Chapter 9. Homeostasis: Active Regulation of the Internal Environment

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Links 1 - 20 of 1803

Stephanie Preston The media is replete with COVID-19 stories about people clearing supermarket shelves – and the backlash against them. Have people gone mad? How can one individual be overfilling his own cart, while shaming others who are doing the same? As a behavioral neuroscientist who has studied hoarding behavior for 25 years, I can tell you that this is all normal and expected. People are acting the way evolution has wired them. The word “hoarding” might bring to mind relatives or neighbors whose houses are overfilled with junk. A small percentage of people do suffer from what psychologists call “hoarding disorder,” keeping excessive goods to the point of distress and impairment. But hoarding is actually a totally normal and adaptive behavior that kicks in any time there is an uneven supply of resources. Everyone hoards, even during the best of times, without even thinking about it. People like to have beans in the pantry, money in savings and chocolates hidden from the children. These are all hoards. Most Americans have had so much, for so long. People forget that, not so long ago, survival often depended on working tirelessly all year to fill root cellars so a family could last through a long, cold winter – and still many died. Similarly, squirrels work all fall to hide nuts to eat for the rest of the year. Kangaroo rats in the desert hide seeds the few times it rains and then remember where they put them to dig them back up later. A Clark’s nutcracker can hoard over 10,000 pine seeds per fall – and even remember where it put them. © 2010–2020, The Conversation US, Inc.

Keyword: Obesity; Attention
Link ID: 27149 - Posted: 03.30.2020

By Jane E. Brody Many people who have struggled for years with excess weight know that the hardest and often the most frustrating job is not getting it off but keeping it off. Recent decades have seen countless popular diet schemes that promised to help people shed unwanted pounds, and as each of these diets failed in the long run, they spawned their successors. A diet, after all, is something people go on to go off. Most people think of a diet as a means to an end, and few who go on a food-restricted diet to lose weight expect to have to eat that way indefinitely. And therein lies the rub, with the current unchecked epidemic of obesity as the sorry result. We live in a land of incredible excess. Rich or poor, most of us are surrounded by calorie-rich vittles, many of them tasty but deficient in ingredients that nourish healthy bodies. “We can’t go two minutes without being assaulted by a food cue,” said Suzanne Phelan, lead author of an encouraging new study in the journal Obesity. Even the most diligent dieters can find it hard to constantly resist temptation. And once people fall off the diet wagon, they often stay off, and their hard-lost pounds reappear a lot faster than it took to shed them. But these facts need not discourage anyone from achieving lasting weight loss. Researchers have identified the strategies and thought processes that have enabled many thousands of people to lose a significant amount of weight and keep it off for many years, myself among them. The new study led by Dr. Phelan, professor of kinesiology and public health at California Polytechnic State University, identified habits and strategies that can be keys to success for millions. Yes, like most sensible weight-loss plans, they involve healthful eating and regular physical activity. But they also include important self-monitoring practices and nonpunitive coping measures that can be the crucial to long-term weight management. © 2020 The New York Times Company

Keyword: Obesity
Link ID: 27119 - Posted: 03.16.2020

Laura Reiley A study published in the journal Cell Metabolism by a group of Yale researchers found that the consumption of the common artificial sweetener sucralose (which is found in Splenda, Zerocal, Sukrana, SucraPlus and other brands) in combination with carbohydrates can swiftly turn a healthy person into one with high blood sugar. From whole grain English muffins to reduced-sugar ketchup, sucralose is found in thousands of baked goods, condiments, syrups and other consumer packaged goods — almost all of them containing carbs. The finding, which researchers noted has yet to be replicated in other studies, raises new questions about the use of artificial sweeteners and their effects on weight gain and overall health. In the Yale study, researchers took 60 healthy-weight individuals and separated them into three groups: A group that consumed a regular-size beverage containing the equivalent of two packets of sucralose sweetener, a second group that consumed a beverage sweetened with table sugar at the equivalent sweetness, and a third control group that had a beverage with the artificial sweetener as well as a carbohydrate called maltodextrin. The molecules of maltodextrin don’t bind to taste receptors in the mouth and are impossible to detect. While the sensation of the third group’s beverage was identical to the Splenda-only group, only this group exhibited significant adverse health effects. The artificial sweetener by itself seemed to be fine, the researchers discovered, but that changed when combined with a carbohydrate. Seven beverages over two weeks and the previously healthy people in this group became glucose intolerant, a metabolic condition that results in elevated blood glucose levels and puts people at an increased risk for diabetes.

