The Mystery of the Obesity Epidemic: Solved? (Hint: It’s simpler than you think)


Was Grandma Right?

It’s been too long since I last wrote, but I’ve been catching up on my sleep. Why will become relevant after you read this article.

Sleep is something we mostly take for granted as part of our daily lives, much like eating and showering. But why do we sleep? What does sleep do for our minds and our bodies? What happens if we don’t sleep, or if we don’t sleep enough?

For those of you who are interested in these questions, I’d highly recommend that you read the transcript of The Science of Sleep, an excellent piece by 60 Minutes that aired on March 16, 2008. Not only did I learn many interesting facts about sleep, I learned about my own health and how sleep affects it. More on that later.

Why do we sleep? After all, from a survival point of view, sleep is not really a good thing, in the sense that we are unconscious and helpless during sleep. So for sleep to have evolved, then it must serve some vital functions. (I should point out though, that sleep might have survival advantages, since if early humans slept in caves and other sheltered places, sleep would have kept them out of the reaches of nocturnal predators. The folks who didn’t sleep much, and who wandered around all night, probably got eaten!)

One clue of how important sleep is in studies done in the 1980’s with rats. When rats were prevented from sleeping (did they use disco music to keep them awake?) they died after 5 days! Sleep seems to be as important to rats as food.

Let me present a quick primer on sleep. When we sleep, we actually go through multiple cycles of different stages of sleep. These stages are stages 1-4 of non REM (NREM) sleep, and stage 5 which is REM (rapid eye movement) sleep. The key stages are Stage 4, or Delta Sleep, and Stage 5, REM sleep. Stage 4 Delta sleep is the deep restorative sleep where our bodies get rebuilt and restored. Stage 5 REM sleep is when we dream, and it appears that our minds get restored during REM sleep. Typically the whole cycle takes about 100 minutes, and we have 3 or 4 of them each night.

Sleep may play an important role in enhancing memory. One study found that when people learned a new skill in the afternoon, and then were tested after a night of sleep, they did 20-30 percent better than those who were tested after twelve hours, but with no sleep in between the learning and testing. This is fascinating, and jibes with a trick I learned in graduate school. When I would study statistics, I’d always review my notes right before going to sleep. The next morning, the memories of those notes were imprinted magically in my mind.

Sleep also plays a critical role in stabilizing mood. One experiment tested people who were sleep deprived by showing them disturbing images within an fMRI scanner, to look at their brain activation. They found the sleep deprived subjects had a disconnect between the brain’s emotional center (the amygdala) and the part of the brain that controls rational thought (the frontal lobe). So they couldn’t control their emotional reactions. They looked more like psychiatric patients. Of course we all know that sleep deprivation makes us cranky and short-tempered, this explains why.

Another important function of sleep is physical rejuvenation. It appears that Stage 4 sleep is essential here. In the 60 Minutes piece they show an experiment where a young man named Jonathan is deprived of only Stage 4 sleep. Each time his brain waves show Stage 4 sleep, loud sounds are played to bring him out of deep sleep. He gets a normal amount of sleep, but a reduced amount of Stage 4 sleep. After 4 nights of this regimen, this 19 year old is starting to look physically like a 70 year old. His body becomes no longer able to metabolize sugar effectively, putting him temporarily at increased risk for Type 2 diabetes.

Other studies confirm this. After just a few nights of partial sleep deprivation, young healthy people show a metabolic change that is similar to what happens as people develop Type 2 diabetes. They no longer metabolize sugar effectively. They deposit more fat. The hormone leptin, which controls appetite, seems to drop, and they want to eat more.

This is truly astonishing. If relatively short term sleep deprivation can cause such a profound shift in the body’s sugar metabolism, then this may be the key to unlock one of the great medical mysteries of the 20th century: Why obesity has increased so rapidly since 1980? Could it be that the obesity epidemic is really a sleep deprivation epidemic? Could it be so simple? Not junk food, television, lack of exercise, and all of those things that people talk about? Could grandma have been right?

Here’s the clue.

In 1960 a survey of a million Americans showed an average of 8.0 hours of sleep per night. Today similar studies show we are only getting 6.7 hours a night. That’s a drop of 16.25% in less than a generation. And teenagers are the most sleep deprived of all, since they require 9-10 hours of sleep, and most get less than 7 hours of sleep, thanks to ridiculously early school start times. Teenagers may be lacking between 22 percent and 30 percent of their needed sleep.

So we have a plausible explanation for why everyone, even children and teenagers, is getting fatter. Sleep deprivation causes shifts in metabolism, creating a pre-diabetic state, and lowering level of the satiety hormone leptin, which causes us to eat more, and store more fat. Add sugary or high carbohydrate foods, and we get even fatter. Add inactivity, and we get even fatter. The damage begins early, perhaps in early teenage years.

So if we want to lose weight, then the old saw of a healthy diet and plenty of exercise may be wrong. The proper advice is probably lots of sleep, a reasonably healthy diet, and a little exercise. Or since exercise improves sleep quality, sleep, exercise, and diet. Without adequate sleep, diet and exercise are doomed to failure, since even young people may unintentionally be turning their bodies pre-diabetic, which makes it very hard not to gain fat.

So that’s why I haven’t written. After a lifetime of staying up late, and cheating sleep, I’m starting to try to get a solid 8 hours of sleep a night. Already I’ve lost a few pounds, even though I haven’t been exercising much. The other advantage of going to bed earlier is that when you are sleeping you are not eating.

So try it. Get 8 or 8 1/2 hours of sleep a night. And make sure your teenagers get 9 or 10 hours a night. No more websurfing or TV late at night. And write me and let me know if your weight drops as a result.

Now I’ve got to stop writing and go to sleep…

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