US states underestimate obesity problem

By Amy Norton

NEW YORK (Reuters Health) – The obesity problem in
individual U.S. states appears much greater than official
health surveys have indicated, according to a new study.

The problem, researchers found, is that the telephone
surveys used to estimate states’ obesity rates are prone to
error — namely, that female respondents underestimate their
weight, on average, while men often add inches to their actual
height.

National estimates of the obesity epidemic, however, are
more on target, because the methodology used is different.

It’s estimated that one third of U.S. adults are obese, and
that national statistic is probably a close reflection of
reality, according to Dr. Majid Ezzati, an associate professor
of international health at the Harvard School of Public Health
in Boston.

But, Ezzati told Reuters Health, his team’s findings
indicate that individual states’ obesity levels are “grossly
underestimated.”

The disparity between national- and state-level obesity
estimates stems from differences in how the data are collected
by the Centers for Disease Control and Prevention. Nationwide
data are gathered through the National Health and Nutrition
Examination Survey (NHANES), where respondents are interviewed
in person about their height and weight, and then asked to have
a physical exam.

State statistics are collected via the Behavioral Risk
Factor Surveillance System (BFRSS), which asks respondents to
give their height and weight over the phone.

By comparing information from this survey with data from
the NHANES project, Ezzati and his colleagues found that every
U.S. state’s obesity burden was underestimated.

In 2000, Americans’ phone-survey responses indicated that
nearly all U.S. states had an obesity rate below 24 percent,
according to the report in the Journal of the Royal Society of
Medicine. But when Ezzati and his colleagues “corrected” these
data using NHANES numbers, they found that most states had
obesity rates higher than 24 percent.

Texas and Mississippi had the highest obesity rates among
men, at 31 percent and 30 percent, respectively. Four states –
Alabama, Louisiana, Mississippi and Texas – tied with
Washington, D.C., for the highest obesity rate among women, at
37 percent.

The study found that young and middle-aged women generally
shaved pounds off of their weight when asked over the phone,
while younger adult — particularly men — tended to
overestimate their height.

All of this matters, Ezzati explained, because public
health policies and programs aimed at fighting obesity are
carried out at the state level. So it’s important to have an
accurate picture of each state’s burden. The findings also
highlight the fact that obesity is “very much a Southern
problem,” Ezzati said.

To ensure that state data are more accurate — and that
adequate resources go to the most needy states — Ezzati
suggests that state survey numbers could be corrected in the
same manner he and his colleagues used.

Better still, the researcher said, phone-survey respondents
could be asked at the end of the interview to have an exam to
verify their weight and height reports.

SOURCE: Journal of the Royal Society of Medicine, May 2006.