Between 1960 and 2008, the prevalence of obesity in US adults increased from 13 to 34 percent, and the prevalence of extreme obesity increased from 0.9 to 6 percent (NHANES surveys). This major shift in population fatness is called the "obesity epidemic".
What caused the obesity epidemic? As I've noted in my writing and talks, the obesity epidemic was paralleled by an increase in daily calorie intake that was sufficiently large to fully account for it. There are two main sources of data for US calorie intake. The first is NHANES surveys conducted by the Centers for Disease Control. They periodically collect data on food intake using questionnaires, and these surveys confirm that calorie intake has increased. The problem with the NHANES food intake data is that they're self-reported and therefore subject to major reporting errors. However, NHANES surveys provide the best quality (objectively measured) data on obesity prevalence since 1960, which we'll be using in this post.
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