Wednesday, November 24, 2010

Preconceptions . . . Again

Maybe it's a waste of time to point out the biased preconceptions one sees in various science journals; most of the intelligent people I assume are the primary readers of this blog can spot them for themselves. But they annoy me so much I can't not point them out.

The latest one occurred in an article titled
"Overweight Primarily a Problem Among Wealthier Women in Low To Middle-Income Countries" and published in the American Journal of Clinical Nutrition.

Researchers at the Harvard School of Public Health reported that in less affluent countries, being overweight is more common among women with higher incomes (they studied only women). In contrast, in more affluent countries like the United States, obesity is associated with poverty.

I think this is intuitively obvious. When it's difficult to get enough food, then only richer people will obtain enough calories to become fat. When food is plentiful but starchy and fatty food is cheaper than meat and vegetables, then the poorer you are, the more apt you are to be fat.

A famous photo of an emaciated boy holding out a bowl and begging for rice, while behind him a fat (by the standards of those days) merchant woman sits among huge bags of rice, illustrates this. The boy isn't counting calories; he's starving.

So initially, I found the study pretty ho-hum. Then I came on this attempt at an explanation:

"The researchers theorize that these findings could be due to a number of factors, including that women in higher income groups are more likely to have diets richer in animal fats than lower-income women."

In other words, they started with the assumption that obesity (and probably all the other ills of a "Western" diet) stem from too much animal fat. So that must surely be the explanation here too.

Couldn't it also be because the richer women were able to buy white bread and jam instead of fiber-filled vegetables the poorer people probably grew themselves?

They do make a couple of other suggestions:

"Also, cultural norms in developing countries may favor fatty body shapes among wealthier women. Richer women are also less likely than poor women to engage in regular physical labor."

I'm sure the difference in physical work does make a difference. But if cultural norms in developing countries favored fatty body shapes among wealthier women (as a sign that you could afford a lot of food), wouldn't you think the same would be true among poor people as well? Wouldn't poor people want to look as if they were rich?

Sometimes the logic in nutrition papers boggles my mind.


  1. This reminds me of something Gary Taubes points out around 16:00 in his grand rounds lecture here: (yes, I know the timestamp ... I did a summary of his talk on my blog!).

    I'm paraphrasing, but Taubes doesn't see this as underfed child and overfed older woman. He doesn't go into detail, but I think the idea is that if you try to fit this data into a preconceived notion (in his case, it's the calorie balance equation), you risk missing the true explanation for the phenomenon.

  2. Thanks, Beth. I don't listen to lectures because they take too long. If you know somewhere that this lecture is written, I'd read it.

    I don't quite understand what Taubes would mean if he said that the child in that picture was not underfed! He's clearly starving. The photo was taken during a famine.