Puberty Comes Sooner for Overweight Girls
Overweight and obesity in young girls appears to speed puberty,
a new study confirms.
But the research also refutes the theory that girls who experience
their first period at a relatively young age are predisposed to
become obese as adults.
Instead, the study suggests that childhood obesity helps drive
both early puberty and adult weight troubles.
For parents concerned about the potential for obesity in their
daughter's future, "the focus should be on the child being overweight
rather than the timing of her first period," said lead researcher
Aviva Must, an associate professor of public health and family
medicine at Tufts University School of Medicine in Boston.
She presented the findings, to be published in the September
issue of Pediatrics, at a special "Back to School" press
briefing on children's health, held Thursday in New York City
and sponsored by the American Medical Association.
According to Must, pediatricians have long noted a correlation
between overweight and "early menarche" (first period) in young
girls. "There are two competing theories as to why this happens,"
One theory holds that excess body fat is a kind of reproductive
signal that a girl is now healthy enough to sustain a pregnancy.
The recent discovery of a fat-cell hormone called leptin "suggests
a mechanism by which that might actually happen," Must said.
The second theory rests on skeletal maturity. "We know that children
who are overweight have advanced bone development -- they grow
faster in all ways, and they are usually taller than their non-overweight
peers," Must said. "That same sort of growth promotion could be
linked to the early onset of the maturational change."
Neither of these theories have yet been proven, however. Another
lingering question has been the association between early menarche
and later obesity in adulthood.
To help solve that issue, Must's team analyzed data from the
Newton Girls Study, which tracked 700 Boston-area girls, all of
whom were first recruited in 1965. The Newton researchers studied
the girls' health and maturation from before their documented
first period through to their 20th period.
In their more recent study, Must and her colleagues contacted
these girls -- now women averaging 42 years of age -- in 1995.
The Tufts team conducted detailed measurements of each woman's
weight and body-fat percentage, and compared that to the timing
of her first period.
"What we found was that maturational timing -- onset of first
period -- was not an important factor for adult obesity, once
we accounted for the earlier overweight [as children]," Must said.
"So, it appears that the timing of menarche is a consequence,
rather than a risk factor for adult overweight."
In fact, women who were overweight before their first period
were 7.7 times more likely to be overweight as adults as women
who were not, the study found.
That means that parents of girls who undergo early menarche --
at 10 or 11, rather than the U.S. average of 12.5 years of age,
for example -- shouldn't necessarily worry that their daughters
will be doomed to obesity in adulthood. Early menarche may "just
be part of normal growth and development for her," Must said.
"It's not a cause for concern nor does it put her at any excess
risk of later overweight."
Parents should be concerned about an overweight or obese child,
however, since it appears that early excess weight gain is linked
to adult obesity, Must said.
Earlier puberty is simply another consequence of that weight
gain, she said, noting that the timing of a first period for American
girls "is down by about 2.5 months from 25 or 30 years ago. We
think that probably has to do with the epidemic of obesity in
children -- that's what's pushing it down."
She said similar trends may be occurring in boys, although because
sexual maturity in boys has no defining event such as menarche,
"it's been a lot harder to study."
Reference Source 101