Chapter 13. Homeostasis: Active Regulation of the Internal Environment
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Hannah Devlin Science correspondent Migraine sufferers have a different mix of gut bacteria that could make them more sensitive to certain foods, scientists have found. The study offers a potential explanation for why some people are more susceptible to debilitating headaches and why some foods appear to act as triggers for migraines. The research showed that migraine sufferers had higher levels of bacteria that are known to be involved in processing nitrates, which are typically found in processed meats, leafy vegetables and some wines. The latest findings raise the possibility that migraines could be triggered when nitrates in food are broken down more efficiently, causing vessels in the brain and scalp to dilate. Antonio Gonzalez, a programmer analyst at the University of California San Diego and the study’s first author, said: “There is this idea out there that certain foods trigger migraines - chocolate, wine and especially foods containing nitrates. We thought that perhaps there are connections between what people are eating, their microbiomes and their experiences with migraines.” When nitrates in food are broken down by bacteria in the mouth and gut they are eventually converted into nitric oxide in the blood stream, a chemical that dilates blood vessels and can aid cardiovascular health by boosting circulation. © 2016 Guardian News and Media Limited
By Meredith Knight In June, international diabetes organizations endorsed provocative new guidelines suggesting physicians should consider gastric bypass surgery for a greatly expanded number of diabetics—those with a body mass index of 30 and above as opposed to just those with a BMI of 40 or more. Research has shown that the surgery helps people lose more weight, maintain the loss longer and achieve better blood glucose levels than those who slim down by changing diet and exercise habits. Now a study in mice suggests the effectiveness of bariatric surgery may stem in part from changes it causes in the brain. According to the study, published in the International Journal of Obesity, gastric bypass surgery causes the hyperactivation of a neural pathway that leads from stomach-sensing neurons in the brain stem to the lateral parabrachial nucleus, an area in the midbrain that receives sensory information from the body, and then to the amygdala, the brain's emotion- and fear-processing center. The obese mice underwent so-called Roux-en-Y bypass surgery, in which surgeons detach most of the stomach, leaving only a tiny pouch connected to the small intestine. Shortly after the surgery, the mice begin to show increased activation in this neural pathway, along with reduced meal size and a preference for less fatty food. They also begin to secrete higher levels of satiety hormones. Similar behavioral and hormonal patterns are found in humans after bypass surgery, suggesting that the brain changes may also be similar—but the authors say looking at this particular circuit in humans with brain imaging is difficult because the resolution is not up to the task. © 2016 Scientific American,
Link ID: 22768 - Posted: 10.19.2016
Analysis of a trial that used the drug canagliflozin found that as people lost weight, their appetite increased proportionately, leading to consumption of more calories and weight loss plateau (leveling off). The findings provide the first measurement in people of how strongly appetite counters weight loss as part of the body’s feedback control system regulating weight. Results are currently available on BioRxiv (link is external) and will publish in Obesity during Obesity Week 2016. A team led by the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) analyzed data from a year-long, placebo-controlled, double-blind trial in people with type 2 diabetes who could eat and drink without restriction by the study. Of the 242 participants, 153 received canagliflozin, a drug that caused a substantial increase in the amount of glucose excreted in their urine. Those people were not directly aware of that calorie loss, which caused a gradual decrease in weight averaging about eight pounds. The team used a validated math model to calculate the changes in the amount of calories consumed during the study. They found no long-term calorie intake changes in the 89 people who got a placebo. However, for every pound of lost weight, the people treated with canagliflozin consumed about 50 calories per day more than they were eating before the study. This increase in appetite and calorie intake led to slowing of weight loss after about six months. The measurements are consistent with the researchers’ analysis of data from a separate trial on a commercial weight loss program not involving canagliflozin. In the weight loss program trial, despite the dieters’ consistent efforts to reduce calorie intake, their increased appetite resulted in a progressive increase in calorie intake — three times stronger than the changes in caloric expenditure that typically accompany weight loss — and weight loss plateau. Findings from the analyses suggest that persistent effort is required to avoid weight regain.
