Demi
Sat, Mar-04-06, 05:22
The Times
London, UK
4 March, 2006
Lack of sleep affects hormones that control appetite. So if you stay tucked up in bed, you may lose weight
If lying in for an extra hour’s sleep each day would be your idea of heaven, how much more perfect would it be if it also meant that you lost weight as well? This might sound like an impossible dream but prepare to suspend your disbelief.
This week, Department of Health officials heard new evidence that sleep and obesity are closely linked — a connection already under the spotlight in America but up until now virtually disregarded in the UK.
We’re sleeping less than we used to. For instance, a survey of the sleep habits of more than a million Americans in 1960 showed that most people slept between eight and nine hours a night. But polls conducted in 2000 by the National Sleep Foundation in the US showed that average sleep duration had fallen to seven hours a night, a similar fall to that in Britain. At the same time, the incidence of obesity has nearly doubled.
At first sight, the two seem unrelated. Why should researchers link two such apparently disparate things as sleep and obesity? Here are some facts that provide clues. When we are sleep-deprived we become voraciously hungry and during times of food starvation we sleep less. This is because the hormones that sharpen appetite and regulate metabolism are modified by sleep. Studies have shown that those who get the least sleep have, on average, the highest body mass index. And, when researchers at the University of Bristol identified eight contributors to childhood obesity, short duration of sleep at the age of 3 was one of them, along with watching too much TV.
Now you might think — quite logically — that the more you sleep, the less you exercise, the more weight you gain. In fact, it’s not that simple, because there’s another player — our hormones. And being sleep-deprived seems to boost the hormones that encourage appetite and reduce levels of those that tell us we’re full.
Dr Shahrad Taheri, of the University of Bristol, is one of the few scientists in Britain examining the apparent link between how much you sleep and how much you weigh. This week, he presented research on the subject to Department of Health officials visiting his obesity clinic in Bristol. And he has just put in a new bid for American research money to investigate whether the teenage obesity explosion is related to the fact that they biologically need so much sleep but modern routines do not allow it.
As Dr Taheri points out, the relationship between sleep and weight isn’t that simple. This is because the body has a finely tuned sense of sleep and wakefulness. If you’re awake, it’s day, and it must be time to eat. If you are asleep, it must be night, so you don’t need much energy and don’t need to eat.
Purely by staying awake, you’re convincing the body that you’re likely to need more fuel. Whatever your activity level, dancing the night away or vegging in front of the TV, your appetite is there. In fact, if you’re sleep- deprived, it actually rises.
Central to this appetite rise are several hormones. A key player is the stress hormone cortisol. Its levels normally rise and fall throughout the day. It normally peaks between about 10am to noon and then falls until it reaches its lowest level at the time you go to bed. But experiments at the University of Chicago have shown that sleep-deprivation causes a rise in cortisol levels. Eve Van Cauter, a sleep researcher, subjected fit young men to six days of sleep restriction (four hours of sleep a night) and found that the normal fall in cortisol was sixfold slower than normal, leading to elevated evening levels of the hormone. Scientists know that having elevated cortisol levels promotes obesity.
Cortisol plays a big part in provoking the munchies when we’re not getting enough sleep. But so do two other hormones that control food intake. Analysing blood samples from sleep-deprived study subjects, Dr Taheri and his colleagues found that two to three hours’ sleep deprivation was associated with about 15 per cent more ghrelin, a stomach hormone that drives appetite, and 15 per cent less leptin.
The less leptin you have, the more your body believes you to be starving. If you are a mouse, that means scurrying about looking for food; if you are a human being, it means a trip to the fridge.
The Chicago group of researchers studied 11 fit 22-year-olds twice. First they restricted their sleep to four hours a night for six days, then, a year later, they extended the same group’s sleep to ten hours a night for six days. On each occasion, they were given the same amount of food. When sleep was restricted, their leptin levels decreased by between 19 and 26 per cent. “The decrease sends an erroneous signal to the brain that more food is needed when, in fact, enough has been eaten,” says Van Cauter.
