Exercise Leads to a Deeper Sleep

Exercise promotes the most rejuvenating component of sleep. Slow-wave sleep, also called Stage 3 sleep or delta sleep is the deepest stage of sleep from which it's hard to rouse an individual. We call this sleep "slow-wave sleep" because when we measure the brainwaves, quite literally the frequency of the waves is very slow, and the waves are very tall and deep.

While we don't always know why, slow-wave sleep is the special component of sleep. It is what gives us a sense of feeling restored in the morning and when we miss this sleep, we feel this in our joints and muscles – that familiar flu-like feeling of just not having had enough sleep.

In a recent study,athletes were exposed to a noise stimulus, not loud enough to wake the subject but enough to produce an interruption in the electronic architecture of their sleep. The changes in sleep architecture are measured by looking at brainwaves. We call these events EEG arousals: the person doesn't wake up but his or her brainwaves change. Anything can cause these events – snoring, a crying baby, pain, the sound of a telephone, even heartburn. In the study non-athletes (people who were identical in every way except for the fact they were not intense, habitual runners) were exposed to the same noise stimulus.

The researchers found that the athletes, despite being exposed to stimuli that clearly interrupted their sleep (as measured by changes in their brainwaves) woke up feeling refreshed. On the other hand, the average person who did not exercise in the same way woke up feeling terrible even though they were exposed to the same noise. What accounts for the difference? One reason may be that the athletes had more slow-wave sleep and this was somehow protective and resulted in a feeling of restoration in the morning.

Another benefit of exercise concerns its ability to speed up our metabolism and in the process elevate the body temperature deep in our core. We burn a lot of energy while engaged in exercise, even if we are just walking briskly and this energy generates heat. It takes the body hours to cool down by tiny degrees in order to return to our resting baseline. This cooling of our body temperature invites sleep.
This means that if you exercise at the right time you can fall asleep faster. The important thing is to make sure not to exercise too close to bedtime. If we do, it takes too long for the body's temperature to cool down and sleep actually takes longer to arrive. Plus we feel too energized to feel sleepy.

Our lives are more hectic than ever and to keep up and stay healthy we need to spend more time in slow-wave sleep. Finally, a growing number of innovative tools are available that can help measure, monitor and improve our sleep. Some of them even make sleep more fun.

Source: USA Today 7/22/11

Pressure to be Thin Can Result in Sleep Loss

Some people may lose sleep over the pressure to be thin -- especially young white girls who are being pushed by female friends to lose weight or stay skinny, according to a new study.


"There is a significant amount of research in other areas regarding pressure on adolescent females to minimize body weight, but this pressure as it relates to sleep health is a less-explored topic and its consequences are mostly unknown," said the study's principal investigator, Katherine Marczyk, a doctoral student in clinical health psychology and behavioral medicine at the University of North Texas in Denton, Texas. "These results are important as this discovery could be one of the first steps in this research," she explained in a news release from the American Academy of Sleep Medicine.

In conducting the study, which was to be presented Tuesday at the annual meeting of the Associated Professional Sleep Societies in Minneapolis, researchers asked 789 Texas middle-school students, all females and averaging 12 years of age, to describe how much pressure they felt to lose weight and be thin.

The girls also pinpointed the sources of this pressure, which included peers, family, friends and the media. Researchers then assessed the girls' quality of sleep to measure how this external pressure to be skinny affected how much sleep they got.

The pressure the girls felt to be thin from girlfriends as well as from the media significantly predicted sleep duration, accounting for 4.5 percent of the difference in how much sleep the girls got.

That discrepancy in sleep duration jumped to 6 percent among white girls (about 60 percent of the study's participants) who faced pressure to be skinny from their friends, the investigators found.

The study authors added that losing sleep could put young girls at risk for other health problems, including increased anxiety and depression.

Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

Source: Health Day, 6/14/11

Sleep Deprived Teens Crave Carbohydrates

Daytime sleepiness is associated with an increased craving for carbohydrates among teens, according to new research.

The study of 262 high school seniors in New Jersey found that their desire for carbohydrates increased with the severity of daytime sleepiness. The likelihood of having a strong craving for carbs was 50 percent higher among those with excessive daytime sleepiness.

The researchers also found that students with strong cravings for carbs were more likely to have depression (34 percent) than those with little or no desire for carbohydrates (22 percent). Students with major depression were nearly three times more likely to have a strong craving for carbohydrates.

"This is one of the first studies in a high school population to show a linear relationship between carbohydrate craving and sleep deprivation," principal investigator Dr. Mahmood Siddique, a clinical associate professor of medicine at Robert Wood Johnson Medical School in New Jersey, said in an American Academy of Sleep Medicine news release.

Sleep plays a major role in regulating appetite and metabolism, Siddique noted in the news release.

"This study is important given the rising epidemic of obesity among teens as well as increasing metabolic syndrome and diabetes among young adult populations," Siddique said. "This study highlights the importance of diagnosing sleep deprivation as a risk factor for obesity among young adults. Those who are depressed and sleep-deprived may be at special risk for obesity."

The study was to be presented Tuesday at SLEEP 2011, an Associated Professional Sleep Societies meeting in Minneapolis.

Most teens require a bit more than 9 hours of sleep a night to feel alert and well-rested during the day, according to the American Academy of Sleep Medicine.

Research presented at meetings is considered preliminary until it is published in a peer-reviewed medical journal.

