Thursday, August 7, 2008

How the Media Contribute to our Health Problems

The New York Times just published an article called "The Overflowing American Dinner Plate", in which they describe changes in the American diet since 1970, the period during which the obesity rate doubled. Bill Marsh used USDA estimates of food consumption from 1970 to 2006. Predictably, he focuses on fat consumption, and writes that it has increased by 59% in the same time period.

The problem is, we aren't eating any more fat than we were in 1970. The US Centers for Disease Control NHANES surveys show that total fat consumption has remained the same since 1971, and has decreased as a percentage of calories. I've been playing around with the USDA data for months now, and I can tell you that Marsh misinterpreted it in a bad way. Here are the raw data, for anyone who's interested. They're in easy-to-use Excel spreadsheets. I highly recommend poking around them if you're interested.

The reason Marsh was confused by the USDA data is they have a column in the "fats" spreadsheet called "total fat". But "total fat" is a misnomer, because it doesn't include fats from meat and milk. What it reflects is primarily concentrated fats like vegetable oil, butter, lard and shortening. That's what has increased by 59%, and it's almost exclusively due to increased use of industrially processed vegetable oil (butter and lard have decreased). Total fat has remained the same because we now eat low-fat cuts of meat and low-fat dairy products to make up for it!

Another problem with the article is it only shows percent changes in consumption of different foods, rather than absolute amounts. This obscures some really meaningful information. For example, grain consumption is up a whopping 42%. That is the largest single food group change if you exclude the misinterpreted fat data. Corn is up 188%, rice 170%, wheat 21%. But in absolute amounts, the increase in wheat consumption is larger than corn or rice! That's because baseline wheat consumption dwarfed corn and rice. We don't get that information from the data presented in the article, due to the format.

So now that I've deconstructed the data, let's see what the three biggest changes in the American diet from 1970 to 2006 actually are:
  • We're eating far more grains, especially white wheat flour
  • We're eating more added sweeteners, especially high-fructose corn syrup
  • Animal fats from milk and meat have been replaced by processed vegetable oils
Wheat + sugar + processed vegetable oil = fat and unhealthy. Sounds familiar, doesn't it? This NYT article is just another example of how superficial journalism can really obscure the truth.

1 comment:

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