Zombie by Day, Owl by Night–Why sleeping preference may be problematic for your waistline.

by Paige on February 19, 2013

Ever wonder where the terms lark and night owl came from?

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If you were to ask someone whether or not they would prefer to wake up at 6 AM, it’s likely they will answer with a definitive yes or no. This difference in sleep preference has to do with what scientists call our biological clock. Think about it as what your body wants to do and when it wants to do it.

This is where the night owl and the lark come in: the two classifications of sleepers—the evening people and the morning people. The evening people can stay up until 2-4 AM and then don’t mind sleeping in through the afternoon the following day.  Keep in mind, that night owls exist on a continuum, outside of the 9-5 workday. The morning people are the ones yawning by 9 PM, hitting the sack shortly after, and are rearing to go at the crack of dawn the next day.

For the majority of US adults, the workday starts as early as 7 AM and ends around 5 PM. Only one type of sleeper works really well in this environment, and that’s the morning person. As for the evening people (44% of women and 37% of men, to be exact), this can be problematic. What do you get when you take a night owl and put him into a 9-5 work week?

Sleep deprivation.

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Researchers are finding that sleep deprivation leads to over-compensating on the weekends–something referred to as “social jetlag”. Which just sets you up for another week of sleeping out of your preferred time schedule, and the cycle perpetuates. Not only this, but a study out of the Journal of Current Biology found that those who were sleeping less during the week, and more on the weekends were more likely to be overweight.

Taken together, research suggests that being a night owl and not getting enough sleep during the week means you have a greater chance of gaining a few extra pounds over the years. Tenuous link?

Don’t reach out for those potato chips just yet…

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A study out of the 2013 Journal of Nutrition and Diabetes reported that lack of sleep was significantly associated with an increase in total energy intake in obese subjects. A group of 118 men and women, who had reported sleeping less than 6.5 hours of sleep per night, were followed over 4 years (2007-2011). Sleep patterns and food intake were measured throughout the study period. With just a 30-min deficit in sleep, subjects were predicted to consume 83 calories more per day.

For the night owls who are sleeping less than the recommended 7.5 hours per night during the week, this could suggest some serious calorie packing over the course of the year if not compensated with exercise.

What about exercise, anyway? Lets face it, when you’re tired, the chance of stepping on that treadmill is slim. The thought of pounding your feet against that belt will start to make your head hurt.

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When researchers looked at a group of non-obese adults during a week of sleep restriction (less than 5.5 hours/night), subjects had 31% lower activity levels and spent 24% less time doing intentional exercise when they were tired. It was estimated that these subjects burned about 250 fewer calories per day when their sleep was restricted.

So, the studies are suggesting that how much sleep you get each night and when you get your sleep don’t just affect how you look at that bag of chips and cardio machine, but both can also strongly influence your productivity and mental alertness (which, has been well established).

As the conflict between our biological clock and society’s social clock continues, it presents an interesting challenge for the night owls to adjust to a routine that goes against their innate preference.  Maybe as industry transitions to a more remote and global work force, we will start to see employees becoming more productive and healthier with flexible hours. Perhaps then we will see less of the “zombie” syndrome that appears to be taking over the cubicle world and costing employers up to $1967/employee every year in productivity losses…sounds to me like a public health solution and a better business model.

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 National Sleep Foundation: Waking America to the Importance of Sleep.


Wittmann M. et al. (2006). J. Chron. International. Social Jetlag: Misalignment of Biological and Social Time. doi:10.1080/07420520500545979.

Ronneberg T. et al. (2012). J Current Biology. Social Jetlag and Obesity. doi: 10.1016/j.cub.2012.03.038

Galli G. et al. J Nutr and Diabetes (2013). Inverse relationship of food and alcohol intake to sleep measures in obesity. doi:10.1038/nutd.2012.33.

