Questions dog low-fat futility study
Sargent nutritionist says the sound bites are hard to swallow
Everyone has a personal reason for skipping dessert, avoiding McDonald’s, or ordering movie popcorn without butter. But the results of a landmark study of low-fat diets published last week in the Journal of the American Medical Association appears to deal a super-sized blow to the idea that going low-fat reduces the risk of certain cancers, heart disease, or stroke.
The eight-year, $415 million study was commissioned by the National Heart, Lung, and Blood Institute (part of the National Institutes of Health) and followed about 49,000 postmenopausal women who were randomly assigned to a “low-fat” or a control group.
On average, both groups of women at the outset were eating about 38 percent of their calories from fat, but those in the low-fat group cut their fat intake to between 24 and 29 percent while increasing their consumption of fruits and vegetables. The women in the control group ate whatever they pleased.
In the end, there was no statistically significant difference in the rate of breast cancer, colon cancer, heart attack, or stroke among the women in the two groups. The story was front-page news (“Low Fat Diet Does Not Cut Health Risks, Study Finds,” New York Times, 2/8/06). Paula Quatromoni, a Sargent College assistant professor of nutrition, has some powerful and well-informed opinions of the survey. When it comes to news about nutrition, Quatromoni urges people to read between the headlines.
BU Today: What was your initial reaction to the results of this study?
Quatromoni: After seeing how it was played out in the media, my initial reaction was, oh boy, here we go again. I think the way it’s been played in the media is misleading. There were a whole lot of messages from that study that didn’t make it into the newspaper. It’s a very complicated message and we want to get it into one sound bite, and that doesn’t work sometimes.
So what are some of the messages that were missed?
For instance, the women who were consuming the most fat at the beginning of the study did have significantly reduced risk of breast cancer after switching to a low-fat diet.
Also, one of the first things I learned as an epidemiology student is that if a study comes up with a null finding, there can be many explanations for that — all of those real-life logistical issues that get in the way of research. For example, these women in the low-fat diet group were originally supposed to cut back to eating 20 percent of their calories from fat [from 38 percent], and they couldn’t do it. They ended up between 24 and 29 percent, which means a much smaller difference between them and the control.
And finally, this study was planned more than 10 years ago. The dietary guidance today doesn’t reflect what is in that study. It was outdated. Take the five servings of fruits and vegetables [that the low-fat group was advised to eat]. That’s only one more serving than the control group averaged. The current recommendations are to eat seven to nine servings of fruits and vegetables a day.
Yes, the fact that the low-fat group couldn’t get down to just 20 percent of calories from fat, even with all the sessions with nutritionists, recipes, and other assistance, really was striking. What do you make of that?
One of the things you have to remember is that the 24 to 29 percent was an average number. Some women were able to get down to 20 percent or even lower. People can do it, although it’s a huge commitment and lifestyle change. One of the things this teaches us is that even with the best resources, people live in the real world, where there is a Dunkin Donuts and a McDonald’s on every corner and restaurants that serve huge portions, and that’s just the food environment that we all live in. What this study did show is that we need to get much more clever about the strategies. It has to go beyond getting people motivated and educated personally to make individual behavior changes. A change of social norms has to take place in terms of what is an acceptable way to prepare food and an acceptable portion size to be on my plate.
There’s no hiding the fact that Americans are getting fatter; 15 years ago only four states had obesity rates above 15 percent , according to the Centers for Disease Control. By 2004, 49 states did [no data for Hawaii], and 42 states had rates over 20 percent. Do the results of this study have an impact on efforts to combat that trend and promote healthy eating?
That’s where I think these kinds of headlines can make things more difficult to promote the average person to lead a healthier lifestyle. People just want to throw their hands up in vain and say, why am I doing this, or turn to their partner and say, why are you making me eat like this? The results of this study don’t mean we should abandon low-fat diets and healthy lifestyles. This is one piece of evidence, and even though this was kind of a Cadillac of studies, each study design has its own set of limitations and you have to be willing to take new evidence as it comes along.
What’s some of the other evidence, some good reasons to eat foods that are lower in fat?
For one thing, if you’re eating a high-fat diet, it’s much more challenging to make sure you’re getting all the other nutrients that are really important. High-fat diets tend to be low in fiber and essential vitamins and minerals.
Also, we are in the midst of an obesity epidemic in this country. And it’s not just about adults; it’s about kids too. This generation of kids could potentially be the first generation ever to have a shorter life expectation than their parents. And that’s because of increased risk of diabetes, heart disease, high cholesterol, and high blood pressure linked to obesity. Obesity is independently related to those diseases and risk factors. It’s a link in the chain. Regardless of how you become obese, whether it’s through genetics, a high-fat diet, or a high-glucose diet.
OK, so if people want to get nutrition advice beyond the sound bites, where should they turn?
I think an excellent source of nutrition information is the Web site of the American Dietetic Association. They have nutrition tips of the day as well as lots of material on different topics, such as finding a diet for combating osteoporosis or finding a diet with more whole grains and fiber or vegetarian options. You can also type in your zip code and it will give you a whole listing of dieticians in your area. Certainly the Web sites of the National Heart, Lung, and Blood Institute, the American Diabetes Association, and the American Heart Association are all tremendous educational resources. But I think the best place to turn is the produce aisle of the supermarket. People need to go there more often. And I think checking out the fish counter and the aisle selling whole grains, beans, and low-fat dairy, too.