NCPA - National Center for Policy Analysis


August 15, 2008

By 2010, 33 percent of American men and 38 percent of American women will obese.  By 2020, obesity prevalence rates will rise to 40 percent for men and 43 percent women, says Christopher Ruhm of the National Bureau of Economic Research (NBER).

According to the National Health Examination Survey (NHES 1) and various National Health and Nutrition Examination Surveys (NHANES), obesity is defined by a body mass index, or BMI, above 30, and morbidly obese is defined as having a BMI of about 40.  To reach this level, a 5'5" woman must weigh more than 240 pounds.

  • From 1960 and 1980, there was little change in the body weight distribution of the U.S. population; however, measured BMI grew 50 percent faster and growth was disproportionately strong among the most overweight.
  • After 1980, the prevalence of people with a BMI above 35, 40 and 45 tripled, quadrupled and quintupled, respectively, suggesting that the fraction of people who are morbidly obese will reach six percent of men and 13 percent of women by 2020.

But what has caused this increase in massive overweight?  According to researchers, excessive body weight grows with age for both men and women, and it is inversely related to socioeconomic status (SES):

  • High SES individuals have higher incomes, are more physically active, smoke less and are lighter.
  • Of those in the highest SES group, 1.9 percent are obese at age 18 and 19.6 percent are obese at age 40.
  • Of those in the low SES group, 4.6 percent are obese at age 18 and 31.3 percent are obese at age 40.

Ruhm claims that current population-wide health campaigns to reduce growth in overweight and mild obesity will be less effective in combating severe obesity.  Instead, additional strategies focusing on the heaviest people will be necessary to reduce severe obesity.

Source: Christopher Ruhm, "Current and Future Prevalence of Obesity and Severe Obesity in the United States," National Bureau of Economic Research, Working Paper No. 13181, June 2007; Ruhm and Charles Baum, "Age, Socioeconomic Status and Obesity Growth," National Bureau of Economic Research, Working Paper No. 13289, August 2007

For Ruhm text:

For Ruhm and Baum text:


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