Chapter 9. Homeostasis: Active Regulation of the Internal Environment
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By Winnie Yu If you want to keep your cool, you might want to pass up those greasy wings and gooey dessert. A new study from the University of California, San Diego, suggests that people whose diets are higher in trans fats are more prone to aggression. Trans fats, or hydrogenated oils, have made the news in recent years because studies have strongly linked them to heart disease and cancer, and some locales have passed laws restricting their use. They are still common, however, in restaurant food and many grocery items. Beatrice Golomb, a physician and associate professor of medicine at U.C. San Diego, wondered if trans fats might affect behavior, after noting how they interact with a type of healthy fat. Past studies found that docosahexaenoic acid—or DHA, a long-chain omega-3 fatty acid—has a calming, antidepressant effect. Trans fats disrupt the chemical process that leads to the conversion of fatty acids into DHA, which led Golomb to suspect that trans fats might be linked to aggression. Her study, which was published in March in PLoS ONE, involved 1,018 men and women older than 20 who filled out a food questionnaire and several other surveys that measure impatience, irritability and aggression. Even after considering other influences, Golomb's team found a strong link between the intake of trans fats and aggression. “Trans-fatty acids were a more consistent predictor of aggression than some traditional risk factors such as age, male sex, education and smoking,” Golomb says. The findings were consistent across both sexes and across all ages, ethnicities and socioeconomic groups. © 2012 Scientific American
Link ID: 17110 - Posted: 08.01.2012
By GRETCHEN REYNOLDS Two groundbreaking new studies address the irksome question of why so many of us who work out remain so heavy, a concern that carries special resonance at the moment, as lean Olympians slip through the air and water, inspiring countless viewers to want to become similarly sleek. And in a just world, frequent physical activity should make us slim. But repeated studies have shown that many people who begin an exercise program lose little or no weight. Some gain. To better understand why, anthropologists leading one of the new studies began with a research trip to Tanzania. There, they recruited volunteers from the Hadza tribe, whose members still live by hunting and gathering. Providing these tribespeople with a crash course in modern field-study technology, the researchers fitted them with GPS units, to scrupulously measure how many miles each walked daily while searching for food. They also asked them to swallow so-called doubly labeled water, a liquid in which the normal hydrogen and oxygen molecules have been replaced with versions containing tracers. By studying these elements later in a person’s urine, researchers can precisely determine someone’s energy expenditure and metabolic rate. The researchers gathered data for 11 days, then calculated the participants’ typical daily physical activity, energy expenditure and resting metabolic rates. They then compared those numbers with the same measures for an average male and female Westerner. Copyright 2012 The New York Times Company
Link ID: 17109 - Posted: 08.01.2012
by Andy Coghlan, Cambridge, UK IT'S early evening, and I'm facing a dilemma of some delicacy - whether or not to break wind. Let me explain... I'm poised to be voluntarily trapped in a room for the night as part of research to find new treatments for obesity at the Wellcome Trust Clinical Research Facility at Addenbrooke's Hospital in Cambridge, UK. The aim of the experiment is to see if brown fat, a special type of fat tissue that turns energy obtained from food into heat, can be coaxed into burning more unwanted white fat than usual. They intend to do this using a simple food supplement - a daily capsule of spicy ingredients such as chilli pepper or cinnamon - aimed at mimicking the effects of being in the cold. Recruited as a control, I've spent the afternoon undergoing a battery of tests to serve as reference data for how people in reasonably good health burn energy. Investigator Andy Whittle at the University of Cambridge explains that comparisons with this data will help establish whether people burn more energy than normal when kept in the cold (at 18 °C for 2 hours) or when given the spicy food capsules. I will be confined to a special room for the night, which serves as a human-scale calorimeter. "We'll treat you as if you're a fire, measuring how much oxygen you take in and how much carbon dioxide you breathe out," says Peter Murgatroyd, who designed the calorimeter. In other words, they will be capturing everything that goes in and out of my body. © Copyright Reed Business Information Ltd.
