When you haven’t slept well, do you tend to eat more the next day, perhaps indulging in food that isn’t so healthy?
Personally, when I’ve had a bad night’s sleep, I’m much more likely to treat myself to cake in the morning and a bigger lunch.
But there might be more to it than an exhausted need for more fuel in the form of comfort food.
Two different areas of research have shown that eating more when you’re tired is part of your body’s natural reaction to a lack of sleep. So our control over the food we eat suddenly isn’t so good.
In this article, I’ll be looking at some interesting effects that scientists have found:
- The sleep deprived brain is more sensitive to food smells.
- The body’s control of both hunger and food intake are affected by a lack of sleep.
Do we really eat more when tired?
Unfortunately, it appears we do eat more when we’re tired; worse still, we tend to eat more than we actually need.
In 2016, researchers from Kings College London reviewed data from 11 sleep and food studies involving 172 people.
All the studies had split people into two groups: one had normal sleep, while the other were kept awake some of the night, resulting in them being tired. They then monitored how much they ate and exercised over the following 24 hours.
Their findings were that:
- The sleep deprived groups ate on average 385 calories more than they would normally (equivalent to four and a half slices of bread).
- These groups favored foods high in fat and protein; carbohydrate intake remained the same.
- The sleep deprived groups didn’t exercise any more than those who slept well.
Dr Gerda Pot explained why this could be a serious problem:
The main cause of obesity is an imbalance between calorie intake and expenditure, and this study adds to accumulating evidence that sleep deprivation could contribute to this imbalance.
Tired brains are more sensitive to smells
In March 2017, researchers from the Northwestern University Feinberg School of Medicine published a study of the brain’s sensitivity to food smells.
They used a brain scan technique called functional magnetic resonance imaging (fMRI) to see what happens in the brain when we smell things.
The researchers randomly selected two groups of people for their study. One group had a normal night’s sleep of around 8 hours, and the other group had only about 4 hours sleep.
Then while undergoing an fMRI scan, they rated the pleasantness and intensity of smells from sweet food, savory food and smells that weren’t food.
In both groups, the fMRI showed the brain’s responses to food compared to non-food smells were enhanced in areas associated with smell and reward. This included the posterior orbitofrontal cortex, piriform cortex and anterior insula.
But the sleep deprived group displayed even higher activity in the brain areas for the food odors than those who had a normal amount of sleep. Their inbuilt reward system also showed an increased level of activity.
The researchers concluded that:
early olfactory [smell] responses to food odors are elevated in a sleep-deprived state.
Feeling more hungry and overeating
Scientists have also looked at whether sleep deprivation affects a system in the brain involved in controlling hunger and food intake – the endocannabinoid (eCB) system.
14 people who normally slept well took part in the study. They were split into two groups: one group only slept for around 4 hours per night for 4 nights in a row. The other group slept normally.
The two groups were then changed around and the experiment repeated. So those with only 4 hours sleep were allowed to sleep normally for the second test.
During the study, people could eat as much as they liked, with snacks available between meals.
The researchers found:
- When sleep deprived, people reported increased hunger and appetite.
- They were also less able to control how many snacks they had.
- The endocannabinoid system showed higher levels of activity with less sleep.
Part of their objective was to look for connections between insufficient sleep and being overweight. One conclusion they reached was:
Our findings suggest that activation of the eCB system may be involved in excessive food intake in a state of sleep debt and contribute to the increased risk of obesity associated with insufficient sleep.
So we’ve seen three opponents in the battle to avoid too much sweet and high calorie food: your brain tells you how good the food will taste and how much you’ll enjoy it; your brain says you’re hungry; and when tired, your ability to resist the temptation of food decreases.
If it’s just an occasional treat, it’s probably not much to worry about. However, there’s increasing evidence of a link between sleep deprivation and obesity, as well as a higher risk of developing diabetes.
How to avoid the sugary food
If you’re worried about your weight or your sugar intake, it doesn’t help if your brain makes naughty food seem more enticing when you’re tired and lacking willpower.
Perhaps the solution is to try and develop your own way to resist the temptation. One possibility is to use mindfulness techniques.
There are a number of useful websites explaining how mindfulness can help you eat more healthily. One example is a program developed by Dr Jean Kristeller.
And a simple technique is to consciously thank your brain for making the treat so attractive. But tell yourself that you know you don’t actually need to eat at that moment, and so will pass on it.
I’ve also found this mindfulness approach helps me resist drinking too much strong coffee when I’m going about my day in a slightly weary trance.
And if you can remember that your brain is compromised when tired, it might help you find some extra willpower when you’re next tempted by food you wouldn’t otherwise choose.