More Questions Than Answers
After Reading Low Fat Diet Study

by Darline Turner Lee, Physician Assistant, ACSM Exercise Specialist

Article Last Reviewed: Sept. 9, 2006

“Low Fat Diet Does Not Cut Health Risks, Study Finds”

That’s the headline on the first page of the February 8, 2006 New York Times Health Section. It also introduced NBC’s Today Show that morning and was the lead in on CNN that evening. I understand the need to grab the audience’s attention. But after hearing and reading the reports, I have more questions. Hold my order for pizza delivery while I try to make some sense out of all of this!

Let’s go to the sources and look at the published articles. The headline refers to data published in the three articles in the February 8, 2006 Journal of the American Medical Association. The abstracts and full reports are available on the Journal of the American Medial Association website at http://www.jama.ama-assn.org. The Women’s Health Initiative study ran for approximately eight years and evaluated the effect of following a low fat diet on heart attacks, strokes and breast and colon cancers.

Researchers followed 48,835 postmenopausal women aged fifty to seventy-nine years old who had no prior breast cancer. There were participants from forty test centers around the country, with nearly nineteen percent minority enrollment. Forty percent of the women were randomly assigned to the study group and ate diets in which twenty percent or less of the calories came from fat, increased their daily consumption of fruits and vegetables to five servings per day and their grain consumption to six servings per day. The remaining sixty percent of the women were randomly assigned to the control group and ate their usual diets.

The researchers reported that there is not a statistically significant difference in invasive breast cancer risk among the women in the study group and the women in the control group. This means the difference in the numbers who developed breast cancer in the study group (six hundred fifty-five) versus the numbers who developed breast cancer in the control group (one thousand seventy-two) weren’t different enough to say that the reason was due to the low fat diet alone.

But there’s more to the story. In the breast cancer study, the women who most adhered to the low fat diet had lower risks of developing breast cancer. Also, women who had higher fat diets at the beginning of the study and made the dietary changes experienced greater reduced risk of developing breast cancer. So while the numbers of women who developed breast cancer did not yield a statistically significant difference, heck, I’d lower the fat in my diet if it will decrease my risk of developing breast cancer. .

In the heart disease portion of the study, the women who made dietary changes significantly reduced their levels of low-density lipoprotein (LDL) cholesterol levels (bad cholesterol), diastolic blood pressure (the bottom blood pressure numbers), and factor VIIc (a substance that promotes blood clots) levels. Women who had lower intakes of saturated fat or trans fat and higher rates of fruits and vegetables showed greater reductions in heart disease risk. The researchers recommend longer studies and focusing on the types of fats eaten, such as fish and olive oils in the typical Mediterranean diet, to see their effects on disease.

Since reading the studies, I have other questions. Were obese women included and did they get diseases more often? Were smokers included? What happened if they quit smoking during the study? If women had positive family histories of any of the diseases, were they excluded from the study? Did activity levels change during the study? How many had other co-existing diseases? If a woman had the breast cancer gene, was she excluded from participation? Are the women on hormone replacement therapy? Who had natural menopause versus surgical menopause (as a result of a hysterectomy?), which usually occurs earlier than natural menopause and ushers in disease risk sooner? All of these factors greatly influence the outcomes of each segment of the study, and the answers will greatly influence future recommendations about how we should change our diets and lifestyles.

Andrew Weil, MD, in the April 2006 edition of his popular newsletter, self healing, acknowledged the confusion about what to eat as a result of these studies. He wrote, “These studies focused solely on reducing total fat, a promising idea among nutrition experts when the studies were first designed, but one replaced by the belief that the types of fat consumed are more significant to overall health.”

Weil suggests allowing enough healthy fat in your diet from olive oil, fish, and nuts to make food appealing, while restricting saturated and trans fats and some polyunsaturated vegetable oils like safflower, sunflower, soybean and corn. He also notes the importance of other aspects of lifestyle like controlling weight, getting regular exercise, not smoking, and keeping an eye on total calories.

So let the researchers do the follow up studies and report the results. Low fat diets alone may not affect disease development, but the types of fat and other health factors may play a greater role than previously suspected in disease development. All of these results and trends deserve report before anyone makes a definitive recommendation for change.