Penev P.D. (2012). J Clin. Endocrin. & Metab. Update on Energy Homeostasis and Insufficient Sleep. doi:10.1210/jc.2012-1067

Steiropoulos N.E. et al. (2010). J Occup Environ Med. Work Productivity in Obstructive Sleep Apnea Patients. doi: 10.1097/JOM.0b013e3181e12b05.

Rosekind M.R. (2010). J. Occp. & Envir. Medicine. The cost of poor sleep: workplace productivity loss and associated costs. doi: 10.1097/JOM.0b013e3181c78c30

Virginia February 19, 2013 at 8:02 am

Has there been a study to prove that sleep patterns can purposely be altered? You have covered your subject well and in an interesting fashion. It would be hoped that a part of therapy suggestion for the fatigued short term sleeper that exercising calls up more energy. It works for this eighty six year old.

Paige February 20, 2013 at 4:48 pm

Hi Virginia–Great points!

So there have been a lot of studies done on “shift-workers” who have abnormal sleep-wake cycles. It has been shown that these individuals struggle with sleepiness and productivity because they lack quality of sleep when they sleep during the day.
i.e. their internal clock is being forced into a different schedule, and often times this “re-training” of the internal clock doesn’t happen.

In the shift-worker studies I have found, adaptations to different sleep patterns were shown to improve via adjusting the start time of shifts AND the amount of lighting/darkness exposure during shifts and breaks. It was also noted in these studies that there is quite the variability between individuals. Individuals may have the same baseline sleep patterns, but can have very different responses in adapting to different shifts (due to intrinsic sleep properties).

Much of the research is beyond my scope of understanding sometimes, but the concept of this internal clock is fascinating to me. And yes, exercise has been shown to certainly boost natural “feel good” hormones, but it will only go so far for those who are really lacking quality sleep!

Karen February 19, 2013 at 1:31 pm

For someone that has struggled for many years with early morning commutes and workouts in order to be in the office by 7AM, I am now able to listen to my internal clock, work between 10 AM and 7 PM, avoid traffic & coffee hour and enjoy my work week. Being productive and successful in my position has given me the confidence to stop stressing about being at my desk from 8-5. If employees are willing to be held accountable for their productivity, employers have much to gain with a healthier, happier workforce.

Paige February 22, 2013 at 8:49 am

Thanks for sharing Karen–

You’re a prime example of how it is possible to match your internal clock with your external clock. I think employers need to start recognizing this more and make the appropriate changes in order to maximize productivity.

However, for those positions where this isn’t feasible, it certainly makes me appreciate all of the late night “shift workers”. A life time of fighting to stay awake all evening and then not getting the quality sleep during the day..just thinking about it is exhausting!

Andrew Maynard February 19, 2013 at 8:07 pm

What has long interested me is – how does your body know that it’s 6:00 AM, and not 10:00 AM? You’d have thought that you could fool it into thinking that you were getting up late and going to bed late, when in fact you were doing the opposite. Sadly, I know from experience this isn’t the case. But why not, if the amount of sleep you get is the same?

Paige February 21, 2013 at 10:12 pm

Hey Andrew–great questions.

So the body’s biological clock (near the hypothalamus) is sensitive to temperature regulation, hormone secretion, and feeding cycles…all producing this rhythm that continues on a 24 hour period. These rhythms are known as the circadian (day) rhythms. This is what varies within the individual. The most influential factors are the light-dark cycles and the melatonin (sleep hormone secreted when its dark) secretion. In addition, the body’s core temperature has been strongly associated with the body clock (at night your body’s core temp is at its lowest).

It’s been found that outdoor light and melatonin ingestion can indeed help with adjusting your clock. Both work to reinforce each other–bright light will advance your body clock to an earlier time. However, melatonin (when taken in the afternoon/evening) will advance the clock to a later time. Individuals will respond differently when exposed to these two factors depending on their own internal rhythms.

