Updated June 08, 2015.
Interpreting science is not easy. Not only do we need knowledge of the field being investigated, of statistics, and of research design, but we need to do battle with the trickiest traps of all, which are in our own heads. There is a great tendency in all of us to criticize the studies that don't support our own views, and go easy on the ones that do. Scientists try to devise the best research they can to collect objective data, but no study is perfect, and anyone can pick it apart to suit their own biases.
The responsibility falls on the media to portray studies in an objective a light as possible, especially where it affects people's health. Unfortunately, science writers also have their biases, and often need to contend with presenting a piece of writing in a way that will "sell".
There are many issues that determine the importance of a study, including the design, the execution, and how "preliminary" it is. These issues are very difficult for the public to understand without help. A headline from a very preliminary study with few subjects may get the same kind of press as a long-term, well done study. And critics of two studies may be given equal weight as well. It's no wonder much of the public has given up on science as it pertains to their health.
The recent research about low fat diets and the risk for breast and colon cancer, heart disease, and stroke is a case in point. This was a very large-scale and well-controlled study. Is it "the final word"? No, partly because during the course of any long term study we will learn some things between the beginning and end of it.
We would have asked different questions in retrospect. (For example, it would have been very helpful if the different kinds of fats had been studied, but the state of nutritional thinking at the time was that fat=bad, period.) Also, the study was limited to post-menopausal women. And yet, the scope and quality of the research design were unprecedented for a study of its kind. To ignore this fact, as some media reports advocate, or to give equal time to the critics, as many did (making it seem as if there were two equal sides), does not do justice to the science conducted. The vast majority of media reports that I read, heard, or saw included a stern warning against giving up on low fat diets. (typical example) The message was clear: "Put down the mayonnaise jar and no one will get hurt."
Did you know that not one major health organization recommends the type of low fat diet in the study? The women in the study were encouraged to eat a diet with 20% of the calories coming from fat. Recommendations from the American Heart Association, the National Cholesterol Education Program, the American Cancer Society, the USDA, and the American Diabetes Association mostly go up to 35% of calories from total fat, if they make a recommendation at all. There is a simple reason for this: reducing total dietary fat has not been shown to be helpful in the general population. It was hoped that this recent study would be definitive, and provide evidence that it is indeed helpful to lower fat intake. But this did not turn out to be the case.
Does this mean there aren't some people who would benefit from a low fat diet? No, undoubtedly there are. No one diet is best for all people, which may explain some of the "null" results in diet studies - there could be different groups within the data who respond in opposite ways, averaging out to zero. But there are many studies which show positive outcomes for low carb diets in terms of health risks, and most of the low carb diets studied were higher in fat than average.
A few more thoughts about current diet science, especially in regards to those of us whose bodies don't tolerate starches and sugars well:
Interpreting science is not easy. Not only do we need knowledge of the field being investigated, of statistics, and of research design, but we need to do battle with the trickiest traps of all, which are in our own heads. There is a great tendency in all of us to criticize the studies that don't support our own views, and go easy on the ones that do. Scientists try to devise the best research they can to collect objective data, but no study is perfect, and anyone can pick it apart to suit their own biases.
The responsibility falls on the media to portray studies in an objective a light as possible, especially where it affects people's health. Unfortunately, science writers also have their biases, and often need to contend with presenting a piece of writing in a way that will "sell".
There are many issues that determine the importance of a study, including the design, the execution, and how "preliminary" it is. These issues are very difficult for the public to understand without help. A headline from a very preliminary study with few subjects may get the same kind of press as a long-term, well done study. And critics of two studies may be given equal weight as well. It's no wonder much of the public has given up on science as it pertains to their health.
The recent research about low fat diets and the risk for breast and colon cancer, heart disease, and stroke is a case in point. This was a very large-scale and well-controlled study. Is it "the final word"? No, partly because during the course of any long term study we will learn some things between the beginning and end of it.
We would have asked different questions in retrospect. (For example, it would have been very helpful if the different kinds of fats had been studied, but the state of nutritional thinking at the time was that fat=bad, period.) Also, the study was limited to post-menopausal women. And yet, the scope and quality of the research design were unprecedented for a study of its kind. To ignore this fact, as some media reports advocate, or to give equal time to the critics, as many did (making it seem as if there were two equal sides), does not do justice to the science conducted. The vast majority of media reports that I read, heard, or saw included a stern warning against giving up on low fat diets. (typical example) The message was clear: "Put down the mayonnaise jar and no one will get hurt."
Did you know that not one major health organization recommends the type of low fat diet in the study? The women in the study were encouraged to eat a diet with 20% of the calories coming from fat. Recommendations from the American Heart Association, the National Cholesterol Education Program, the American Cancer Society, the USDA, and the American Diabetes Association mostly go up to 35% of calories from total fat, if they make a recommendation at all. There is a simple reason for this: reducing total dietary fat has not been shown to be helpful in the general population. It was hoped that this recent study would be definitive, and provide evidence that it is indeed helpful to lower fat intake. But this did not turn out to be the case.
Does this mean there aren't some people who would benefit from a low fat diet? No, undoubtedly there are. No one diet is best for all people, which may explain some of the "null" results in diet studies - there could be different groups within the data who respond in opposite ways, averaging out to zero. But there are many studies which show positive outcomes for low carb diets in terms of health risks, and most of the low carb diets studied were higher in fat than average.
A few more thoughts about current diet science, especially in regards to those of us whose bodies don't tolerate starches and sugars well:
- Make no mistake about it, a low fat diet is, in an essential sense, a high-sugar diet. Starches start breaking down into sugars in our mouths. The reason the American Diabetes Association started saying it was OK for diabetics to eat some sugar wasn't that sugar is so great, but the finding that our bodies treat starch and sugar the same way. Therefore, there was no good reason to recommend one over the other.
- It is likely that the very worst foods for all of us are those that are high in carbs AND fat, like donuts and French fries. A diet that is high in both sugar and fat is the very worst of both worlds.
- If a low fat diet is working for you, there's no need to change! But if it isn;t, the current evidence shows you don't need to fear adding healthy sources of fat to your diet.
Source...