Sunday, April 22, 2007

David Friedman on Obesity and Rising Incomes

From Milton Friedman's son David Friedman's blog, his latest posting "Obesity: A Conjecture."

Humans evolved in an environment where food was costly, fat scarce, sweetness a useful signal that fruit was ripe. We are designed by evolution to put on weight when we can as a precaution against future famines and to favor fat and sugar when we can get them. In a world where food is inexpensive and plentiful we are inclined to overeat, in particular to eat more fat and sugar than is good for us.

The obvious explanation of the increase in obesity is that real incomes around the world have been trending up for decades. Now poor people in the U.S., and increasingly in poorer parts of the world, can afford to eat all the calories they want. Since all the calories they want represents more than what they require, the result is that they get fat.

Watch a map graphic that shows obesity (BMI) rising in the U.S. from 1985 to 2003 (takes a few seconds to load).

In a very interesting previous post, David poses the "restaurant puzzle:" A restaurant provides two different products: Food and a place to eat it. Both are valuable, both are costly to the restaurant. Yet restaurants price only the food. The table is free, however long you use it. Why?

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