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Sleep loss linked to weight gain in teens -

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LISA MILLAR: They might be accused of lazing around, but now it seems the amount of sleep a
teenager gets could contribute to their weight problems.

A study by the University of South Australia found that if teenagers didn't sleep enough,
particularly on school nights, they were more likely to be overweight or obese.

Nine to 12-year-olds should be sleeping at least 10 hours a night and teenagers at least 8.5 hours.

The lead researcher Professor Tim Olds says the findings show that its vital parents try to enforce
curfews and regular sleep patterns in their children.

He's speaking to Nance Haxton in Adelaide.

TIM OLDS: The first time in Australia, we surveyed over the course of about five years, a little
more than 4,000 children, we got data on 9,000 days that they lived, so we had a look at their
complete use of time.

I guess one of the most striking things was this association between the risk of overweight and
obesity and sleep duration, so the kids who slept less were more likely, much more likely to be
obese or overweight.

Now, that's been found in a number of studies, just in the last few years in different countries,
this is the first Australian study, certainly for a long time.

But one of the really striking things was that it was true on certain days but not on other days,
so the big differences between the amount of time that overweight kids slept and lean kids slept
was particularly on Sunday nights, was very strong there, but it was less marked on holidays, on
Saturdays where there is virtually no difference across the weight categories.

NANCE HAXTON: Could there be a causal link here? Could the obesity actually be causing the poor
sleep patterns?

TIM OLDS: It's possible, that's what people thought for a while, that things such as sleep apnoea,
you know, that these kids had trouble breathing and that kept them awake, that certainly doesn't
seem to be the case of our study.

Firstly, because it only happens on certain days, it doesn't happen on holidays, or school...
Saturdays, it only happens on school days and on Sundays.

Secondly because it runs right across the weight spectrum, so the very lean kids sleep much, much
more than normal weight kids and obese kids sleep much, much less than normal weight kids.

So it looks as if it goes the opposite direction, it's the poor sleep or the low duration sleep
which is causing the obesity.

NANCE HAXTON: So what's really the next step from here? What lessons can be learnt from this study?

TIM OLDS: Most importantly is that kids, particularly older adolescents, are accumulating sleep
deficit, over the school days, the school week, if we were to even out the sleep, so the same
amount each night, then they need to be getting one hour more sleep on each of the school nights
and this intermittent sleep deprivation, even with the catch up sleep doesn't protect them against
the risk of overweight and obesity, and probably doesn't protect them against the risk of the other
things associated with poor sleep as well.

NANCE HAXTON: Does the study look at why the poor sleep could be causing this obesity?

TIM OLDS: Our study doesn't but there's pretty strong evidence from other studies, laboratory
experiments which show that when kids or adults are sleep deprived, you get a deregulation of
hormones which control appetite, in particular you get a sharp increase in a hormone which
stimulates appetite, and a decrease in another hormone which suppress appetite, so it just
increases hunger, and particularly hunger for energy dense food.

NANCE HAXTON: So really parents should be trying whatever way they can to encourage their children
to sleep more - ultimately?

TIM OLDS: I think the words whatever way they can are important because it is difficult, it's
difficult particularly with older teenagers for parents to get them to bed on time.

We've looked at what kept kids up, those who had late bedtimes, and therefore got less sleep, they
don't stay up watching television, they actually watch less television, they stay up talking to
each other, doing homework, part-time work, listening to music, things of that sort.

It's a very difficult issue for parents, but the take home message is you should really try to
enforce those curfews, the evening curfews.

LISA MILLAR: Good luck parents. That was Professor Tim Olds from the University of South Australia
speaking to Nance Haxton.