Low Fat Diet Over Time

There is some evidence to support the idea that a low-fat diet might prove its mettle over a longer time. Though the data showed conclusively that rates of actual disease were not affected over 8 years, some risk factors-conditions that tend to herald disease-were lower among the dieters. In addition to lower LDL levels, low-fat eaters had a lower incidence of polyps, a precursor of colon cancer. Epidemiologist Shirley Beresford of the University of Washington, lead author of the study's report on colon cancer, was optimistic that the polyp findings might lead to lower colon cancer rates over the next decade. Regarding breast cancer, researchers found that those who had eaten the most fat before starting the diet (and therefore experienced the most radical change in their fat intake) benefited considerably more than average participants. This result might indicate that switching from a heavily fat-laden diet to a modestly low-fat one could lower the risk of breast cancer. Researchers plan to continue monitoring a subset of the participants, to see if any of the possible leads eventually translate into statistically significant drops in disease rates.

Some nutrition experts found cause for celebration in a secondary aspect of the study's results-debunking the low-carb craze. Beginning in the mid-1990s, a nutritional theory centered on minimizing carbohydrates took off in America, with the Atkins, Zone and South Beach diets leading the trend. According to this theory, eating too many carbs makes people fat by causing blood sugar to spike and the body to overproduce insulin, which allegedly makes people feel hungrier and continue to eat in a vicious cycle. In January 2006, researchers released preliminary data from the WHI study, in which they looked at weight patterns among the two groups of participants. Even though the low-fat diet was not designed to promote weight loss-it did not restrict total calories or require women to exercise-researchers found that, on average, women in the low-fat group weighed two pounds less at the end of the study than at the beginning. Women in the control group did not lose any weight. Since the low-fat dieters replaced fat calories with carbohydrate-heavy fruits and grains, they were eating a fairly high-carb diet. "Some of these fad diets promote the idea that if you suddenly cut carbs, it's going to miraculously make you lose weight," Barbara Howard of the MedStar Research Institute in Hyattsville, Indiana, told the Washington Post. "This [study] shows that's probably unfounded." Rather, a low-fat diet appears to be a good way of maintaining an even body weight and staving off the extra pounds people tend to put on during middle age.

Despite the swirl of questions over the study's design, the WHI program exemplifies a rigorous scientific approach to testing theories about health. Too often, statistician Freedman stated, doctors and other members of the scientific community "give strong advice based on flimsy evidence." Doing experiments, like the WHI clinical trial, is the only way to replace guesswork with scientifically valid information.

At the same time, the study also highlights the intense difficulties of studying the health effect of broad lifestyle factors like diet. Collecting good data on people's adherence to a program is always a challenge, and results almost always present a more complex picture than researchers would like. "I think we've learned that nutrition is never simple and there are no simple solutions," said Dr. Howard, the MedStar researcher. Instead of serving as the last word on low-fat, leaders of the study are now seeing it more as a jumping-off point for further investigations, such as follow-up studies on breast cancer rates among high-risk women and whether lower incidence of polyps ultimately translates to less colon cancer.

One thing all the experts agree on is that, however much weight doctors ought to give to the study, it does NOT mean that women (or men, for that matter) should allow themselves free rein to eat all the fat they like. A low-fat diet does not, it appears, provide much of a shield against diseases it was thought to ward off, but that doesn't mean it isn't a generally healthy way to eat. JoAnne Menard, a study participant from the Seattle area, said that in spite of the findings, "I don't have any doubt that I'm eating healthier and have been in the last 10 years [since the study began] and will continue to." The evidence that too much saturated fat leads to heart disease is strong, so eating Big Macs for breakfast, lunch and dinner is definitely a bad idea, and Walter Willet of the Harvard School of Public Health insisted to the Washington Post that "diet and lifestyle do make a big difference" in terms of general health. He recommends a balanced diet rich in fruits, vegetables and whole grains and low in saturated fat. The study is one more reminder, however, that there is no single, magical food formula for living a long, healthy life.

Sources

Howard, Barbara et al. "Low-Fat Dietary Pattern and Risk of Cardiovascular Disease." JAMA, February 8, 2006, page 655.

Kolata, Gina. "Low-Fat Diet Does Not Cut Health Risks, Study Finds." New York Times, February 8, 2006, page A1.

Prentice, Ross et al. "Low-Fat Dietary Pattern and Risk of Invasive Breast Cancer." JAMA, February 8, 2006, page 629.

Stein, Rob. "Low-Fat Diet's Benefits Rejected." Washington Post, February 8, 2006, page A1.

Stein, Rob. "Low-Fat Diet Prompts Modest Weight Loss." Washington Post, January 4, 2006, page A3.

"Reducing Total Fat Intake May Have Small Effect on Risk of Breast Cancer, No Effect on Risk of Colorectal Cancer, Heart Disease or Stroke." Press release on the study from the National Institutes of Health. (February 7, 2006) www.nih.gov/ news/ pr/ feb2006/ nhlbi-07.htm.