There are times when we just want to chill at home and eat some junk food while in our pyjamas right? And that’s normal but do you ever crave nothing but just junk food? If so it could have a lot to do with lack of sleep.
A study has found that a lack of sleep makes people crave junk food and spend more money to get their hands on it.
Tiredness can boost activity in areas of the brain related to appetite and comfort eating, and hormones that tell us when we are hungry.
The disruption to the body’s normal functions can lead to an increased likelihood of overeating, and over time, obesity, the researchers suggested.
It may explain why some people are more likely than others to reach for the biscuits by the afternoon.
Britain and US are among the most overweight and sleep deprived nations in the world – and evidence is growing the two are linked.
Dr Julia Rihm, lead author of the study, and her team enrolled 32 healthy men aged between 19 and 32 for the study.
Participants visited their laboratory for a normal dinner of pasta and veal in a creamy mushroom sauce with an apple and strawberry yoghurt, on two separate nights.
On each visit they were instructed to either return home after the meal to sleep normally or to spend the night at the lab, where they would be kept awake.
Their desire for snack foods, brain activity, and hormone levels were assessed the next morning.
Then they were given three Euros (£2.70/$3.40) to spend on snacks – such as popular brands of German chocolate bars or chips – or everyday household items or university merchandise.
In an online auction, images of the goods flashed up on screen with prices going up in stages of 0.25 Euros (£0.22/$0.28).
The participants were told to bid the maximum amount they were willing to spend on the item and that they could spend their total of three euros if they wanted to.
Only after sleep deprivation were the participant’s willing pay extra for the junk food items – which they were allowed to eat afterward.
Using MRI (magnetic resonance imaging) brain scans, the team showed losing sleep fired neurons in their amygdala and hypothalamus.
The amygdala is an area of grey matter that has been linked to reward-seeking behaviour – such as eating under stress. The hypothalamus controls appetite.
The results showed an increased amount of activity in these parts of the brain in those who had lost shut-eye.
Dr. Rihm said: ‘We found a full night of sleep deprivation compared with a night of habitual sleep increased the subjective values of snack food rewards compared with non-food rewards.’
She added: ‘These data suggest one way a lack of sleep can promote overeating and obesity risk.
‘This behavioural result was paralleled by increased amygdala and hypothalamus activity selectively after sleep deprivation.
‘Furthermore, the connectivity between the amygdala and hypothalamus was increased after sleep deprivation for food rewards.’
Blood tests also showed levels of ghrelin, the hormone that tells us to eat, were higher.
Dr Rihm said: ‘We found ghrelin concentrations were increased after sleep deprivation compared with habitual sleep.
‘Despite similar hunger ratings due to fasting in both conditions, participants were willing to spend more money on food items only after sleep deprivation.’
Dr Rihm added: ‘Sleep loss is associated with increased obesity risk, as demonstrated by correlations between sleep duration and change in body mass index or body fat percentage.’
Staying up all-night without eating – which is what happened in the study published in the Journal of Neuroscience – is unlikely to happen in real life.
However, Dr Rihm said the findings are still representative of how sleep deprivation builds up over a period of time.
Their results suggest that a lack of sleep may encourage more eating by disrupting the subjective value of food.
Dr Rihm and colleagues added this ‘thereby potentially increases the likelihood of overeating and consequentially weight gain and obesity risk.’