Over millions of years, our species has evolved as diurnal – we are only active when the sun is out. We are supposed to get up with sunrise and go to sleep with a sunset. Nobody really knows exactly why animals need to sleep, but we do know that even invertebrates, flies, for example, sleep. And no animals, including us, can survive sleep deprivation. Not having sufficient sleep time, 7 hours at least, causes serious problems, affecting your attention, productivity, and metabolism.

Effect on appetite
In one study, folks who were made to only sleep 5 hours had a totally messed up profile of hormones that regulate appetite. Ghrelin, a hormone made by the stomach that acts on your brain to make you feel hungry, was elevated by 15%. At the same time, leptin, a satiety hormone made by fat cells, was about 15% down.

As a result of this, those who do not sleep enough feel hungrier, tend to overeat and consume unnecessary calories. Another reason for overeating when not having enough sleep could be feeling stressed and unhappy. Food, especially one that tastes sweet and is rich in calories, is known to provide a positive reward and make you feel happier. When you are tired and unhappy your cravings to eat are elevated, and you tend to eat more.

Effect on glucose metabolism
Insufficient sleep also messes up glucose metabolism. In those who only slept 4 hours per day in a 5 day experiment, insulin levels were elevated so that insulin-to-glucose ratio was increased. This is characteristic of developing insulin resistance, a signature of diabetes.

Effects of shift work
Those who do shift work at night when we are supposed to be sleeping develop so-called shift work disorder, characterized by fatigue, gastrointestinal problems, and elevated risk for obesity, cardiovascular disease, diabetes and mortality. This is scientifically called “circadian misalignment” messes up important hormones that control metabolism. Leptin, a hormone that signals satiety, was at decreased level, which supposedly can make you feel hungry. Cortisol, a hormone that regulates both sugar and fat metabolism, was elevated at times when it is normally low. Insulin was also elevated – a sign of developing diabetes. Working during your biological night hours is certainly not a good way to make a living.

Effect on weight gain
Because whose who sleep less eat more, they tend to be fatter and sicker. Not sleeping enough also causes weight gain as faster pace.

Over 6 years, those who slept 5 to 6 hours, had twice the rate of weight gain as compared to the average sleepers (7 to 8 hours). Those 5 to 6 hour sleepers had 27% higher rate of obesity, which in turn is a major risk factor for diabetes and heart disease. Weight gain in adulthood is one of the risk factors for many chronic diseases. Individuals who gained from 11 to 22 pounds as adults, had 1.5 to 3 times higher risk of disease (cardiovascular, diabetes, hypertension) than those who kept their weight stable.

Effect on attention and concentration
Working as a teacher I personally know how hard it is for kids to concentrate when classes start at 7:30 and it is still dark outside (which means that they had to get up at 7 or earlier). I struggle as well, but at least I have my huge cup of coffee in the morning. Research shows that starting classes one hour later or 9 am has a significant positive effect on student performance.

Another hazard of insufficient sleep is the risk of motor vehicle crashes and work-related injuries. In developed countries, drowsy driving accounts for about 10% of all traffic accidents. Interestingly, most of them occur between 4 and 6 am, time just before sunrise when we need sleep the most and also in the afternoon hours when tired workers drive home and lose concentration at the wheel.

I also have a couple of personal observations regarding sleep:

It is not easy to go to sleep on time. When I don’t force myself to go to bed, I will usually stay up late. A small dose of alcohol (24oz beer) helps.

Light interrupts sleep. If I wake up and turn the light on, it is hard to go to sleep after that. On the other hand, bright light wakes you up fast. That is probably because your sleep cycle is set by the natural sunlight. I knew somebody who had a timer set in the morning to turn on light in the house. Not a bad idea, especially in wintertime when you have to get up before sunrise.

Insufficient sleep weakens immune system. If I do not get enough sleep for a few weeks, I usually get very sick with a flu or another disease. Then I go back to having enough sleep for a few weeks. Immune system also needs sufficient sleep to function properly. (Note: as I was working of this article, I saw a news story on Yahoo that not having enough sleep doubles risk of getting sick with the flu).

Do we need more sleep during winter time? I tend to need an extra hour of sleep in winter time. This could be due to a shorter or dimmer day during this season. If you are like that, it may be a good idea to elongate your sleep time to 8 hours at least.

While following a sleeping regime alone is not sufficient to make you fitter and healthier, it is a necessary part of healthy lifestyle. Have a solid 7 to 8 hours of sleep every day; go to sleep and wake up at the same time. This will keep you happy, energetic, keep your metabolism in balance, and make you feel eager to be physically active and exercise. Not having enough sleep will mess up your metabolism, break you exercise regime, and cause you to overeat, feel depressed and tired. You will be more likely to lie on the couch and get some rest rather than exercise.

Our society underestimates importance of sleep. Center for Disease Control study has found that about 30% of American workers sleep less than 6 hours per night, which is not sufficient. Most people do not exercise, and are not willing to invest time and effort in their health, so they do not care about sleep either. They think they can get by with a big cup of coffee or a shot of 5-hour energy. And pay a high price later. Getting sufficient sleep it probably the easiest lifestyle change toward better health you could implement. You just need to get serious about it.

The bottom line is:

get at least 7 hours of sleep, avoid night shift work and have a rock-solid sleep regime.


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