Is poor sleep contributing to the country's weight issues?

by Debra Melani, University of Colorado Anschutz

edited by Sadie Harley, reviewed by Andrew Zinin

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Some 70% of teens trying to adapt to a fall schedule are missing out on sleep. Early bells and tough classes combine with delayed biological clocks during adolescence, keeping their nightly sleep duration during the school year below the recommended eight to 10 hours for their age group.

While most parents worry about (and lose sleep over) their teens' moods and grades, recent research suggests sleep deprivation can affect another U.S. health concern: the obesity crisis.

"It (sleep) is still emerging as that third pillar of a healthy lifestyle, but I think people are increasingly recognizing that sleep is also an important aspect of weight management," said Stacey L. Simon, Ph.D., a sleep expert and professor of pediatrics at the University of Colorado Anschutz School of Medicine.

What does research reveal about sleep and weight?

Repeated studies in adults have shown that restricting volunteers' sleep leads them to consume between 200 and 300 extra calories, said Seth Creasy, Ph.D., an associate professor of endocrinology, metabolism and diabetes.

Simon and Creasy, an obesity medicine researcher at the CU Anschutz Health and Wellness Center and the Colorado Nutrition Obesity Research Center on campus, were part of a study published this year that reviewed sleep as a behavioral treatment for obesity.

"So diet and physical activity are still the two main drivers of weight gain from a behavioral standpoint, but sleep can help support both of those," Creasy said.

The early bell's toll: Poor sleep raises risk across the lifespan

Simon's research focuses largely on sleep in adolescents, whose circadian rhythms prevent them from falling asleep early, prompting calls for later school start times. Despite the American Academy of Pediatrics recommendation in 2014 that middle and high schools begin no earlier than 8:30 a.m., compliance has lagged, Simon said.

"A majority of schools start much earlier than that. Certainly, what we see in our sleep clinic at Children's (Hospital Colorado) is that, during the school year, teens are forced to sleep outside of their biological clock."

Given the toll the obesity crisis takes on people's health and the country's health care system, Creasy and Simon hope their research will help support behavioral interventions at home and in health care for all ages.

"We're really seeing this across the lifespan: that individuals with short sleep duration are at increased risk for higher body weight," Simon said. Excess weight contributes to higher rates of type 2 diabetes, cardiovascular disease, some types of cancer, musculoskeletal diseases and premature mortality.

The cardiometabolic health consequences of delayed sleep timing in teens are a chief concern for Simon. "We've seen that, in adolescents, short sleep duration and late timing of sleep are associated with poorer insulin sensitivity, which could over time increase risk for obesity and type 2 diabetes."

What is keeping teens from sleeping well?

An estimated 70% of high school students and 30% of adults don't get their recommended amount of sleep. The substantial lack of sleep in teens is particularly notable because of their unique developmental period, Simon said.

Teens have a natural delay in their circadian rhythms working against them: "Their brains are just programmed to not feel sleepy until very late." In a recent sleep study by Simon and colleagues, parents and teens noted high anxiety levels, busy schedules and heavy use of electronic devices that added to their stress and lack of sleep.

Teens have more autonomy when it comes to important behaviors, like what types of foods they eat and when and how often they eat, sleep and exercise.

"So it's sort of this confluence of factors that all increase risk for greater weight gain. And, unfortunately, we know that those behaviors that are set even in adolescence can endure into adulthood," Simon said.

Although the research still lags, some early evidence suggests females might draw an even shorter stick when it comes to the issue of sleep and weight gain

"Our research found that adolescent females actually had earlier circadian timing compared to males, which may suggest an even greater sleep need," Simon said. And yet, females report higher levels of insomnia, she said. "So they may need more sleep, but they're actually getting less."

Why would sleep deprivation affect calorie consumption?

People actually expend more energy tossing and turning or staying up with insomnia, so the energy balance equation by itself cannot explain weight gain. "They may be overcompensating for those burned calories," Simon said.

Studies have linked shorter sleep duration with an increase in the hunger hormones leptin and ghrelin. "So they are getting those cues to feel hungry, and they're feeling less satisfied after consuming food. So that again could lead to overconsumption," Simon said.

"And there's been some really interesting research done looking at the reward system in the brain and how it's impacted by short sleep," she said. "It seems like when we aren't getting enough sleep at night, then it's almost like our brain is searching for some reward." Often, food—especially the high-sugar, high-fat variety—is the most available prize.

On the intervention side, researchers looked at people who routinely slept less than about six hours a night and extended their sleep each night for two weeks, Creasy said. "These people started getting closer to the recommended amounts, about seven and a half hours of sleep," he said. "And just naturally, those people started eating less by 270 calories per day."

How might inadequate sleep affect physical activity?

It is harder to study how lack of sleep can affect calories burned the next day, so fewer studies exist on the energy expenditure side, Creasy said. However, it makes sense that simply being tired after a bad night's sleep could increase sedentary behavior, he said.

Creasy was involved in one study where researchers restricted sleep for a group of New York City residents and then monitored their activity in their free-living environment, he said. "These people didn't use cars. So it was safe for them to be sleep-restricted for six weeks."

"They were more sedentary. They ended up actually sitting more throughout the day, even adjusting for the amount of time that they were awake."

Simon's team has done studies involving teens who are regularly sleep-deprived on school nights, in which researchers orchestrate a schedule that allows at least one extra hour in bed per night for the teens.

"And what we found was, not only were they successful at getting extra sleep during that study period, but they also had a decrease in their sedentary behavior time. And so it was almost like that hour or so before bed that they were otherwise on their phones or engaged in some of those sedentary behaviors, when we intervened, they just replaced that time with sleep."

Key medical concepts

Obesity

Clinical categories

Sleep medicineSleep & RecoveryWeight managementPediatricsChildren's health Provided by University of Colorado Anschutz Who's behind this story?

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