If you haven't slept much, you tend to have donuts, fries and pizza. A new study has discovered why you crave more high-calorie, high-fat foods after a sleepless night — and how to thwart those unhealthy choices. Blame your nose — or olfactory system — for being affected by sleep deprivation in two ways, according to the study. First, it goes into hyperdrive, sharpening food odors to the brain so it can better distinguish between food and non-food odors. But then there is a breakdown in communication with other brain areas that receive food signals. And with that, decisions about what to eat change.
"When you're sleep-deprived, these areas of the brain may not get enough information and you overcompensate by choosing foods with a richer energy signal," said the study's senior author.
“But it could also be that these other areas do not monitor the acuity signals in the olfactory cortex. That can also lead to choosing donuts and chips,” he added.
Previous research has shown that sleep deprivation increases certain endocannabinoids, which are naturally produced by the body and are important for feeding behavior and how the brain responds to odors, including food smells.
“We put all this together and asked whether changes in food intake after sleep deprivation are related to how the brain responds to food odors, and whether this is due to changes in endocannabinoids.” “What makes our brains react differently so that we eat differently?”
The researchers examined that question in a two-part experiment with 29 men and women, ages 18 to 40. The study participants were divided into two groups. They got a normal night's sleep and four weeks later they were only allowed to sleep four hours. The experience was reversed for the second group. The day after each night (good sleep and underprivileged sleep), scientists served the participants a controlled menu for breakfast, lunch and dinner, but then also offered them a buffet of snacks. Scientists measured how much and what they ate.
“We found that participants changed their food choices.” “After they had no sleep, they ate foods with a higher energy density (more calories per gram) such as donuts, chocolate chip cookies and chips.”
Researchers also measured the participants' blood levels of two endocannabinoid compounds — 2AG and 2OG. One of the compounds, 2-OG, was elevated after the night of sleep deprivation and this increase was related to changes in food selection.
In addition, scientists put subjects in an fMRI scanner before the buffet. They then presented them with a number of different food odors and non-food odors, while observing the piriform cortex, the first cortical brain region to receive input from the nose.
They saw that the activity in the piriform cortex differed more between food odors and non-food odors when subjects were not sleepy.
The piriform cortex normally sends information to another brain region, the insular cortex. The insula receives signals that are important for food intake, such as smell and taste, and how much food is in the stomach.
But the insula of a person with little sleep showed decreased connectivity (a measure of communication between two brain regions) with the piriform cortex. And the extent of this reduction was related to the increase in 2-OG and how many subjects changed their food choices when they got too little sleep.
“When the piriform cortex doesn't communicate well with the insula, people start eating more energy-rich foods.”
The solution? Other than sleeping more, paying more attention to how our noses sway our food choices can help.
“Our findings suggest that sleep deprivation makes our brains more sensitive to the lure of food odors, so it might be worth taking a detour to avoid the snack bar the next time you take a 6-hour flight.”
