February 14, 2006

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Low Fat Takes (Another) Dive

Did you see it? Huh? Huh? Hard on the heels of my article last week explaining that yes, a low carbohydrate diet will, perforce, be a diet that gets a higher proportion of its calories from fat - in other words, a high fat diet - comes the big news. All over the mainstream media came the word that a low fat diet doesn't prevent heart disease or cancer.

BWAHAHAHAHAHAHA! Okay, everybody, stand up from your computers and join me in the Smug Dance. (cue the music!)

Okay, that's enough. Everyone sit down and resume reading. Let's look at this study and the coverage of it, and see what it means, and doesn't mean, for us, and for nutrition in general.

The study that appears in this month's Journal of the American Medical Association (JAMA) is nothing short of immense. Over eight years, 48, 835 healthy postmenopausal women, aged 50 to 79 years old were randomly assigned either to a low fat diet, or to continuing to eat as they had. During those eight years, the low fat group averaged 29% of their calories from fat, while the control group averaged 37% of their calories from fat. The low fat group also ate more fruits, vegetables, and grains than the control group.

The study was originally intended to look at the effect of a low fat diet on breast cancer risk. It wound up concluding that not only did a low fat diet have no statistically significant effect on preventing breast cancer, it also didn't prevent colon cancer, heart disease, or stroke. Since the all along the big-guns objection to our low carb way of eating has been "All that fat will give you heart disease! Or cancer!" this is useful ammunition.

It's also interesting that the greater intake of fruits, vegetables, and grains didn't have any detectable protective effect. We're told these are the best possible foods. Yet eating more of them didn't help, at least when combined with fat restriction. I wonder how twice as many vegetables and half as many grains would have done...

There are serious limitations to this study. First of all, it only included women. Secondly, including, as it did, only women in the 50-to-79 age group, it tells us little about the effects of a careful nutritional program of whatever kind begun earlier in life.

(I "got nutrition" like other people "get religion" - the blinding bolt from the blue that changes your life forever - when I was nineteen. While I have made some nutritional missteps since then - like a low fat/high carb diet - the most egregious junk has been out of my life for almost thirty years. If we could find several thousand like me and test us, it would make an interesting study.)

Too, the control group in the study simply continued to eat their "normal" diet - which is likely to have included bad fats like hydrogenated vegetable oils, plenty of refined carbs, processed foods, and all that wonderful stuff that's part of the Standard American Diet. The low fat group didn't put any restrictions on what sort of fat they ate, so we have no way of knowing how many of them ate, say, diet margarine - a source of trans fats - instead of good old full-fat butter. Both these factors must be assumed to have affected the results.

It would be very interesting to see a study that looked at a low fat diet and a higher fat diet, with both diets excluding refined carbs and hydrogenated oils. But that's a whole different study, and would probably take another $400 million and another eight years.

After eight years, the low fat folks weighed just a pound or two less, on average, than the "normal" diet folks. This is being trumpeted as "proof" that a low fat diet doesn't make you fat. What they're not saying is that it's pretty clear proof that a low fat diet is no better at making you thin than the Standard American Diet. It would be interesting to see an eight year trial of a low fat diet against a low carb diet, wouldn't it?

The usual suspects are weighing in on this.

Dr. Dean Ornish, whose empire is built on the notion that a low fat diet is the ultimate in disease prevention, is insisting that the diet just wasn't low fat enough. It seems to me that if cutting fat back that far was going to give fabulous results, cutting fat back substantially ought to yield at least some results. It didn't.

But Ornish insists that we need to cut back to only 10% of calories from fat, you see, and eat no animal foods at all. Then we'll see the miraculous results he's promised. That no nation, race, or tribe in history has ever eaten such a diet, much less thrived on it, apparently doesn't matter. Nor does the fact that many peoples eating more fat than Americans - like, say, the French and the Italians - are healthier than we are.

People who hate the idea of limiting their diet in any way are crowing that this proves that you might as well eat whatever you want. After all, "eating healthy" doesn't work. They are, of course, ignoring the possibility that a low fat diet wasn't the right way to eat healthy.

The "cut calories and exercise" enthusiasts are saying, "Low carbohydrate diets have already been discredited, and now low fat diets are too - so just eat a balanced diet, watch your calories, and get a lot of exercise." Which floors me, since I haven't seen a scrap of actual research to show that low carb diets don't work, and aren't healthy - just assertions.

And the mainstream journalists and medicos are saying that this shows that we don't need to cut out all fats, we just need to cut out "bad fats." They then go on to define "bad fats" as hydrogenated oils and saturated fats. This, of course, will be the new rallying cry of those who are sure that we're digging our graves with our sugar-free, steak-loving teeth - "But it's saturated fat!"

I have no argument against cutting out hydrogenated oils. They're evil, and I won't touch them. But the idea that saturated animal and tropical fats are bad for us is just as simplistic and wrong-headed as the idea that fats in general are bad for us. If animal fats caused heart disease and cancer the rate of these diseases would have dropped during the 20th century, when we were busily replacing those "bad" fats with "healthy" vegetables oils.

But that's not what happened. Instead, as we replaced traditional animal and tropical fats with vegetable oils and (God forbid) hydrogenated vegetable shortening, the rates of both heart disease and cancer skyrocketed. In light of this, it's hard to see how naturally saturated fats are dangerous. (I say "naturally saturated" because hydrogenation is simply a process of artificially saturating a fat that was originally unsaturated, and therefore liquid.)

I'll say more about good and bad fats in the future, but a good general rule is "If you can picture how they got the oil out of the food, it's probably okay." Can you picture how they get the oil out of corn or soy beans? Do you even know what a "safflower" is? No? Don't eat it.

It would be easy to assume from the big reaction in the press that this study was the first to show a low fat diet isn't effective for protecting health. It's not. There have been many.

A 1996 study in Lancet concluding that women who ate a high fat diet had a lower risk of breast cancer than those who ate a high carbohydrate diet.

Another 1996 study, this one pooling and reexamining data from seven studies of the effects of a low fat diet on breast cancer, finding no evidence that fat is a culprit.

Here's one that looked at specific types of fat and breast cancer risk, and concluded "No associations were observed for animal or vegetable fat intakes."

A Japanese study that shows a decreasing risk of breast cancer with an increased intake of fish oils and saturated fats.

And the Big Casino, the Harvard Nurses Study, looking at 88,795 women. In this article, written in 1999, 14 years after the study began, they conclude "We found no evidence that lower intake of total fat or specific major types of fat was associated with a decreased risk of breast cancer."

The same study had already concluded in 1987 "...a moderate reduction in fat intake by adult women is unlikely to result in a substantial reduction in the incidence of breast cancer." Indeed, the women who ate the most fat were almost 20% less likely to get breast cancer than the women who ate the least fat.

Here's a trial of a low carb/high fat diet against a low fat/high carb diet for treatment of obesity and the health problems that go with it. The low carbers lost more weight, and had greater improvement in their heart disease risk indicators.

Here's a study that starts off with the statement, "It has been known for decades that low-fat, high-carbohydrate diets can increase plasma triglyceride levels..." Have they howdied with Dr. Ornish?

I could go on, but you get the point: All the hoopla about this study mostly indicates that the media hasn't been paying attention. The holes in low fat diet theory have been showing for a long, long time.

So where does this leave us? Well, at least in position to laugh at all those post-New Year ads crowing about how few fat grams this or that starch-and-sugar-laden junk food has. And in a good place to say to all of our critics, "Why are you recommending a diet that's been clinically disproven?"

Posted by HoldTheToast at February 14, 2006 12:19 PM