Much like the age-old chicken and egg question, scientists have wondered which came first, the lack of sleep or the obesity.
A new study by the University of Pennsylvania School of Medicine might flip the script on what many believed to be the correlation.
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According to Science Daily, a growing body of research has suggested that poor sleep quality is linked to an increased risk of obesity by deregulating appetite, which in turn leads to more calorie consumption.
But the Pennsylvania study suggests the opposite might be true. Published recently in the journal PLOS Biology, the researchers say it's not that sleep loss leads to obesity, but rather that excess weight can cause poor sleep.
"We think that sleep is a function of the body trying to conserve energy in a setting where energetic levels are going down. Our findings suggest that if you were to fast for a day, we would predict you might get sleepy because your energetic stores would be depleted," said study co-author David Raizen, an associate professor of neurology and a member of the Chronobiology and Sleep Institute at Penn.
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Raizen emphasized that while these findings, which were in microscopic worms, "may not translate directly to humans, C. elegans offer a surprisingly good model for studying mammalian slumber. Like all other animals that have nervous systems, they need sleep. But unlike humans, who have complex neural circuitry and are difficult to study, a C. elegans has only 302 neurons — one of which scientists know for certain is a sleep regulator."
To study the link between metabolism and sleep, Science Daily wrote, “the researchers genetically modified C. elegans to ‘turn off’ a neuron that controls sleep. These worms could still eat, breathe, and reproduce, but they lost their ability to sleep. With this neuron turned off, the researchers saw a severe drop in adenosine triphosphate (ATP) levels, which is the body's energy currency. “
"That suggests that sleep is an attempt to conserve energy; it's not actually causing the loss of energy," Raizen explained.
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