Link ID: 22756 - Posted: 10.15.2016
By GRETCHEN REYNOLDS Exercise may aid in weight control and help to fend off diabetes by improving the ability of fat cells to burn calories, a new study reports. It may do this in part by boosting levels of a hormone called irisin, which is produced during exercise and which may help to turn ordinary white fat into much more metabolically active brown fat, the findings suggest. Irisin (named for the Greek goddess Iris) entered the scientific literature in 2012 after researchers from Harvard and other universities published a study in Nature that showed the previously unknown hormone was created in working muscles in mice. From there, it would enter the bloodstream and migrate to other tissues, particularly to fat, where it would jump-start a series of biochemical processes that caused some of the fat cells, normally white, to turn brown. Brown fat, which is actually brown in color, burns calories. It also is known to contribute to improved insulin and blood sugar control, lessening the risk for Type 2 diabetes. Most babies, including human infants, are plump with brown fat, but we humans lose most of our brown fat as we grow up. By the time we are adults, we usually retain very little brown fat. In the 2012 study, the researchers reported that if they injected irisin into living mice, it not only turned some white fat into brown fat, it apparently also prevented the rodents from becoming obese, even on a high-fat, high-calorie diet. But in the years since, some scientists have questioned whether irisin affects fat cells in people to the same extent as it seems to in mice — and even whether the hormone exists in people at all. A study published last year in Cell Metabolism by the same group of researchers who had conducted the first irisin study, however, does seem to have established that irisin is produced in humans. They found some irisin in sedentary people, but the levels were much higher in those who exercise often. © 2016 The New York Times Company
Link ID: 22744 - Posted: 10.12.2016
Allison Aubrey The World Health Organization has already urged us to cut back on sugar, limiting added sugars to no more than 10 percent of our daily calories. So, how might policymakers get people to follow this advice? In a new report, the WHO is urging governments around the world to tax soda and other sugary drinks. In its report, the World Health Organization points to systematic reviews of policies aimed at improving diet and preventing lifestyle diseases, such as obesity and diabetes. "The evidence was strongest and most consistent for the effectiveness of sugar-sweetened beverage taxes in the range of 20-50% in reducing consumption," the WHO's meta-review concludes. Dr. Douglas Bettcher, director of the WHO's Department for the Prevention of Noncommunicable Diseases, says that "consumption of free sugars, including products like sugary drinks, is a major factor in the global increase of people suffering from obesity and diabetes." "If governments tax products like sugary drinks, they can reduce suffering and save lives. They can also cut healthcare costs and increase revenues to invest in health services," Bettcher was quoted as saying in a WHO release on the report. The International Council of Beverages Associations, which represents soda companies and other beverage-makers around the globe, says it's disappointed with the new WHO report. "We strongly disagree with the committee's recommendation to tax beverages, as it is an unproven idea that has not been shown to improve public health based on global experiences to date," an ICBA release concludes. © 2016 npr
Link ID: 22743 - Posted: 10.12.2016
By Clare Wilson Glug glug glug. I’m drinking a big glass of ice water after getting thirsty, and it’s flowing easily down my throat like a river. But a study of thirsty and well hydrated people suggests this isn’t always the case. We rarely pay attention to the business of swallowing, but it may play a subtle role in controlling our fluid intake, on top of our conscious feelings of thirst. If we are dehydrated, swallowing is effortless; if we are overhydrated, swallowing feels more difficult, putting us off drinking, according to a study by Michael Farrell at Monash University in Melbourne, Australia, and his team. “Normally it’s something we are not really conscious of – away it goes,” says Farrell. But when his team asked volunteers to rate the sensation of taking a small sip of water, they found that people who had recently drunk a lot of water said it took much more effort to swallow than those who were mildly hydrated – their difficult ratings rose from one out of ten to nearly five. Is eight really great? When people were overhydrated, brain scans showed that swallowing was linked with more activity in certain regions of the brain, including the prefrontal cortex, which is responsible for conscious thought processes. “It suggests a mechanism for inhibition of drinking that we don’t usually think about,” says Zachary Knight at the University of California, San Francisco. © Copyright Reed Business Information Ltd.