Keyword: Obesity; Chemical Senses (Smell & Taste)
Link ID: 27113 - Posted: 03.12.2020

By Susana Martinez-Conde Parents tend to be just a bit biased about their children’s looks (not me though—my kids are objectively beautiful), but as it turns out, this type of self-deception is not as benign as one might think. According to recent research, many parents appear to suffer from a sort of denial concerning their kids’ weights, which poses a considerable obstacle to remediating childhood obesity by way of promoting healthy eating habits at home. The latest of such studies was published last month in the American Journal of Human Biology, and conducted by a team of scientists at the University of Coimbra in Portugal. Daniela Rodrigues and her collaborators, Aristides Machado-Rodrigues and Cristina Padez, recruited hundreds of parents and children for their research. All the participating children were between 6 and 10 years old and attended elementary school in Portugal. A total of 834 parents completed questionnaires that included a variety of questions, such as whether they thought that their children’s weight was a bit too little, a bit too much, way too much, or just fine. In turn, the team collected the weights and heights of the 793 participating children, at their respective schools. The results were in line with the researchers’ predictions, but nonetheless remarkable. Of the 33% parents who misperceived their children’s weight, 93% underestimated it. Moreover, parents who underestimated their kids’ weights were 10 to 20 times more likely to have an obese child. Several factors were associated with the parental weight underestimation, including a higher BMI (body mass index) for the mothers, younger ages for the children, lower household income (for girls) and urban living (for boys). However, such associations did not explain why parents underestimated their children’s weights to begin with. © 2020 Scientific American

Keyword: Obesity; Attention
Link ID: 27106 - Posted: 03.09.2020

Amelia Hill A low carbohydrate diet may prevent and even reverse age-related damage to the brain, research has found. By examining brain scans, researchers found that brain pathways begin to deteriorate in our late 40s – earlier than was believed. “Neurobiological changes associated with ageing can be seen at a much younger age than would be expected, in the late 40s,” said Lilianne R Mujica-Parodi, a professor in the department of biomedical engineering at Stony Brook University in New York. “However, the study also suggests that this process may be prevented or reversed based on dietary changes that involve minimising the consumption of simple carbohydrates,” added Mujica-Parodi. To better understand how diet influences brain ageing, researchers concentrated on young people whose brains showed no signs of ageing. This is the period during which prevention may be most effective. Using brain scans of nearly 1,000 individuals between the ages of 18 to 88, researchers found that the damage to neural pathways accelerated depending on where the brain was getting its energy from. Glucose, they found, decreased the stability of the brain’s networks while ketones – produced by the liver during periods of carbohydrate restrictive diets – made the networks more stable. “What we found with these experiments involves both bad and good news,” said Mujica-Parodi, “The bad news is that we see the first signs of brain ageing much earlier than was previously thought. “However, the good news is that we may be able to prevent or reverse these effects with diet … by exchanging glucose for ketones as fuel for neurons,” she added in the study, which is published in PNAS. © 2020 Guardian News & Media Limited

Keyword: Alzheimers; Obesity
Link ID: 27103 - Posted: 03.07.2020

By Gretchen Reynolds Taking up exercise could alter our feelings about food in surprising and beneficial ways, according to a compelling new study of exercise and eating. The study finds that novice exercisers start to experience less desire for fattening foods, a change that could have long-term implications for weight control. The study also shows, though, that different people respond quite differently to the same exercise routine and the same foods, underscoring the complexities of the relationship between exercise, eating and fat loss. I frequently write about exercise and weight, in part because weight control is a pressing motivation for so many of us to work out, myself included. But the effects of physical activity on waistlines are not straightforward and coherent. They are, in fact, distressingly messy. Both personal experience and extensive scientific studies tell us that a few people will lose considerable body fat when they start exercising; others will gain; and most will drop a few pounds, though much less than would be expected given how many calories they are burning during their workouts. At the same time, physical activity seems to be essential for minimizing weight gain as we age and maintaining weight loss if we do manage to shed pounds. Precisely how exercise influences weight in this topsy-turvy fashion is uncertain. On the one hand, most types of exercise increase appetite in most people, studies show, tempting us to replace calories, blunting any potential fat loss and even initiating weight creep. But other evidence suggests that physical fitness may affect people’s everyday responses to food, which could play a role in weight maintenance. In some past studies, active people of normal weight displayed less interest in high-fat, calorie-dense foods than inactive people who were obese. © 2020 The New York Times Company

