But those who logged eight hours or more in bed each night also showed a bigger fat gain, although it was less substantial than that seen in "short sleepers."
On average, short sleepers showed a 32 percent gain in visceral fat, versus a 13 percent gain among those who slept six or seven hours per night, and a 22 percent increase among men and women who got at least eight hours of sleep each night.
A similar pattern was seen with superficial abdominal fat. Even when the researchers considered factors like calorie intake, exercise habits, education and smoking, sleep duration itself remained linked to abdominal-fat gain.
The study does not prove that too little or too much sleep directly leads to excess fat gain. But the findings support and extend those of other studies linking sleep duration -- particularly a lack of sleep -- to weight gain and even to higher risks of diabetes and heart disease.
Sleep is a powerful force on your overall health, including your tendency to gain excess weight. In this latest study, sleep duration was linked to gains in abdominal fat even after researchers accounted for other factors that could influence weight, such as calories consumed and exercise habits.
What this means is that if you’re not taking your sleep needs seriously, you could be unknowingly sabotaging your weight. This is true not only if you sleep too little, but also if you sleep too much.
Why Does Too Much or Too Little Sleep Cause Weight Gain?
The physiological functions of virtually all organisms are governed by 24-hour circadian rhythms. Your circadian clock is an essential time-tracking system, which your body uses to anticipate environmental changes and adapt to the appropriate time of day.
Your circadian rhythm has evolved over hundreds of generations to align your physiology with your environment, and your body clock assumes that like your ancestors, you sleep at night and stay awake during daylight hours.
If you confuse the situation by depriving yourself of enough hours of sleep, or even eating meals at odd hours (times at which your internal clock expects you to be sleeping), you send conflicting signals to your body.
One way this occurs is by altering levels of important hormones linked with appetite and eating behavior. When you are sleep deprived, your body decreases production of leptin, the hormone that tells your brain there is no need for more food. At the same time it increases levels of ghrelin, a hormone that triggers hunger.
In one study, researchers found people who received only four hours of sleep a night for two nights experienced:
- 18 percent reduction in leptin
- 28 percent increase in ghrelin
Also, the sleep-deprived subjects in the study seemed to eat more sweet and starchy foods, rather than vegetables and dairy products. Researchers suspected these cravings stemmed from the fact that your brain is fueled by glucose (blood sugar); therefore, when lack of sleep occurs, your brain searches for carbohydrates.
In short, sleep deprivation puts your body into a pre-diabetic state, and makes you feel hungry, even if you’ve already eaten.
The new study above also found that sleep habits directly influence weight gain around your abdominal area. This is the type of fat linked to heart disease, type 2 diabetes, strokes and other chronic diseases, so it’s a matter that goes way beyond aesthetics.
Sleeping too much is also a risk factor for weight gain, and this may be due to a less active lifestyle or even depression that is resulting in too much sleep (and unhealthy lifestyle habits). One study showed that people who slept for nine or 10 hours every night were 21 percent more likely to become obese over a six-year period.
How Much Sleep is Just Right?
For most people the struggle is how to get enough sleep, rather than trying to avoid sleeping too much. But if you could sleep as much as you wanted, what would be the ideal amount?
Generally, it’s recommended that you get at least eight hours of sleep a night. But this is based on the notion that our ancestors slept around nine hours each night, and therefore we should too. But according to Professor Jim Horne of the Sleep Research Centre, this is a myth.
In reality, this misguided belief was based on a 1913 study that found children aged 8 to 17 slept for nine hours a night. Adults may have slept less. So according to Horne, it’s perfectly possible for some adults to thrive on five, six or seven hours of sleep a night.
However, sleep researchers have also found that it takes just a single night of sleeping only four to six hours to impact your ability to think clearly the next day. So the research is really all over the place.
The truth is, there really is no magic number of hours that’s right for everyone.
Your Basal Sleep Need
Your age and activity level will determine your sleep needs to some extent. Children and teens, for instance, need more sleep than adults. However, your sleep needs are individual to you. You may require more or less sleep than someone of the same age, gender and activity level.
Part of the reason for the difference has to do with what the National Sleep Foundation (NSF) calls your basal sleep need and your sleep debt:
- Basal Sleep Need: The amount of sleep you need an a regular basis for optimal performance
- Sleep Debt: The accumulated sleep lost due to poor sleep habits, sickness, environmental factors and other causes
Studies suggest that healthy adults have a basal sleep need of seven to eight hours each night. However, if you haven’t been sleeping well and have accumulated a sleep debt, you may still feel tired even if you’ve slept a full seven or eight hours one night. If you have a sleep debt, you may be especially tired at the times when your circadian rhythm naturally dips -- such as overnight or in the mid-afternoon.
Once you have a sleep debt, especially one that’s the result of chronic sleep deprivation, it can be difficult to get back to your basal sleep need, so the key is to try and get enough sleep so that you feel well-rested in the morning on most (if not every) nights of the week.
Top Tips for Staying Well Rested
If you are having trouble sleeping, please do not ignore the problem or simply wait for it to go away. You need quality sleep just as much as you need food, water, and pure air -- and there are very simple methods to help you get yours.
Please read my comprehensive sleep guide 33 Secret’s to a Good Night’s Sleep for my full set of recommendations, but to start, make certain you are exercising regularly.
A Stanford University Medical School study found that after 16 weeks in a moderate-intensity exercise program, subjects were able to fall asleep about 15 minutes earlier and sleep about 45 minutes longer at night. However, don't exercise too close to bedtime or it may keep you awake.
Next, address the emotional component of insomnia by using the Meridian Tapping Technique/Emotional Freedom Technique (MTT/EFT). MTT/EFT can help balance your body's bioenergy system and resolve some of the emotional stresses that are contributing to your insomnia at a very deep level. The results are typically long lasting and the improvement is remarkably rapid.
Also be sure that your sleeping environment is comfortable and conducive to sleep. This includes keeping the temperature cool, adding in some white noise if you need it and making sure your room is pitch-black.
If there is even the tiniest bit of light in the room it can disrupt your circadian rhythm and your pineal gland's production of melatonin and serotonin. For this reason, I highly recommend adding room-darkening drapes to your bedroom, or if this is not possible wearing an eye mask to block out any stray light.
Again, you can read my full set of recommendations in 33 Secret’s to a Good Night’s Sleep, but these are a few to get you started. In addition, you can also try these eight natural sleep remedies for times when sleep is especially difficult.