Link ID: 17095 - Posted: 07.28.2012
By Helen Briggs BBC News The idea that exercise is more important than diet in the fight against obesity has been contradicted by new research. A study of the Hadza tribe, who still exist as hunter gatherers, suggests the amount of calories we need is a fixed human characteristic. This suggests Westerners are growing obese through over-eating rather than having inactive lifestyles, say scientists. One in 10 people will be obese by 2015. And, nearly one in three of the worldwide population is expected to be overweight, according to figures from the World Health Organization. The Western lifestyle is thought to be largely to blame for the obesity "epidemic". Various factors are involved, including processed foods high in sugar and fat, large portion sizes, and a sedentary lifestyle where cars and machines do most of the daily physical work. BBC © 2012
Link ID: 17094 - Posted: 07.28.2012
By Deborah Kotz, Globe Staff The approval this week of a new weight loss pill called Qsymia means that doctors will soon be able to prescribe two new drugs to help overweight people shed pounds. Last month, the US Food and Drug Administration approved the pill Belviq, the first drug approved for obesity in 13 years. Both drugs will hit pharmacies later this year and their cost, yet to be determined, will probably be about $100 to $200 a month. I asked Dr. Richard Siegel, co-director of the Diabetes Center at Tufts Medical Center, to sort out the pros and cons of these new medications and who might be appropriate candidates for drug therapy. Here are edited excerpts from our interview. Which people are most likely to benefit from these drugs? Both drugs were approved for those who are obese -- defined as a body mass index of 30 or above -- or overweight with a BMI of at least 27 and a weight-related complication such as diabetes, high blood pressure, or high cholesterol. (Note: A 5’5” person who is 163 pounds has a BMI of 27, and at 180 pounds has a BMI of 30.) How much weight can people expect to lose? It’s variable but the clinical trials performed by the drug manufacturers found that Belviq leads to an average drop in body weight of about 5 percent, while Qsymia leads to an average decline of 10 percent. I tell patients that the more effort they put into it, the more results they can get from weight-loss drugs. Yes, they can lose a few pounds if they just take a pill and do nothing else, but if they join a support group, meet with a nutritionist to map out a new eating plan, and start exercising, they might exceed those average weight losses seen in study participants. © 2012 NY Times Co.
Link ID: 17070 - Posted: 07.21.2012
By Ferris Jabr Between October and June they shuffle out of auditoriums, gymnasiums and classrooms, their eyes adjusting to the sunlight as their fingers fumble to awaken cell phones that have been silent for four consecutive hours. Some raise a hand to their foreheads, as though trying to rub away a headache. Others linger in front of the parking lot, unsure of what to do next. They are absolutely exhausted, but not because of any strenuous physical activity. Rather, these high school students have just taken the SAT. "I was fast asleep as soon as I got home," Ikra Ahmad told The Local, a New York Times blog, when she was interviewed for a story on "SAT hangover." Temporary mental exhaustion is a genuine and common phenomenon, which, it is important to note, differs from chronic mental fatigue associated with regular sleep deprivation and some medical disorders. Everyday mental weariness makes sense, intuitively. Surely complex thought and intense concentration require more energy than routine mental processes. Just as vigorous exercise tires our bodies, intellectual exertion should drain the brain. What the latest science reveals, however, is that the popular notion of mental exhaustion is too simplistic. The brain continuously slurps up huge amounts of energy for an organ of its size, regardless of whether we are tackling integral calculus or clicking through the week's top 10 LOLcats. Although firing neurons summon extra blood, oxygen and glucose, any local increases in energy consumption are tiny compared with the brain's gluttonous baseline intake. So, in most cases, short periods of additional mental effort require a little more brainpower than usual, but not much more. Most laboratory experiments, however, have not subjected volunteers to several hours' worth of challenging mental acrobatics. And something must explain the feeling of mental exhaustion, even if its physiology differs from physical fatigue. Simply believing that our brains have expended a lot of effort might be enough to make us lethargic. © 2012 Scientific American,
