The Athlete's Way

Sweat and the biology of bliss

Insomnia Increases Junk Food Cravings

Sleep deprivation blunts brain function linked to eating healthy foods.

We all know the feeling of craving sugar, salt, and fat after a poor night’s sleep. Two new studies shed light on the link between sleep deprivation and junk food cravings.

On August 6, 2013 researchers from UC Berkeley published a study in the journal Nature Communications showing that sleepless nights have a direct impact on brain regions that control decision making and make us more inclined to crave fast food rather than healthier options.

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In June 2013, another team of researchers led by Lauren Hale, PhD, Associate Professor of Preventive Medicine at Stony Brook University School of Medicine, presented research showing that well-rested teenagers make healthier dietary choices than their sleep-deprived peers.

Sleep Deprivation Blunts High-Level Brain Function

Researchers at UC Berkeley found that sleep deprivation increases the activity of deeper, primal brain regions that respond directly to rewards. The combination of increased primal drives and reduced executive function of the frontal lobes creates a double-whammy that makes people more likely to reach for potato chips and pizza than leafy greens or lean meats.

For the new study the researchers used functional magnetic resonance imaging (fMRI) to scan the brains of 23 healthy young adults –once after a solid night of sleep – and again after a sleepless night. The results of the brain imaging showed an increase of lower brain function and a decrease of upper brain function which caused participants to crave junk foods when they were sleep deprived.

The UC Berkeley researchers measured brain activity as participants viewed a series of 80 food images that ranged from high-to low-calorie options and from healthy-to-unhealthy foods. Participants rated their desire for each of the items when they were well-rested and then sleep-deprived. As an incentive, they were given the food they most craved after the fMRI scan.

The food options used in the experiment ranged from fruits and vegetables, such as strawberries, apples and carrots, to high-calorie burgers, pizza and doughnuts. Across the board, participant’s who were sleep deprived were more inclined to crave high-calorie junk foods.

Matthew Walker, a UC Berkeley professor of psychology and neuroscience and senior author of the study, says the findings indicate that, "getting enough sleep is one factor that can help promote weight control by priming the brain mechanisms governing appropriate food choices. What we have discovered is that high-level brain regions required for complex judgments and decisions become blunted by a lack of sleep, while more primal brain structures that control motivation and desire are amplified,"

Walker adds, "high-calorie foods also became significantly more desirable when participants were sleep-deprived. This combination of altered brain activity and decision-making may help explain why people who sleep less also tend to be overweight or obese."

Previous studies have found a link between insomnia and increased appetite, and cravings for sweet, salty foods and calorically dense foods. This is the first study to identify a specific brain mechanism linked to food cravings a sleepless night. "These results shed light on how the brain becomes impaired by sleep deprivation, leading to the selection of more unhealthy foods and, ultimately, higher rates of obesity," said Stephanie Greer, a doctoral student in Walker's Sleep and Neuroimaging Laboratory and lead author of the paper.

I have written extensively about the link between the cognitive function of the cerebrum (up brain) and the powerful nature of the more primal cerebellum (down brain) to drive behavior and performance. If you’d like to read more about this please check out my Psychology Today blogs: “Primitive Brain Area Linked to Human Intelligence”,“Gesturing Engages All Four Brain Hemispheres” and “Toward a New Split-Brain Model: Up Brain/Down Brain.”

Well-Rested Teenagers Inclined to Eat Healthier Foods

In June 2013 another study presented at the conference SLEEP 2013 which is the annual meeting of the Associated Professional Sleep Societies, revealed clues to understanding the link between sleep and obesity.

The authors of this study found that teens who reported sleeping fewer than seven hours per night (which was 18 percent of respondents) were more likely to consume fast food two or more times per week and less likely to eat healthful food such as fruits and vegetables.

The results took into account factors such as age, gender, race and ethnicity, socioeconomic status, physical activity and family structure. The researchers found that short sleep duration had an independent effect on both healthy and unhealthy food choices regardless of other factors.

"Not only do sleepy teens on average eat more food that's bad for them, they also eat less food that is good for them," said Dr. Hale. She adds, "While we already know that sleep duration is associated with a range of health consequences, this study speaks to some of the mechanisms, i.e., nutrition and decision making, through which health outcomes are affected."

The participants in the study fell into one of three categories: short sleepers, who received fewer than seven hours per night; mid-range sleepers, who had seven to eight hours per night; and recommended sleepers, who received more than eight hours per night. The American Academy of Pediatrics currently recommends that adolescents get between nine and 10 hours of sleep per night.

First author of the study, Allison Kruger, MPH, a community health worker at Stony Brook University Hospital said, "We are interested in the association between sleep duration and food choices in teenagers because adolescence is a critical developmental period between childhood and adulthood. Teenagers have a fair amount of control over their food and sleep, and the habits they form in adolescence can strongly impact their habits as adults."

Conclusion: Tackling Insomnia Could Reduce Obesity

Willpower is a depletable resource that is decreased by sleep deprivation. Sleep disorders are an epidemic in the United States. These studies offer proof that tackling insomnia could reduce obesity. 

The SLEEP study research team concluded that addressing sleep deficiency may be a novel and effective way to improve obesity prevention and health promotion interventions. Dr. Hale said that an important next step for researchers will be to explore whether the association between sleep duration and food choices is causal.

"If we determine that there is a causal link between chronic sleep and poor dietary choices, then we need to start thinking about how to more actively incorporate sleep hygiene education into obesity prevention and health promotion interventions," Hale said. The research from UC Berkeley is proof positive that sleep deprivation causes people to crave junk foods at a neurobiological level.

If you would like to read more on ways to improve your sleep and make healthier food choices please check out my Psychology Today blogs: “Why Is a Camping Trip the Ultimate Insomnia Cure” and “New Rules for a Healthy Heart.”

Christopher Bergland is a world-class endurance athlete, coach, author, and political activist.

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