Paper Palate

The findings of a major long-term study of the effects of low fat diets on the health of middle-aged to elderly women are sweeping the major newspapers of the world today, mostly because the results go against conventional nutritional wisdom: switching to a diet low in fat does no good in protecting agasint cancer or heart disease.

The 415 million dollar study, published in today’s Journal of the American Medical Association, concludes that there is no statistical difference in incidences of colon cancer, breast cancer, heart disease and strokes between women who ate low-fat diets and those who ate whatever they wanted. Conducted by the National Heart, Lung and Blood Institute, the stody followed the health of 49,000 women, aged 50-79 over an eight year period.

The New York Times story quoted Dr. Dean Ornish, a well-known proponent of the health benefits of low-fat diets and author of Eat More, Weigh Less, as saying that the women in the study were not made to lower their intake of fat to low enough levels, nor that they were instructed to eat enough fruits and vegetables; furthermore, he added that eight years was not enough time for a low fat diet to show positive health results.

However, the Washington Post reported that “About 40 percent were counseled to eat more fruits and vegetables and to cut their overall fat intake, with the goal of reducing their total fat consumption to no more than 20 percent of their daily calories.”

In order to stave off the possibility that readers may decide that lower-fat diets do no good at all and decide to just eat what they want, the Chicago Tribune article quoted one of the authors of the study, Dr. JoAnne Manson as saying, “These results do not suggest that people have carte blanche to eat fatty foods without health problems.” One possibility mentioned is that the women started their low-fat diet regimes too late to do any good–which is the first thing that popped into my mind on the issue.

In fact, most of the news reports neglect quite a few limiting factors to the study, many of which popped up as I read the articles. Ruth Kava of the American Council on Science and Health enumerates them in an article posted on their website today.

One question that came to mind was the fact that no mention of the women’s exercise or activity level is made in the study: from my perspective, diet alone is not the key to good health–our bodies evolved to be active and to move, not sit like lumps. In addition, no distinction was made between unsaturated and saturated fats in this study; all fats were treated as equally suspect. There was no mention made of trans-fatty acids, probably because the science of them was not as particularly well-known as it is now. Finally, there was a statistically insignificant lowering of risk for breast cancer that might have been more significant if the study had lasted longer.

All in all, it is an interesting study, and a good example of how rigorous application of the scientific method does not always lead to the results one expects.

What I most hope, however, is that the reporting of this study in the popular press does not lead to Americans saying, “Screw it! Low fat diets do nothing, so let me eat cake and to hell with it all!”

As much as I might hope for that, I fear that many people will take this study as an excuse to continue eating unbalanced, fat-filled, fast food diets, possibly to the ultimate detriment of their health.