Sleep deprivation may cause overeating by boosting chemicals for appetite as well as those that increase the pleasure of eating sweet or salty high-fat foods 
 
 Too little sleep may bring on a form of the marijuana “munchies”, say scientists who found that sleep-deprived people craved crisps, sweets and biscuits far more than healthier foods. 
 
 The US researchers believe that skimping on sleep alters brain chemicals in much the same way as the hunger-boosting ingredient in cannabis, which has long propped up snack sales at 24-hour convenience stores. 
 
 
 
 After several nights of poor sleep, healthy volunteers who took part in the study reached for snacks containing more calories - and nearly twice as much fat - than ones they favoured after sleeping well for the same period, the scientists say. 
 
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 When sleepy, the participants had terrible trouble resisting the snacks, even when they were full, said Erin Hanlon, who led the study at the University of Chicago. 
 
 
 
 Research has shown time and again that sleep loss raises the risk of obesity, but the reasons are complex and unclear. Insufficient sleep disrupts hormones that govern appetite and satiety. But those who sleep less have more time to eat, and may be too tired to exercise. To muddy the waters further, obesity can lead to breathing problems that themselves disrupt sleep patterns. 
 
 
 
 In a small study published in the journal Sleep, Hanlon invited 14 men and women in their twenties to spend two four-day sessions at the university’s clinical research centre. The volunteers’ time in bed was controlled, so that on one visit they averaged 7.5 hours of sleep a night, but on the other only 4 hours 11 minutes a night. During their stays, the volunteers ate identical meals, dished out at 9am, 2pm and 7pm. 
 
 
 
 After the fourth night of each leg of the study, the participants were offered a range of snacks. The sleep-deprived felt a strong urge to binge on fatty foods, and this was most intense in the late afternoon and early evening, when snacking is most linked to weight gain. They avidly consumed high-fat snacks even when they had eaten a solid meal containing 90% of their recommended daily calories only two hours earlier. Typically, the sleepy participants ate 300 calories in snacks, far more than they needed to make up for their extra hours awake. 
 
 
 
 To delve into why sleep loss might trigger poor eating habits, the scientists looked at various substances in the volunteers’ blood, including ghrelin, which boosts appetite, and leptin, which tells the brain when the stomach is full. Previous studies have shown that sleep loss goes hand-in-hand with high ghrelin and low leptin levels. 
 
 
 
 Skipping breakfast primes brain to seek high-calorie food, study finds Read more 
 
 But Hanlon looked also at levels of chemicals called endocannabinoids. She found that when sleep-deprived, volunteers had higher and more persistent levels of endocannabinoid 2-AG, a chemical that ramps up the pleasure felt when eating, especially sweet or salty high-fat foods. “We know that marijuana activates the endocannabinoid system and causes people to overeat when they are not hungry, and they normally eat yummy sweet and fatty foods,” Hanlon said. “Sleep restriction may cause overeating by acting in the same manner.” 
 
 
 
 In well-rested volunteers, levels of 2-AG rose in the morning, peaked around midday, and declined again. But in the sleep-deprived, levels rose 33% higher, peaked at 2pm, and remained high until 9pm. Writing in the journal, Hanlon says this may boost and prolong the pleasure people get from snacking, putting them more at risk of weight gain: “The early afternoon drive for hedonic eating may be stronger and last longer in a state of sleep debt.” 
 
 
 
 In a commentary published alongside the report, Frank Scheer, director of medical chronobiology at Brigham and Women’s Hospital in Boston, says the new findings make for “compelling evidence” that endocannabinoids and food reward mechanisms underpin the excessive eating and weight gain that comes with sleep loss. The results raise the possibility of anti-obesity drugs that target endocannabinoids, but he warns that these would need “careful consideration” because of the dangers of unintended side effects. ||||| People who don’t get enough sleep may pack on the pounds because they’ve got the munchies — the same munchies that pot smokers say they get, researchers said Monday. 
 
 An experiment aimed at explaining why people overeat after a poor night’s sleep suggests that food becomes much more appealing, and that the brain’s own marijuana-like chemicals are responsible. 
 
 “We know that when people use marijuana, they overeat. And they tend to eat things that are yummy and rewarding,” said Erin Hanlon, a research associate in endocrinology at the University of Chicago who helped lead the study. 
 
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 Hanlon, working as partof a team that’s been studying sleep and eating habits, looked at a brain chemical called endocannabinoid 2-arachidonoylglycerol (2-AG for short). It resembles the same chemicals found in cannabis, but it's made in the brain and affects pain, pleasure and appetite. 
 
 When volunteers were deprived of sleep, their levels of 2-AG stayed higher, for longer, and they also snacked on unhealthier foods, Hanlon’s team reported in the journal Sleep. 
 
 “When you activate the cannabinoid system you are exciting the reward system.” 
 
 “We know that when you activate the cannabinoid system, it modulates brain reward pathways,” Hanlon told NBC News. “When you activate the cannabinoid system you are exciting the reward system.” 
 
 The effect: People found junk food much harder to resist. 
 
 It was a small but intense study of 14 people in their 20s, who agreed to spend four days at a stretch in the university’s sleep center, where they stayed in rooms where light and sound were controlled. Everyone got carefully prepared and measured meals so the researchers could see exactly what they ate. 
 
 The volunteers were allowed to sleep for eight and a half hours or for just four and a half hours. The researchers took blood samples and controlled what and when the volunteers could eat. 
 
