Chapter 13. Homeostasis: Active Regulation of the Internal Environment

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Michael Byrne Hunger is complicated. It's not merely a single drive, though this is mostly how may experience it consciously: a single dimension of hunger magnitude. We are more or less hungry, sometimes not at all. But there's something else lurking in the brain: anti-hunger. We can be hungry and not hungry simultaneously, in a sense. In more concrete terms, we can imagine that there is in the brain a certain subset of "hunger neurons." When we feel hungry—as during periods of fasting—it means that these neurons are active. Otherwise, the hunger neurons are silent. Hunger neurons are quite real: neuroscientists have demonstrated their function by stimulating hunger neurons artificially, causing mice to eat at weird times and gain weight. But something interesting happens as we start cranking hunger neurons (agouti-related protein, or AgRP, neurons) up. There's a limit. Mice won't just eat themselves to death. This indicates that there's something else to hunger, a moderating factor. This factor is described for the first time this week in Nature Neuroscience by researchers at Harvard Medical School: a new population of neurons that intermingle with AgRP neurons and basically have the opposite effect. Anti-hunger. Anti-hunger is in itself not a brand new idea. For a long time, neuroscientists looked to pro-opiomelanocortin (POMC) neurons, which are likewise intermingled with the AgRP hunger neurons, for filling this role. This is reasonable: genetic mutations and manipulations to the POMC neurons have been observed to lead to obesity in mice. © 2017 Vice Media LLC

Keyword: Obesity
Link ID: 23044 - Posted: 01.02.2017

By JANE E. BRODY The adornments in the office of Eric L. Adams, the Brooklyn borough president, are hardly typical: a full-size refrigerator stocked with fresh fruits and vegetables; a work station where he prepares and blends these plant-based ingredients for his meals and snacks; and a convection oven and hot plate where he cooks them. In an adjacent anteroom, there’s a stationary bike, 15-pound weights, a multipurpose fitness tower and a TRX suspension trainer hanging on the door. His laptop is mounted on a music stand so he can use it while working out on a mini-stepper. Eight months ago, Mr. Adams learned during a health checkup for abdominal pain that he had Type 2 diabetes. He said his average blood sugar level was so high that the doctor was surprised he had not already lapsed into a coma. His hemoglobin A1C level — a lab test that shows the average level of blood glucose over the previous three months — was 17 percent, about three times normal. He wasted no time in tackling his disease with fervor. Spurning the American tendency to treat every ailment with medication, he instead explored the body’s ability to heal itself. Mr. Adams, a 56-year-old former police captain, now needs a new publicity photo. He no longer resembles the roly-poly image on official posters. By adopting a vegan diet, preparing his own meals and working exercise into his everyday routines, he’s shed 30 pounds and completely reversed his diabetes, a pancreatic disorder that can lead to heart attacks, stroke, nerve damage, kidney disease, visual loss and cognitive impairment. Within three months, his A1C level was down to a normal 5.7. He now strives to inform his millions of constituents about how to counter this health- and life-robbing disease, which has reached epidemic proportions in this country, even among children. Starting on the home front, he stripped the Brooklyn Borough Hall drink machine of sugary beverages and the snack machine of everything cooked in oil or unnaturally sweetened. Those searching for a pick-me-up can indulge in plain or sparkling water, diet soda, nuts, dried fruit, protein bars and whole-grain baked chips. © 2017 The New York Times Company

Keyword: Obesity
Link ID: 23043 - Posted: 01.02.2017

Alan Yu Being overweight can raise your blood pressure, cholesterol and risk for developing diabetes. It could be bad for your brain, too. A diet high in saturated fats and sugars, the so-called Western diet, actually affects the parts of the brain that are important to memory and make people more likely to crave the unhealthful food, says psychologist Terry Davidson, director of the Center for Behavioral Neuroscience at American University in Washington, D.C. He didn't start out studying what people ate. Instead, he was interested in learning more about the hippocampus, a part of the brain that's heavily involved in memory. He was trying to figure out which parts of the hippocampus do what. He did that by studying rats that had very specific types of hippocampal damage and seeing what happened to them. In the process, Davidson noticed something strange. The rats with the hippocampal damage would go to pick up food more often than the other rats, but they would eat a little bit, then drop it. Davidson realized these rats didn't know they were full. He says something similar may happen in human brains when people eat a diet high in fat and sugar. Davidson says there's a vicious cycle of bad diets and brain changes. He points to a 2015 study in the Journal of Pediatrics that found obese children performed more poorly on memory tasks that test the hippocampus compared with kids who weren't overweight. He says if our brain system is impaired by that kind of diet, "that makes it more difficult for us to stop eating that diet. ... I think the evidence is fairly substantial that you have an effect of these diets and obesity on brain function and cognitive function." © 2016 npr

