Sleep, Stress and Snacks

A lack of sleep makes our brains go nuts for unhealthy food, says a new study.

When sleep-deprived people are shown images of junk food, fMRI scans show that their brains’ reward centers light up with far more intense anticipation than those of people who’ve slept a full night. The Fourthmeal marketing team, I assume, are grinning knowingly.

The relationship between cravings and conscious control is a complex one, and studies have found that the balance between the two can easily be tilted. Under stress, our brains are much more likely to return to old junk-food and drug addictions, as well as other bad habits like nail-biting.

We know this not just from psychological research, but from years of fMRI studies showing that stress weakens activity in areas like the medial prefrontal cortex (mPFC) and the orbitofrontal cortex (OFC) – parts of the brain that are crucial for self reflection, regulation of emotions, and conscious decision-making. Meanwhile, studies show that stress changes the connectivity of our brain’s more primitive “reward” areas, such as the nucleus accumbens and the ventral tegmental area.

The overall effect of these changes is that when you’re feeling stressed – whether it’s about money, lack of sleep, or just a feeling of hunger – your normal self control begins to lose the struggle against your desires for quick gratification.

As a matter of fact, the brains of people exposed to chronic stress often lose (or fail to develop) healthy connectivity between the OFC and those ancient reward centers – a trait that’s found in the brains of many psychopaths. So when you’re operating on an empty stomach or four hours of sleep, you could say that your brain has quite literally gone a little bit psycho.

"Hold all my calls, Peggy - I've got to finish this cost/benefit analysis."

This new study, led by Marie-Pierre St-Onge at Columbia University, focused on another type of stress-related change in brain activity: reward centers’ responsiveness to images of healthy vs. unhealthy foods in the brains of sleep-deprived people:

The same brain regions activated when unhealthy foods were presented were not involved when we presented healthy foods. The unhealthy food response was a neuronal pattern specific to restricted sleep.

In other words, even healthy people with strong self control can turn into sugar addicts when they’re running on less than a full night’s sleep. These results also confirm a fact discovered in some earlier studies: that sleep-deprived people eat more, in general, than their well-rested counterparts do.

Indeed, food intake data from this same study showed that participants ate more overall and consumed more fat after a period of sleep restriction compared to regular sleep. The brain imaging data provided the neurocognitive basis for those results.

In short, it’s clear that stress, sleep and eating disorders are all intimately linked – not just psychologically, but also in terms of the brain’s physical structure and functionality.

So if you’re trying to break a bad habit, make sure you’re getting plenty of healthy food and a solid eight hours every night. And if you’re running on less than a full tank today, give yourself the benefit of some extra patience and compassion – the rewards are worth it.

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