguards them against the development of metabolic syndrome and Type 2 diabetes.

In addition, when consumed with vegetables, olive oil performs nutritional double duty: it helps people digest and absorb carotenoids, the phytonutrients that give plants their dark color and may protect against and fight cancer. "The more fat you eat with the carotenoids, the more you'll absorb," Flynn says. Cooking vegetables in fat further increases carotenoid absorption. "That may be due to the membranes breaking down and releasing the carotenoids into the fat," she theorizes. In her diet, she recommends sautéing or roasting vegetables with olive oil.

Lycopenes, the carotenoids in tomatoes that many (but certainly not all) scientists believe to reduce the risk of both prostate and breast cancer, are poorly absorbed from fresh tomatoes. The lycopene in processed tomatoes is more readily bioavailable. In her book, Flynn urges dieters to cook tomatoes in olive oil to maximize lycopene absorption into the bloodstream. By the end of the ten-month Komen study, the carotenoid levels in the blood of participants had risen markedly.

Nutritional merits aside, olive oil's greatest advantage to cancer survivors and other dieters is probably culinary rather than medicinal: it adds flavor to food while making you feel full. When dinner is delicious and your stomach's not growling, you're more likely to stick with your diet, rather than sliding back to old eating habits.

And that is likely to be Flynn's greatest contribution to health. As both a researcher and a teacher, she strives to teach people how to develop healthy eating habits without having to give up flavor and the pleasure of certain kinds of fats. She lectures on nutrition to Brown medical students, and she offers two popular undergraduate courses: a basic nutrition course and another on the relationship between diet and disease. Her student evaluations are consistently so enthusiastic that in 2005 the medical school honored her with the Dean's Teaching Excellence Award.

Flynn is also trying to extend her dietary ideas beyond the middle class. Since 2005 she has served on the board of the Rhode Island Community Food Bank, where as a volunteer she has run studies to determine whether a six-week cooking program can help food pantry clients improve their nutrition and their food purchases. "Mary has a generosity of spirit that translates into everything she does, quietly at the food bank, and publicly through her research," says Ellen Kasle.

Next up for Flynn is a study of the impact of her diet on prostate cancer patients. Anthony Mega '84, a Miriam Hospital oncologist and associate professor of medicine at the Alpert Medical School, recently approached her about working together with prostate cancer patients, many of whom gain weight during androgen deprivation therapy, a common treatment. The therapy causes many patients to put on abdominal fat, and it raises their insulin levels, which can lead to metabolic syndrome and put them at risk for heart disease, stroke, and diabetes. For these men, like women with breast cancer, losing those extra pounds is serious business.

Flynn and Mega ran a small pilot study of her plant-based olive oil diet on twenty men, sixteen of whom completed the study. Last fall, Flynn revealed their preliminary findings at the American Dietetic Association's Food and Nutrition Conference and Expo in Boston: during the study's eight weeks, the men had lost an average of nearly twelve and a half pounds—more than 5 percent of their original weight. On average they'd trimmed more than two inches off their waistlines. And their triglyceride levels dropped from the danger zone into the safe range.

Although the study was too small to be definitive, the results were promising. And it ensures that Flynn will not soon tire of finding more people to help with olive oil and the Mediterranean diet.

Charlotte Bruce Harvey is the BAM's managing editor.