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20
U.s. childhood obesity rates
Percent
10
2–5 years
6–11 years
12–19 years
0
1963−
1965
1966−
1970
1971−
1974
1976−
1980
1988−
1994
Year
Kids getting bigger
Health surveys by the U.s. centers for Disease control and Prevention have documented a
steady rise, beginning around 1980, in the proportion of children ages 2 to 19 who are obese.
soURce: cDc
1999−
2000
2001−
2002
2003−
2004
2005−
2006
2007−
2008
first isolated in the late 1970s. Obesity
rates began to climb at about the same
time, with the Centers for Disease
Control and Prevention documenting
increases starting around 1980.
About 30 percent of obese adults
carry antibodies against adenovirus-36,
while about 10 percent of normal-weight people do, Atkinson and others
have shown.
The 10 percent of lean people with
antibodies against the virus may have
gotten infected recently and not yet
gained weight, or they may have had a
mild infection that never reached fat
cells, Atkinson speculates. He discounts
two studies that failed to show a link
between the virus and body weight on
the basis of those studies’ methods —
one involved military subjects, for exam-
ple, who have incentives to control their
body weight.
Back Story | an epidemic of hypotheses
obesity has risen dramatically in the United states and many other countries
during the past 30 years. a combination of increased calorie intake and decreased
physical activity is the most obvious explanation, but other factors may play a role
as well. a team of researchers led by David B. allison of the University of alabama
at Birmingham considered some of those possible contributors in a 2009 paper in
older mothers
studies have shown that the offspring of
older mothers are more likely to be obese;
birthrates have increased since the 1970s
among women 30 and older.
air-conditioning
It takes energy both to keep cool in hot
weather and warm when the mercury drops.
some researchers have proposed that
increasingly climate-controlled lifestyles have
made people soft in more ways than one.
medication
certain antidepressants, birth control drugs
and other medications that have become
more common in recent decades produce
weight gain as a side effect.
Less sleep
sleep deprivation leads to metabolic changes
that foster weight gain; epidemiological
data suggest that sleep duration has fallen
steadily over the past century.
environmental contaminants
the increase of endocrine-disrupting chemicals in the environment over the past few
decades has raised a number of concerns,
including the possibility that the compounds
might interfere with hormones that regulate
metabolism.