Keyword: Obesity; Learning & Memory
Link ID: 23039 - Posted: 12.31.2016

By Laura Beil, Justin Shamoun began to hate his body a few weeks into seventh grade. He was a year younger than his suburban Detroit classmates, having skipped a grade. Many of his peers were entering puberty, their bodies solidifying into sleek young men. Justin still had the doughy build of a boy. After gym class one day, someone told Justin he could probably run faster if he weren’t so fat. The remark crushed him. Ashamed, he started hiding his body under ever-baggier clothes and making excuses to skip P.E., the pool, anywhere required to expose bare skin. Finally, he decided to fix himself. He dove headlong into sports and cut back on food. Before long, he was tossing his lunch into the garbage and picking at his dinner. He ate just enough to blunt his hunger, until the time came when he ate barely at all. The thought that he had an eating disorder never occurred to him. Long considered an affliction of women, eating disorders — the most deadly of all mental illnesses — are increasingly affecting men. The National Eating Disorders Association predicts that 10 million American men alive today will be affected, but that number is only an estimate based on the limited research available. The official criteria for diagnosing eating disorders were updated to be more inclusive of men only in 2013. And last year, Australian researchers writing in the Journal of Eating Disorders noted that “the prevalence of extreme weight control behaviors, such as extreme dietary restriction and purging” may be increasing at a faster rate in men than women. © 2016 Scientific American

Keyword: Anorexia & Bulimia; Sexual Behavior
Link ID: 23036 - Posted: 12.31.2016

By GINA KOLATA It was Oct. 11, 2015, and a middle-aged man and a young woman, both severely obese, were struggling with the same lump-in-the-throat feeling. The next day they were going to have an irreversible operation. Were they on the threshold of a new beginning or a terrible mistake? They were strangers, scheduled for back-to-back bariatric surgery at the University of Michigan with the same doctor. He would cut away most of their stomachs and reroute their small intestines. They were almost certain to lose much of their excess weight. But despite the drastic surgery, their doctor told them it was unlikely that they would ever be thin. Nearly 200,000 Americans have bariatric surgery each year. Yet far more — an estimated 24 million — are heavy enough to qualify for the operation, and many of them are struggling with whether to have such a radical treatment, the only one that leads to profound and lasting weight loss for virtually everyone who has it. Most people believe that the operation simply forces people to eat less by making their stomachs smaller, but scientists have discovered that it actually causes profound changes in patients’ physiology, altering the activity of thousands of genes in the human body as well as the complex hormonal signaling from the gut to the brain. It often leads to astonishing changes in the way things taste, making cravings for a rich slice of chocolate cake or a bag of White Castle hamburgers simply vanish. Those who have the surgery naturally settle at a lower weight. © 2016 The New York Times Company

Keyword: Obesity
Link ID: 23027 - Posted: 12.27.2016

By GINA KOLATA Bariatric surgery is an option that obesity medicine specialists say is too often ignored or dismissed. Yet it is the only option that almost always works to help very heavy people lose a lot of weight and that also can mysteriously make some chronic conditions vanish. Here are some answers about bariatric surgery and what it does. HOW MANY AMERICANS ARE ELIGIBLE FOR BARIATRIC SURGERY? Twenty-four million, according to the American Society for Metabolic and Bariatric Surgery. The criteria are a body mass index above 40, or a B.M.I. of at least 35 along with other medical conditions like diabetes, hypertension, sleep apnea or acid reflux. HOW MANY HAVE THE SURGERY EACH YEAR? Fewer than 200,000. WHAT ARE THE OPERATIONS? There are four in use today. The two most popular procedures are the Roux-en-Y gastric bypass and the gastric sleeve. Both make the stomach smaller. The bypass also reroutes the small intestine. A simpler procedure, the gastric band, is less effective and has fallen out of favor. And a much more drastic operation, the biliopancreatic diversion with duodenal switch, which bypasses a large part of the small intestine, is rarely used because it has higher mortality and complication rates. HOW MUCH DO THE OPERATIONS COST? The average cost of a sleeve gastrectomy is $16,000 to $19,000, and the average cost of a gastric bypass is $20,000 to $25,000. Most insurance plans cover the cost for patients who qualify, though some plans require that patients try dieting for a certain amount of time first. DOES THE SURGERY SAVE MONEY ON OTHER HEALTH CARE COSTS IN THE END? © 2016 The New York Times Company

