Uh-oh. I think I'm having an Emily Litella moment: what's all this fuss I hear about Loaf Hat Diets? Oh, never mind.

I'm referring, of course, to the bombshell published in today's Journal of the American Medical Association, which declares, essentially, that a low fat diet provides virtually no discernable advantage when it comes to reducing your risk of heart disease or cancer.

Brace yourselves for a dietary dust-up of epic proportions over this exhaustive and seemingly definitive federal study, which followed nearly 50,000 middle-aged women for eight years at a cost of $415 million dollars. The study was begun in 1993, and focused on reducing its participants' fat intake without making any distinctions between good fats and bad.

Dr. Peter Libby, a cardiologist and professor at Harvard Medical School, described the diets in the study as having “an antique patina.” He pointed out that most people have advanced beyond the notion of limiting your total fat intake to the idea that people should eat different kinds of fats.

A Mediterranean-style diet combined with regular exercise is Dr. Libby's current prescription for good health, but there have been no large clinical trials to test such a diet. “If they did a study like that and it was negative, then I'd have to give up my cherished hypotheses for data.”

Dr. Barbara V. Howard, an epidemiologist and principle investigator in the study, said, “We are not going to reverse any of the chronic diseases in this country by changing the composition of the diet. People are always thinking it's what they ate. They are not looking at how much they ate or that they smoke or that they are sedentary.”

But does this study really prove conclusively that a low fat diet does nothing to prevent heart disease or cancer? The study did not distinguish between good fats, such as the cholesterol-lowering omega 3 fatty acids found in fish and nuts, for example, and those artery-clogging trans fats, which are indisputably bad for you. This seems like a fundamental flaw to me.

What really disturbs me about this study is that people will latch onto these findings as proof that what you eat doesn't matter. Many people will interpret the results to mean that there's no harm in eating a high fat diet, despite the fact that being overweight can cause significant health problems.

One longtime low fat advocate, Dr. Dean Ornish, has already written a column challenging numerous aspects of the study. Others will no doubt weigh in with their own interpretations of this confounding collection of data. I'm especially curious to know what Marion Nestle, Professor of Nutrition, Food Studies and Public Health at NYU, will have to say.

For me, trying to decipher the significance of this study brought to mind Donald Rumsfeld's unforgettable ode to uncertainty:

As we know,

There are known knowns.

There are things we know we know.

We also know there are known unknowns.

That is to say we know there are some things we do not know.

But there are also unknown unknowns,

the ones we don’t know we don’t know.

(Feb. 12, 2002, Department of Defense news briefing)

I don't know what else to say, except maybe “pass the butter.”