Keyword: Obesity
Link ID: 27077 - Posted: 02.27.2020

By Abby Sher The rules were simple. Whenever Madonna sang, we strutted our stuff up and down the matted blue carpet. If the music stopped, we struck a pose in front of the full-length mirror. “Your face is crooked!” my friend Diana shrieked. “Your legs are 10 feet long!” I yelled back. It wasn’t an insult; it was true. The mirror in my bedroom was old and warped, like in a fun house. We spent hours in front of it, jutting out our hips and crossing our eyes; laughing at how ugly we looked. How round and pointy, long and short we could be, all at the same time. I don’t know exactly when it became painful for me to look at my reflection. Maybe when I was told to cover the mirrors in our house for my father’s funeral (a Jewish tradition). I was 11 at the time and couldn’t understand how these pale lips and string bean legs of mine were here, while my dad was forever gone. So I kept staring at my body in that glass, feeling a new kind of grief and confusion rip through me. A few weeks later, I started junior high, where looks were everything. I used a mirror so I could run turquoise eyeliner across my lids or zero in on a blooming pimple. But I got more and more frustrated by what I saw. My splotchy skin and bushy eyebrows felt untamable; my arms too long. By high school, I grew out my frizzy bangs to hide my face and wore baggy overalls with a tiny cowbell around my neck, as if I were lost in the fields and needed to find my way home. It wasn’t until after college that I dove headlong into an eating disorder. There was no definitive moment where I said, I’m going to try starving myself today. Instead it was a gradual whittling away at my body. I became obsessed with shrinking myself down to a size 0; spending hours at the gym until I was dizzy and frantic, fueling myself on coffee and sugarless gum. © 2020 The New York Times Company

Keyword: Anorexia & Bulimia; Attention
Link ID: 27068 - Posted: 02.25.2020

By Richard Klasco, M.D. A. The theory of the “sugar high” has been debunked, yet the myth persists. The notion that sugar might make children behave badly first appeared in the medical literature in 1922. But the idea did not capture the public’s imagination until Dr. Ben Feingold’s best-selling book, “Why Your Child Is Hyperactive,” was published in 1975. In his book, Dr. Feingold describes the case of a boy who might well be “patient zero” for the putative connection between sugar and hyperactivity: [The mother’s] fair-haired, wiry son loved soft drinks, candy and cake — not exactly abnormal for any healthy child. He also seemed to go completely wild after birthday parties and during family gatherings around holidays. In the mid-’70s, stimulant drugs such as Ritalin and amphetamine were becoming popular for the treatment of attention deficit hyperactivity disorder. For parents who were concerned about drug side effects, the possibility of controlling hyperactivity by eliminating sugar proved to be an enticing, almost irresistible, prospect. Some studies supported the theory. They suggested that high sugar diets caused spikes in insulin secretion, which triggered adrenaline production and hyperactivity. But the data were weak and were soon questioned by other scientists. An extraordinarily rigorous study settled the question in 1994. Writing in the New England Journal of Medicine, a group of scientists tested normal preschoolers and children whose parents described them as being sensitive to sugar. Neither the parents, the children nor the research staff knew which of the children were getting sugary foods and which were getting a diet sweetened with aspartame and other artificial sweeteners. Urine was tested to verify compliance with the diets. Nine different measures of cognitive and behavioral performance were assessed, with measurements taken at five-second intervals. © 2020 The New York Times Company