Keyword: Obesity
Link ID: 23026 - Posted: 12.27.2016

By NICHOLAS BAKALAR Using a sauna may be more than just relaxing and refreshing. It may also reduce the risk for Alzheimer’s disease and other forms of dementia, a new study suggests. Researchers in Finland analyzed medical records of 2,315 healthy men ages 42 to 60, tracking their health over an average of about 20 years. During that time, they diagnosed 204 cases of dementia and 123 cases of Alzheimer’s disease. The study, in Age and Ageing, controlled for alcohol intake, smoking, blood pressure, diabetes and other health and behavioral factors. It found that compared with men who used a sauna once a week, those who used a sauna four to seven times a week had a 66 percent lower risk for dementia and a 65 percent lower risk for Alzheimer’s disease. The senior author, Jari Antero Laukkanen, a professor of clinical medicine at the University of Eastern Finland, said that various physiological mechanisms may be involved. Sauna bathing may, for example, lead to reduced inflammation, better vascular function or lowered blood pressure. “Overall relaxation and well-being can be another reason,” he added, though the findings were only an association. “We need more studies to clarify mechanisms and confirm our findings.” © 2016 The New York Times Company

Keyword: Miscellaneous
Link ID: 23018 - Posted: 12.26.2016

By STEPH YIN Inuit who live in Greenland experience average temperatures below freezing for at least half of the year. For those who live in the north, subzero temperatures are normal during the coldest months. Given these frigid conditions, anthropologists have wondered for decades whether the Inuit in Greenland and other parts of the Arctic have unique biological adaptations that help them tolerate the extreme cold. A new study, published on Wednesday in Molecular Biology and Evolution, identifies gene variants in Inuit who live in Greenland, which may help them adapt to the cold by promoting heat-generating body fat. These variants possibly originated in the Denisovans, a group of archaic humans who, along with Neanderthals, diverged from modern humans about half a million years ago. “As modern humans spread around the world, they interbred with Denisovans and Neanderthals, who had already been living in these different environments for hundreds of thousands of years,” said Rasmus Nielsen, a professor of integrative biology at the University of California, Berkeley and an author of the paper. “This gene exchange may have helped some modern humans adapt to and conquer new environments.” The new study follows earlier research by Dr. Nielsen and colleagues, which found genetic mutations that might help the Inuit metabolize unsaturated fatty acids common in their diet of whales, seals and fish. In this study, Dr. Nielsen’s team focused on another distinct region in the Inuit genome, which seems to affect body fat distribution and other aspects of development. The researchers compared the genomes of nearly 200 Inuit with genomes of Neanderthals, Denisovans and modern populations around the world. © 2016 The New York Times Company

Keyword: Evolution
Link ID: 23011 - Posted: 12.23.2016

Hannah Devlin Science Correspondent Scientists have offered a genetic explanation for why some people are obese and healthy while others develop diabetes and heart disease as a result of their weight. The study identified three genes, which appear to influence whether fat is compartmentalised and stored around the outside of the body or whether it spills into the circulatory system. Higher levels of fat in the blood supply increase the risk of type 2 diabetes and can lead to fatty deposits around the heart and liver. Professor Haja Kadarmideen, a geneticist who led the work at the University of Copenhagen, said: “People who have the ability to store large amounts of fat are able to be fat, but not unhealthy.” Yo-yo weight gain driven by gut bacteria's 'memory' of obesity, says study Read more Previous studies have found that while being overweight or obese is a risk factor for diabetes, liver disease and heart disease, about 15-20% of those who are obese appear to suffer no health consequences. Other research, involving more than 100,000 adults in Denmark, found that those with an “overweight” body mass index (or BMI) were more likely to live longer than those in the “healthy”, “underweight”, and “obese” categories, suggesting that the relationship between weight, health and lifespan is not straightforward. “We wanted to ask what is it that allows some people to be overweight and remain healthy,” said Kadarmideen. © 2016 Guardian News and Media Limited

