Obesity rates have more than doubled among U.S. children and
quadrupled among U.S. adolescents in the past three decades,
according to the Centers for Disease Control and Prevention. One in
every three young people is obese.
The authors of the new study looked at how children’s body mass
index (BMI), a measure of weight in relation to height, changed over
time, from age one to age 18. They found being consistently obese
was associated with certain exposures in the womb, and with having
asthma and other problems in adolescence.
Past studies looking at risk factors for obesity and the
consequences of being obese have focused on weight at one point in
time, Dr. Wilfried Karmaus said.
“The main difference to previous studies is that we didn’t assess
obesity at one static moment in time but the development over time,”
Karmaus, from the School of Public Health at the University of
Memphis in Tennessee, said.
He and his colleagues analyzed data from the Isle of Wight birth
cohort, based in the UK and originally designed to study asthma and
They tracked 1,456 infants born between January 1989 and February
1990 until they were 18 years old. Height and weight were measured
at ages one, two, four, 10 and 18 years.
The researchers found children’s BMIs as they grew up fit into four
distinct patterns, or “trajectories.”
As Karamus explained, “We have an early persistent obesity group
which starts very early and you can detect this group before the age
of four years.”
Then there was a “delayed overweight” group of kids who became heavy
a little more slowly, and an “early transient overweight” group in
which kids were heavy as babies, but had a more normal weight when
they were older.
The fourth trajectory included kids who had a normal weight
“These four groups - we can detect them before the age of four
years, this was one of the surprises we had,” Karmaus told Reuters
Health. “The development is probably set in stone by the age of four
About four percent of the children studied fell into the early
persistent obesity trajectory, 12 percent were in the delayed
overweight trajectory and 13 percent were in the early transient
overweight trajectory. Roughly 72 percent of kids fell into the
normal trajectory, according to findings published in the Journal of
Epidemiology and Community Health.
Having a mother who smoked during pregnancy was a strong risk factor
for being in the early persistent obesity trajectory. So was having
a mother who was overweight early in pregnancy, which suggests
children may “inherit” obesity through the type of metabolism they
acquire in the womb, Karmaus said.
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Evaluating the children when they were 18, he and his colleagues
also found that those in the early persistent obesity group had
twice the risk of asthma and higher blood pressure than
The study “provides further evidence to support the importance of
prevention of childhood obesity,” Dr. Youfa Wang told Reuters Health
in an email.
Wang, from the University at Buffalo, State University of New York,
has studied childhood obesity but was not involved with the new
“Overall previous research has suggested that about one-third of
overweight and obese children and about one-half of overweight or
obese adolescents would become overweight or obese adults," Wang
The new findings are consistent with those from earlier studies, he
“Knowing children’s BMI will help parents and children to monitor
their weight status and related health behaviors such as eating and
exercise, and help make related behavioral changes to maintain a
healthy weight,” Wang said.
Suggestions to start childhood obesity prevention very early on may
actually mean that prevention needs to start with the pregnant
mother, Karmaus said.
Parents can also make sure kids themselves are moving around enough
as toddlers, and not wait until they’re older to address weight
“I think it’s important to identify the trajectories early on
because at that time the child’s metabolism may still be plastic and
can be changed, but later in life, obesity prevention is very
difficult,” Karmaus said.
Journal of Epidemiology and Community Health, online June 3, 2014.
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