11 October 2019

Craving junk food after a sleepless night? This is the real reason why

Ever had to face the day on little to no sleep and all you could think about was something sweet, greasy and starchy to eat? There is a good scientific explanation for that.

Sleep deprivation can happen to anyone from time to time. Not only can it affect your mood and concentration, but also your weight. As explained by science, this has to do with the production of ghrelin, the hormone that makes you hungry – but it also makes you more likely to crave junk food.

We tend to think it might be because your body needs more energy – but a new study established that it involves your nose, or olfactory system.

Blame it on your nose

When you’ve had little sleep, your sense of smell goes into overdrive, which makes your brain respond to food odours and help it differentiate better between food- and non-food odours

Then there is also a breakdown in the communication with other brain areas responsible for food signals – and that is when you tend to reach for that doughnut instead of your normal breakfast, according to the news report.

"When you're sleep deprived, these brain areas may not be getting enough information, and you're overcompensating by choosing food with a richer energy signal," said senior author Thorsten Kahnt, assistant professor of neurology at Northwestern University Feinberg School of Medicine.

"But it may also be that these other areas fail to keep tabs on the sharpened signals in the olfactory cortex. That could also lead to choosing doughnuts and potato chips," Kahnt added.

The science behind it

Kahnt and his colleagues investigated what causes us to eat differently when sleep deprived by conducting experiments on 29 men and women between the ages of 18 and 40. The participants were split up into two groups – one that got a normal night’s sleep and the other that was only allowed four hours of sleep per night. The day after, both groups were offered a controlled menu for breakfast and lunch, but also a buffet of snacks.

"We found participants changed their food choices," Kahnt said. "After being sleep deprived, they ate food with higher energy density (more kilojoules per gram) like doughnuts, chocolate chip cookies and potato chips."

The participants’ blood levels were also monitored to check for two endocannabinoid compounds, 2AG and 2OG. Endocannabinoid compounds are brain neurotransmitters that control aspects such as appetite.   

The participants who got the least amount of sleep had elevated levels of 2OG, which could be responsible for their choice in junk food.

But the role of the nose also played an important part in this study – scientists placed the participants in an fMRI scanner before serving the food. The participants were presented with a variety of food and non-food odours, and their piriform cortex (the area of the brain that receives information from the nose) was monitored.

In the sleep-deprived group, there was reduced communication between the piriform cortex and the rest of the brain.

"When the piriform cortex does not properly communicate with the insula, then people start eating more energy-dense food," said Kahnt.

How can you combat this?

Whether your sleep deprivation is temporary or chronic, it’s important to tackle the issue to help you make the healthiest food choices and regulate your weight.

One way is to be more aware of how your body responds to sleep deprivation and understanding why you are suddenly craving unhealthy food. Another way is to address your sleep disorder in its entirety to help solve the issue.

So, if you're sitting at your desk, nodding off and dreaming about a burger and chips from the office canteen, this article on how to survive your day after little sleep may help.

Image credit: iStock


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