Emma Marris Large-brained animals may be less likely to go extinct in a changing world, perhaps because they can use their greater intelligence to adapt their behaviour to new conditions, according to an analysis presented to a meeting of conservation biologists this week. The finding hints at a way to prioritize future conservation efforts for endangered species. Brain size relative to body size is fairly predictable across all mammals, says Eric Abelson, who studies biological sciences at Stanford University in Palo Alto, California. “As body size grows, brain size grows too, but at slower rate,” he says. Plotting brain size against body size creates a tidy curve. But some species have bigger or smaller brains than the curve would predict for their body size. And a bigger brain-to-body-size ratio usually means a smarter animal. Abelson looked at the sizes of such deviations from the curve and their relationships to the fates of two groups of mammalian species — ‘palaeo’ and ‘modern’. The palaeo group contained 229 species in the order Carnivora from the last 40 million years, about half of which are already extinct. The modern group contained 147 species of North American mammals across 6 orders. Analysis of each group produced similar results: species that weighed less than 10 kilograms and had big brains for their body size were less likely to have gone extinct or be placed on the International Union for Conservation of Nature red list for endangered species. For species larger than about 10 kilograms, the advantage of having a large brain seems to be swamped by the disadvantage of being big. Large species tend to reproduce later in life, have fewer offspring, require more resources and larger territories, and catch the attention of humans, either as food or as predators. Hunting pressure or reductions in available space can hit them particularly hard. © 2012 Nature Publishing Group
Link ID: 17063 - Posted: 07.18.2012
By Linda Carroll Teens who play on more than one sports team during the year are far less likely to become overweight or obese, a new study suggests. In fact, Dartmouth College researchers concluded that the obesity rate among high schoolers could be cut by more than 26 percent if all teens signed up for multiple team sports, according to the study, published today in the journal Pediatrics. The researchers also found that kids who bike or walk to school are less likely to become obese. If every kid in the country biked or walked to school at least four days a week, then obesity could be cut by 22 percent, they reported. “I know that coordinating schedules can be difficult in terms of getting kids to practices and games,” said study co-author Keith Drake, a post doctoral research fellow at the Hood Center for Children and Families at the Geisel School of Medicine at Dartmouth. “But it does look to us like getting kids involved in sports may be the best chance we have to get them physically active and to help them maintain a healthy body weight.” Playing on a single team didn’t appear to have a strong effect. Still, Drake said: “Playing on one team is probably better than playing on none.” Drake and his colleagues surveyed 1,718 New Hampshire and Vermont high school students and their parents for the new study. The new report is part of a seven-year review of adolescent health that started in 2002 and included five separate surveys of the kids and their parents. © 2012 NBCNews.com
CBC News Keeping track of how much you eat by writing it down each day, rather than what you eat, is key for weight loss, a new U.S. study suggests. The No. 1 piece of advice would be to keep a food journal to document every morsel that passes your lips and thereby help monitor daily calorie intake, concluded researchers at the Fred Hutchinson Cancer Research Center in Seattle, Wash. “It is difficult to make changes to your diet when you are not paying close attention to what you are eating.” said lead investigator Anne McTiernan. Participants in the study were given a printed booklet to record their food and beverage consumption, but a food journal doesn't have to be fancy. "Any notebook or pad of paper that is easily carried or an online program that can be accessed any time through a smart phone or tablet should work fine," McTiernan said. Other specific behaviours that support weight loss include not skipping meals and avoiding eating in restaurants – especially at lunch. The findings were published online Friday in the Journal of the Academy of Nutrition and Dietetics The study focus was on how self-monitoring and other diet-related behaviors, as well as meal patterns, effect weight change in overweight and obese postmenopausal women. © CBC 2012
Link ID: 17045 - Posted: 07.16.2012
By Kay Lazar Mary Regan has witnessed a transformation outside the front door of her Union Square office in Somerville — new “corrals” provide more parking spaces for bicyclists, angled parking has replaced parallel parking for cars to keep doors from flying open into bicycle lanes, and those lanes have been freshly painted. At the nearby farmers’ market, $1 in food stamps is worth $2 in produce to help low-income customers afford fresh fruits and vegetables. “I’ve heard people here say that farmers’ markets used to seem like an elite, foreign thing,” said Regan, a community organizer at a nonprofit organization for affordable housing. “But now that they can use their [food stamps] and get twice as much for the same amount of money, they are buying more healthy foods.” A decade after an ambitious experiment dubbed Shape Up Somerville was launched to lower obesity rates in elementary school children, the campaign has been expanded and woven into the fabric of everyday life in this diverse city of 78,000, where 52 languages are spoken in the public schools and almost two-thirds of students come from families so poor that they receive free or reduced-price school lunches. City decisions about roads, bridges, other transportation projects, real estate development, and parks include an analysis of how the plans might affect residents’ physical activity or ability to shop for healthy food. Two city employees ensure healthy goals are considered at every step, particularly by collaborating with community groups. © 2012 NY Times Co.
