Map of life expectancy at birth from Global Education Project.

Wednesday, April 20, 2005

The Inexplicable Being of Fatness

If there's one thing CDC is very good at, it's confusing the hell out of people. Now they have achieved new heights of public bafflement, something I had thought impossible.

On the same day that they come out with a twelve-pyramid, on-line interactive new and improved version of what us oldsters used to know as the four major food groups,* they issue a massive recalculation and retraction of their previous claims about fatness and mortality. Maybe being too fat is just the seventh leading cause of death, not the second, and maybe they set the official overweight line too low.

On the one hand they have an excuse -- epidemiology is a delphic science, which answers our questions in riddles. On the other hand, they have no excuse. Their job is to communicate clearly and truthfully with the public, and they might as well let the oracle speak for itself rather than further mucking up its muddy pronouncements.

Here's the problem. When we try to analyze the real world factors that affect people's health and longevity, they come all bundled together in most imaginable combinations. If you just look at the relationship between people's body fat content, or even worse though much more convenient, their Body Mass Index and their health, you'll see associations but you won't have learned anything about causation. Some people are slim because they smoke 2 packs a day, or have digestive disorders, or even cancer. People who are healthy and energetic, in our modern food rich environment, are likely to take in more calories than our ancestors on the African savannah, and just maybe, if we could control for everything else, we'd conclude that's a little bit bad for them, but we just can't do it. In the modern world, their other advantages over a portion of the very slim -- fewer people among them who are already sick, getting enough of all the essential micronutrients even though our diets aren't usually of the highest quality, a tendency toward sociability and conviviality, you name it -- overcome the disadvantages of a few too many fat cells.

Epidemiology really can't sort all this out. I would say that it's not a question of where to draw the official "overweight" line, but that the very concept of such a line that is wrong. The story is just more complicated than that. But most people aren't going to use a multiple regression equation to figure out how to live their lives anyway. What the average person needs to know is simple, even if you didn't learn it in kindergarten. It's not good to have a fat tummy. Be as active as you can. Base your diet on vegetables, whole grains, and fruits, throw in some fish and, if you must eat meat, keep it lean (range fed), non-fat dairy or other sources of calcium, and use vegetable oil (not palm oil but definitely olive oil) instead of lard or butter. Don't eat trans fats, which is easy if you stay away from junk food, and save eating sugar for very special occasions. For the vast majority of people, if you stay active and keep to those principles, you don't need to count calories. Just eat when you're hungry and stop when you aren't. Save the pyramids for your mystic practices.

This means doing most of your shopping in the produce department and steers you away from most products of the biggest "food" manufacturers. (The stuff that Frito-Lay and CocaCola produce is not actually food.) That makes it hard for the federal government to say in English. But it ain't rocket science.

*As I recall from my college studies, these were hohos, cheesesteaks, pizza, and beer.

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