Link ID: 22739 - Posted: 10.11.2016
By Michelle Roberts Some people are genetically wired to prefer the taste of fatty foods, putting them at increased risk of obesity, according to UK researchers. The University of Cambridge team offered 54 volunteers unlimited portions of chicken korma, followed by an Eton mess-style dessert. Some of the meals were packed with fat while others were low-fat versions. Those with a gene already linked to obesity showed a preference for the high-fat food and ate more of it. Fat genes The gene in question is called MC4R. It is thought about one in every 1,000 people carries a defective version of this gene which controls hunger and appetite as well as how well we burn off calories. Mutations in MC4R are the most common genetic cause of severe obesity within families that has so far been identified. Humans probably evolved hunger genes to cope in times of famine, say experts. When food is scarce it makes sense to eat and store more fat to fend off starvation. But having a defect in the MC4R gene means hunger can become insatiable. In the study, published in the journal Nature Communications, the researchers created a test menu that varied only in fat or sugar content. The three versions of the main meal on offer - chicken korma - were identical in appearance, and as far as possible, taste, but ranged in fat from low to medium and high. The volunteers were offered a small sample of each and then left to eat as much as they liked of the three dishes. The same was then done for a pudding of strawberries, meringue and cream, but this time varying the sugar content rather than the fat. © 2016 BBC.
Joe Palca Most of us have been tempted at one time or another by the lure of sugar. Think of all the cakes and cookies you consume between Thanksgiving and Christmastime! But why are some people unable to resist that second cupcake or slice of pie? That's the question driving the research of Monica Dus, a molecular biologist at the University of Michigan. She wants to understand how excess sugar leads to obesity by understanding the effect of sugar on the brain. Dus's interest in how animals control the amount they eat started with a curious incident involving her two Bichon Frise dogs. One day, Cupcake and Sprinkles got into a bag of dog treats when Dus wasn't around. The dogs overdid it. "I couldn't believe that these two tiny, 15-pound animals had huge bellies for three days and they couldn't stop themselves from eating," she recalls. Dus was already an expert in fruit fly genetics, so she decided to study flies to see if she could unravel the puzzle of how the brain controls eating behavior. Her lab has a working hypothesis. Dus believes a diet high in sugar actually changes the brain, so it no longer does a good job of knowing how many calories the body is taking in. She thinks there are persistent molecular changes in the brain over time – changes that pave the way for excessive eating and eventually, obesity. Monica Dus is a researcher at the University of Michigan. She just won a $1.5 million Young Innovator grant from the National Institutes of Health to study how a high-sugar diet may lead to obesity by changing brain chemistry. © 2016 npr
Link ID: 22725 - Posted: 10.05.2016
By GINA KOLATA It is not easy to be fat in America, even though more than a third of adults are obese. Donald J. Trump brought the issue of fat shaming to the fore during and after last week’s debate, when he disparaged a former Miss Universe winner who gained weight and when he said the hacking of the Democratic National Committee’s emails might have been done by “somebody sitting on their bed that weighs 400 pounds.” But there also is a body of evidence showing that the effects of fat shaming and stigmatizing go far beyond such remarks, beyond the stares fat people get on the street, the cutting comments strangers make about their weight and the “funny” greeting cards featuring overweight people. It turns out that fat prejudice differs from other forms in ways that make it especially difficult to overcome. The problems with fat shaming start early. Rebecca Puhl, the deputy director of the University of Connecticut’s Rudd Center for Food Policy and Obesity, and her colleagues find that weight is the most common reason children are bullied in school. In one study, nearly 85 percent of adolescents reported seeing overweight classmates teased in gym class. Dr. Puhl and her colleagues asked fat kids who was doing the bullying. It turned out that it was not just friends and classmates but also teachers and — for more than a third of the bullied — parents. “If these kids are not safe at school or at home, where are they going to be supported?” Dr. Puhl asked. The bullying problem is not limited to the United States. Dr. Puhl and her colleagues found the same situation in Canada, Australia and Iceland. Women face harsher judgment than men, Dr. Puhl reports. The cutting remarks can begin when a woman’s body mass index is in the overweight range, while for men the shaming tends to start when they are obese. And women who are obese report more than three times as much shaming and discrimination as men of equal obesity. © 2016 The New York Times Company
