Low Fat Diets: What’s a Woman to Do?

If you are confused about some of the latest scientific findings from the ongoing, large-scale Women’s Health Initiative, welcome to the club! One recent finding, in particular, surprised researchers and consumers alike: Low-fat diets apparently offer no real benefits in terms of reducing the risk of cardiovascular disease (CVD) and certain cancers.

The objective of the Women’s Health Dietary Modification Trial was to test whether a low-fat diet high in fruits, vegetables and grains would reduce the incidence of cancer and CVD in postmenopausal women. Over a period of 8.1 years, the researchers studied almost 49,000 women (ages 50–79) of diverse backgrounds and ethnicities who were randomly assigned to a low fat dietary intervention or used as controls. The intervention consisted of asking the participants to reduce their overall fat intake to 20% of total daily calories, while simultaneously increasing their intake of fruits and veggies to five servings per day and upping their grain intake to at least six servings per day.

At the end of the study period, the researchers found that the low-fat dieters did not have a significantly lower risk of CVD, stroke, colorectal cancer or breast cancer. The results were published in three separate articles in the February 8, 2006, issue of The Journal of the American Medical Association (JAMA).

Unfortunately, these findings appear to raise more questions than answers. The researchers acknowledged the study’s limitations, which included its focus on older women and its failure to observe key nutrients relevant to CVD. Also, the study did not target a particular type of fat, which some experts say might have produced different results (only total fat intake was assessed). Finally, the data reported was obtained from self-reported dietary questionnaires, which are often biased.

Some experts, such as Dean Ornish, MD, have been widely quoted as saying the women did not reduce their fat intake to low enough levels, failed to eat enough fruits and veggies and were not studied for long enough. Others have faulted the study for not citing the specific kinds of fat eaten by the participants.

“It’s important to consider the whole study before putting the butter back on your veggies,” says Jenna Bell-Wilson, PhD, MS, RD, LD, assistant professor of medical dietetics at Ohio State University and an IDEA contributing editor. “By focusing only on total fat intake, the researchers failed to assess the merits of healthy fats that have been shown to have disease-fighting properties. For example, did these women eat nuts, seeds and salmon each day, or did they gorge on ice cream? Also, the women only slightly increased their intake of fruits and veggies, so it is possible that the increase was not sufficient to produce results. Finally, the study did not discount the importance of healthy omega-3 fatty acids, gleaned from nuts and fatty fish, such as mackerel and salmon.”

The bottom line, says Bell-Wilson, is to eat a balanced diet and exercise regularly. “It’s the whole package that keeps us healthy,” she advises. “It’s your fitness level, reducing stress, eating healthy foods, staying mentally stimulated and keeping involved in social interactions.”