Junk food cravings could be due to sleep deprivation

A study claims that sleep deprivation makes a person more likely to crave junk food which could explain the link between sleep deprivation and obesity.

A sleepless night makes us more likely to reach for doughnuts or pizza than for whole grains and leafy green vegetables, suggests a new study from UC Berkeley that examines the brain regions that control food choices. The findings shed new light on the link between poor sleep and obesity

Using functional magnetic resonance imaging (fMRI), UC Berkeley researchers scanned the brains of 23 healthy young adults, first after a normal night's sleep and next, after a sleepless night. They found impaired activity in the sleep-deprived brain's frontal lobe, which governs complex decision-making, but increased activity in deeper brain centers that respond to rewards. Moreover, the participants favored unhealthy snack and junk foods when they were sleep deprived.

"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," said Matthew Walker, a UC Berkeley professor of psychology and neuroscience and senior author of the study published Aug. 6 in the journal Nature Communications.

Moreover, he added, "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 linked poor sleep to greater appetites, particularly for sweet and salty foods, but the latest findings provide a specific brain mechanism explaining why food choices change for the worse following a sleepless night, Walker said.

"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. Another co-author of the study is Andrea Goldstein, also a doctoral student in Walker's lab.

In this newest study, researchers measured brain activity as participants viewed a series of 80 food images that ranged from high-to low-calorie and healthy and unhealthy, and rated their desire for each of the items. As an incentive, they were given the food they most craved after the MRI scan.

Food choices presented in the experiment ranged from fruits and vegetables, such as strawberries, apples and carrots, to high-calorie burgers, pizza and doughnuts. The latter are examples of the more popular choices following a sleepless night.

On a positive note, Walker said, 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."

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Why night owls gain weight

This article looks at why night owls tend to gain more weight than those to go to sleep early.

Night owls are more likely to gain weight than people who get good sleep because they tend to graze the kitchen for junk food in the wee hours of the morning, a new study suggests.

Researchers at the University of Pennsylvania found that people who were kept up until 4 a.m. in a sleep lab ate more than 550 additional calories during the late-night hours.

"People consumed a substantial amount of calories during those late-night hours when they would normally be in bed," said study author Andrea Spaeth, a doctoral candidate in the psychology department at the University of Pennsylvania. "Those calories also were higher in fat compared to the calories consumed at other times of day."

As a result, subjects kept up late gained more weight during five days of sleep deprivation than people in a control group who were allowed to get good sleep, Spaeth said.

Late-night overeating is likely the result of hormonal changes that occur in people who are sleep-deprived, said Dr. W. Christopher Winter, medical director of the Martha Jefferson Sleep Medicine Center in Charlottesville, Va.

They tend to experience an increase in their levels of ghrelin, a hormone that stimulates hunger cravings, and a decrease in levels of leptin, a hormone that makes people feel full.

"Now you're in a situation where you are craving bad food and more of it, and your body feels less full when it gets that bad food," Winter said.

The research team monitored the eating habits of about 200 people who, for five days straight, were kept up until 4 a.m. and then allowed only four hours of sleep. They remained in the lab the whole time, going through in groups of four or five at a time.

Subjects were allowed to eat whenever they liked, and trained monitors in the sleep lab maintained a running tally of the amount consumed and the times at which they ate.

Researchers then compared their calorie intake and weight gain to that of a control group allowed a good night's sleep in the same lab with the same food availability.

"The only difference between the two groups was sleep," Spaeth said. "They lived in a suite, and in the suite there was a kitchen with a fridge and microwave."

The eating habits of the control group remained unchanged. The sleep-deprived group began eating additional calories between 10 p.m. and 4 a.m., and they tended to eat fattier foods during that time period. "That does kind of mimic the real world, when you're up late at night and you drift over to your fridge," Spaeth said.

There was one key difference between the lab and the real world. Since the study took place in a hospital, the suite's kitchen was stocked with hospital food. "I'm wondering if the effect would be stronger in the real world, where you have access to more calorically dense foods," Spaeth said.

The findings are published in the July issue of the journal Sleep.

Previous studies have shown a link between inadequate sleep and weight gain, Winter said, but this research is valuable because it provides precise observations in a laboratory setting.

"Anytime you're dealing with studies in the field, you're often relying on some sort of food diary or the recall of the patient," Winter said. "It's amazing how much food a person can eat and not remember. It's hard to keep track of people in terms of their eating and in terms of their sleep. When people are in a lab, they can perfectly control conditions and report them."

Blacks gained more weight than whites, and males gained more weight than females. Researchers currently are undertaking follow-up research involving detailed calorie counting to try to explain these differences, Spaeth said.

The study adds more weight to the growing mound of evidence suggesting that people who want to control their weight need to get seven to eight hours' sleep a night, Winter said.

