Should You Eat a Low Fat Diet?

I have written before about how poorly the news media covers science. Today there is a very important result on low-fat diets being reported in the Washington Post and the New York Times. The studies show that low-fat diets do not protect against heart attack, stroke, or cancer. Many people are quite disappointed by this result, but facts are what count not what people want. The point of the study is that a low-fat diet does not provide health benefits. Here is a quote from the top of the Washington Post article.

“Based on our findings, we cannot recommend that most women should follow a low-fat diet,” said Jacques Rossouw of the National Heart, Lung and Blood Institute, which funded the $415 million study.

But later there is this contradictory statement.

Willett and other researchers fear that the findings will leave the public skeptical about all health advice, or will be misinterpreted to mean that diet and lifestyle are unimportant. A large and convincing body of evidence shows that eating a diet rich in fruits, vegetables and whole grains and low in saturated and trans fats; avoiding smoking; exercising regularly; and maintaining an appropriate weight have a powerful effect on health, they said.

Can these two statements be resolved? I have a guess that they can, but it is just a guess. If the studies controlled for body weight then there could be an indirect effect. If somebody eats a high fat diet but maintains a healthy weight then she is not harmed by the diet. There may not be anything intrinisically dangerous about fats, but they may make it easier to gain weight which is harmful. Why do I beleive the studies controlled for body weight? It is good science to try to control all but one variable. Here the variable is the fraction of fat in the diet.

If my guess is true the articles have failed to make the important point of the studies.

Technorati tags: , medicine


6 Responses to “Should You Eat a Low Fat Diet?”

  1. My husband and I celebrated the news with mocha cheesecake! To our health!

  2. I just re-read Gina Kolata’s piece. Another point that needs to be emphasized is that the low-fat diet meant that between 24% and 29% of the day’s calories came from fats, while the normal diet had 35% to 37% of the calories from fat. Which is certainly not a go-ahead to eat cheesecake morning, noon, and night. The comparison appears to have been between sensible diets, one of which had roughly 30% less fat in it.

    Now, if we want to explore the other extreme, I’ll sign up for the all-cheesecake group! OK, maybe I wouldn’n’t.

  3. Medical studies are hard. I am sure that they would have loved to get some people down to 10% fat, in order to see a very strong effect if there was one. Unfortunately, hey did not even succeed in getting to their goal of an average of 20% in the intervention group.

  4. […] In today’s New York Times, Gina Kolata follows up on this week’s story about low fat diets not having any health benefits. Apparently there were two earlier studies on trying to control childhood obesity, that showed despite strong school based interventions to improve nutrition and exercise, the rate of obesity was unaffected. Those studies were apparently never cited by other papers. […]

  5. […] I have been blogging about the Women’s Health initiative as the results on low-fat diets and calcium supplements have been  released. These studies have shown that some highly recommended life style interventions do not show signifcant health benefits. Today the was a nice article in the Washington Post trying to explain how these results could occur. […]

  6. […] I was delighted today to see an article in the Washinton Post that follows up on several health stories that were recently published on low-fat diets. I have been struggling trying to understand what is really happening from the reports in the popular news media. There seem to be only two types of publications available, the popular literature that ducks the scientific concepts like control groups and the mathematics required to discuss the statistics, or the full blown specialist article that can only be read by someone working in the field. Today’s article seemed to be aimed somewhere in the middle which gives me and opportunity to understand the issues better. It is written by doctors from the VA Outcomes Group which is associated with Dartmouth Medical School. […]

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