- The relationship between poor sleep and weight gain is an established fact.
- According to one study, excess weight is what causes poor sleep, not the other way around.
Poor quality sleep has been shown on multiple occasions to lead to weight gain. In fact, in humans, acute sleep disruption can cause increased appetite and insulin resistance. As a result, people who chronically sleep less than 6 hours per night have a higher likelihood of obesity and type 2 diabetes. However, how sleep and diet are related is still unclear. According to a study published in the journal Plos Biologybeing overweight may well lead to poor sleep.
“We wanted to know what actually causes sleep. There is a link between sleep deprivation and other chronic diseases, such as diabetes, but it’s just an association. It’s not clear if it’s is short sleep that is responsible for the predisposition to obesity, or whether it is obesity that is responsible for a tendency to short sleep”said Alexander van der Linden, associate professor of biology at the University of Nevada (USA) and co-author of the study.
To study the relationship between metabolism and sleep, he and his colleagues conducted an experiment on tiny worms called Caenorhabditis elegans (C. elegans) and modified a gene, KIN-29, to turn off a neuron that controls sleep. Because this gene is homologous to the salt-inducible kinase (SIK-3) gene in humans, which is known to signal sleep pressure. As a result, the worms lost their ability to sleep. Scientists then discovered that levels of adenosine triphosphate (ATP), the body’s energy currency, were very low in insomniac worms.
“This suggests that sleep is an attempt to conserve energy; it does not actually cause energy loss”indicated the co-author of the study, David Raizen, associate professor of neurology and member of the Chronobiology and Sleep Institute of Penn (United States).
Releasing fat stores may contribute to better sleep
By knocking out KIN-29 to create insomniac worms, the mutant gene also accumulated excess fat similar to human obesity. Therefore, researchers believe that the release of fat stores is a mechanism that could improve sleep. Being unable to release fat, the mutant worms would therefore have become insomniac. To validate this theory, the scientists again manipulated the genes of the worms, this time so that they expressed an enzyme releasing their fat. The animals were then able to sleep.
According to the researchers, these data would partly explain why obese people are prone to insomnia. “There could be a signaling problem between fat stores and brain cells controlling sleep”Raizen said.
A reliable model of mammalian sleep
“Our work suggests that if you fast for a day, you may fall asleep because your energy stores are depleted. There is a common and general perception in the field of sleep that sleep is a matter of the brain or nerve cells, and our experience indicates that this is not necessarily true,” he added.
Although these worm discoveries do not translate directly to humans, C.elegans provides a reliable model of mammalian sleep, the researchers say. In fact, like all other animals with a nervous system, worms need sleep. But unlike humans, who have complex neural circuits, C.elegans has only 302 neurons, including a sleep regulator.
If there is indeed still much to discover about sleep, this experiment could advance the understanding of one of its fundamental functions and, in the future, perhaps help to treat its disturbances, hope the scientists.
“Chronic lack of sleep is common in our modern societies”
In general, specialists believe that weight gain may be the result of chronic sleep deprivation. For example, a British study published in theEuropean Journal of Clinical Nutrition in 2016 showed that sleep deprived people took in an average of 385 extra calories within 24 hours of a bad night’s sleep.
“Our results suggest that sleep is a possible third factor in weight gain, after diet and exercise”the researchers said. “Reduced sleep duration is one of the most basic and probably the easiest factors to correct for health benefits. Chronic sleep deficit is common in our modern societies, and further research is needed. to estimate its long-term consequences on obesity, and to what extent improving sleep can be a preventive factor.”