Study: Low-Fat Diet Big Letdown

Judy LaCour has spent more than 10 years cutting out fat in her diet in a mammoth government study in which no one involved wants to call a bust.

And, yet, after spending $415 million trying to get nearly 20,000 mostly overweight postmenopausal women to radically change their eating habits in hopes of reducing cancer and heart disease, researchers are acknowledging less than spectacular results.

After an average of roughly eight years, there was little difference in rates of breast cancer, colorectal cancer and heart disease in women who reduced their fat consumption than among nearly 30,000 study participants who didn't.

"I was surprised," said LaCour, a 66-year-old Seattle-area participant. "I thought there would be more definitive answers about the value of the low-fat diet."

The researchers did, too. Even so, scientists say the results don't mean dieters should just throw up their hands and eat cake.

Researchers suggested that the participants — with an average age of 62 — may have started their healthy eating too late. They also didn't reduce fats as much as the diet demanded. And while some initially lost a few pounds, the diet was not designed for weight loss and most remained overweight, a major risk factor for cancer and heart problems.

The results appear in Wednesday's Journal of the American Medical Association.

Heart and cancer specialists said the overall results were not surprising, since scientific thinking on the role different fats play in disease prevention has evolved since this study was designed.

The diet "focused on reduction in total fat and did not differentiate between the so-called good fats and bad fats," said Dr. Elizabeth Nabel, director of the National Heart, Lung and Blood Institute, the study's sponsor.

Reducing "bad" fats including saturated and trans fats found in processed and fried foods, and increasing consumption of "good fats" including olive oil, might have yielded better results, especially for heart disease, the researchers and other scientists said.

"These results do not suggest that people have carte blanche to eat fatty foods without health problems," said Dr. JoAnn Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital, a co-author of the study.

"Don't throw the baby out with the bathwater," stressed The Early Show medical correspondent Dr. Emily Senay Wednesday. "It would be a shame if women … read this and thought, "I can throw all my lifestyle interventions away. They don't matter.' They probably do, but maybe not exactly as they should, in this trial.

"We have to eat healthy. We have to exercise. We have to maintain a healthy weight. We have to not smoke. These things, in many other trials, have been shown over and over again to reduce the risk of all these diseases."
The researchers declined to call the venture a failure, pointing to signs of less breast cancer in women who cut out the most fat, and in less heart disease in women who ate low amounts of unhealthy fats.

Still, Manson said, the results "are somewhat disappointing. We would have liked this dietary intervention to have a major impact on health."

The diet-group women cut overall fat consumption and increased vegetables, fruits and grains. The other group continued their usual eating habits.

The study is part of the Women's Health Initiative, a landmark government project involving tens of thousands of postmenopausal U.S. women. An earlier WHI study linked long-term use of hormone pills with breast cancer and heart disease risks.

The new study was designed mainly to investigate breast cancer risk. Dietary fat was initially thought to be implicated because breast cancer rates are high in Western countries with fatty diets, but recent studies have failed to show any relationship, said Dr. Michael Thun of the American Cancer Society.

Recent research also has suggested that for breast cancer in particular, earlier eating habits may have the most influence on risk. Another target was colon cancer, which some studies have linked with red meat.

Breast cancer rates in both groups were about 3 percent, marginally higher than for postmenopausal women in the general U.S. population, probably because these women got routine mammograms, said study investigator Ross Prentice of the Fred Hutchinson Cancer Research Center. Colon cancer rates in both groups were similar to national rates for similarly aged women — roughly 1 percent in both groups.

Both groups had relatively low rates of heart disease, about 2.5 percent compared with just over 4 percent among postmenopausal women nationally, Prentice said.

What are the implications for men?

"Probably the same for colorectal cancer and heart disease," Senay said, "because the disease processes are very similar."