Did you want fries with that data?

I've mentioned the good work of Sandy Szwarc over at Junkfood Science before. She's just posted two articles about the findings of the dietary intervention study that is part of the ongoing Women's Health Initiative. Here is Part One and here is Part Two. It's fascinating. You want the details? Go over to Sandy's place, but here's a quick summary:

The Women's Health Initiative study itself is huge, and was set up to examine a large number of assumptions and hypotheses. In this particular case, researchers were able to look at the effects of "healthy eating" on a wide range of health problems, including cardiovascular disease, a variety of invasive cancers, and weight loss. Earlier, smaller studies had found correlations between "unhealthy eating" and all of these health issues, suggesting there might be a cause-and-effect thing going on.

And given our willingness to ascribe virtue to "healthy eating," I think we've all (scientists and the rest of us) taken it as pretty much a given that eating virtuously will protect us from cancer, heart disease, obesity, and moral decay. This particular study was designed to get the numbers to back that up. Well, maybe not moral decay, as such. But certainly, if health risk can be attributed to personal choices, then we can blame sick people for their problems, right?

The deal was this: a very large group of women were taught the precepts of "healthy" eating, and most were remarkably compliant throughout the study period (which was about 8 years). An equally large group, matched to the first in age range, socioeconomic status, ethnicity, and so on, served as a control group and was allowed to eat whatever they wanted. There were in fact real, statistically significant differences between the diets of the two groups: the "healthy eaters" ate much less fat, much more fiber (including whole grains and vegetables) and fewer calories overall than the control group.

The differences at the end of eight years? Extremely minimal, and not even remotely statistically significant. The two groups had very similar incidences of heart disease, cancers, and obesity. Some of the women in the "healthy eating" group lost weight initially, but had gained most of it back by the end of the study.

There were some suggestions in the data that some of the cancer risks, for example, changed a little over time; it would be interesting to see a longer study period. I think that there are some folks who would maintain that the "healthy" diet was not restrictive enough. And there are others who have been saying all along that dietary changes are not by themselves sufficient. But what's most fascinating is how the media and some of the researchers alike are grasping at these tiny differences as if they are a sure ticket to good health. And, of course, virtue.

Again, go check out Sandy's posts: Part One and Part Two. She's got links, statistical explanations, you name it.