Keyword: ADHD; Obesity
Link ID: 27060 - Posted: 02.21.2020

Ian Sample Science editor Consuming a western diet for as little as one week can subtly impair brain function and encourage slim and otherwise healthy young people to overeat, scientists claim. Researchers found that after seven days on a high fat, high added sugar diet, volunteers in their 20s scored worse on memory tests and found junk food more desirable immediately after they had finished a meal. The finding suggests that a western diet makes it harder for people to regulate their appetite, and points to disruption in a brain region called the hippocampus as the possible cause. “After a week on a western-style diet, palatable food such as snacks and chocolate becomes more desirable when you are full,” said Richard Stevenson, a professor of psychology at Macquarie University in Sydney. “This will make it harder to resist, leading you to eat more, which in turn generates more damage to the hippocampus and a vicious cycle of overeating.” Previous work in animals has shown that junk food impairs the hippocampus, a brain region involved in memory and appetite control. It is unclear why, but one idea is that the hippocampus normally blocks or weakens memories about food when we are full, so looking at a cake does not flood the mind with memories of how nice cake can be. “When the hippocampus functions less efficiently, you do get this flood of memories, and so food is more appealing,” Stevenson said. To investigate how the western diet affects humans, the scientists recruited 110 lean and healthy students, aged 20 to 23, who generally ate a good diet. Half were randomly assigned to a control group who ate their normal diet for a week. The other half were put on a high energy western-style diet, which featured a generous intake of Belgian waffles and fast food. © 2020 Guardian News & Media Limited

Keyword: Learning & Memory; Obesity
Link ID: 27050 - Posted: 02.19.2020

By Jane E. Brody I’ve long thought the human body was not meant to run on empty, that fasting was done primarily for religious reasons or political protest. Otherwise we needed a reliably renewed source of fuel to function optimally, mentally and emotionally as well as physically. Personal experience reinforced that concept; I’m not pleasant to be around when I’m hungry. There’s even an official name for that state of mind, confirmed by research: Hangry! But prompted by recent enthusiasm for fasting among people concerned about their health, weight or longevity, I looked into the evidence for possible benefits — and risks — of what researchers call intermittent fasting. Popular regimens range from ingesting few if any calories all day every other day or several times a week to fasting for 16 hours or more every day. A man I know in his early 50s said he had lost 12 pounds in about two months on what he calls the 7-11 diet: He eats nothing from 7 p.m. until 11 a.m. the next morning, every day. I was skeptical, but it turns out there is something to be said for practicing a rather prolonged diurnal fast, preferably one lasting at least 16 hours. Mark P. Mattson, neuroscientist at the National Institute on Aging and Johns Hopkins University School of Medicine, explained that the liver stores glucose, which the body uses preferentially for energy before it turns to burning body fat. “It takes 10 to 12 hours to use up the calories in the liver before a metabolic shift occurs to using stored fat,” Dr. Mattson told me. After meals, glucose is used for energy and fat is stored in fat tissue, but during fasts, once glucose is depleted, fat is broken down and used for energy. Most people trying to lose weight should strive for 16 calorie-free hours, he said, adding that “the easiest way to do this is to stop eating by 8 p.m., skip breakfast the next morning and then eat again at noon the next day.” (Caffeine-dependent people can have sugar- free black coffee or tea before lunch.) But don’t expect to see results immediately; it can take up to four weeks to notice an effect, he said. © 2020 The New York Times Company

Keyword: Obesity
Link ID: 27045 - Posted: 02.18.2020

By Jane E. Brody Climate change is not the only source of dire projections for the coming decade. Perhaps just as terrifying from both a health and an economic perspective is a predicted continued rise in obesity, including severe obesity, among American adults. A prestigious team of medical scientists has projected that by 2030, nearly one in two adults will be obese, and nearly one in four will be severely obese. The estimates are thought to be particularly reliable, as the team corrected for current underestimates of weight given by individuals in national surveys. In as many as 29 states, the prevalence of obesity will exceed 50 percent, with no state having less than 35 percent of residents who are obese, they predicted. Likewise, the team projected, in 25 states the prevalence of severe obesity will be higher than one adult in four, and severe obesity will become the most common weight category among women, non-Hispanic black adults and low-income adults nationally. Given the role obesity plays in fostering many chronic, disabling and often fatal diseases, these are dire predictions indeed. Yet, as with climate change, the powers that be in this country are doing very little to head off the potentially disastrous results of expanding obesity, obesity specialists say. Well-intentioned efforts like limiting access to huge portions of sugar-sweetened soda, the scientists note, are effectively thwarted by well-heeled industries able to dwarf the impact of educational efforts by health departments that have minuscule budgets by comparison. With rare exceptions, the sugar and beverage industries have blocked nearly every attempt to add an excise tax to sugar-sweetened beverages. Claims that such a tax is regressive and unfairly targets low-income people is shortsighted, according to Zachary J. Ward, public health specialist at Harvard and the lead author of the new report, published in The New England Journal of Medicine in December. © 2020 The New York Times Company