Keyword: Obesity; Genes & Behavior
Link ID: 23005 - Posted: 12.22.2016

By PHIL BARBER SAN FRANCISCO — Paraag Marathe’s structured, analytical mind has served him well in the offices of Silicon Valley and the National Football League. He figured that he could lean on those traits the first time he spoke publicly about his sister, Shilpa, and how anorexia had taken her life. But composure failed Marathe in 2011, six years after Shilpa’s death, while he spoke to survivors and grieving family members at an event for Andrea’s Voice, a nonprofit foundation that tries to promote education about eating disorders and their treatments. “Not only did I break down a little bit during that speech,” said Marathe, 39, the San Francisco 49ers’ chief strategy officer and executive vice president for football operations. “It was also one of those weird moments afterwards. I emotionally collapsed in the arms of somebody there who had lost her daughter.” The memories were back. Marathe had watched his brilliant sister succumb to self-destructive thoughts and starve herself. He had seen Shilpa wither to less than 50 pounds in the last years of her life, had felt the shame and puzzlement that her condition brought to his family. Fueled by regret — why had he not noticed sooner, and why wasn’t he more assertive in trying to help Shilpa? — Marathe has found his voice. He will patiently tell you that 30 million Americans are believed to suffer from eating disorders, and that medical insurance plans rarely cover treatment of the condition. He will remind you that anorexia has the highest fatality rate among mental illnesses — about 10 percent, according to a 2011 meta-analysis published in Archives of General Psychiatry and cited by the National Institute of Mental Health. Eating-disorder caregivers and advocates welcome Marathe’s help in shattering the myth that anorexia afflicts only well-to-do white girls and women. The illness claims men, too, and frequently remains a taboo subject in less affluent or nonwhite families, said Kristina Saffran of Project HEAL, an organization that raises money to cover care from diagnosis to recovery. © 2016 The New York Times Company

Keyword: Anorexia & Bulimia
Link ID: 22992 - Posted: 12.15.2016

By GINA KOLATA Dr. Frank Sacks, a professor of nutrition at Harvard, likes to challenge his audience when he gives lectures on obesity. “If you want to make a great discovery,” he tells them, figure out this: Why do some people lose 50 pounds on a diet while others on the same diet gain a few pounds? Then he shows them data from a study he did that found exactly that effect. Dr. Sack’s challenge is a question at the center of obesity research today. Two people can have the same amount of excess weight, they can be the same age, the same socioeconomic class, the same race, the same gender. And yet a treatment that works for one will do nothing for the other. The problem, researchers say, is that obesity and its precursor — being overweight — are not one disease but instead, like cancer, they are many. “You can look at two people with the same amount of excess body weight and they put on the weight for very different reasons,” said Dr. Arya Sharma, medical director of the obesity program at the University of Alberta. Not only can that explain why treatment is so difficult and results so wildly variable, but it can explain why prevention efforts often fail. After trial and error, here are six stories from people who finally found diets, drugs and other methods that helped them keep the weight off. If obesity is many diseases, said Dr. Lee Kaplan, director of the obesity, metabolism and nutrition institute at Massachusetts General Hospital, there can be many paths to the same outcome. It makes as much sense to insist there is one way to prevent all types of obesity — get rid of sugary sodas, clear the stores of junk foods, shun carbohydrates, eat breakfast, get more sleep — as it does to say you can avoid lung cancer by staying out of the sun, a strategy specific to skin cancer. One focus of research is to figure out how many types of obesity there are — Dr. Kaplan counts 59 so far — and how many genes can contribute. So far, investigators have found more than 25 genes with such powerful effects that if one is mutated, a person is pretty much guaranteed to become obese, said Dr. Stephen O’Rahilly, head of the department of clinical biochemistry and medicine at Cambridge University. © 2016 The New York Times Company