As for the quality of sleep–from what I have read, it seems as though the more cycles of REM (deep sleep), the better. An REM cycle lasts for about 90 minutes. So a 7-hr night sleep is equal to about 5 full cycles. I’m assuming more cycles in one bout is more effective on cognitive function and alertness, but I will have to continue that search on PubMed and report back.

Allyson February 19, 2013 at 11:48 pm

Paige, this is great! I had heard about (and experienced!) the effects of not getting enough sleep, but to see it all tied together here gives a great picture of what can happen to our bodies when our sleep schedules are messed up. I makes me not feel so bad for struggling during my 9-5 days :). I wonder what studies on show about high school students who start school at 7am vs. 10am? It seems like these effects would be even clearer to see with teenagers!

Paige February 22, 2013 at 8:42 am

Thanks Allyson!

Great point–I can remember starting at 7am in middle school, and some classmates really struggled to stay attentive throughout the day. I haven’t looked at any studies that focused on such an intervention, but I will keep my eye out for one.

ZebZ February 20, 2013 at 7:54 pm

From my early teen years delivering the morning paper, to enlisting in the military service out of high school the early bird continued through college and commuting to work, driving the young swimmers to morning swim practices, international travel and now retired the early bird remains the life style. Sleeping late in the morning gives me a headache. Reminds me of the rule on many good things ….. what you miss you can never catch up. Have many friends upon retirement have converted to the night owl, to prove they are in control and not the yankee dollar.


Paige February 22, 2013 at 8:38 am

It’s interesting you say this about your friends, because the majority of older adults actually transition into earlier sleep patterns like yourself (although it sounds like you’ve been a morning person your entire life).

Researchers propose that as we age, the internal clock shifts to an earlier phase of wakening, and the length of sleep time is reduced. Some studies have attributed this to the changes in the onset melatonin secretion (sleep hormone) and a reduction in the body’s propensity to sleep during the night. It seems as though the signals to initiate sleep and the signals to enter deep REM sleep becomes weaker as we age.

Sounds like you’re listening to your own clock and not fighting it–what would be interesting to see is if this shift in sleep preference as we age could explain the need for that habitual afternoon nap…

Thanks for the comment!

Loon February 25, 2013 at 6:06 pm

I believe I read an article about the difficulties primary school students have, whose school-day, here in Germany, starts at eight am. Unfortunately for you, it was in a German newspaper… and I don’t have it on hand anymore.

Ashley Patriarca February 27, 2013 at 6:34 pm

It’s amazing how much difference even a half hour can make. When I wake up at 6:30, as I must do to get to work on time now, I’m groggy for a good few hours after that. It doesn’t matter how much water or caffeine I ingest. If I wake up at 7, I’m sunshiney and energetic all bloody day. I will say, though, that I’m slowly starting to adjust. I now wake up at 7 naturally on the weekend, whether I plan to let myself sleep in or not.

Also, I imagine that part of the reason for the increased waistline is not just the lack of desire for exercise, but also poorer food choices. You’re simply less likely to want to cook and are more likely to go grab something quick from a fast-food place. I know I am on the days that I work late :(

Taylor February 28, 2013 at 9:11 am

Wow! This piece was very informative and interesting. I like how you related humans and our biological clocks to owls and their biological being. I didn’t know that people who sleep less during the week and more on weekends have a higher chance to be overweight, that was an astonishing new fact! Only thing is, I would have liked to see some information about adolescents and their biological clocks with the social effect. One last thing, what are some symptoms of sleep deprivation? Thanks! #SPX9

Angela March 3, 2013 at 6:21 pm

Thanks for the post! I found your links interesting, too, especially the one that discussed ‘chronotypes’. It was interesting to read that these are being recognised and researched.

Angela March 15, 2013 at 4:46 pm

PS: Did you see this study on links between night shifts and (ovarian) cancer? It also features studies of ‘night owls’: http://www.bbc.co.uk/news/health-21790347

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