Chapter 13. Homeostasis: Active Regulation of the Internal Environment

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By Anahad O’Connor Many nutrition experts blame processed foods for the obesity epidemic, suggesting that a return to home cooking would turn it around. But now some researchers are pushing back against that idea, arguing that it oversimplifies the obstacles that poor and middle-class families face. The case against processed foods has been growing. A flurry of studies last month provided new evidence that these foods, which are typically loaded with salt, sugar, fat and chemical additives, heighten the risk of obesity and chronic disease. Scientists at the National Institutes of Health found that people ate more calories and quickly gained weight on a diet of mostly ultra-processed foods like frozen entrees, diet beverages, fruit juices, pastries, baked potato chips, canned foods and processed meats. Then a pair of large studies in the journal BMJ showed that people who ate significant amounts of these foods had increased mortality rates and cardiovascular disease compared to people who avoided them. These findings and others prompted health experts — including Dr. Francis Collins, the director of the N.I.H. — to urge Americans to limit their intake of ultra-processed foods. But that might be easier said than done. Highly processed foods have become the dominant food source for many Americans, accounting for almost 60 percent of the calories we eat. Americans across the socioeconomic spectrum consume them in increasing amounts. But studies show that their intake is highest among low-income families. Many households depend on them because they are cheap, convenient and, in some cases, their only option. © 2019 The New York Times Company

Keyword: Obesity
Link ID: 26325 - Posted: 06.12.2019

By Malia Wollan “Fasting is mental over physical, just like basketball and most other stuff in life,” says Enes Kanter, the 6-foot-11 center for the Portland Trail Blazers. Raised in Turkey, Kanter, 27, is a Muslim who has fasted from sunrise to sunset during the month of Ramadan since he was 8. This season, Ramadan aligned with the N.B.A. playoffs, so Kanter fasted through seven playoff games. During the year he forgoes food and water a day or two a week. “Don’t be scared to try it,” he says. Intermittent fasting has become a trendy tool for losing weight and boosting mental acuity and productivity. Adherents typically restrict eating to a window of eight or fewer hours during the day, or they limit caloric intake a few days per week. Studies suggest that following such diets can lead to weight loss and reduced risk of cardiovascular disease and may even protect against age-related neurological disorders like Alzheimer’s. For his part, though, Kanter is trying desperately not to lose any weight. His team’s trainers worried about him going 16 hours without food or water on game days, and so before dawn and twice after dark he partook of carbohydrate feasts: pasta, quesadillas, burritos, sandwiches, sports drinks and nutrition bars. “As many calories as I can put in my body,” he says. Don’t fast if you are at all prone to eating disorders or have a medical condition that might make it dangerous. (While Ramadan fasting is compulsory for Muslims, exceptions are made for children, pregnant women and the ill, among others.) Break your fast carefully by resisting the hurried, gobbler mind-set. “Don’t lose control of yourself,” Kanter says. “Go slow.” Start with lighter fare like soup or salad. Wait 10 minutes before beginning heavier courses. © 2019 The New York Times Company

Keyword: Obesity
Link ID: 26320 - Posted: 06.11.2019

By Joshua Sokol For half the year, a little brown bird on the northernmost islands of the Galápagos uses its wickedly sharp beak to pick at seeds, nectar and insects. But when the climate dries out, it drinks blood. Yes, there is such a thing as a vampire finch. Yes, it is what it sounds like. Galápagos finches have been used since Darwin’s time to illustrate evolution in action. Even among them, Geospiza septentrionalis is an outlier, one of the few birds in the world to intentionally draw and drink blood. And the species is only found on Wolf and Darwin islands, two of the most remote and off-limits places in the entire archipelago. The vampire finch has a method. First, one bird hops on the back of a resting Nazca booby, pecks at the base of the seabird’s wing, and drinks. Blood stains the booby’s white feathers. Other finches crowd around to wait their turn, or to watch and learn. Because adult boobies can fly away, the attacks are almost never fatal. The only casualties are chicks that flee from the finches on foot and, unable to find their way back, starve. Drinking blood is an unusual diet, and research published last year showed that vampire finches have evolved specialized bacteria in their guts to aid digestion. Even more surprising, according to a paper this week in the journal Philosophical Transactions of the Royal Society B, is that some of these bacteria are similar to ones found in the vampire bats of Central and South America. Se Jin Song, a biologist at the University of California San Diego and the study’s lead author, had previously studied the convergent evolution of gut bacteria. Do disparate animals with the equivalent of fad diets — eating only ants and termites, for instance — develop similar gut microbiota over evolutionary time? © 2019 The New York Times Company