By Deborah R. Glasofer, Joanna Steinglass Every day on the dot of noon, Jane* would eat her 150-calorie lunch: nonfat yogurt and a handful of berries. To eat earlier, she felt, would be “gluttonous.” To eat later would disrupt the dinner ritual. Jane's eating initially became more restrictive in adolescence, when she worried about the changes her body was undergoing in the natural course of puberty. When she first settled on her lunchtime foods and routine—using a child-size spoon to “make the yogurt last” and sipping water between each bite—she felt accomplished. Jane enjoyed her friends' compliments about her “incredible willpower.” In behavioral science terms, her actions were goal-directed, motivated by achieving a particular outcome. In relatively short order, she got the result she really wanted: weight loss. Years later Jane, now in her 30s and a newspaper reporter, continued to eat the same lunch in the same way. Huddled over her desk in the newsroom, she tried to avoid unwanted attention and feared anything that might interfere with the routine. She no longer felt proud of her behavior. Her friends stopped complimenting her “self-control” years ago, when her weight plummeted perilously low. So low that she has had to be hospitalized on more than one occasion. The longed-for weight loss did not make her feel better about herself or her appearance. Jane's curly hair, once shiny and thick, dulled and thinned; her skin and eyes lost their brightness. There were other costs as well—to her relationships, to her career. Instead of dreaming about a great romance, Jane would dream of the cupcakes she could not let herself have at her niece's birthday party. Instead of thinking about the best lead for her next story, she obsessed over calories and exercise. © 2016 Scientific American
The make-up of the bacteria found in human faeces may influence levels of dangerous fat in our bodies, say researchers from King's College London. Their analysis of stool samples in a study of more than 3,600 twins found evidence that some of this bacteria is inherited. What is contained in faeces bacteria could therefore partly explain why obesity passes down through families. The study is published in Genome Biology. The research team extracted information from study participants about the human faecal microbiome - the bacteria present in faeces samples - and compared these to six different measures of obesity, including body mass index (BMI) and different types of body fat. The researchers found the strongest links with visceral fat, where participants with a high diversity of bacteria in their faeces had lower levels of visceral fat. This type of body fat is bad news because it is stored in the stomach area around important organs such as the liver, pancreas and intestines and is linked with higher risks of cardiovascular disease and diabetes. Dr Michelle Beaumont, lead study author from the department of twin research and genetic epidemiology at King's College London, said although the study showed a clear link, it was not yet possible to explain why it existed. One theory is that a lack of variety in faecal bacteria could lead to the domination of high levels of gut microbes which are good at turning carbohydrates into fat. © 2016 BBC.
Link ID: 22694 - Posted: 09.26.2016
By GINA KOLATA You must lose weight, a doctor told Sarah Bramblette, advising a 1,200-calorie-a-day diet. But Ms. Bramblette had a basic question: How much do I weigh? The doctor’s scale went up to 350 pounds, and she was heavier than that. If she did not know the number, how would she know if the diet was working? The doctor had no answer. So Ms. Bramblette, 39, who lived in Ohio at the time, resorted to a solution that made her burn with shame. She drove to a nearby junkyard that had a scale that could weigh her. She was 502 pounds. One in three Americans is obese, a rate that has been steadily growing for more than two decades, but the health care system — in its attitudes, equipment and common practices — is ill prepared, and its practitioners are often unwilling, to treat the rising population of fat patients. The difficulties range from scales and scanners, like M.R.I. machines that are not built big enough for very heavy people, to surgeons who categorically refuse to give knee or hip replacements to the obese, to drug doses that have not been calibrated for obese patients. The situation is particularly thorny for the more than 15 million Americans who have extreme obesity — a body mass index of 40 or higher — and face a wide range of health concerns. Part of the problem, both patients and doctors say, is a reluctance to look beyond a fat person’s weight. Patty Nece, 58, of Alexandria, Va., went to an orthopedist because her hip was aching. She had lost nearly 70 pounds and, although she still had a way to go, was feeling good about herself. Until she saw the doctor. “He came to the door of the exam room, and I started to tell him my symptoms,” Ms. Nece said. “He said: ‘Let me cut to the chase. You need to lose weight.’” © 2016 The New York Times Company