Keyword: Obesity
Link ID: 27028 - Posted: 02.10.2020

By Nicholas Bakalar Flavonols, a large class of compounds found in most fruits and vegetables, may be associated with a reduced risk for Alzheimer’s disease. Flavonols are known to have antioxidant and anti-inflammatory effects, and animal studies have suggested they may improve memory and learning. A study in Neurology involved 921 men and women, average age 81 and free of dementia, who reported their diet using well-validated food questionnaires. During an average follow-up of six years, 220 developed Alzheimer’s disease. People with the highest levels of flavonol intake tended to have higher levels of education and were more physically active. But after controlling for these factors plus age, sex, the Apo E4 gene (which increases the risk for dementia) and late-life cognitive activity, the scientists found that compared with those in the lowest one-fifth for flavonol intake, those in the highest one-fifth had a 48 percent reduced risk for Alzheimer’s disease. The study covered four types of flavonols: kaempferol, quercetin, isorhamnetin and myricetin. All except quercetin showed a strong association with Alzheimer’s risk reduction. These flavonols are available as supplements, but the lead author, Dr. Thomas M. Holland, a professor of medicine at Rush Medical College in Chicago, said that foods are a better source. “You get a broader intake of vitamins, minerals and bioactives in food than in the supplements,” he said. © 2020 The New York Times Company

Keyword: Alzheimers
Link ID: 27015 - Posted: 02.04.2020

By Gretchen Reynolds In a world that encourages inactivity, even our babies may be moving too little, according to an innovative new study of physical activity patterns during a child’s first year of life. The study, which used tiny activity trackers to monitor babies’ movements, found associations between infants’ squirming, kicking, crawling or stillness and the levels of fat around their middles, raising provocative questions about just how early any links between inactivity and obesity might begin. We already have considerable evidence, of course, that children in the Western world tend to be sedentary. According to recent estimates, most school-age children in the United States sit for more than eight hours a day, while children as young as 2 or 3 years of age can be sedentary for 90 percent or more of their waking hours. These statistics are concerning, because other studies suggest that inactive children face much higher risks of becoming overweight or obese than children who move more often. But little has been known about how much — or little — tiny babies move and if there might be correlations between their activities and their rotundity, and if such correlations matter. So, for the new study, which was published this month in Obesity, a group of researchers from Johns Hopkins University and other institutions decided to fit baby-size trackers to infants’ ankles and watch how they wiggled. They began by turning to new mothers already participating in a large, ongoing study of the health of mothers and newborns and asking if they could now track their babies’ activities. The researchers wound up recruiting 506 young boys and girls from various socioeconomic levels, more than half of them African-American. The researchers visited these infants in their homes when the babies were 3, 6, 9 and 12 months old, weighing and measuring the children, gently checking their body fat with calipers and fitting them with tiny accelerometers. © 2020 The New York Times Company

Keyword: Obesity; Development of the Brain
Link ID: 26978 - Posted: 01.22.2020

By Aaron E. Carroll Childhood obesity is a major public health problem, and has been for some time. Almost 20 percent of American children are affected by obesity, as well as about 40 percent of adults. Over all, this costs the United States around $150 billion in health care spending each year. Pediatricians like me, and many other health professionals, know it’s a problem, and yet we’ve been relatively unsuccessful in tackling it. About six years ago, some reports seemed to show that rates had stabilized in children and even decreased in those ages 2 to 5. Later studies showed this trend to be an illusion. If anything, things have gotten worse. Efforts to help can backfire. People on diets often gain weight. Although individual studies have pointed to potential interventions and solutions, these have not yet translated into actual improvements. Part of the problem may be flawed research. A recent paper in Pediatric Obesity provided a guide on how to do better. Its suggestions fall into five general themes. 1) When things look better, it’s critical to ask “compared to what?” In short, you need a control group. Over time, changes in behaviors or measurements often follow a pattern known as regression toward the mean. Outliers (in this case those who are more overweight) tend to move toward the average. Thus, interventions might look as if they’re working when they’re not. Control groups — participants who don’t receive the intervention — can help ensure that we’re seeing real effectiveness. Even then, things can get tricky. In a randomized controlled trial, it’s important to keep the comparisons directly between the intervention and control groups. A common mistake is comparing each group after the intervention with the same group before the intervention. In other words, people could compare a dieting group to itself, before and after, and compare the control group to itself, before and after, to see if the © 2020 The New York Times Company