Keyword: Evolution; Obesity
Link ID: 26312 - Posted: 06.10.2019

Mara Gordon Kids with obesity face a host of health problems related to their weight, like high blood pressure, diabetes, and joint problems. Research points to another way heavier children and teens are at risk: their own doctors' bias. This prejudice has real health consequences for kids, making families less likely to show up for appointments or get recommended vaccines. I am a family physician at a community health center in Washington, D.C., and many of my young patients have obesity. It's no surprise. Obesity is the most common chronic disease that affects children and teens in the U.S. One third of American kids are overweight or obese. But I often feel totally unprepared to talk about it in a way that puts kids at ease. We have to cram in a physical exam, shots, and parent questions into a 15-minute appointment, and a discussion about a healthy lifestyle sometimes feels like an afterthought. I remember one recent visit with a teenage girl and her mom, tripping over the words I chose. "Let's talk about your weight," I said, offering a reassuring smile. It didn't seem to work. I still think about the look of shame on my patient's mom's face, as if her daughter's obesity were a personal failing. © 2019 npr

Keyword: Obesity
Link ID: 26302 - Posted: 06.05.2019

By Larissa Zimberoff At the urging of doctor friends and a few popular books, I embarked on a diet plan earlier this year called intermittent fasting. The basics are that I could eat the foods I enjoyed and most of my regular meals, but it had to be within a short time frame of eight to 10 hours. Outside of that, I would stick to water, tea and black coffee. Proponents of the plan, also known as time-restricted eating, say that intermittent fasting could help me lose weight, always a worthwhile goal. It would also give my gut a much-needed break from processing food, improve focus and lessen daily inflammation. In the long-term, it might even help me live longer. I’ll admit, the words “intermittent fasting” sounded a little daunting. But Dr. Jason Fung, author of “The Obesity Code,” assured me that it could easily be incorporated into my daily routine. “Anytime you’re not eating is a fast — anything above four hours is fasting,” he said. “A lot of times people eat because they have to, versus really enjoying what they are eating. If you don’t want the sandwich, skip it. Your body knows what to do, it will take your body fat. That’s why you carry it around with you.” In other words, by voluntarily submitting to an absence of food for long periods during the day, my body would transition from burning sugar for fuel to burning fat. Two things made me think I might be able to stick with an intermittent fasting plan. First, I have Type 1 diabetes, which means eating requires thinking. For most of my life, I have spent my days making in-air computations about what I might or might not consume: weighing pros and cons about specific foods while factoring in things like carbs, fat and fiber. Protein too, if I’m super diligent. The more I eat, the more I have to think. © 2019 The New York Times Company

Keyword: Obesity
Link ID: 26296 - Posted: 06.04.2019

By Jane E. Brody When a child is born with a rare disorder that few doctors recognize or know how to manage, it can pay big dividends for parents to be proactive, learn everything they can about the condition, and with expert medical guidance, come up with the best way to treat it. That is the approach Lara C. Pullen of Chicago adopted when her son, Kian Tan, was born 15 years ago last month at 7½ pounds, seemingly well-formed and healthy. But within 24 hours, Dr. Pullen, who already had two daughters, said Kian had stopped moving, wouldn’t nurse and felt as floppy as a rag doll. Two and a half weeks later, a genetic test showed that Kian had Prader-Willi syndrome, a genetic disorder that occurs once in every 15,000 to 25,000 live births. While at first it is a struggle to get enough food into these babies because they’re too weak to suck, within two or three years their main symptom is an insatiable appetite that results in extreme obesity unless the child, who is driven by constant hunger, is kept from sneaking and stealing food. Prader-Willi syndrome is caused by the failed expression of several genes on chromosome 15 derived from the child’s father. The genes are either missing or inactivated by a mistake that occurs during sperm development or, in some cases, the father’s entire chromosome 15 is not inherited by the fetus. The disorder is only rarely inherited, but when a father has Prader-Willi syndrome caused by a deletion in chromosome 15, there’s a 50 percent chance each child he fathers will inherit the defective chromosome. In addition to an excessive appetite, its range of symptoms includes short stature, sleep apnea, extreme daytime sleepiness, visual defects, underdeveloped genital organs, poor coordination, mild to moderate intellectual disability, speech problems, a high tolerance for pain, temper tantrums, obsessive behaviors and blood sugar irregularities. © 2019 The New York Times Company

