As an undergraduate student, I have seen many things, but nothing quite compares to finals week. Perfectly rational students turn into all-nighter pulling zombies who eye the in-library Starbucks like it’s their sole life line to civilization. If you go onto any undergraduate’s Facebook during this time, you’ll see plenty of friends begging not only for the week to be over, but for friends to bring them pizza, Chinese food, a burger and fries, or Mexican lest they potentially lose their prime study spot in the library.

It’s fascinating to watch and wonder why they crave these foods nearly as much as they crave the caffeine that fuels their ability to keep studying.

Two small studies that suggest a link between lack of sleep and cravings for junk food might provide the answer.

Columbia University researchers compared brain activity in volunteers after a period of receiving normal night’s sleep and after a period where they received only four hours of sleep. They then conducted functional magnetic resonance imaging (fMRI) scans while the participants were shown pictures of unhealthy and healthy foods. fMRIs measure blood flow in the brain to see which areas are active.

The areas of the brain associated with pleasure and reward were more active when participants were sleep deprived than when well rested. This effect was even more pronounced when participants looked at pictures of unhealthy foods.

The authors hypothesized to cnn.com that being tired may make you more likely to want junk food because your body wants a fast way to get more energy to get through the day.

But just because you want that fast food meal after working a late shift or that cupcake in the display case during a late night shopping run doesn’t mean you’ll actually eat it, right?

…well, there might be a chance you would. Just like being tired may affect what type of food you want, it may also affect your decision making when it comes to food choices.

A second study suggests that the brain functions that help us make difficult choices, including food choices, may be dulled when we’re sleep deprived.

As reported by diagnosticimaging.com, during the Associated Professional Sleep Societies annual meeting in Boston, researchers from the University of California, Berkeley, presented their new study. The researchers conducted fMRIs on young adults while showing pictures of food and asking them how much they craved them. They repeated the procedure twice, one when the participants had gotten a normal night’s sleep and then a second time when they had been awake for 24 hours.

Lead author Stephanie Greer reported that while this study did not find differences in the reward centers, what they did find was diminished activity in the decision making areas of the brains when students were sleep deprived. In essence, sleep deprivation impaired their decision making skills.

This could explain why people, especially sleep-deprived college students, don’t even blink twice at eating high calorie foods that they might typically shun.

These two studies may also have implications for the purported association between sleep and obesity. It may be no coincidence that average sleep time has been decreasing as society’s collective BMI has been increasing.

So if you find yourself day dreaming at your desk about sugar plums, take a moment and contemplate why. It may just be the sleep deprivation talking.

St-Onge, M. P., McReynolds, A., Trivedi, Z. B., Roberts, A. L., Sy, M., & Hirsch, J. (2012). Sleep restriction leads to increased activation of brain regions sensitive to food stimuli. The American Journal of Clinical Nutrition, 95(4), 818-824.

Durning, M. V. (2013, June 11). fmri connects lack of sleep, desire for junk food. Retrieved from http://www.diagnosticimaging.com/mri/content/article/113619/2081466.

By: Jenny Claire Knight