It’s a warning we have heard for years: Not getting enough sleep can lead to gaining weight. Now, a new study has found that not only do we consume more food following a night of total sleep deprivation, but we also consume more fat and less carbohydrates.
The new study, from researchers at the University of Pennsylvania School of Medicine, pinpoints the region of the brain known as the salience network as leading us to eat more fat.
Most research in this area has focused on changes in metabolic hormones that lead to weight gain, while only a few have begun to examine how changes in brain activity may play a role, according to the researchers.
“We wanted to uncover whether changes in regional brain function had an impact on our eating behavior following sleep deprivation,” says the study’s senior author, Hengyi Rao, Ph.D., a research assistant professor of Cognitive Neuroimaging in Neurology and Psychiatry.
“This work has implications for the approximately 15 million Americans who work the evening shift, night shift, rotating shifts, or other employer arranged irregular schedules.”
The study sequestered 34 sleep-deprived subjects and 12 control subjects in a sleep lab for five days and four nights for round-the-clock monitoring. All the study subjects received one night of regular sleep and were then randomized to either total sleep deprivation or control for the remaining three nights, the researchers explained.
A baseline functional MRI (fMRI) to examine brain connectivity changes associated with food intake was conducted on all subjects the morning following the first night of sleep. Sleep-deprived subjects were then matched to control subjects in age, body mass index (BMI), ethnicity or gender.
On the second night, the sleep deprivation subjects were kept awake while the control subjects slept for eight hours. Functional MRI testing of both groups continued on days two, three, and four at the same time each day. All subjects had access to a variety of foods that they could consume as desired, according to the researchers.
The researchers found that sleep deprived subjects consumed close to 1,000 calories during overnight wakefulness. Despite this, they consumed a similar amount of calories the day following sleep deprivation as they did the day following baseline sleep.
However, when comparing the macronutrient intake between the two days, researchers found the subjects consumed a greater percentage of calories from fat and a lower percentage of calories from carbohydrates during the day following total sleep deprivation.
The researchers also found that sleep deprived subjects displayed increased connectivity within the “salience network,” which is thought to play a role in determining contextually dependent behavioral responses to stimuli. It also is one of several key brain networks that carry out various aspects of brain function.
Increased connectivity in the salience network correlated positively with the percentage of calories consumed from fat and negatively correlated with the percentage of carbohydrates after sleep deprivation, the researchers reported.
The salience network is located toward the front of the brain and consists of three sections, the dorsal anterior cingulate cortex, bilateral putamen, and bilateral anterior insula. Activity in these structures is linked to both emotion and bodily sensations, such as the heart racing, stomach churning, pain, thirst, embarrassment, and attempting mental challenges, the researchers explained.
Changes in caloric intake and content after sleep deprivation may relate to changes in the “salience” of food, and in particular fatty food, in individuals who are sleep deprived, the researchers postulate.
“We believe this is the first study to examine the connection between brain network connectivity and actual macronutrient intake after baseline sleep and after total sleep deprivation,” Rao said.
Most other studies rely on self-reported hunger levels of food cravings, or on brain responses to pictures of different types of foods, he noted.
“Although this study examined the effects of acute total sleep deprivation, similar changes may occur in response to the chronic partial sleep restriction that is so prevalent in today’s society,” he concluded.
The study was published in Scientific Reports.