Keyword: Obesity; Genes & Behavior
Link ID: 26292 - Posted: 06.03.2019

By Veronique Greenwood After a long hike on a hot day, few things are more rewarding than a tall, frosty glass of water. The rush of pleasure that comes with a drink might feel like a sign from your body that you’ve done the right thing, a reward for remedying your dehydration. But that pleasing sensation isn’t actually linked to your real need for a drink. In a study published Wednesday in the journal Neuron, a group of scientists who have studied how thirst works in the bodies of mammals report that the neural systems related to the feeling of reward work independently of those involved in monitoring water intake. Staying hydrated is high on most organisms’ list of priorities. Mammals have multiple ways of tracking the water they’ve consumed, a subject Yuki Oka, a neuroscientist at the California Institute of Technology, has long studied in mice. The mechanisms in other mammals, including humans, may be similar. One method he and colleagues explored in earlier research involves the gulping motion made by the throat as liquid is swallowed. That gulping sends a message to the brain that water has been consumed, quieting the neurons that generate the urge to drink. But that happens regardless of whether the substance gulped was water or oil, suggesting that the act of gulping only briefly convinces your brain that your thirst is quenched. The body also tracks the presence of water in the gut, and when it becomes clear that water is not arriving, thirst returns. Dr. Oka and colleagues report in their latest study that injecting water directly into the stomachs of mice did quench thirst, albeit after a longer lag. © 2019 The New York Times Company

Keyword: Drug Abuse
Link ID: 26287 - Posted: 06.01.2019

By Kelly Servick Genes are a powerful driver of risk for autism, but some researchers suspect another factor is also at play: the set of bacteria that inhabits the gut. That idea has been controversial, but a new study offers support for this gut-brain link. It reveals that mice develop autismlike behaviors when they are colonized by microbes from the feces of people with autism. The result doesn’t prove that gut bacteria can cause autism. But it suggests that, at least in mice, the makeup of the gut can contribute to some hallmark features of the disorder. “It’s quite an encouraging paper,” says John Cryan, a neuroscientist at University College Cork in Ireland who was not involved in the research. The idea that metabolites—the molecules produced by bacterial digestion—can influence brain activity “is plausible, it makes sense, and it will help push the field forward.” Many studies have found differences between the composition of the gut microbiomes in people with and without autism. But those studies can’t determine whether a microbial imbalance is responsible for autism symptoms or is a result of having the condition. To test the effect of the gut microbiome on behavior, Sarkis Mazmanian, a microbiologist at the California Institute of Technology (Caltech) in Pasadena, and collaborators put fecal samples from children with and without autism into the stomachs of germ-free mice, which had no microbiomes of their own. The researchers then mated pairs of mice colonized with the same microbiomes, so their offspring would be exposed to a set of human microbes early in development. © 2019 American Association for the Advancement of Science