Link ID: 22693 - Posted: 09.26.2016
By Carey Goldberg I’d just gotten used to the idea that I’m a walking mountain of microbes. The sizzling field of research into the microbiome — our full complement of bugs — is casting new light on our role as homes to the trillions of bacteria that inhabit each of us. At least most of them are friendly, I figured. But now comes the next microbial shift in my self-image, courtesy of the new book “The Mind-Gut Connection.” My trillions of gut microbes, it seems, are in constant communication with my brain, and there’s mounting evidence that they may affect how I feel — not just physically but emotionally. Does this mean — gulp — that maybe our bugs are driving the bus? I spoke with the book’s author, Dr. Emeran Mayer, professor of medicine and psychiatry at UCLA, executive director of the Oppenheimer Center for Neurobiology of Stress and Resilience and expert in brain-gut microbiome interactions. Edited excerpts: So we’re not only packed with trillions of gut microbes but they’re in constant cross-talk with our brains — that’s the picture? First of all, you have to realize that these are invisible creatures. So even though there are 100 trillion of them living in our gut, you wouldn’t be able to see them with the naked eye. It’s not like something tangible sitting inside of you, like another organ. © Copyright WBUR 2016
Link ID: 22673 - Posted: 09.20.2016
Researchers at the National Institutes of Health have discovered a two-way link between depression and gestational diabetes. Women who reported feeling depressed during the first two trimesters of pregnancy were nearly twice as likely to develop gestational diabetes, according to an analysis of pregnancy records. Conversely, a separate analysis found that women who developed gestational diabetes were more likely to report postpartum depression six weeks after giving birth, compared to a similar group of women who did not develop gestational diabetes. The study was published online in Diabetologia. Gestational diabetes is a form of diabetes (high blood sugar level) occurring only in pregnancy, which if untreated may cause serious health problems for mother and infant. “Our data suggest that depression and gestational diabetes may occur together,” said the study’s first author, Stefanie Hinkle, Ph.D., staff scientist in the Division of Intramural Population Health Research at the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “Until we learn more, physicians may want to consider observing pregnant women with depressive symptoms for signs of gestational diabetes. They also may want to monitor women who have had gestational diabetes for signs of postpartum depression.” Although obesity is known to increase the risk for gestational diabetes, the likelihood of gestational diabetes was higher for non-obese women reporting depression than for obese women with depression.
Napping for more than an hour during the day could be a warning sign for type-2 diabetes, Japanese researchers suggest. They found the link after analysing observational studies involving more than 300,000 people. UK experts said people with long-term illnesses and undiagnosed diabetes often felt tired during the day. But they said there was no evidence that napping caused or increased the risk of diabetes. The large study, carried out by scientists at the University of Tokyo, is being presented at a meeting of the European Association for the Study of Diabetes in Munich. Their research found there was a link between long daytime naps of more than 60 minutes and a 45% increased risk of type-2 diabetes, compared with no daytime napping - but there was no link with naps of less than 40 minutes. The researchers said long naps could be a result of disturbed sleep at night, potentially caused by sleep apnoea. And this sleeping disorder could increase the risk of heart attacks, stroke, cardiovascular problems and other metabolic disorders, including type-2 diabetes. Sleep deprivation, caused by work or social life patterns, could also lead to increased appetite, which could increase the risk of type-2 diabetes. But it was also possible that people who were less healthy or in the early stages of diabetes were more likely to nap for longer during the day. Shorter naps, in contrast, were more likely to increase alertness and motor skills, the authors said. © 2016 BBC.