Keyword: Obesity
Link ID: 22976 - Posted: 12.12.2016

By Karinna Hurley Autonomy, peer relationships, and parental conflict — these are the universal themes that made the popular 1990s comic Zits identifiable for anyone who has, or has been, a teenager. In one strip, hands in pockets and making a sullen sideways glance, Jeremy slouches next to his father. His t-shirt reads, “question authority.” Next to him, his equally chagrined father sports the t-shirt: “do not question my authority.” While his parents work to steer the 16-year-old in the right direction on his path to adulthood, Jeremy is equally determined to forge his own way. For the most part, their suggestions, pleas, and cajoles, don’t make it past his headphones. Figuring out how to effectively appeal to adolescents was the first challenge facing researchers in a fascinating new study published in the Proceedings of the National Academy of Sciences. Their goal was to induce teens to change one critically important behavior — food choice — in a completely novel way. The researchers set-up a scenario where healthy eating itself became an avenue for fighting authority. While such a unique value-based intervention also has the potential to be applicable to other groups and values, it’s hard to find a better place to start in today’s society than healthy eating. One of the major initiatives developed and championed by outgoing First Lady Michelle Obama was aimed at reducing childhood obesity. Because, despite the consequences — heart disease, stroke, diabetes — about one in three American adults and nearly one in five children are obese. Carrying extra weight is harmful to individuals and also costly to society. But changing eating habits, one factor in being overweight, is just plain hard. It is not enough to know the consequences of eating junk food: In movie theaters, on best-seller lists and billboards, the warnings are all around us. Yet, even widespread public health messages and access to kitchen gardens, like on the South Lawn of the White House, have not yet curbed rising obesity levels. © 2016 Scientific American

Keyword: Obesity
Link ID: 22961 - Posted: 12.07.2016

By PAGAN KENNEDY Abby Solomon suffers from a one-in-a-billion genetic syndrome: After just about an hour without food, she begins to starve. She sleeps in snatches. In her dreams she gorges on French fries. But as soon as she wakes up and nibbles a few bites, she feels full, so she ends up consuming very few calories. At 5 feet 10 inches tall, she weighs 99 pounds. Now 21 years old, she is one of the few people in the world to survive into adulthood with neonatal progeroid syndrome, a condition that results from damage to the FBN1 gene. This mutation mangles noses and eyes and destroys the layer of fat under the skin so that even teenagers look middle-aged. It also interferes with the body’s ability to make a hormone called asprosin, which regulates blood sugar. Atul Chopra, a medical geneticist at Baylor College of Medicine, told me that people with the disorder don’t experience ordinary hunger — instead they waver on the edge of hypoglycemia and must constantly snack to keep from passing out. And yet when I asked Ms. Solomon if she wished she could magically repair her damaged gene, she answered without hesitation: “I wouldn’t change it for anything.” This is because her painful body may hold the clues to a lifesaving treatment for millions of people with obesity and diabetes. Dr. Chopra told me that, as far as medical science is concerned, Abby Solomon is worth thousands of the rest of us. By observing her, scientists can see how a hormone deficiency affects a living person, from her thoughts to her liver function. Several years ago, she spent a day inside a metabolic chamber in a lab so that Dr. Chopra could measure everything she breathed and ate. The results showed that Ms. Solomon takes in about half the calories of a typical woman her age, and also expends half as much energy. “Nothing comes close to starting with people who are naturally different,” he said. This is why he searches out patients at the extreme ends of the spectrum — those who are wired to weigh 80 pounds or 380 pounds. He said, “We have the opportunity to help a bigger swath of humanity when we learn from these outliers.” © 2016 The New York Times Company

Keyword: Obesity; Genes & Behavior
Link ID: 22919 - Posted: 11.28.2016

By Tracy Vence Lose weight, gain it back. That’s the frustrating routine for many individuals who have experienced only short-term success with diets. To examine the microbial and metabolic factors underlying this weight loss-regain cycle, researchers at the Weizmann Institute of Science in Rehovot, Israel, ran a series of experiments using a mouse model of recurrent obesity. The composition of a mouse’s microbiome is predictive of post-diet weight regain, which is in part modulated by metabolites released by the bugs, the researchers found. Their results were published today (November 24) in Nature. “This work adds some insight on how the microbiome acts as a buffer to changes in our diet,” study coauthor Eran Segal of the Weizmann Institute said during a press briefing this week (November 22). In particular, the researchers found evidence to suggest that mice that were once obese tend to experience alterations in microbiome composition that persist during and after weight loss. They also linked the metabolic health of mice to levels of the dietary flavonoids apigenin and naringenin, among other metabolites exchanged between the host and microbiome. See “How Diet Influences Host-Microbiome Communication in Mice” There is hope, however. Segal and colleagues also reported that microbiome- and metabolite-mediating therapies—such as antibiotic treatment, fecal transplant, or postbiotic supplementation—can ameliorate the rate of weight regain in mice predisposed to recurrent obesity. © 1986-2016 The Scientist

