Wednesday, May 4, 2011

Sleep deprivation leads to obesity

I could think of hundreds of things to blame and a thousand reasons why I haven’t got the chance to post anything this past year, but it’s mainly because I was so pre-occupied with the over-demanding school-life, I can’t think of anything good to write.

You can say I’ve been experiencing a “blogger’s-block” this past year.

But, today a very interesting scientific paper that I read for my Chronobiology class has really struck my attention and has given me this longing urge to write again.

As most of you might have experienced, especially when your level of education gets higher, the demands of school works increase. There seem to be disproportionality between the amount of work you’re given and the amount of time you’re given to do the work. Thus, requires you to sacrifice a huge amount of your time in order to reach a certain deadline.

You feel like the times that you usually use to prepare and eat your breakfast/lunch/dinner, take a shower, clean your apartment, participating in social events, for instance, would be better invested to catch up with your assignment’s deadline. Sometimes, it leads us to even do some drastic measures from consuming caffeine and/or energy drinks at 11 PM to stay up late or to not sleep at all.

Which brings me to this controversial, half a million dollar, scientific research done by Frank A. J. L. Scheer, et al., in 2009.

“Adverse metabolic and cardiovascular consequences of circadian misalignment”

[yes, these are one of the many “fancy” scientific words that I have to deal with in my four years worth of education]

Sleep deprivation, mostly experienced by shift workers, is highly associated with increased risk of obesity, diabetes, and cardiovascular disease.

This paper basically discusses the molecular level of what’s happening in the body when people are sleep deprived for a period of time.

For the study, they took 10 adults where they are somewhat forced to eat and sleep at a particular time frame for 10 days. They were given 4 “isocaloric meals” within 28-hour-“day,” instead of the normal 24-hour-day, which what usually happens when we are sleep deprived (sleeping at 4AM instead of 12AM –--4 hour shift from our normal circadian period).

Heart rate, blood pressure, oxygen consumption, respiratory exchange ratio, heart modulation, brain activity during sleep, and core body temperature (by injecting a rectal temperature at all times ...sounds gory, I know) were monitored daily.

Blood fluids were also taken daily to observe how certain chemicals in the body react to the 28-hour-day cycle. The following are the six chemicals measured and their behavior within 24 hour:

- Leptin: gives the feeling of satiety after a meal.
Lowers during the early morning and peaked before going to bed (which explains why we feel hungry in the morning and feel sleepy after a full meal)

- Epinephrine and norepinephrine: (adrenaline hormones) increases heart’s activity. Lowers before going to sleep and fluctuates during the day.

- Glucose: all the carbohydrates and sugars that we consume are all breakdown into this small glucose molecule. After consumption, glucose will be broken down by insulin.

- Insulin: breaks down glucose. Found in very high level after a meal.

- Cortisol: convert stored glucose and fats in the body to produce more energy. Peaked after waking up and lowest before going to bed.

As shown in the graph, misalignment between the normal expression of the chemicals tested (green) and the expression after forced 28 hour cycle (red) occurred.

There is less expression of leptin when the sleep phases are misaligned (upper left graph). As explained previously, low leptin in the body means it will signal the brain to feel hungry and so made us to consume more meal than we normally do.

Additionally, sleep deprivation is also associated to high expression of glucose AND insulin (bottom left graph). Meaning that there is less insulin sensitivity in the body that result in less glucose (carb and sugars) molecules being broken down. A long exposure to such condition could lead to type 2 diabetes, where the insulin hormones have pretty much exhausted their ability to break down any glucose. ---A very significant result from this paper.

The level of norepinephrine, which is associated to increasing heart rates, also increase (middle-right graph). Which explains the higher blood pressure in sleep deprived individuals that might lead to cardiovascular diseases/abnormality later on.

Such experiment is very costly (~$500,000) and it involves isolating human subjects in a laboratory setting for a couple of days, forcing them to adapt to an unusual sleep cycle, basically turning them into “lab-rats”, in which might be very controversial for some people. I figure this kind of study will not be done very often, but the results are really worth sharing, especially for those nocturnal homo sapiens out there.

One thing to be taken out from this really long blog is that


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