By GINA KOLATA A few years ago, Richard Kahn, the now-retired chief scientific and medical officer of the American Diabetes Association, was charged with organizing a committee to prescribe a diet plan for people with diabetes. He began by looking at the evidence for different diets, asking which, if any, best controlled diabetes. “When you look at the literature, whoa is it weak. It is so weak,” Dr. Kahn said in a recent interview. Studies tended to be short term, diets unsustainable, differences between them clinically insignificant. The only thing that really seemed to help people with diabetes was weight loss — and for weight loss there is no magic diet. But people want diet advice, Dr. Kahn reasoned, and the association really should say something about diets. So it, like the National Institutes of Health, went with the Department of Agriculture’s food pyramid. Why? “It’s a diet for all America,” Dr. Kahn said. ”It has lots of fruits and vegetables and a reasonable amount of fat.” That advice, though, recently came under attack in a New York Times commentary written by Sarah Hallberg, an osteopath at a weight loss clinic in Indiana, and Osama Hamdy, the medical director of the obesity weight loss program at the Joslin Diabetes Center at Harvard Medical School. There is a diet that helps with diabetes, the two doctors said, one that restricts — or according to Dr. Hallberg, severely restricts — — carbohydrates. “If the goal is to get patients off their medications, including insulin, and resolve rather than just control their diabetes, significant carb restriction is by far the best nutrition plan,” Dr. Hallberg said in an email. “This would include elimination of grains, potatoes and sugars and all processed foods. There is a significant and ever growing body of literature that supports this method.” She is in private practice at Indiana University Health Arnett Hospital and is medical director of a startup developing nutrition-based medical interventions. © 2016 The New York Times Company
Link ID: 22654 - Posted: 09.15.2016
By ANAHAD O’CONNOR The sugar industry paid scientists in the 1960s to play down the link between sugar and heart disease and promote saturated fat as the culprit instead, newly released historical documents show. The internal sugar industry documents, recently discovered by a researcher at the University of California, San Francisco, and published Monday in JAMA Internal Medicine, suggest that five decades of research into the role of nutrition and heart disease, including many of today’s dietary recommendations, may have been largely shaped by the sugar industry. “They were able to derail the discussion about sugar for decades,” said Stanton Glantz, a professor of medicine at U.C.S.F. and an author of the JAMA paper. The documents show that a trade group called the Sugar Research Foundation, known today as the Sugar Association, paid three Harvard scientists the equivalent of about $50,000 in today’s dollars to publish a 1967 review of research on sugar, fat and heart disease. The studies used in the review were handpicked by the sugar group, and the article, which was published in the prestigious New England Journal of Medicine, minimized the link between sugar and heart health and cast aspersions on the role of saturated fat. Even though the influence-peddling revealed in the documents dates back nearly 50 years, more recent reports show that the food industry has continued to influence nutrition science. Last year, an article in The New York Times revealed that Coca-Cola, the world’s largest producer of sugary beverages, had provided millions of dollars in funding to researchers who sought to play down the link between sugary drinks and obesity. In June, The Associated Press reported that candy makers were funding studies that claimed that children who eat candy tend to weigh less than those who do not. The Harvard scientists and the sugar executives with whom they collaborated are no longer alive. One of the scientists who was paid by the sugar industry was D. Mark Hegsted, who went on to become the head of nutrition at the United States Department of Agriculture, where in 1977 he helped draft the forerunner to the federal government’s dietary guidelines. Another was Dr. Fredrick J. Stare, the chairman of Harvard’s nutrition department. © 2016 The New York Times Company
Link ID: 22649 - Posted: 09.13.2016