Source: Health Day 6/16/11

Does Late Night Eating Cause Weight Gain?

A link between late-night eating and weight gain has been debated for years. But though many dieters suspect a connection, it has not been borne out in studies.

Most of the research on the matter has been carried out in animals, and with mixed results. A 2005 study of primates at Oregon Health & Science University found that late-night meals did not lead to extra weight gain; whether consumed at 10 a.m. or 10 p.m., a calorie was just a calorie.

But a study on adult men and women, published in April in the journal Obesity, has added support to the claim that eating late does have a greater effect on the waistline.

In the study, researchers followed the sleeping and eating patterns of 52 people over seven days. About half the subjects were “late sleepers,” meaning the midpoint of their sleep cycles was 5:30 a.m. or later. The others were “normal sleepers,” whose midpoints were before 5:30 a.m.

At the end of the study, the scientists found that the late sleepers had higher body mass indexes, typically downed more calories at dinner, and ate fewer fruits and vegetables. The late sleepers also slept fewer hours, a habit that is generally linked to weight gain. But even after adjusting for these and other variables, the scientists discovered that eating after 8 p.m. was associated with a higher body mass index, suggesting that late-evening calories are, for some reason, more hazardous to your weight.

THE BOTTOM LINE

Recent studies suggest that eating at night may in fact lead to more weight gain, though it’s not clear why.

Source: Anahad O'Conner NY Times Health 5/16/11

The value of sleep -- again!

NEW YORK (Reuters Health) - Getting too little sleep might prevent dieters from losing as much body fat as they otherwise would have, a small study suggests.

The findings, published Monday in the Annals of Internal Medicine, add to evidence that sleep habits play a role in weight regulation. They also suggest that people embarking on a weight-loss plan may want to make sure they are catching enough shut-eye each night, researchers say.

The study included 10 overweight men and women who lived in a sleep lab for two separate two-week periods. During both, they were kept on the same calorie-restricted diet; but for one period, the participants slept for 8.5 hours per night, while during the other, they got 5.5 hours.

Researchers found that the dieters lost the same amount of weight under both conditions -- just under 7 pounds, on average. But during the sleep-restricted period, they mainly lost muscle rather than fat.

When participants got 8.5 hours of sleep, more than half of their weight loss came from shedding fat; when they got 5.5 of sleep, only one-quarter of their weight loss came from fat -- translating to a 55 percent reduction in fat loss.

Instead, the majority of people's weight loss during the sleep-restricted period came from lean body tissue, which refers to muscle and any other body tissue that is not fat.

"So they lost the same amount of weight, but the composition was different," said senior researcher Dr. Plamen Penev, an assistant professor of medicine at the University of Chicago.

Successful dieters always shed a certain amount of muscle, Penev noted in an interview, but ideally one wants to limit that loss in favor of shedding excess body fat. Insufficient sleep, the current findings suggest, might interfere with that.

The study has a number of limitations. Besides its small size, it also looked only at short-term weight loss. More research is needed to see how sleep duration might affect dieters' body composition over time, Penev said.

It's also unclear how well these findings from a tightly controlled sleep-lab setting might translate to the "real world," according to Penev.

Still, the findings do add to a body of research linking sleep habits to body weight. A number of studies have found that self-described "short sleepers" -- typically defined as those who get less than 6 hours of sleep each night -- tend to weigh more or gain more weight over time than people who get seven to eight hours of sleep per night.

Those studies do not, however, prove that sleep differences are the reason for the weight differences. Small sleep-lab studies such as the current one help researchers zero in on the effects of sleep itself.

Lab studies have suggested, for example, that sleep loss may alter people's levels of the "hunger hormones" leptin and ghrelin. Leptin is secreted by fat cells; low blood levels of the hormone promote hunger, while increases tell the brain that body is full and encourage calorie burning. Ghrelin is secreted by the stomach to boost appetite.

In their study, Penev and his colleagues found that under the sleep-restricted condition, participants reported greater hunger during the day compared with the 8-hour sleep condition -- even though they consumed the same number of calories during both periods. They also had higher blood levels of acylated ghrelin, one form of the appetite-boosting hormone.

This, Penev said, raises the question of whether, outside the tight control of the lab, the sleep-deprived dieters would have eaten more.

"The study suggests that if you are trying to lose weight by restricting your calories, it may be more difficult if you are sleep deprived," Dr. Shahrad Taheri, of the University of Birmingham in the UK, told Reuters Health in an email.

As for how much sleep is enough, "I don't think at this stage we can recommend a specific number of hours of sleep, as sleep is very individualized," said Taheri, who co-authored an editorial published with the study.

"But what we can do," Taheri added, "is pay more attention to our daily routines of eating, physical activity, and also sleep."

Penev agreed that there is no one-size-fits-all prescription for sleep. He suggested that people try to notice how much sleep they generally need to feel refreshed the next morning; for some people that may be 6 hours, for others it may be 8.

Both Penev and Taheri said that more studies are needed in real-world settings. According to Penev, a study might, for instance, follow patients at a weight-loss clinic to see how their typical sleep habits correlate with their weight-loss success.

As for why fewer hours in bed may cause the body to preferentially lose muscle over fat, Penev said he and his colleagues can only theorize. Their guess is that the extra waking hours increase the need for glucose (sugar) in the brain and other parts of the nervous system -- and they get that extra fuel from breaking down muscle.
Source:Mon, Oct 4 2010
By Amy Norton