Keyword: Autism
Link ID: 26283 - Posted: 05.31.2019

By Diana Kwon Few things are more refreshing than enjoying a cool beverage after spending a day under the hot summer sun. But gulping down a drink does not always quench thirst. Seawater, for example, may look appealing to someone stranded in the middle of the ocean, but taking a swig of it will only worsen dehydration. Scientists have now discovered that in rodents, signals from both the throat and gut control feelings of thirst. These distinct pathways may explain why consuming a beverage is typically refreshing but does not always sate one’s thirst, according to a study by Yuki Oka, a neuroscientist at the California Institute of Technology, and his colleagues at the California Institute of Technology, published May 29 in Neuron. Last year, Oka’s team reported that the simple act of gulping activated a circuit in the lamina terminalis, a region near the front of the brain, which ultimately led to the suppression of activity in neurons responsible for generating feelings of thirst. This throat-brain pathway, which the researchers identified in mice, switched on regardless of what an animal consumed—water, saline solution and oil produced similar effects. But the fact that all of these substances were able to inhibit the brain’s “thirst” neurons indicated that there was something missing. After all, if any liquid could satisfy an animal’s thirst, it might not consume enough water to remain hydrated. According to Oka, behavioral studies in animals dating back decades suggested that there was an additional mechanism in the gut that signaled the presence of water to the brain. So in their latest investigation, Oka’s team set out to map the brain circuits responsible for receiving these signals. By injecting fluids directly into the guts of mice, the researchers discovered that in order for the rodents to feel fully hydrated, this second gut-based circuit needed to be activated. Without these gastrointestinal signals—which, unlike ones from the throat, selectively responded to the presence of water—the brain’s “thirst” neurons quickly revved up again, driving the animals to drink more. © 2019 Scientific American

Keyword: Miscellaneous
Link ID: 26280 - Posted: 05.30.2019

By James Gallagher Health and science correspondent, BBC News Ultra-processed foods - such as chicken nuggets, ice cream and breakfast cereals - have been linked to early death and poor health, scientists say. Researchers in France and Spain say the amount of such food being eaten has soared. Their studies are not definite proof of harm but do come hot on the heels of trials suggesting ultra-processed foods lead to overeating. Experts expressed caution but called for further investigation. What are ultra-processed foods? The term comes from a way of classifying food by how much industrial processing it has been through. The lowest category is "unprocessed or minimally processed foods", which include: • fruit • vegetables • milk • meat • legumes such as lentils • seeds • grains such as rice • eggs "Processed foods" have been altered to make them last longer or taste better - generally using salt, oil, sugar or fermentation. This category includes: • cheese • bacon • home-made bread • tinned fruit and vegetables • smoked fish • beer Then come "ultra-processed foods", which have been through more substantial industrial processing and often have long ingredient lists on the packet, including added preservatives, sweeteners or colour enhancers. Prof Maira Bes-Rastrollo, from the University of Navarra, told BBC News: "It is said that if a product contains more than five ingredients, it is probably ultra-processed." Examples include: • processed meat such as sausages and hamburgers • breakfast cereals or cereal bars • instant soups • sugary fizzy drinks • chicken nuggets • cake • chocolate • ice cream • mass-produced bread • many "ready to heat" meals such as pies and pizza | meal-replacement shakes How bad were the findings? The first study, by the University of Navarra, in Spain, followed 19,899 people for a decade and assessed their diet every other year. There were 335 deaths during the study. But for every 10 deaths among those eating the least ultra-processed food, there were 16 deaths among those eating the most (more than four portions a day). © 2019 BBC

Keyword: Obesity
Link ID: 26278 - Posted: 05.30.2019

By C. Claiborne Ray Q. Humans can’t drink seawater. So what do sea lions, whales, dolphins and sea birds drink? A. Marine animals may consume both freshwater and saltwater. They rely on various adaptations for survival when only saltwater is available. Many marine mammals have specialized organs called reniculate kidneys with multiple lobes, increasing their urine-concentrating efficiency beyond that of humans. These animals can handle high concentrations of salt in seawater without becoming dehydrated by salt buildup, as humans would. Experts now believe, however, that many of these creatures drink seawater only occasionally. Instead they get low-salt water from what they eat or manage to produce it on their own. Whales, for example, have the specialized kidneys but need far less water than land mammals. Whales get water mostly from the small sea creatures, like krill, that form much of their diet. Seabirds, on the other hand, have special organs called salt glands above their eyes that extract excess salt from the bloodstream and excrete it through the nostrils. © 2019 The New York Times Company