By SARAH HALLBERG and OSAMA HAMDY Earlier this year, the Food and Drug Administration approved a new weight-loss procedure in which a thin tube, implanted in the stomach, ejects food from the body before all the calories can be absorbed. Some have called it “medically sanctioned bulimia,” and it is the latest in a desperate search for new ways to stem the rising tides of obesity and Type 2 diabetes. Roughly one-third of adult Americans are now obese; two-thirds are overweight; and diabetes afflicts some 29 million. Another 86 million Americans have a condition called pre-diabetes. None of the proposed solutions have made a dent in these epidemics. Recently, 45 international medical and scientific societies, including the American Diabetes Association, called for bariatric surgery to become a standard option for diabetes treatment. The procedure, until now seen as a last resort, involves stapling, binding or removing part of the stomach to help people shed weight. It costs $11,500 to $26,000, which many insurance plans won’t pay and which doesn’t include the costs of office visits for maintenance or postoperative complications. And up to 17 percent of patients will have complications, which can include nutrient deficiencies, infections and intestinal blockages. It is nonsensical that we’re expected to prescribe these techniques to our patients while the medical guidelines don’t include another better, safer and far cheaper method: a diet low in carbohydrates. Once a fad diet, the safety and efficacy of the low-carb diet have now been verified in more than 40 clinical trials on thousands of subjects. Given that the government projects that one in three Americans (and one in two of those of Hispanic origin) will be given a diagnosis of diabetes by 2050, it’s time to give this diet a closer look. © 2016 The New York Times Company
Link ID: 22645 - Posted: 09.12.2016
By GRETCHEN REYNOLDS A busy brain can mean a hungry body. We often seek food after focused mental activity, like preparing for an exam or poring over spreadsheets. Researchers speculate that heavy bouts of thinking drain energy from the brain, whose capacity to store fuel is very limited. So the brain, sensing that it may soon require more calories to keep going, apparently stimulates bodily hunger, and even though there has been little in the way of physical movement or caloric expenditure, we eat. This process may partly account for the weight gain so commonly seen in college students. Scientists at the University of Alabama at Birmingham and another institution recently experimented with exercise to counter such post-study food binges. Gary Hunter, an exercise physiologist at U.A.B., oversaw the study, which was published this month in the journal Medicine & Science in Sports & Exercise. Hunter notes that strenuous activity both increases the amount of blood sugar and lactate — a byproduct of intense muscle contractions — circulating in the blood and augments blood flow to the head. Because the brain uses sugar and lactate as fuel, researchers wondered if the increased flow of fuel-rich blood during exercise could feed an exhausted brain and reduce the urge to overeat. Thirty-eight healthy college students were invited to U.A.B.’s exercise lab to determine their fitness and metabolic rates — and to report what their favorite pizza was. Afterward, they sat quietly for 35 minutes before being given as much of their favorite pizza as they wanted, which established a baseline measure of self-indulgence. At a later date, the volunteers returned and spent 20 minutes tackling selections from college and graduate-school entrance exams. Hunter says this work has been used in other studies “to induce mental fatigue and hunger.” Next, half the students sat quietly for 15 minutes, before being given pizza. The rest of the volunteers spent those 15 minutes doing intervals on a treadmill: two minutes of hard running followed by about one minute of walking, repeated five times. This is the sort of brief but intensive routine, Hunter says, that should prompt the release of sugar and lactate into the bloodstream. These students were then allowed to gorge on pizza, too. But by and large, they did not overeat. © 2016 The New York Times Company
By Jessica Hamzelou As any weight-watcher knows, carb cravings can be hard to resist. Now there’s evidence that carbohydrate-rich foods may elicit a unique taste too, suggesting that “starchy” could be a flavour in its own right. It has long been thought that our tongues register a small number of primary tastes: salty, sweet, sour and bitter. Umami – the savoury taste often associated with monosodium glutamate – was added to this list seven years ago, but there’s been no change since then. However, this list misses a major component of our diets, says Juyun Lim at Oregon State University in Corvallis. “Every culture has a major source of complex carbohydrate. The idea that we can’t taste what we’re eating doesn’t make sense,” she says. Complex carbohydrates such as starch are made of chains of sugar molecules and are an important source of energy in our diets. However, food scientists have tended to ignore the idea that we might be able to specifically taste them, says Lim. Because enzymes in our saliva break starch down into shorter chains and simple sugars, many have assumed we detect starch by tasting these sweet molecules. Her team tested this by giving a range of different carbohydrate solutions to volunteers – who it turned out were able to detect a starch-like taste in solutions that contained long or shorter carbohydrate chains. “They called the taste ‘starchy’,” says Lim. “Asians would say it was rice-like, while Caucasians described it as bread-like or pasta-like. It’s like eating flour.” © Copyright Reed Business Information Ltd.