Low-Fat Diets Don't Work? Don't Believe It!
Sensationalistic Newspaper Headlines Misrepresent Three Major, Yet Flawed Studies.
Here is What the Studies Actually Found.
Talk about bingeing! The opportunity for sensationalistic, yet misleading headlines proved irresistible to editors across the land as their newspapers proclaimed: "Eating Lean Doesn't Cut Risk (LA Times);1" "Low-Fat Diet Cuts Health Risks? Fat Chance (San Diego Union-Tribune);2" "Low-Fat Diet Does Not Cut Health Risks (NY Times).3" The headlines referred to 3 studies published on February 8, 2006, in the Journal of the American Medical Association.4-6 The studies cost $415 million and involved nearly 49,000 women ages 50 and over. Women placed on a low-fat diet were followed for 8 years, at which time there was no improvement in their incidence of heart disease, strokes, breast and colon cancer in comparison to the control group not placed on a diet. However, these results were nullified by the fact that the women placed on the low-fat diet did not adhere to it.
Before being placed on the low-fat diet, the women's regular diets provided 37% of their calories from fat. The target of the study was to reduce fat calories to 20%. Unfortunately, few low-fat dieters reached the target, and by the sixth year of the study the average fat intake was 29% of calories. In other words, most women in the low-fat group did not follow the low-fat diet. This meant that none of the findings of these studies was meaningfull -- except this one:
When you place people on a low-fat diet, but they do not follow the diet and do not substantially reduce their fat intake, there will be few health benefits.
Thus, it would have been more accurate for the newspapers to proclaim: "When people don't follow low-fat diets, health benefits are few." That is quite different then the newspapers announced.
The results of the 3 studies were irrelevant for other reasons. First, the low-fat diet used in the studies made no distinction between healthful and unhealthful fats. The low-fat diet discouraged all types of oils. Olive oil was discouraged the same as lard and trans fats with their known health toxicities. A reduction in healthful oils would have negated any benefit from reducing unhealthful oils, and no overall benefits would be expected. This was another key flaw of the studies.
A second problem with these studies was how calories were counted. According to Dr. Marion Nestle, a highly regarded expert on nutrition at New York University, there may have been problems with the food-intake questionnaire with which the women reported their food consumption. Based on the numbers provided, Dr. Nestle questioned the accuracy of the women's reporting.1 I would add that it has long been known that food diaries kept by subjects are often inaccurate in the types and especially in the amounts of food consumed.
Other experts criticized the study because 8 years was not a sufficient time frame to demonstrate significant effects on heart disease or cancer.
The 3 Studies Demonstrated Important Low-Fat Benefits
The negative headlines were also misleading because the studies, despite their flaws, suggested important benefits for people on low-fat diets.
Women who consumed the most fats at the beginning of the study and then had the greatest reduction in fat intake demonstrated the lowest risk of breast cancer.
The lowest risk of heart disease was seen in women who reduced fat intake to the lowest levels.
Women who substantially reduced fat intake also had a lower incidence of polyps of the colon, which often precede colon cancer.
These are not minor findings. Thus, the headlines should have read: "Low-fat diets suggest major benefits on risks of heart disease and cancer."
Current Concepts on Fats and Diet
Last year, when I published my new book on statin medications and natural alternatives for reducing cholesterol and other cardiac risks, I included a long chapter on diet. Here are a few excerpts from the book:7
The extensive research on the heart-healthy Mediterranean diet demonstrates the same thing: cholesterol problems are not due to the amount of fats people eat, but the types of fats. Italians and Greeks eat as much fat as Americans, but theirs is primarily olive oil, which provides large amounts of heart-healthy monounsaturated fats. Olive oil also contains phenols that are similar to those found in green tea and red wine that inhibit LDL-C oxidation. Thus, a 2003 study in the New England Journal of Medicine reported: "Greater adherence to the traditional Mediterranean diet is associated with a significant reduction in total mortality.8"
The diet of the people of Okinawa, who have the longest lifespans on the planet, contains high amounts of fat (from fish and soy) and carbohydrates (from vegetables and rice), but is low in saturated fats. Eskimos live on very high-fat foods, but Eskimos have low incidences of heart disease and arthritis because the fats they eat are very rich in omega-3 fatty acids.