Link ID: 17044 - Posted: 07.16.2012
Children who increase the number of hours of weekly television they watch between the ages of two and four years old risk larger waistlines by age 10. A Canadian study found that every extra weekly hour watched could add half a millimetre to their waist circumference and reduce muscle fitness. The study, in a BioMed Central journal, tracked the TV habits of 1,314 children. Experts say children should not watch more than two hours of TV a day. Researchers found that the average amount of television watched by the children at the start of the study was 8.8 hours a week. This increased on average by six hours over the next two years to reach 14.8 hours a week by the age of four-and-a-half. Fifteen per cent of the children in the study were watching more than 18 hours per week by that age, according to their parents. The study said the effect of 18 hours of television at 4.5 years of age would by the age of 10 result in an extra 7.6mm of waist because of the child's TV habit. As well as measuring waist circumference, the researchers also carried out a standing long jump test to measure each child's muscular fitness and athletic ability. An extra weekly hour of TV can decrease the distance a child is able to jump from standing by 0.36cm, the study said. BBC © 2012
By Myron Levin and Stuart Silverstein For several years, doctors and medical spas around the country have touted a fat-melting device called the LipoTron 3000, or Lipo-Ex, as a revolutionary way for people to slim down. Signature Medical Spa in Tampa, Fla., in an online pitch for its “Lipo-Ex Spring Fling Fat-Off!,” described the technology as “truly the only non-invasive way to reduce fat.” Praise also came from Sculpt Medical Spa in Chicago, which called the procedure “the most innovative, effective, and technologically advanced” non-surgical method of removing fat. These testimonials have translated into millions of dollars in sales for physicians, med spas, and the device’s manufacturer, RevecoMED International of Fullerton, Calif. But there’s a problem: The LipoTron, which targets fat with radiofrequency waves, has never been cleared or approved by the U.S. Food and Drug Administration, which would make it illegal under federal law to sell or promote it for weight loss. The FDA is aware of the activity. But an investigation by FairWarning found that the agency has not taken enforcement action — even though it has known about the situation at least since January, 2010. At that time, two whistleblowers, one a former LipoTron distributor, provided sales records and a trove of other documents to an FDA criminal investigator. © 2012 msnbc.com
Link ID: 17033 - Posted: 07.12.2012
By GINA KOLATA Is a calorie really just a calorie? Do calories from a soda have the same effect on your waistline as an equivalent number from an apple or a piece of chicken? For decades the question has percolated among researchers — not to mention dieters. It gained new momentum with a study published last month in The Journal of the American Medical Association suggesting that after losing weight, people on a high-fat, high-protein diet burned more calories than those eating more carbohydrates. We asked Dr. Jules Hirsch, emeritus professor and emeritus physician in chief at Rockefeller University, who has been researching obesity for nearly 60 years, about the state of the research. Dr. Hirsch, who receives no money from pharmaceutical companies or the diet industry, wrote some of the classic papers describing why it is so hard to lose weight and why it usually comes back. The JAMA study has gotten a lot of attention. Should people stay on diets that are high in fat and protein if they want to keep the weight off? What they did in that study is they took 21 people and fed them a diet that made them lose about 10 to 20 percent of their weight. Then, after their weight had leveled off, they put the subjects on one of three different maintenance diets. One is very, very low in carbohydrates and high in fat, essentially the Atkins diet. Another is the opposite — high in carbohydrates, low in fat. The third is in between. Then they measured total energy expenditure — in calories burned — and resting energy expenditure. © 2012 The New York Times Company
Link ID: 17020 - Posted: 07.10.2012
By Laura Hambleton, Maureen Michael likes food. Most days, she has three or four meals, and on occasion she eats yet another in the middle of the night. But she rarely worries about her weight, and at 5-foot-8 and 155 pounds, she looks quite trim. “I eat anything, and I eat a lot,” the 51-year-old District resident said. “I like large portions. I have one of those metabolisms, I guess.” Just the other day, Michael ate a salad and two large helpings of spaghetti and meatballs for dinner — after having a hearty bowl of ice cream. For breakfast the next morning, she ate two scrambled eggs, half a package of Polish sausage, English muffins and orange juice. For lunch, she consumed a 12-inch seafood sub and some Doritos, and that night’s dinner featured two pork chops, potatoes and broccoli. That Michael’s weight remains steady even though she eats whatever she wants and does not exercise interests scientists studying the nation’s obesity epidemic. By looking at people who are near their ideal body weight, these reseachers at the National Institutes of Health’s Metabolic Clinical Research Unit in Bethesda hope to figure out what causes so many others to be overweight or uncontrollably fat. Michael is among the one-third of American adults who are at a good weight relative to their height and build. Another third are overweight, and the rest are obese. Unlike Michael, very few people keep their weight in check without paying attention to what they eat and being conscientious about physical activity. © 1996-2012 The Washington Post
Analysis by Jesse Emspak The phrase, "use your brainpower" may soon become literal. Engineers at MIT have developed a tiny prototype fuel cell that creates electricy from the body's natural sugars. The fuel cell could be used to power brain implants for treating epilepsy, Parkinson's diseases and paralysis. Currently, devices implanted in the body are typically powered by lithium-ion batteries, but they have a limited lifetime and need to be replaced. Opening up the body to replace a battery is not something doctor like to do, but doing it in the brain is even less desirable. The researchers, led by Rahul Sarpeshkar, an associate professor of electrical engineering and computer science, built the fuel cell using a platinum catalyst at one end and a layer of carbon nanotubes at the other. It rests on a silicon chip, allowing it to be connected to electronics that would be used in brain implants. coughing robot As glucose passes over the platinum, electrons and hydrogen ions are stripped off as it is oxidized. That's what makes the current. At the other end of the cell, oxygen mixes with the hydrogen to make water when it hits the layer of single-walled carbon nanotubes. The cell produces up to 180 microwatts, enough to power a brain implant that might send signals to bypass damaged region, or stimulate part of the brain (a treatment used in disorders such as Parkinson's). © 2012 Discovery Communications, LLC.