People who can't get a good night's sleep -- such as people who are traveling or working late to meet a deadline -- need to pay extra attention to their food cravings, he added.

"God knows I'm aware of it," Winter said. "I'm usually traveling a lot, and I can feel myself craving food I don't really need and didn't know I wanted. I know when I'm going through an airport late at night and I see chocolate-covered pretzels, I know I'm not craving them because I'm hungry. I think if patients are more aware of those things, they're going to say, 'I'm not going to eat this because I'm not hungry, and it's not going to do me any good.'"

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What causes late-night snack cravings?

This article discusses a study on the circadian rhythm and how it influences certain cravings late at night.

A study published in the most recent version of the journal Obesity found that the body's internal clock, the circadian system, increases hunger and cravings for sweet, starchy and salty foods in the evenings. While the urge to consume more in the evening may have helped our ancestors store energy to survive longer in times of food scarcity, in the current environment of high-calorie food, those late night snacks may result in significant weight gain.

"Of course, there are many factors that affect weight gain, principally diet and exercise, but the time of eating also has an effect. We found with this study that the internal circadian system also likely plays a role in today's obesity epidemic because it intensifies hunger at night," said Steven Shea, Ph.D., director for the Center for Research on Occupational and Environmental Toxicology at Oregon Health & Science University and senior author on the study. "People who eat a lot in the evening, especially high-calorie foods and beverages, are more likely to be overweight or obese."

Indeed, eating a lot in the evening can be counterproductive since the human body handles nutrients differently depending on the time of day. For example, sugar tolerance is impaired in the evening. Additionally, consuming more calories in the evening predisposes people to more energy storage; we simply don't expend as much energy after an evening meal in comparison to morning meals.

Furthermore, artificial light enables people to stay up later than they probably should and often people don't get enough sleep. "If you stay up later, during a time when you're hungrier for high-calorie foods, you're more likely to eat during that time," Shea said. "You then store energy and get less sleep, both of which contribute to weight gain."

"If weight loss is a goal, it's probably better to eat your larger, higher-calorie meals earlier in the day," said Shea. "Knowing how your body operates will help you make better choices. Going to bed earlier, getting enough sleep and choosing lower-calorie foods rather than higher-calorie foods in the evening can all help with weight loss."

Conducted by Shea and two Boston-area researchers, Frank Scheer, Ph.D. and Christopher Morris, Ph.D. of Brigham and Women's Hospital and Harvard Medical School, the study examined the appetite and food preference of 12 healthy non-obese adults throughout a 13-day laboratory stay in very dim light in which all behaviors were scheduled, including timing of meals and sleep. Dr. Scheer, first author on the study, explained that "by the end of this long protocol, all of the participants' meals and activities were spaced evenly across the day and night, allowing examination of the true internal circadian effects on appetite, while controlling for other effects on appetite including the amount of food recently consumed."

The researchers found that the internal circadian system regulated hunger, with participants feeling the least hungry in the morning (8 a.m.) and most hungry in the evening (8 p.m.). Similar rhythms were found in appetite for types of food, such as sweet, starchy and salty, and the estimate of how much food participants could eat. The study concludes that the internal circadian system causes an evening peak in appetite that may promote larger, higher-calorie meals before the fasting period necessitated by sleep.

"Our study suggests that because of the internal circadian regulation of appetite, we have a natural tendency to skip breakfast in favor of larger meals in the evening. This pattern of food intake across the day is exactly what Sumo wrestlers do to gain weight." said Steven Shea. "So, it seems likely that the internal circadian system helps with efficient food storage. While this may have been valuable throughout evolution, nowadays it is likely to contribute to the national epidemic of obesity."

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Link Between Lack of Sleep and Junk Food Binging

Lack of sleep can result in a person eating greater quantities of high-calorie junk food resulting in weight gain over time

Lack of sleep can lead you to eat larger portions of high-calorie foods and increase your long-term risk of weight gain, according to a small new study.

Swedish researchers asked 16 normal-weight males to choose their ideal portions of high-calorie meals and snacks. They did this when they had a normal night of about eight hours sleep and again when they went a night without sleep.

The participants chose larger portion sizes after the night with no sleep. They did this both before and after a breakfast, which suggests that sleep deprivation increases food intake regardless of whether a person feels full, said study author Pleunie Hogenkamp, of Uppsala University.

"Bearing in mind that insufficient sleep is a growing problem in modern society, our results may explain why poor sleep habits can affect people's risk to gain weight in the long run," Hogenkamp said in a university news release.

The study was published online Feb. 18 in the journal Psychoneuroendocrinology.

In a previous study, the same team of researchers found that young, normal-weight men who went a single night without sleep had increased activation of a brain region involved in the desire to eat.

Although the study found an association between lack of sleep and increased appetite for high-calorie foods, it did not prove a cause-and-effect relationship.

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