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 With TV, a minimum five-hour-a-day habit increased the odds of
obesity by 78 percent compared with teens who didn't have TV time,
the study found. Such heavy use of other screens was tied to a 43
percent greater risk of obesity, researchers report in the Journal
of Pediatrics.
"The landscape has changed so quickly with regards to how much we
all use mobile screen devices and computers," said lead study author
Dr. Erica Kenney, a public health researcher at Harvard University
in Boston.
"We have known for years now that spending too much time watching
television contributes to a higher risk of developing obesity among
kids, mostly because watching too much TV can lead to an unhealthy
diet," Kenney added by email. "We see similar associations between
other screen device use and diet, physical activity, and obesity
risk as we've seen in the past for TV."
To assess how screens large and small influence the risk of obesity,
researchers looked at nationally representative survey data
collected in 2013 and 2015 on 24,800 adolescents in grades 9 to 12.
Nearly 17 percent of youth said they watched no TV on weekdays,
while 7.8 percent said they watched five hours or more daily.
Nearly one in five teens in the study spent at least five hours a
day using smaller screens during the week.
The survey also asked how many sugary drinks teens consumed and
inquired about teens' height and weight.
More than 25 percent of boys and about 20 percent of girls reported
consuming at least one soda or other sugar-sweetened beverage a day.
Approximately two-thirds of boys and three-quarters of girls said
they didn't get daily exercise.
Overall, 14 percent of the teens in the study were obese.
After adjusting for age, sex, race and ethnicity and other time with
tiny screens, TV viewing was associated with significantly higher
odds of consuming one or more sugary drinks and an increased risk of
obesity.
More time with other screens was independently linked to higher odds
of insufficient sleep, drinking more sugary beverages and
inactivity.
The study can't prove that television or time on smaller screens
causes obesity, however.
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It's also possible that excessive screen time was caused by obesity,
inactivity or fatigue rather than these things being caused by too
much time with TVs, smartphones or tablets, the authors note.
Some previous research has found TV causes obesity and that kids who
cut back on television can improve their weight, said Dr. David
Hill, a researcher at the University of North Carolina School of
Medicine and chair of the American Academy of Pediatrics Council on
Communications and Media.
The role of other screens has been less clear, with at least one
study suggesting only passive TV watching affects obesity risk,
Hill, who wasn't involved in the current study, said by email.
"This study helps us understand that the link between obesity and
media use may extend to other types of screens," Hill said.
This connection may be at least in part due to ads teens see for
unhealthy foods, Hill added. Decreased sleep is also tied to
obesity, and too much screen time is known to interfere with the
amount and quality of sleep teens get.
"We encourage parents to work with kids to examine what they need to
accomplish in a day to be successful: how much sleep should they
get, when should they eat, how much time do they need for homework,
exercise, and family activities," Hill said. "Screen media time
should then fit in around those activities or complement them rather
than displacing them."
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