Lack of sleep is considered unhealthy and increases the risk of getting fat. Scientists from Cologne have researched why this is so.
Waking up after a short night craving chocolate, burgers and other junk food – this phenomenon is familiar to many people. So far, a disturbed hormone balance was considered the reason for the strange – and unhealthy – connection.
Above in the video: These foods help fight cravings!
The “tiredness appetite” could also arise quite differently, as researchers from the University of Cologne are now reporting in the “Journal of Neuroscience”. They found evidence that sleep deprivation activates the reward system in the brain and increases the desire for fatty snacks.
The negative effects of too little sleep on health have already been proven by several studies. For example, epidemiological studies have shown that people with chronic sleep deprivation have an increased risk of obesity or type 2 diabetes. The hormonal balance has often been seen as the reason for this: too little sleep messes it up, as a result, the cravings for fatty or sweet foods are aroused, according to the assumption.
A team led by Julia Rihm, who conducts research in the field of biological psychology at the University of Cologne, has now put this assumption to the test. The scientists invited 32 healthy, slim men to the laboratory, where they served them dinner on two evenings several days apart. Participants were then instructed to either go home and go to bed normally, or to stay in the lab where they were kept awake.
The morning after, the scientists sent all of the test subjects to an MRI tube. There, the activity of their brains was recorded while they worked on a task: the men were asked to explain how willing they are to pay for certain snacks or for non-food items. In addition, blood was drawn from them to measure their hormone levels and given a scale to rate how hungry they were.
For Jan Peters, also from the University of Cologne and co-author of the study, the joint analysis of these three factors is what makes the study special: “We recorded both hormonal changes and the influence on behavior and effects on the brain,” he explains in conversation with dpa.
Those who sleep less pay more for food
The researchers found that sleep loss increases the subjective value of food compared to non-food. Although the feeling of hunger should be the same in both test groups, since the participants went without food for the same time in both the sleepless and the restful night, there was a clear difference: with sleep deprivation, the test subjects were more willing to spend more money on snacks than not – to hand out food.
“This effect could be expected based on the studies to date,” summarizes neuroscientist Peters. However, hormones are not responsible for this, as the blood analyzes showed. Rather, the MRI images showed increased activity in two areas of the brain: in the amygdala, which is located in the temporal lobes of the brain and belongs to the limbic system, and in the hypothalamus, which is located in the diencephalon.
Little sleep increases the risk of obesity
Even one night of sleep deprivation triggers a cycle that sets a food-specific, neural reward system in motion, the researchers report. The offer of snacks acted like a reward stimulus for the participants in the experiment, to which the limbic system reacts and in particular the amygdala, which processes affect or pleasure-oriented sensations. According to Jan Peters, further experiments must be carried out to clarify why these regions are activated more strongly in people who are overtaken.
In view of the research results, the scientist is reluctant to give recommendations for action: “Apparently, in cross-section, little sleep increases the risk of a whole range of health problems, including obesity.” The new study provides a further component in explaining the Context: “We are now a little closer to understanding which mechanism at the neuronal level triggers this behavior and which perhaps plays a subordinate role.”
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