It might begin to sound redundant, all these posts about sleep and all but what can I say, if when you look outside the only thing you feel like doing is napping until next spring…anyhoo, since we are awake let’s try do something useful: LEARN.

What about? sleep and eating habits. What does one have to do with the other, I will tell you in a minute. Not that long ago there came a study in which they found a correlation between the lack of sleep and obesity when analyzing the sleeping patterns and living conditions of a german population. However, at that time there was no clue -other than hypothetical- as to why.

Now, and after reading a piece on Psypost I can tell you.

It was known for quite some time that sleep deprivation causes a number of changes in certain prefrontal areas of the brain which are important to determine the salience of an stimulus for an individual, and that in this context would be important when making a decision about which food to choose (for instance, a delightful smell plus an appetizing appearance: GO!). Another piece of information that was already in place was that lack of sleep also affects the amigdala and the ventral striatum, areas which are intimately related to emotional responses like fear or anxiety, and that also play a role in the motivation to eat, specially when the stimulus -the food item- is very salient -attractive-.

From this starting point, what a bunch of researchers from the University of Berkeley (USA) did was to test with the help of an fMRI scanner whether lack of sleep causes changes to what we eat and also how does our brain react when facing one type of food or another.

The 23 guinea pigs of this study were -human- healthy subjects that were scanned both after a night of good sleep and after an all nighter (no sleep at all), so really sleep deprived. At both times and while on the scanner they were shown a series of images of food items of varied caloric content, ranging from the healthy fruits and veggies to the evil and delicious muffins, hamburgers and fries, and were asked how much they’d like to eat each of those. After the test, the experimenters rewarded their guinea pigs with their most wanted food choice. Isn’t that nice?

In general their findings can be summarized as a general decrease in the activity of the control areas, those prefrontal regions of the brain, when the people were sleep deprived, whereas the activity compared to a resting state -after a good night sleep- was increased in the amigdala, the more “emotional” region, and because of the inhibition of the prefrontal-controlling areas, when we haven’t rested enough we are more prone to self indulge in cravings.

Which kind? Like a pothead with the munchies we’d just go for all those things we should keep the farthest, the hypercaloric not very healthy friends: hamburger, ice-cream or chips. In all these people they observed an increased preference for hypercaloric foods after a sleepless night, but curiosly the degree of preference was higher the more dramatic they considered subjectively their lack of sleep to be. So if you are a pathologic insomniac probably one sleepless night won’t affect you or your eating habits much.

Despite knowing now that we might get obese if we don’t sleep well because we eat what we shouldn’t we still don’t know WHY it is that these are the kind of things we want to eat. One hypothesis is that we eat these high calorie foods to compensate the activity of those waking hours where we should be resting, even though we go the extra mile and eat as if we were going to run a marathon, from there the obesity. But there are also doubts as to whether this effect will not depend as well on the time of the day, since a lot of the hunger-saciety hormones operate under a circadian rythm, and also if different people will react differently -remember that this study was performed in young, healthy, lean subjects and we know that’s quite far from representative of today’s society, i’m afraid-.

Whatever the case, this is a very interesting study as it opens the door to a better understanding of the changes our XXI century way of life is impinging on our biology, not only on our time tables but on our waists!  Now…off to bed. And leave that croissant where I can see it 😉