Link ID: 16982 - Posted: 06.28.2012
By MATTHEW PERRONE WASHINGTON (AP) — The Food and Drug Administration has approved Arena Pharmaceutical’s anti-obesity pill Belviq, the first new prescription drug for long-term weight loss to enter the U.S. market in over a decade. Despite only achieving modest weight loss in clinical studies, the drug appeared safe enough to win the FDA’s endorsement, amid calls from doctors for new weight-loss treatments. The agency cleared the pill Wednesday for adults who are obese or are overweight with at least one medical complication, such as diabetes or high cholesterol. The drug should be used in combination with a healthy diet and exercise. Obesity Society President Patrick O'Neil said he’s encouraged by the drug’s approval because it underscores the notion that lifestyle changes alone are not enough to treat obesity. ‘‘This is good news because it tells us that the FDA is indeed treating obesity seriously,’’ said O'Neil, who teaches at Medical University of South Carolina and was the lead researcher on several studies of Belviq. ‘‘On the other hand, it’s not the answer to the problem — or even a big part of the answer.’’ Even if the effects of Belviq are subtle, experts say it could be an important first step in developing new treatments that attack the underlying causes of obesity. ‘‘The way these things tend to work is you have some people who do extremely well and other people don’t lose any weight at all. But if we had 10 medicines that were all different and worked like this, we would have a real field,’’ said Dr. Louis Aronne, director of the weight loss program at Weill-Cornell Medical College. © 2012 NY Times Co
Link ID: 16981 - Posted: 06.28.2012
By Ferris Jabr Every September arctic ground squirrels in Alaska, Canada and Siberia retreat into burrows more than a meter beneath the tundra, curl up in nests built from grass, lichen and caribou hair, and begin to hibernate. As their lungs and hearts slow, the rivers of blood flowing through their bodies dwindle and their core body temperatures plummet, dipping below the freezing point of water. Electrical signals zipping along crisscrossing neural highways vanish in many areas of the brain. Seven months later the squirrels wake up and return to the surface—famished, eager to mate and perfectly healthy. How hibernating mammals survive for so long at such low temperatures without any food or water beyond what they have stored in their own fat fascinates scientists for many reasons. Hibernation is an amazing biological feat and an opportunity to learn new ways of pushing the human body beyond its ostensible limits, as well as healing it when it breaks down. The arctic ground squirrel's brain, in particular, seems to be incredibly resilient. When ground squirrels hibernate their neurons shrink and many connections between neurons shrivel. But their brains periodically compensate for this loss with massive growth spurts, multiplying neural links beyond what existed before hibernation. Learning how the ground squirrel's brain recuperates could not only help scientists understand the brain's plasticity, but also suggest new ways to reverse or prevent cellular damage in neurodegenerative diseases. In particular, recent research on hibernating brains is changing the way some scientists think about misshapen tau proteins, which are a hallmark of Alzheimer's disease. Most small hibernating mammals—hamsters, hedgehogs, bats—turn down their body's thermostat during hibernation, relinquishing one of the defining features of all mammals: warm blood. Arctic ground squirrels are the most extreme example. In August 1987 Brian Barnes of the University of Alaska Fairbanks (U.A.F.) captured 12 arctic ground squirrels and implanted tiny temperature-sensitive radio transmitters in the animals' abdomens. © 2012 Scientific American
Link ID: 16975 - Posted: 06.27.2012
