When ever my patients bring up diet, they ask about fat. It’s an important topic because trans fats, high cholesterol, obesity, diabetes, and atherosclerosis all seem to go hand in hand. Dr. Atkins devotees say fat is fine; Dr. Ornish aficionados say it should be avoided at almost all costs. But a recent study by the Women’s Health Initiative (WHI) suggests that the link between dieting and fat intake may not be as strong as we think.
The WHI study was begun in 1993 with nearly 50,000 women between the ages of 50 and 79 years. In one part of the WHI, half the women were asked to eat as usual and given generic diet-related education material. The other half were assigned to follow a low-fat diet and participate in a variety of nutritional counseling sessions. The goal of the low-fat-diet group was to reduce their fat intake from 38% of calories to 20%. In reality, though, they only got it down to 29%. After following these guidelines for eight years, researchers found that the women did not have any additional protection against cancer or heart disease, and their weight was about the same as those following their usual diet.
What’s most striking here is not the result, but the fact that even though these women agreed to participate in a study with a goal of 20% fat intake, and were given significant assistance, they were only able to bring it down to 29%. My patients' experiences, and I admit my own, support how difficult it is to control total fat intake. That’s why I encourage my patients to monitor what kinds of fats they eat, not just how much fat. I recommend a diet low in saturated fat, trans fat and cholesterol.
It’s also important to note that this study (like all studies) has some limitations:
• The women were asked to self-report their fat intake, and in many studies people have been shown to under-report their calorie and fat intake. (Just like the old commercial - when it comes to potato chips,most people can’t stop with just a few.) • Another issue to consider is the age of the study population. Women in the WHI were between 50 and 79 years old. It is possible that by this time in a person’s life, a modest diet change over a relatively short period of time may not be enough to prevent disease. I would be interested in finding out if reduced risks of heart disease, cancer, and other chronic diseases would be more apparent through a longer study with a younger population.
Robert W. Lash, M.D. is an associate professor of internal medicine at the University of Michigan Medical School. His clinical interests include thyroid disease, diabetes, endocrine disorders in pregnancy, osteoporosis and metabolic bone disease, and medical education. A member of the LLuminari team of experts, a board certified internist and endocrinologist, Dr. Lash has an active clinical practice and is a hospitalist at the University of Michigan.