What does this all mean in practical terms? Well, for a start, if you are dieting, make sure that you get enough sleep. If you are sleep deprived, leptin drops so much that your body thinks you’re undernourished to the extent of about 900 calories a day; imagine how hard it is to resist that degree of hunger. Now imagine that you are trying to reduce your calorie intake further because you are on a diet. Not surprisingly your body thinks you are starving and reacts with soaring levels of ghrelin, making you super-hungry. So sleep-loss bamboozles leptin and ghrelin, making them false reporters of true calorie intake.
The US National Institutes of Health has taken this work seriously and is inviting grants in this area. It is planning sleep-extension studies to investigate what happens to the body if it gets plenty of sleep.
In Britain, we are still deeply sceptical. Dr Taheri thinks this may be because sleep is so fundamental that we each think our own individual experience typical, so skinny men sleeping four hours a night will dismiss this out of hand, as will fat people who sleep 12 hours a night. But it’s the general pattern across the whole population that’s important. As is sleep.
“How much sleep we have affects our IQ, our suicide risk, our chance of substance abuse and our weight,” says Dr Taheri. “If we don’t take it seriously, we will pay the consequences.” Time for a bit more vitamin Z?
Six reasons to have a long lie-in
Sleep deprivation may cause obesity (see main story). A study published in the journal Sleep in 2004 found that those who slept nine hours or more had a significantly lower body mass than those who slept five hours or less.
People have some of their best ideas in bed. A study by the East of England Development Agency found that nearly a third of us think that we have our most creative thoughts when between the sheets.
Sleep may help you to live longer. Researchers from Pennsylvania State University believe that women may live longer than men because they sleep more soundly.
You can solve problems while you’re asleep. Scientists at Lübeck University, in Germany, have found that volunteers who could “sleep on” a number puzzle were much better at solving it than those kept awake.
Sleep may have a protective effect against cancer. Researchers from Stanford University, in California, think that the changing hormone balance of the body as it sleeps may be influential.
Sleep helps you to remember facts. Scientists from the University of Chicago discovered that volunteers who found their recall of memorised words letting them down at night could remember them the next morning if they slept well.
http://www.timesonline.co.uk/newspaper/0,,175-2066767_2,00.html
London, UK
4 March, 2006
Lack of sleep affects hormones that control appetite. So if you stay tucked up in bed, you may lose weight
If lying in for an extra hour’s sleep each day would be your idea of heaven, how much more perfect would it be if it also meant that you lost weight as well? This might sound like an impossible dream but prepare to suspend your disbelief.
This week, Department of Health officials heard new evidence that sleep and obesity are closely linked — a connection already under the spotlight in America but up until now virtually disregarded in the UK.
We’re sleeping less than we used to. For instance, a survey of the sleep habits of more than a million Americans in 1960 showed that most people slept between eight and nine hours a night. But polls conducted in 2000 by the National Sleep Foundation in the US showed that average sleep duration had fallen to seven hours a night, a similar fall to that in Britain. At the same time, the incidence of obesity has nearly doubled.
At first sight, the two seem unrelated. Why should researchers link two such apparently disparate things as sleep and obesity? Here are some facts that provide clues. When we are sleep-deprived we become voraciously hungry and during times of food starvation we sleep less. This is because the hormones that sharpen appetite and regulate metabolism are modified by sleep. Studies have shown that those who get the least sleep have, on average, the highest body mass index. And, when researchers at the University of Bristol identified eight contributors to childhood obesity, short duration of sleep at the age of 3 was one of them, along with watching too much TV.
Now you might think — quite logically — that the more you sleep, the less you exercise, the more weight you gain. In fact, it’s not that simple, because there’s another player — our hormones. And being sleep-deprived seems to boost the hormones that encourage appetite and reduce levels of those that tell us we’re full.
Dr Shahrad Taheri, of the University of Bristol, is one of the few scientists in Britain examining the apparent link between how much you sleep and how much you weigh. This week, he presented research on the subject to Department of Health officials visiting his obesity clinic in Bristol. And he has just put in a new bid for American research money to investigate whether the teenage obesity explosion is related to the fact that they biologically need so much sleep but modern routines do not allow it.
