Tuesday, June 12, 2012
Sleep is Important to Maintaining a Healthy Body Weight....Again
You may recall that I recently wrote about a study showing that sleep may affect the expression of "obesity genes." Today, I read about two other recent studies once again highlighting the link between sleep and overall health/weight.
According to the first study, conducted at Columbia University, when your brain is sleep-deprived, you are more likely to crave junk food. This study used an MRI to compare brain activity in 25 volunteers after getting a good night's rest and again after a night with four hours of sleep. The researchers ran scans while showing the subjects various images of unhealthy and healthy foods. When participants were sleep-deprived, the parts of their brains associated with craving and reward were more active than when they had more sleep, particularly when looking at the images of unhealthy foods. One hypothesis is that a tired brain is looking for an energy pickup as though it were food deprived. Other recent studies may lend credence to these findings, showing that those who are sleep-deprived tend to snack more and gain more weight. Scientists are still trying to determine the possible hormonal and appetite factors that trigger these effects.
The second study, conducted at UC Berkeley, showed that higher order brain functions associated with decision-making are inhibited in those who are sleep deprived, which in turn affects the food choices a person makes. This study was similar to the above in using MRI imaging to determine 23 participants' desires for various foods after being well rested versus being awake for twenty four hours. After being awake for the extended period, participants expressed a stronger preference for unhealthy foods. However, not only were subjects' brains tested for heightened pleasure-seeking activity (as in the above study), but also for decision-making activity. The researchers found that pleasure-seeking activity was not increased, but decision-making activity was diminished, and this may have played a greater role in the ability to weigh healthy versus unhealthy choices.
It sounds like both studies say that sleep deprivation affects food choice, but one attributes this to craving/reward and the other to decision-making (but not craving/reward). So why the difference? Well, one thing to remember is that these were both fairly small studies, so more extensive work needs to be undertaken to draw definitive conclusions. Another consideration, pointed out directly in the article, is that there could be a difference depending on the amount of sleep deprivation; in the Columbia study, participants had four hours of sleep, whereas in the Berkeley study, subjects had no sleep. Perhaps both craving/reward and decision-making play a role in food choice, but decision-making impairment becomes more pronounced relative to the reward centers of the brain as sleep deprivation increases. Right now, there is no concrete information on whether this theory is correct, but it is certainly worth exploring. As mentioned above, both studies still need additional confirmation with future research.
Although we should read these results as very preliminary and wait to see what future research either confirms or disputes, we can still observe that both studies in some way support past research showing a link between sleep and weight. So once again, the lesson is, take care of your body with some rest!
Image credit: http://www.healthytimesblog.com/2011/03/5-amazing-facts-about-sleep/