Keyword: Miscellaneous
Link ID: 26273 - Posted: 05.29.2019

By Megan Schmidt “The women’s winter is here. The freeze is upon us,” warns a Game of Thrones parody about men and women’s office temperature preferences. If you have a Y chromosome, you probably haven’t experienced “women’s winter.” As the video explains, women’s winter is “when spring turns to summer and there’s blossom on the trees, the office air doth turns to ice and all the women freeze.” Although the skit is now a few years old, it perfectly captures women’s daily struggle with overly air-conditioned workplaces. To some people, thermostat complaints might seem trivial. But a new study has found that cold offices do more than make women shiver. Thermostat settings geared for men’s comfort — typically cooler temperatures — may actually disadvantage women by lowering their ability to perform some tasks. The study, published in PLOS One, found that women are better at math and word tests when room temperatures are warmer. The women in the study answered more questions correctly and submitted more answers overall during the timed tests. Men, on the other hand, performed marginally better on the same tests at cooler room temperatures, the researchers found. Temperature didn’t influence performance on the logic test for either gender. Study author Agne Kajackaite, a behavioral economics researcher at the WZB Berlin Social Science Center, said the research illustrates that “the battle for the thermostat is not just a complaint about comfort levels.” When it comes to women succeeding in the classroom or in the workplace, room temperatures may make a big difference.

Keyword: Sexual Behavior; Learning & Memory
Link ID: 26266 - Posted: 05.24.2019

By Gretchen Reynolds Skipping breakfast before exercise might reduce how much we eat during the remainder of the day, according to a small but intriguing new study of fit young men. The study finds that the choice to eat or omit a meal before an early workout could affect our relationship to food for the rest of the day, in complicated and sometimes unexpected ways. Weight management is, of course, one of the great public — and private — health concerns of our time. But the role of exercise in helping people to maintain, lose or, in some instances, add pounds is problematic. Exercise burns calories, but in many past studies, people who begin a new exercise program do not lose as much weight as would be expected, because they often compensate for the energy used during exercise by eating more later or moving less. These compensations, usually subtle and unintended, indicate that our brains are receiving internal communiqués detailing how much energy we used during that last workout and, in response, sending biological signals that increase hunger or reduce our urge to move. Our helpful brains do not wish us to sustain an energy deficit and starve. Previous studies show that many aspects of eating and exercise can affect how much people compensate for the calories burned during exercise, including the type and length of the exercise and the fitness and weight of the exercisers. Skipping or consuming breakfast also can matter. When we eat a meal, our bodies rely on the carbohydrates in those foods as a primary source of energy. Some of those carbohydrates are stored in our bodies, but those internal stores of carbohydrates are small compared to the stores of fat. Some researchers believe that our brains may pay particular attention to any reductions in our carbohydrate levels and rush to replace them. © 2019 The New York Times Company

Keyword: Obesity
Link ID: 26257 - Posted: 05.22.2019

By Gina Kolata At least six million obese teenagers in the United States are candidates for weight-loss surgery, experts estimate. Fewer than 1,000 of them get it each year. Many of these adolescents already have complications of obesity, like diabetes or high blood pressure. But doctors have been uncertain just how well surgery works for young patients, and whether they can handle the consequences, including a severely restricted diet. A new study provides some hopeful answers. Researchers followed 161 teenagers aged 13 to 19, and 396 adults aged 25 to 50, for five years after weight-loss surgery. The teenagers actually fared better than the adults. The adolescents lost at least as much weight, and were more likely to see high blood pressure and diabetes ease or go away, the investigators reported on Wednesday in the New England Journal of Medicine. “This really changes the game,” said Dr. Amir Ghaferi, a bariatric surgeon at the University of Michigan, who was not involved in the research. The paper, he said, added to evidence that obesity, like cancer, is best treated early, before long-term damage from related conditions, such as high blood pressure and diabetes, sets in. To have the surgery, teenagers in the study had to meet the same criteria as adults: a body mass index of at least 35 — for instance, a person who is 5 feet 2 inches tall and weighs 192 pounds or more — and obesity-related health problems. Alternately, the adolescents could have a B.M.I. of at least 40 — such as a person who is 5 feet 2 inches tall and weighs at least 220 pounds — without other conditions linked to obesity. There is no exact data on the number of teenagers who meet those criteria in the United States, said Dr. Thomas Inge, chief of pediatric surgery at Children’s Hospital Colorado and lead author of the new study. © 2019 The New York Times Company