Keyword: Obesity
Link ID: 22916 - Posted: 11.26.2016

By Julie Hecht If you assume dogs are always ready for more food, try again. Like you, dogs make decisions about which types of food to eat. For example, if someone shows you two plates, one with a glorious piece of your favorite pie and another plate with a piece of your favorite pie with a side of carrots, many of you are going to go for the pie alone. You'd adopt a less-is-more strategy because pie plus carrots is kinda gross. Monkeys do this too. In 2012, Kralik and colleagues found that while monkeys will eat grapes on their own and cucumbers on their own, when given the choice between a grape alone and a grape accompanied by a slice of cucumber, monkeys preferred the grape alone. It’s not that monkeys won't eat cucumbers, they’d just prefer grapes by themselves. Monkeys based their choice not on the overall quantity of the food, but instead on a qualitative decision. How about dogs? A recent study by Kristina Pattison and Thomas Zentall of the University of Kentucky examined whether companion dogs also adopt a less-is-more strategy. The researchers first determined whether dogs had a preference between two foods, in this case carrots and cheese. Ten companion dogs—all of whom would voluntarily eat both string cheese and baby carrots—were found to prefer the cheese over the carrots (all the dogs occasionally chose carrots, suggesting that carrots are not valueless). But when given the choice to eat a piece of cheese on its own or a piece of cheese together with carrot, dogs chose a single piece of cheese over a piece of cheese "tainted" by the presence of carrot. © 2016 Scientific American,

Keyword: Obesity
Link ID: 22915 - Posted: 11.26.2016

Mo Costandi Lucy Cheke and her colleagues at the University of Cambridge recently invited a few participants into her lab for a kind of ‘treasure hunt’. The participants navigated a virtual environment on a computer screen, dropping off various objects along their way. They then answered a series of questions to test their memory of the task, such as where they had hidden a particular object. When examining what might have influenced their performance, you might expect that Cheke would have been more concerned with the participant’s IQ – not their waistline. Yet she found a clear relationship between their Body Mass Index – a measure of your weight relative to your height – and apparent memory deficits: the higher a participant’s BMI, the worse they performed on the Treasure Hunt task. In doing so, Cheke has contributed to a small but growing body of evidence showing that obesity is linked to brain shrinkage and memory deficits. This research suggests that obesity may contribute to the development of neurodegenerative conditions such as Alzheimer’s Disease. Surprisingly, it also seems to show that the relationship between obesity and memory is a two-way street: being overweight or obese not only impacts on memory function, but may also affect future eating behaviour by altering our recollections of previous eating experiences. Cheke’s interest in the subject began unexpectedly. “At the time I was looking at the ability to imagine a future state, particularly in terms of making decisions about food,” says Cheke. “If you’re hungry, you’ll imagine your future self as being hungry, too, but obese people seem to make such decisions on fact-based judgements rather than imagining.” © 2016 Guardian News and Media Limited

Keyword: Obesity
Link ID: 22910 - Posted: 11.25.2016

Hannah Devlin Science correspondent People who struggle to maintain a healthy weight after dieting may do so because their gut bacteria retains a “memory” of their past weight, according to scientists. The study, in mice, suggests that yo-yo dieting is not simply a reflection of people returning to unhealthy eating habits, but could be driven by long-term changes in gut bacteria brought about by obesity. The scientists observed that the changes to the gut microbiome brought about by obesity persisted for five times as long as the actual period spent dieting and predisposed the mice to rapidly regain weight. Eran Elinav, an immunologist at the Weizmann Institute in Israel and lead author, said that the findings, if replicated in people, could help develop more evidence-based methods for weight loss. “It may explain some – more than some – of our failure to control weight by dieting,” he said. Simon Cork, a medical researcher at Imperial College London, said the study was one of the first to show that gut bacteria could actively drive weight gain, rather than simply being associated with it. However, he cautioned that it was unclear whether the findings could be extrapolated to people. “We do know that this yo-yo effect is caused by quite a few different mechanisms and it’s likely that gut bacteria is only going to play a small role,” he said. “Ultimately, the main reason why people yo-yo is because they don’t stick to the diet.” In the study, published in Nature, obese mice were switched from a high fat diet to balanced nutrition until they were indistinguishable from a control group of mice in terms of weight and a range of metabolic factors, such as blood sugar levels. © 2016 Guardian News and Media Limited

