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Can writing your thesis make you crave chocolate?

Friday, March 05, 2010 Posted by Peter Janiszewski, PhD
It has been rather silent on Obesity Panacea as of late. While we have up to this point been able to work around each other’s busy periods and thus regularly contribute to the blog, this time around work ramped up for both of us at the same time. I have spent the majority of this semester working on my PhD thesis, an effort which went into overdrive during the last 3 weeks.

Basically, I had been glued to my laptop reading countless studies and writing my thesis for about 10-14 hrs per day. I can now finally say that I have finished writing my thesis, and yesterday all 219 pages of it, including references to over 250 studies, were finally printed. The plan is for me to defend the thesis sometime mid –late April.

During the past 3 weeks, as I was working away night and day on the thesis, I noticed a significant increase in the craving of sweet snacks – things that I normally have no taste for. All I could think about was chocolate, pastries, or lattes from Starbucks. Being the nerd that I am, I tried to find some research on this topic to see if what I experienced was a normal consequence of extended mental work.

It turns out a colleague of mine, Jean-Phillipe Chaput, has actually done a study testing this very notion.

JP and colleagues eloquently explain in the introduction to their paper,

“From a physiological standpoint, the biological requirements of physical and mental work are not the same because mental work represents a type of activity that relies on brain, which utilizes glucose for its energy metabolism as opposed to physical activity, which solicits skeletal muscle metabolism that relies on fat metabolism to a significant extent.”

In other words, when you exercise your muscles you can use sugar, fat, and even protein as a fuel source, but when you exercise your brain you can only use glucose. This would seem to support my sensation of increased sugar craving while working nonstop on my thesis.

However, in the study they carried out, including 14 females doing 45-min sections of either rest, or 2 different mental tasks, while the energy intake during a buffet meal post task was significantly higher after the mental tasks, they failed to show a specific preference for sweet foods. However they did find that levels of blood sugar and insulin (the hormone that controls sugar levels) were much more variable, fluctuating wildly, during the mental tasks than during the rest session.

So this small study suggests that while mental work certainly elevates hunger, and caloric intake, it does not seem to have a specific effect on intake of sweets. However, it is possible this study was not powered to sort out such differences – a larger study, and one that also includes men is obviously necessary. I’m putting my money on increased sweet cravings.

Have a great weekend,

Oh, and our big surprise is still coming – it has just taken us a while to get it together amidst the heavy workload.


Chaput, J., Drapeau, V., Poirier, P., Teasdale, N., & Tremblay, A. (2008). Glycemic Instability and Spontaneous Energy Intake: Association With Knowledge-Based Work Psychosomatic Medicine, 70 (7), 797-804 DOI: 10.1097/PSY.0b013e31818426fa

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5 Response to "Can writing your thesis make you crave chocolate?"

  1. Kate Porter Said,

    Congratulations on getting your thesis published! If my experience is any guide, getting the thesis office to approve all the formatting is a lot harder than actually defending the thing :-) But good luck with your defense, anyway.

    I also think that there are a couple of other reasons why that particular study might not be applicable to your situation:
    1. The tasks tested were of very short duration--45 minutes (as opposed to 10-14 hr/day).
    2. Consumption was monitored only AFTER the tasks were completed. My experience is that when I'm done with a crazy task, I generally want to just sleep--it's during the task that I get (as you said) cravings for chocolate and pastries.
    3. There's mental tasks, and there's mental tasks. I'm wondering whether the kinds of mental challenges given to psych study participants are qualitatively similar in any way to active reading and writing of a dissertation. I know there are some kinds of tasks that definitely drive me to chocolate a lot sooner than others.

    Posted on March 5, 2010 at 2:38 PM

  2. Peter Janiszewski, PhD (Cand.), MSc Said,

    Thanks Kate - I appreciate it! In truth, 2 of the 3 studies making up my thesis have been previously published - I believe I have actually blogged about both of them on Obesity Panacea.

    Regarding the formatting - I totally agree. Even to get the thesis to this point was a nightmare - Word has some serious limitations. I remember having a lot of trouble with the final formatting with my MSc thesis as well - I had to resubmit like 3 times and over such minutiae.

    Great points regarding the study! You helped fill in a number of important limitations that I simply had no energy to get after - still recovering from nonstop writing:)

    Have a a great weekend Kate!

    Posted on March 5, 2010 at 3:46 PM

  3. Brandon Said,

    If I recall it correctly, writing my thesis made me crave death not chocolate. I guess we all have different preferences.

    Joking aside, I find your research summaries very interesting. Keep it up the good work.

    Posted on March 5, 2010 at 3:50 PM

  4. Carolyn Said,

    When my husband was in the final few months of his dissertation and defense he basically stopped eating. I had to beg him to stop reading/writing and eat something. He wasn't tempted by sweets or anything else that I could see. He lost a lot of weight that year. He is naturally very lean and seems to stay that way without much effort.

    What I wonder is why some people can be distracted from eating, which seems to me to be a mission-critical activity to the body, and others (like me) have to be talked away from the table.

    Congratulations on your thesis publication!

    Posted on March 6, 2010 at 6:54 PM

  5. scicurious Said,

    Nice to know I'm not the only one subsisting on chocolate. I just prefer to call it brainfood.


    Posted on March 8, 2010 at 12:53 PM


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We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.


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