Keyword: Obesity
Link ID: 26242 - Posted: 05.17.2019

Aimee Cunningham Nutrition advice can be confusing. Studies that bolster the health benefits of a food or nutrient seem inevitably to be followed by other work undercutting the good news. One reason for the muddle is that nutrition studies sometimes depend on people’s self-reporting of past meals. And because people may forget or even lie about what they’ve been consuming, that data can be flawed, creating conflicting reports about what’s healthy and what’s not, research has shown. But even if people had a photographic memory of all of their meals, that alone wouldn’t provide enough information. How bodies react to and process food can vary widely from person to person and be dependent on genes, the microbes that live inside the gut, a person’s current health, what the food contains or even how it was made (SN: 1/9/16, p. 8). “The problem is that nutrition research is rocket science,” says David Ludwig, a pediatric endocrinologist at Boston Children’s Hospital. “There are potentially thousands of different nutrients and factors in food that could influence our biology or our senses as we eat. Those can interact in unpredictable and complicated ways.” Given the complexity that comes with researching diet, one approach is to study people in a controlled environment, so that researchers know exactly what the participants are eating. A study that tied eating highly processed foods to weight gain, published online May 16 in Cell Metabolism, did just that. Here’s what the researchers learned — and what they still can’t answer. © Society for Science & the Public 2000 - 2019

Keyword: Obesity
Link ID: 26241 - Posted: 05.17.2019

By Diana Kwon When Cynthia Bulik started studying eating disorders back in the early 1980s, what she read in the scientific literature clashed with what she saw in the clinic. At the time, theories about the causes of these conditions were focused primarily on explanations based on family dynamics and sociocultural factors. These descriptions could not explain how, despite dangerously low body weights, patients with eating disorders were often “hyperactive and said they felt well, and only started feeling poorly when we nourished them,” says Bulik, who is currently a professor at both the University of North Carolina and the Karolinska Institute in Sweden. “I became convinced that there had to be something biological going on.” Since then, a growing body of research has confirmed Bulik’s observations. Cases of individuals developing rapid alterations in eating behaviors after various infections—the first of which emerged nearly a century ago—have built up over decades. For example, symptoms of eating disorders often occur in pediatric acute-onset neuropsychiatric syndrome (PANS), a condition in which children experience sudden behavioral changes, typically after a streptococcal infection. In addition, over the last few years, several large-scale epidemiological investigations based on data from population registers in Scandinavia—compiled by Bulik and others—have linked eating disorders and autoimmune diseases, including Crohn’s, celiac and type 1 diabetes. © 2019 Scientific American

Keyword: Anorexia & Bulimia; Neuroimmunology
Link ID: 26222 - Posted: 05.09.2019

Richard Harris Scientists who recently announced an experimental genetic test that can help predict obesity got immediate pushback from other researchers, who wonder whether it is really useful. The story behind this back-and-forth is, at its core, a question of when it's worth diving deep into DNA databanks when there's no obvious way to put that information into use. The basic facts are not in dispute. Human behavior and our obesity-promoting environment have led to a surge in this condition over the past few decades. Today about 40% of American adults are obese and even more are overweight. But genetics also plays an important role. People inherit genes that make them more or less likely to become seriously overweight. While some diseases (like Huntington's and Tay-Sachs) are caused by a single gene gone awry, that's certainly not the case for common conditions, including obesity. Instead, untold thousands of genes apparently play a role in increasing obesity risk. Many of those gene variants contribute a miniscule risk. Sekar Kathiresan, a cardiologist at Harvard and a geneticist at the Broad Institute, set out to see whether he and his team could find a bunch of these genetic variants and add up their effects. The goal was to identify genetic patterns that put people at the highest risk. This genetic information "could explain why somebody's so big, why they have so much trouble keeping their weight down," Kathiresan says. His team identified more than 2 million DNA variants of potential interest. He figures most of those variants are irrelevant, but his hunch is, hidden somewhere in there are a few thousand changes that each contribute at least a tiny bit to a person's risk of developing obesity. © 2019 npr

