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Statistics Often Use Self-Reported Weight & Height, Which May Be Flawed

May 2, 2006 -- Obesity may be more common that previously thought in the U.S.

In the Journal of the Royal Society of Medicine, researchers note that national obesity statistics typically rely on self-reported weight and height, which are often wrong.

Those inaccuracies often make people sound lighter or taller than they actually are, write Majid Ezzati, PhD, and colleagues. Ezzati works at the Harvard School of Public Health.

Self-reported weight and height don't always match reality, so U.S. obesity statistics are too low, Ezzati's team argues.

The researchers recalculated America's obesity statistics, adjusting for those errors. The result: The nation's obesity estimates went up.

Corrected Obesity Statistics

Obesity is defined as a body mass index (BMI) over 30, according to the CDC.

In 2002, 28.7% of men and 34.5% of women in the U.S. were obese, Ezzati and colleagues estimate.

The uncorrected estimate for that year indicated that 16% of men and 21.5% of women were obese.

Ezzati's team based their corrections on data from two large, national surveys of U.S. adults:

  • Behavioral Risk Factor Surveillance System (BRFSS): Given by telephone
  • National Health and Nutrition Examination Survey (NHANES): given in person, with some participants measured and weighed afterwards

Ezzati and colleagues compared BRFSS and NHANES data for similar years. They found that people tended to report their height and weight more accurately in person than over the phone, but that all self-reports generally missed the mark.

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