Researchers find teen
dieting associated with weight gain and obesity
BY MITCH LESLIE
Teenage girls who diet are
more likely to become obese than their non-dieting peers,
according to a new Stanford study. Seemingly paradoxical,
the findings jibe with research on adults and argue for a
national weight education program, the researchers say.
Scientific research on the
connection between dieting and weight loss has given
conflicting results, possibly because many studies rely
on the potentially biased testimony of dieters
themselves. Some studies merely asked questions like,
"Did you lose weight when you were on a diet?"
and never put anyone on a scale. Moreover, few
researchers have examined the relationship between
dieting and weight during the teen years, when obesity
often begins.
Led by Eric Stice, PhD, a
Stanford postdoctoral fellow during the study and now an
associate professor of psychology at the University of
Texas, researchers tracked the weight and dieting habits
of 692 teenage girls from 9th through 12th grade. Once a
year, each girl had her weight and height measured and
then filled out a general health questionnaire. Included
among the questions were several asking whether the girl
was currently dieting or exercising to lose weight, had
ever used laxatives, vomiting or appetite suppressants to
control weight, or had ever fasted or been a binge eater.
The study incorporated
several precautions to encourage accurate answers. First,
the researchers weighed the girls instead of accepting
their reports of their own weight.
In addition, the study was
blinded to prevent bias from coloring their answers --
the girls were told only that they were participating in
a survey of behaviors and attitudes, not a study of
weight control. In past dieting research where scientists
revealed their aims, the pounds seemed to drop away --
and to stay off. But in the few blinded studies, dieting
has proven ineffective or, even worse, seems to lead to
weight gain.
As the researchers write
in the December issue of the Journal of Consulting and
Clinical Psychology, overall the girls gained weight
steadily during the four years, at an average rate of
about 3 pounds per year. The rate of obesity also rose
from 16 percent to 21 percent.
Girls who had resorted to
extreme weight-loss measures like laxatives and appetite
suppressants were more likely to gain weight, as were
those who had engaged in binge eating. Dieting, laxative
and appetite suppressant use, and exercise for weight
loss also greatly increased the likelihood of becoming
obese, the analysis showed.
The results must be
interpreted cautiously, says co-author Chris Hayward, MD,
associate professor of psychiatry and behavioral
sciences. "We are not saying dieting per se causes
weight gain." Rather, Hayward explained, the
analysis merely detected an association between weight
gain and dieting that is not yet explained.
One possible explanation
is that the girls may think they are dieting but aren't
actually reducing their eating enough to make a
difference. Another possibility is that the girls who
resort to dieting or the more extreme weight loss methods
are already prone to obesity -- for genetic or
environmental reasons, Hayward said.
To discourage teens from
trying extreme and unhealthy behaviors, Hayward and
colleagues envision a national educational campaign along
the lines of the successful public-health campaign
against smoking.
Other Stanford authors on
the paper include postdoctoral fellow Rebecca Cameron,
PhD; professor of psychiatry and behavioral sciences C.
Barr Taylor, MD; and associate professor of medicine Joel
Killen, PhD.
Grants from the National
Institutes of Mental Health, the National Institute for
Child Health and Development, the Stanford Center on
Adolescence, and the W.T. Grant Foundation supported the
work. SR
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