It has been recognised that sleep restriction alters responses to food, contributing to disordered eating and metabolic disturbance. The underlying neural mechanisms for this effect, however, are not entirely understood.
A recent study was designed to determine whether there is a neural system that is preferentially activated in response to unhealthy compared with healthy foods.(1)
The study involved twenty-five normal-weight individuals, who normally slept 7–9 hours per night. The subjects completed both phases of this randomised controlled study so that in-person differences, if any, could be observed.
Each of the subjects was tested after a period of five nights of either 4 or 9 hours in bed. To monitor regional brain activity functional magnetic resonance imaging (fMRI) was performed on the individuals who presented in a fasted state (no food between the sleep period and the test). While undergoing fMRI the subjects were presented with healthy and unhealthy food stimuli and then the neuronal responses to unhealthy, relative to healthy food stimuli after each sleep period were assessed and compared.
After a period of restricted sleep, viewing unhealthy foods led to greater activation in the superior and middle temporal gyri, middle and superior frontal gyri, left inferior parietal lobule, orbitofrontal cortex, and right insula compared with healthy foods. These areas of the brain are involved in sensory and emotional processing, reward and decision making – the sights, sounds, smells, tastes, and touch are all turned up a notch, your feelings towards these stimuli are heightened and your ability to make seemingly rational decisions is diminished.
These same stimuli presented after a period of habitual sleep did not produce noticeably different activity patterns specific to unhealthy foods.
The effect of sleep deprivation on brain function in relation to food, especially hyper-palatable food, is similar to that of an individual with drug addiction. The same areas in the brain are relatively activated or inhibited in both cases and lead to similar behavioural manifestations such as increased desire, preoccupation, impulsivity, and continued use despite negative consequences.
Evolutionarily this makes sense (it always does, it just takes time for our limited brains to understand it) – when the body is in a starvation state one of the initial body responses is insomnia which activates these same brain areas to ensure that you are sufficiently motivated to overcome fear so that you seek out food despite consequences such as predators or an inhospitable environment; that you notice food that may ordinarily be less noticeable; and you pursue this task without any other mental distractions. It’s a powerful built in drive designed to achieve the primary objective – survival.
For those who are interested in achieving and maintaining a healthy, fit and lean body your first port of call needs to be ensuring sound, quality sleep.
Reference:
1- St-Onge MP, Wolfe S, Sy M, Shechter A, Hirsch J. Sleep restriction increases the neuronal response to unhealthy food in normal-weight individuals. Int J Obes (Lond). 2014 Mar;38(3):411-6. doi: 10.1038/ijo.2013.114. Epub 2013 Jun 19. PubMed PMID: 23779051; PubMed Central PMCID: PMC3883872.
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