Keyword: Obesity
Link ID: 26972 - Posted: 01.20.2020

By Philippa Roxby Health reporter A sleep disorder that can leave people gasping for breath at night could be linked to the amount of fat on their tongues, a study suggests. When sleep apnoea patients lost weight, it was the reduction in tongue fat that lay behind the resulting improvements, researchers said. Larger and fattier tongues are more common among obese patients. But the Pennsylvania team said other people with fatty tongues may also be at risk of the sleep disorder. The researchers now plan to work out which low-fat diets are particularly good at slimming down the tongue. Tongue tied "You talk, eat and breathe with your tongue - so why is fat deposited there?" said study author Dr Richard Schwab, of Perelman School of Medicine, Philadelphia. "It's not clear why - it could be genetic or environmental - but the less fat there is, the less likely the tongue is to collapse during sleep." Sleep apnoea is a common disorder that can cause loud snoring, noisy breathing and jerky movements when asleep. It can also cause sleepiness during the day, which can affect quality of life. The most common type is obstructive sleep apnoea, in which the upper airway gets partly or completely blocked during sleep. Those who are overweight or who have a large neck or tonsils are more likely to have the condition. Researchers at the Perelman School of Medicine, University of Pennsylvania, scanned 67 people with obstructive sleep apnoea who were obese and had lost 10% of their body weight, improving their symptoms improved by 30%. © 2020 BBC.

Keyword: Sleep; Obesity
Link ID: 26946 - Posted: 01.10.2020

By Nicholas Bakalar The right diet might help you sleep better. In a study of 77,860 postmenopausal women, researchers found that consuming foods that had a low glycemic index is associated with a reduced risk for insomnia. Foods with low glycemic indexes — for example, vegetables, nuts and whole grain breads — have carbohydrates that are slowly absorbed and cause lower, and slower, rises in blood glucose and insulin levels after being consumed. For this study, in the American Journal of Clinical Nutrition, participants completed lengthy questionnaires about what foods they ate and how often. They also reported their degree of insomnia at the start of the study and after three years of follow-up. Compared with the one-fifth of participants whose diet had the lowest glycemic index, those with the highest were 11 percent more likely to have insomnia. Some low-glycemic index foods — whole grains and dairy foods, for example — were not associated with reduced insomnia. But people who ate the most fruits and vegetables were about 14 percent less likely to have insomnia, and the largest consumers of fiber were 13 percent less likely. In contrast, women who ate the most refined grains had a 16 percent higher risk of insomnia than those who ate the least. Although the study controlled for many health and behavioral characteristics, the study showed only an association and could not prove cause and effect. “Randomized controlled trials examining dietary patterns in relation to insomnia are needed to clarify these findings,” the authors write. © 2019 The New York Times Company

Keyword: Sleep; Obesity
Link ID: 26917 - Posted: 12.27.2019

New results from the largest long-term study of brain development and children's health raise provocative questions about obesity and brain function. Does excess body weight somehow reduce brain regions that regulate planning and impulse control? Is obesity a result of that brain difference? Or are eating habits, lifestyle, family circumstances and genetics to blame? Previous studies in children and adults have had conflicting results. The new research doesn't settle the matter and outside experts cautioned that misinterpreting it could unfairly perpetuate weight stigma. But an editorial published with the study Monday in JAMA Pediatrics called it an important addition to mounting evidence of a link between weight, brain structure and mental function. If follow-up research confirms the findings, it could lead to new ways to prevent obesity that target improved brain function. "We don't know which direction these relationships go nor do they suggest that people with obesity are not as smart as people at a healthy weight,"said Dr. Eliana Perrin, a Duke University pediatrics professor who co-wrote the editorial. The federally-funded study involved 3,190 U.S. children aged 9 and 10. They had height and weight measurements, MRI brain scans and computer-based tests of mental function including memory, language, reasoning and impulse control. Nearly 1,000 kids — almost 1 in 3 —were overweight or obese, similar to national statistics. Inflammatory changes early in life ©2019 CBC/Radio-Canada