The lesson is that Atkins, who said "All fats are good," was wrong. Good fats are good, and bad fats are bad. Americans consume large quantities of bad fats -- saturated fats and hydrogenated oils -- that elevate cholesterol levels and cause cardiovascular disease. Indeed, every society that has adopted western dietary habits has suffered major increases in heart attacks and strokes. People from diet-healthy societies who come here and adopt our ways of eating get all of our diseases.
Advocates of low-fat diets with moderate amounts of protein and high-quality complex carbohydrates have plenty of evidence supporting their perspective. Studies repeatedly show that when people stick with low-fat diets, incidences of coronary disorders, heart attacks, and cardiac deaths plummet. Dr. Caldwell Esselstyn of the Cleveland Clinic reminds us that "although coronary artery disease is the leading killer of men and women in the USA, it is rarely encountered in cultures that base their nutrition primarily on grains, legumes, lentils, vegetables, and fruit.9" In other words, the doctor is advocating a low-fat, moderate-protein -- high quality -- diet based on natural foods. Dr. Dean Ornish has clearly demonstrated that for people with advanced coronary disease, strict restriction of fat, especially saturated and hydrogenated fat, can halt and sometimes reverse atherosclerosis.10,11
A low-fat, high-quality diet does not mean going crazy on carbohydrates. It does not mean you can eat unlimited amounts of "low-fat" foods filled with sugars and calories. It does not mean breads and pastries made from refined white flour or loaded with sugar. Bad carbohydrates are just as bad as bad fats. You must select your carbohydrates just as carefully as you select fats.
In the book, I also explain that low-fat diets work for some people and low-carb diets work for others because of genetically-determined metabolic differences. I explain how people can learn which metabolic type they are and how to adjust their diets accordingly. Metabolic differences explain why the widely differing diets of Drs. Dean Ornish and Robert Atkins are right for some people and not others.
The Bottom Line
The 3 low-fat studies published in JAMA were performed by very good people. Many of these researchers have produced excellent work in the field of health and nutrition. However, these 3 studies add little to our current knowledge, and instead serve to confuse a picture that has become quite clear about healthful nutrition:
Good nutrition means a diet based on vegetables and fruits, with a healthful diversity of complex carbohydrates, low-fat protein, and healthful fats. A healthful lifestyle also means not smoking, a moderate degree of regular exercise, and avoidance of prolonged excessive stress.
1. Maugh TH, Chong JR. Eating lean doesn't cut risk. Los Angeles Times, Feb. 8, 2006:A-1.
2. Low-fat diet cuts health risks? Fat chance. San Diego Union-Tribune, Feb. 8, 2006:A-1.
3. Kolata G. Low-fat diet does not cut health risks, study finds. New York Times, Feb. 8, 2006:www.nytimes.com.
4. Howard BV, et al. Low-fat dietary pattern and risk of cardiovascular disease. JAMA, Feb. 8, 2006;295:655-666.
5. Prentice RL, et al. Low-fat dietary pattern and risk of invasive breast cancer. JAMA, Feb. 8, 2006;295:629-642.
6. Beresford SA, et al. Low-fat dietary pattern and risk of colorectal cancer. JAMA, Feb. 8, 2006;295:643-654.
7. Cohen, JS. What You Need to Know about Statin Drugs and Their Natural Alternatives. Square One Publishers, New York: January 2005.
8. Trichopoulou, A, Costacou, T, Bamia, C, Trichopoulos, D. Adherence to a Mediterranean Diet and Survival in a Greek Population. New England Journal of Medicine 2003;348:2599?]2608.
9. Esselstyn, CB. Becoming Heart Attack Proof. Cleveland Clinic Foundation:www.heartattackproof.com.
10. Ornish, D, Scherwitz, LW, Billings, JH, et al. Intensive lifestyle changes for reversal of coronary heart disease. JAMA 1998;280(23):2001?]7.
11. Ornish D. Avoiding revascularization with lifestyle changes: The Multicenter Lifestyle Demonstration Project. American Journal of Cardiology 1998;82(10B):72T?]76T.
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