A trend for children and adolescents to
stay up later and sleep less may be linked
to rising levels of obesity, according to
a review of existing research published.
Bristol University researcher Shahad Taheri
said televisions, computers, mobile phones
and other gadgets should be banned from children's
bedrooms to enable them to get a good night's
sleep.
Writing in the journal Archives of Disease
in Childhood, Taheri said there was increasing
evidence that shortened sleeping times result
in metabolic changes that may contribute to
obesity, insulin resistance, diabetes and
heart disease.
A UK study published last year indicated
that insufficient sleep in infants aged 30
months was associated with obesity by the
time they reached the age of seven.
Taheri said this suggested that sleep loss
at a young age may alter the body's mechanisms
that regulate appetite and energy expenditure.
Limited sleep is also a problem for teenagers,
whose need for sleep increases during the
critical years of adolescent development.
Other research, published by Taheri in 2004,
found that adults sleeping only five hours
had almost 15 percent higher levels of ghrelin
-- a hormone released by the stomach to signal
hunger -- than those managing eight hours.
The same group of short sleepers also had
more than 15 percent less Leptin, a hormone
produced by fat tissue when energy levels
are low.
Children waking up tired from not enough
sleep were also likely to take less physical
exercise, adding to the likelihood of putting
on weight, Taheri said.
They would miss the beneficial effects of
physical activity, not least its tendency
to lead to better sleep.
"Sleep is probably not the only answer to
the obesity pandemic," Taheri said.
"But its effect should be taken seriously,
as even small changes in energy balance are
beneficial."
He said children should observe regular sleeping
and waking times, avoid large meals at bedtimes
and have a quiet dark bedroom that was neither
too hot nor cold.
Adolescents should be allowed to sleep in
longer at weekends, but no more than two to
three hours beyond normal waking time, as
this disrupts the body's internal clock.