Keyword: Obesity
Link ID: 26888 - Posted: 12.11.2019

By Laura Sanders Bulging stomachs often take the blame for ending holiday indulging. But bulging guts might be the real appetite killer, a study in mice suggests. The results, published November 14 in Cell, could point out new ways to treat obesity, or even help explain how gastric bypass surgeries limit eating. Those procedures result in food moving faster through the stomach into the intestines, stretching the gut in a way that might signal fullness, the authors speculate. Zachary Knight, a neuroscientist at the University of California, San Francisco, and colleagues identified and studied nerve cells in mice’s intestines that sense mechanical stretching. To simulate full intestines, the team activated these nerve cells with light and chemicals. As a result, the mice ate less food. Physically stretching the mice’s intestines with a salty liquid or a diuretic also caused the mice to eat less. Different stretch-sensing cells in the stomach also curbed mice’s appetites, but to a lesser extent, the researchers found. These nerve cell endings relay messages up the vagus nerve (SN: 11/13/15), which then zips signals to the brain. These messages about intestinal stretching help influence the eat-or-not decision, researchers suspect. L. Bai et al. Genetic identification of vagal sensory neurons that control feeding. Cell. Vol. 179, November 14, 2019, p. 1129. doi: 10.1016/j.cell.2019.10.031 © Society for Science & the Public 2000–2019.

Keyword: Obesity
Link ID: 26834 - Posted: 11.20.2019

By David S. Ludwig and Steven B. Heymsfield Most diet trials in the best journals fail even the most basic of quality control measures. That’s the finding of a study by us to be published today in JAMA Network Open. Investigators receiving funding for any clinical trial from the National Institutes of Health must register in advance what they plan to test, among other design features, to ensure that the data are fairly analyzed. Comparing the original registries with the final published studies, we found that diet trials in the past decade were about four times as likely as drug trials to have a discrepancy in the main outcome or measurement — raising concern for bias. This quality-control problem of diet trials in comparison to ones on pharmaceuticals leads to a bigger issue: underinvestment in nutrition research and in how we tackle the mysteries of a healthy diet. Although the problems with observational studies have received much attention (“Association doesn’t prove causation,” as scientists say), clinical trials can suffer from equally important limitations. In a clinical trial, investigators assign volunteers to receive different treatments — such as a a low-carbohydrate versus low-fat diet — ideally in random order. Beyond registry issues, trials may provide misleading results for many reasons, including small size, short duration and weak interventions (they lack power to actually make the intended change in behavior). These failures are disturbing because epidemics of diet-related disease will shorten life expectancy and impose huge economic costs on the United States in coming years. We continue to lack effective dietary prevention, in part because clinical trials have been too poorly designed and conducted to reach definitive conclusions. We’re still debating questions that have raged for decades: Should we focus on reducing carbs or fat? Is red meat harmful? Is sugar toxic? What about artificially sweetened beverages or moderate amounts of alcohol? © 2019 The New York Times Company

Keyword: Obesity
Link ID: 26820 - Posted: 11.14.2019

By Veronique Greenwood When a bird preens its feathers, it uses a little of nature’s own pomade: an oil made by glands just above the tail. This oil helps clean and protect the bird’s plumage, but also contains a delicate bouquet of scents. To other birds — potential mates or would-be rivals — these smells carry many messages, not unlike the birdsongs and fancy feathers that are more obvious to human observers. These scents may signal that a bird would be dangerous to encounter or might be ready to mate, or any number of other cues. However, new research using dark-eyed juncos, a common North American bird, suggests that these odoriferous messages may not be entirely of the bird’s own making. In a study published last month in the Journal of Experimental Biology, biologists reported that microbes living peacefully on the birds’ oil glands may play an important role in making the scent molecules involved. That implies that the birds’ microbiomes may influence both the smell and the behavior it provokes in other birds. Birds’ scented messages are the focus of the research of Danielle Whittaker, managing director of the Beacon Center for the Study of Evolution in Action at Michigan State University and an author of the paper. Some years ago, after she gave a talk, Kevin Theis, a colleague who studied scent-producing bacteria living on hyenas and who is a co-author of the new paper, asked her whether she had ever looked at the birds’ microbes. “I had never thought about bacteria at all,” said Dr. Whittaker. “But all the compounds I was describing were known byproducts of bacterial metabolism.” Dr. Whittaker took samples of bacteria living on the oil glands of 10 captive dark-eyed juncos and then injected the glands with an antibiotic. When she compared the microbes before and after the treatment, the results seemed to show that two groups of bacteria in particular had taken a hit from the treatment. Furthermore, when she compared the scent molecules in the oil before and after the treatment, there were significant differences. © 2019 The New York Times Company

Keyword: Chemical Senses (Smell & Taste)
Link ID: 26812 - Posted: 11.11.2019