Keyword: Obesity; Genes & Behavior
Link ID: 26214 - Posted: 05.07.2019

By Nicholas Bakalar Girls who have serious or repeated infections in childhood are at higher risk for developing eating disorders in adolescence, a new study has found. The study, in JAMA Psychiatry, tracked 525,643 girls — every girl born in Denmark from 1989 through 2006. The researchers recorded all prescriptions that were filled for antibiotics and other anti-infective medications, as well as hospitalizations for infection, through 2012. There were 4,240 diagnoses of eating disorders during that time. Compared with girls who had never been hospitalized for infection, those who had been hospitalized were at a 22 percent increased risk for anorexia, a 35 percent increased risk for bulimia and a 39 percent increased risk for other eating disorders. Filling three or more prescriptions for anti-infective drugs was associated with similar increases in the risk, and the more infections or hospitalizations a girl had, the more likely she was to develop an eating disorder. This is an observational study so it cannot determine cause and effect, and the authors acknowledge that other mechanisms — genetic factors, or stress and anxiety, for example — could increase the risk of both eating disorders and infection. The lead author, Lauren Breithaupt, a research fellow at Harvard, said that the reasons for the link are unknown, but “it could be that the anti-infective agents are upsetting the microbes in the gut. Changing the microbiome could affect behaviors through the connection of the gut to the brain through the vagus nerve.” © 2019 The New York Times Company

Keyword: Anorexia & Bulimia; Neuroimmunology
Link ID: 26194 - Posted: 05.02.2019

By Gina Kolata The study subjects had been thin all their lives, and not because they had unusual metabolisms. They just did not care much about food. They never ate enormous amounts, never obsessed on the next meal. Now, a group of researchers in Britain may have found the reason. The people carry a genetic alteration that mutes appetite. It also greatly reduces their chances of getting diabetes or heart disease. The scientists’ study, published on Thursday in the journal Cell, relied on data from the U.K. Biobank, which includes a half million people aged 40 to 69. Participants have provided DNA samples and medical records, and have allowed researchers to track their health over years. A second study in the same journal also used data from this population to develop a genetic risk score for obesity. It can help predict, as early as childhood, who is at high risk for a lifetime of obesity and who is not. Together, the studies confirm a truth that researchers wish more people understood. There are biological reasons that some struggle mightily with their weight and others do not, and the biological impacts often are seen on appetite, not metabolism. People who gain too much weight or fight to stay thin feel hungrier than naturally thin people. The study of the appetite-dulling mutation was led by Dr. Sadaf Farooqi, professor of metabolism and medicine at the University of Cambridge, and Nick Wareham, an epidemiologist at the university. The study drew on Dr. Farooqi’s research into a gene, MC4R. She has probed it for 20 years, but for the opposite reason: to understand why some people are overweight, not why some are thin. © 2019 The New York Times Company

Keyword: Obesity; Genes & Behavior
Link ID: 26156 - Posted: 04.19.2019

Tina Hesman Saey There’s a new way to predict whether a baby will grow into an obese adult. Combining the effect of more than 2.1 million genetic variants, researchers have created a genetic predisposition score that they say predicts severe obesity. People with scores in the highest 10 percent weighed, on average, 13 kilograms (about 29 pounds) more than those with the lowest 10 percent of scores, the team reports April 18 in Cell. The finding may better quantify genes’ roles in obesity than previous prediction scores, but still fails to account for lifestyle, which may be more important in determining body weight, other researchers say. Still, the study shows that “your genetics really start to take hold very early in life,” says coauthor Amit Khera, a cardiologist at Massachusetts General Hospital and the Broad Institute of MIT and Harvard. Weight differences showed up as early as age 3, and by age 18, those with the highest scores weighed 12.3 kilograms more on average than those with the lowest scores, Khera and his colleagues found. Some people with high genetic scores had normal body weights, but those people may have to work harder to maintain a healthy weight than others, he says. People with the highest scores were 25 times more likely to have severe obesity — a body mass index (BMI) greater than 40 — than those with the lowest scores. BMI is a measurement of body fat based on height and weight. A BMI of 18.5 (calculated as kilograms per meters squared of height) to 24.9 is considered healthy. BMIs 30 and above are considered obese. |© Society for Science & the Public 2000 - 2019

Keyword: Obesity; Genes & Behavior
Link ID: 26155 - Posted: 04.19.2019