 After four nights no one got to eat anything until 3 p.m., and then they could eat their fill of their favorite foods. 
 
 They could then snack as they liked and got another meal at 7:30 p.m. 
 
 Everyone overate at the 3 p.m. meal, taking in typically 2,000 calories in one sitting, or virtually all the day’s requirements. “Regardless of sleep condition, when you are presented with a whole bunch of foods that you like and you can graze what you like, people will eat more than they normally would,” Hanlon said. 
 
 But the people who were awakened every day at 5.30 am, cutting their sleep almost in half, went on to eat another 1,000 calories later in the day, Hanlon’s team reported. 
 
 And they went for the “highly palatable, rewarding snacks” such as sweets or chips. Those who got plenty of sleep also overate, but only by about another 600 calories, the team reported. 
 
 Blood levels of 2-AG are typically low overnight and rise slowly to peak in the early afternoon. In the sleep-deprived volunteers, levels of 2-AG rose higher and stayed high through the evening. 
 
 “At the same time where we see people having this lack of ability to inhibit snack intake corresponds to the time that we see an increase in concentrations of circulating endocannabinoids,” Hanlon said. 
 
 “It corresponds to the same period. It also corresponds to the time people report they feel hungrier.” 
 
 These endocannabinoids have been linked with appetite by other groups, who found they activated the brain’s central feeding system. 
 
 And other research has shown sleep deprivation affects the “appetite hormones” ghrelin and leptin, although those effects are not clear-cut. 
 
 “With this well-controlled experimental study, Hanlon and colleagues have added compelling new evidence for an involvement of endocannabinoids and food reward mechanisms underlying excess food intake and weight gain following sleep restriction,” Frank Scheer, a sleep disorders specialist at Harvard Medical School who was not involved in the study, wrote in a commentary. 
 
 Two thirds of Americans are overweight or obese. And the CDC says more than a third of Americans are not getting enough sleep. Obesity and a lack of sleep both raise the odds of heart disease and other health problems and a lack of sleep is clearly linked with obesity. 
 
 Hanlon believes the relationship between poor sleep and overeating is almost certainly complicated and probably doesn’t lie in a single biological compound. 
 
 “We know sleep restriction inhibits cognitive performance. It inhibits impulsivity. You are more driven to overeat,” she said. 
 
 “If you have a Snickers bar, and you’ve had enough sleep, you can control your natural response,” she added. “But if you’re sleep-deprived, your hedonic drive for certain foods gets stronger, and your ability to resist them may be impaired so you are more likely to eat it. Do that again and again, and you pack on the pounds.” 
 
 “We know sleep restriction inhibits cognitive performance. It inhibits impulsivity. You are more driven to overeat." 
 
 A next step is to see how and where the 2-AG is getting overproduced. 
 
 “I’d love to be able to figure out where the endocannabinoids are coming from,” Hanlon said. “We know that it is made in the brain. “ But it might also be made in the stomach or in fat cells, she said. 
 
 And would changing it affect people’s tendency to nosh after a poor night’s sleep? 
 
 There was a drug that turned off the same brain circuit that causes the munchies. It was called rimonabant, and drug maker Sanofi started to market it under the brand names Acomplia and Zimulti. But it caused depression and was pulled off the market. 
 
 “We are hoping to bring awareness to fact that individuals need to think of adequate sleep and a good sleep routine as important aspects of maintaining good health,” Hanlon said. People need to stop invoking “the old adage of I’ll sleep when I am dead”, she added. 
 
 Helping people sleep better is more easily said than done, however. Study after study finds that the artificial lights in computer and television screens can cause insomnia. So can can overuse of social media. And the CDC says that there's no real proven sleep aid, even though nearly 9 million Americans say they take sleeping pills. ||||| Purchase The Current Issue 
 
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– If you've wondered why you nosh like crazy after a night of tossing and turning, scientists think they've figured it out: Your brain may compensate for the lack of sleep by releasing chemicals similar to those that pot smokers breathe in, resulting in the tired person's version of the "munchies," NBC News reports. In the study published in the journal Sleep, a University of Chicago team led by Dr. Erin Hanlon found that blood levels of an endocannabinoid known as 2-arachidonoylglycerol (aka 2-AG)—a chemical produced in the brain that's similar to those found in pot and that typically appears in the blood at peak levels in the afternoon and stays low overnight—actually kept rising after the afternoon spike and remained high all evening in subjects who were sleep-deprived. Not only did the drowsy participants find it harder to resist nibbling, they chose not-so-healthy snacks. People who use marijuana and overeat also "tend to eat things that are yummy and rewarding," Hanlon says. In this admittedly small study (14 people in their 20s), the subjects camped out for four days at a time at a sleep center, with some volunteers allowed to doze for 8.5 hours a night while others only got 4.5 hours. On the fifth day, the subjects' first meal was delayed until 3pm, followed by unlimited snacks, then a second meal at 7:30pm. All subjects gorged during the first meal, taking in around 2,000 calories each, but the subjects with less shut-eye ate 1,000 more calories during the rest of the day (and mostly salty or sweet junk food); the rested subjects consumed just 600 more calories. Some of the tired subjects had trouble resisting these "reward" foods even when full, per the Guardian. "If you have a Snickers bar, and you've had enough sleep, you can control your natural response," Hanlon tells NBC. "But if you're sleep-deprived, your hedonic drive for certain foods gets stronger, and your ability to resist them may be impaired, so you are more likely to eat it. Do that again and again, and you pack on the pounds." (Here's something else that can have a similar effect.)