Keyword: Obesity
Link ID: 22909 - Posted: 11.25.2016

By Andy Coghlan It may sound like a healthy switch, but sometimes people who drink diet soft drinks put on more weight and develop chronic disorders like diabetes. This has puzzled nutritionists, but experiments in mice now suggest that in some cases, this could partly be down to the artificial sweetener aspartame. Artificial sweeteners that contain no calories are synthetic alternatives to sugar that can taste up to 20,000 times sweeter. They are often used in products like low or zero-calorie drinks and sugar-free desserts, and are sometimes recommended for people who have type 2 diabetes. But mouse experiments now suggest that when aspartame breaks down in the gut, it may disrupt processes that are vital for neutralising harmful toxins from the bacteria that live there. By interfering with a crucial enzyme, these toxins seem to build up, irritating the gut lining and causing the kinds of low-level inflammation that can ultimately cause chronic diseases. “Our results are providing a mechanism for why aspartame may not always work to keep people thin, or even cause problems like obesity, heart disease, diabetes and metabolic syndrome,” says Richard Hodin at Massachusetts General Hospital in Boston. Irritating bacteria © Copyright Reed Business Information Ltd.

Keyword: Obesity; Chemical Senses (Smell & Taste)
Link ID: 22908 - Posted: 11.25.2016

By Joshua A. Krisch “In Drosophila, there is a well-documented interaction between sleep and metabolism, whereby flies suppress sleep or increase their activity when starved,” said coauthor William Ja of the Scripps Research Institute in Florida, in a press release. “However, the acute effects of food consumption on sleep have not yet been tested, largely because there was no system available to do so.” Ja and colleagues placed fruit flies in a small plastic chamber, which allowed the researchers to record fly activity before and after feeding. The recordings revealed that the fruit flies became lethargic or fell asleep for about 30 minutes following a large meal and that, the more the flies ate, the longer they remained asleep. Then, the researchers focused on a subset of leucokinin receptors previously implicated as potential drivers of post-meal sleep. Indeed, the researchers found that flies in which leucokinin receptor neurons were silenced remained alert even after a large meal. “Using an animal model, we’ve learned there is something to the food coma effect, and we can now start to study the direct relationship between food and sleep in earnest,” Ja said in the press release. “This behavior seems conserved across species, so it must be valuable to animals for some reason.” © 1986-2016 The Scientist

Keyword: Obesity
Link ID: 22905 - Posted: 11.25.2016

Sara Reardon Lasers shone into the brains of mice can now activate individual neurons — and change the animals behaviour. Scientists have used the technique to increase how fast mice drink a milkshake, but it could also help researchers to map brain functions at a much finer scale than is currently possible. Neuroscientists at Stanford University in California conducted their experiments on mice that were genetically engineered to have light-sensitive neurons in a brain region called the orbitofrontal cortex. That area is involved in perceiving, and reacting to, rewards. By shining a laser at specific neurons, the researchers increased the pace at which the mice consumed a high-calorie milkshake. The results, reported on 12 November at the annual meeting of the Society for Neuroscience in San Diego, California, illustrate for the first time that the technique, known as optogenetics, can control behaviour by activating a sequence of individual cells. One goal of optogenetics is to create automated systems that manipulate the brain on the fly using only light, says Michael Häusser, a neuroscientist at University College London, UK. This might be done by engineering neurons to contain one protein that makes the cell fire when activated by a flash of coloured light, and another that causes the cell to flash in a different colour when it fires. A device that detected this second colour could quickly determine sites of activity associated with certain behaviours and customize which cells the first light would stimulate in response. Such a system might be able to alter the neural processes that link alcohol with reward in addiction, or a visual trigger with flashbacks in post-traumatic stress disorder. © 2016 Macmillan Publishers Limited,

Keyword: Obesity; Drug Abuse
Link ID: 22884 - Posted: 11.18.2016