As Dr Taheri points out, the relationship between sleep and weight isn’t that simple. This is because the body has a finely tuned sense of sleep and wakefulness. If you’re awake, it’s day, and it must be time to eat. If you are asleep, it must be night, so you don’t need much energy and don’t need to eat.
Purely by staying awake, you’re convincing the body that you’re likely to need more fuel. Whatever your activity level, dancing the night away or vegging in front of the TV, your appetite is there. In fact, if you’re sleep- deprived, it actually rises.
Central to this appetite rise are several hormones. A key player is the stress hormone cortisol. Its levels normally rise and fall throughout the day. It normally peaks between about 10am to noon and then falls until it reaches its lowest level at the time you go to bed. But experiments at the University of Chicago have shown that sleep-deprivation causes a rise in cortisol levels. Eve Van Cauter, a sleep researcher, subjected fit young men to six days of sleep restriction (four hours of sleep a night) and found that the normal fall in cortisol was sixfold slower than normal, leading to elevated evening levels of the hormone. Scientists know that having elevated cortisol levels promotes obesity.
Cortisol plays a big part in provoking the munchies when we’re not getting enough sleep. But so do two other hormones that control food intake. Analysing blood samples from sleep-deprived study subjects, Dr Taheri and his colleagues found that two to three hours’ sleep deprivation was associated with about 15 per cent more ghrelin, a stomach hormone that drives appetite, and 15 per cent less leptin.
The less leptin you have, the more your body believes you to be starving. If you are a mouse, that means scurrying about looking for food; if you are a human being, it means a trip to the fridge.
The Chicago group of researchers studied 11 fit 22-year-olds twice. First they restricted their sleep to four hours a night for six days, then, a year later, they extended the same group’s sleep to ten hours a night for six days. On each occasion, they were given the same amount of food. When sleep was restricted, their leptin levels decreased by between 19 and 26 per cent. “The decrease sends an erroneous signal to the brain that more food is needed when, in fact, enough has been eaten,” says Van Cauter.
What does this all mean in practical terms? Well, for a start, if you are dieting, make sure that you get enough sleep. If you are sleep deprived, leptin drops so much that your body thinks you’re undernourished to the extent of about 900 calories a day; imagine how hard it is to resist that degree of hunger. Now imagine that you are trying to reduce your calorie intake further because you are on a diet. Not surprisingly your body thinks you are starving and reacts with soaring levels of ghrelin, making you super-hungry. So sleep-loss bamboozles leptin and ghrelin, making them false reporters of true calorie intake.
The US National Institutes of Health has taken this work seriously and is inviting grants in this area. It is planning sleep-extension studies to investigate what happens to the body if it gets plenty of sleep.
In Britain, we are still deeply sceptical. Dr Taheri thinks this may be because sleep is so fundamental that we each think our own individual experience typical, so skinny men sleeping four hours a night will dismiss this out of hand, as will fat people who sleep 12 hours a night. But it’s the general pattern across the whole population that’s important. As is sleep.
“How much sleep we have affects our IQ, our suicide risk, our chance of substance abuse and our weight,” says Dr Taheri. “If we don’t take it seriously, we will pay the consequences.” Time for a bit more vitamin Z?
Six reasons to have a long lie-in
Sleep deprivation may cause obesity (see main story). A study published in the journal Sleep in 2004 found that those who slept nine hours or more had a significantly lower body mass than those who slept five hours or less.
People have some of their best ideas in bed. A study by the East of England Development Agency found that nearly a third of us think that we have our most creative thoughts when between the sheets.
Sleep may help you to live longer. Researchers from Pennsylvania State University believe that women may live longer than men because they sleep more soundly.
You can solve problems while you’re asleep. Scientists at Lübeck University, in Germany, have found that volunteers who could “sleep on” a number puzzle were much better at solving it than those kept awake.
Sleep may have a protective effect against cancer. Researchers from Stanford University, in California, think that the changing hormone balance of the body as it sleeps may be influential.
Sleep helps you to remember facts. Scientists from the University of Chicago discovered that volunteers who found their recall of memorised words letting them down at night could remember them the next morning if they slept well.
http://www.timesonline.co.uk/newspaper/0,,175-2066767_2,00.html