By Jennifer Huget One of the best-kept secrets among women over 50 is not so secret any more, thanks to a study published last week that shows eating disorders and body-image problems aren’t uncommon among that demographic. There’s been lots of concern over the years about young women’s eating disorders. But a disturbing picture of older women’s bingeing, purging and using extreme measures such as diet drugs, diuretics, laxatives and excessive exercise to promote weight loss is starting to emerge. The new study, conducted through the Eating Disorders Program at the University of North Carolina School of Medicine and published June 21 in the International Journal of Eating Disorders, was based on an online survey of 1,849 women age 50 or older. Their average age was 59, and about 92 percent of respondents were white. Only 42 percent of the women were of normal weight, according guidelines set by the U.S. Centers for Disease Control and Prevention. Among the others, 29 percent were overweight and 27 percent obese. (Two percent were underweight.) Fully two-thirds of the women reported being unhappy with their appearance. More than one-third — 36 percent — said they’d spent at least half of their past five years dieting. Forty percent said they weighed themselves more than once a week, and — ugh, this sounds familiar — 41 percent reported checking their body daily through such measures as pinching their belly fat or noting whether their thighs rubbed together. And almost 80 percent said their weight and shape was either moderately important to or the most important factor influencing their self-perception. © 2011 The Washington Post Company
Keyword: Anorexia & Bulimia
Link ID: 16969 - Posted: 06.26.2012
By Nathan Seppa HOUSTON — Men with low testosterone who are given replacement doses of the hormone shed weight steadily for years, researchers in Germany reported June 23 at a meeting of the Endocrine Society. Study participants, nearly all of whom were overweight or obese at the start of the study, lost 36 pounds on average. “This was an unintended effect,” said study coauthor Farid Saad, a research endocrinologist at Bayer Pharma in Berlin. “The big surprise was that when we analyzed the data [we found] that these men had lost weight continuously...year by year.” The men didn’t diet as part of the study, and any increase in their activity was voluntary, Saad said. He and his colleagues studied 116 men, average age 61, who had low testosterone levels. Each received quarterly injections of the hormone for five years. At the start, 71 percent were obese and another 24 percent were overweight. After five years, 97 percent of the men showed a reduction in waist circumference, on average losing “three to four trouser sizes,” Saad said. Average weight dropped from 236 pounds to about 200. “This definitely offers some insight that we can apply to our clinical practices,” said Vineeth Mohan, a clinical endocrinologist at Cleveland Clinic Florida in Weston. High testosterone levels have been linked to prostate cancer risk (SN: 10/8/05, p. 238), and a small portion of men taking high doses of it experience mania (SN: 2/19/00, p. 119). But in this study, Saad said, men received testosterone in doses just high enough to bring them back to normal levels. Three men in the test group were diagnosed with prostate cancer during the study, a rate lower than the incidence found in routine screening programs for men that age, he said. © Society for Science & the Public 2000 - 2012
By Susan Carnell One of the strangest findings to emerge from the world of obesity science lately is that people who sleep less tend to weigh more. But until recently, we have been stifling our yawns and scratching our heads about why: Does lack of sleep alter our biology? Or does it affect our eating behavior? Now two brain-imaging reports suggest the answer is both. The first study, published in March in the Journal of Clinical Endocrinology & Metabolism, looked at the effects of one night of no sleep. The second, published in April in the American Journal of Clinical Nutrition, tested the impact of nearly a week of more commonly experienced levels of sleep deprivation (four hours of sleep for six nights). Both studies used functional MRI to measure brain activation as their subjects viewed food pictures—analogous to being bombarded with a stream of McMuffin ads after a long night of working (or partying). Each study discovered that sleep loss caused areas within a key motivation network, including the striatum and anterior cingulate cortex, to go into overdrive at the mere sight of food. The same circuit perks up when addicts view images of their substance of choice. “Calories are energy, and your brain subconsciously knows they will wake you up,” says Marie-Pierre St-Onge of Columbia University, lead investigator of the April study. She likens the superresponsive sleep-poor brain to that of someone who has lost weight on a drastic diet—devouring the first snack you can get your hands on is a “no-brainer.” © 2012 Scientific American