1. Study suggests learning to make healthy choices can counter the effects of large portions

    February 11, 2018 by Ashley

    From the Penn State press release:

    People are often told that eating everything in moderation can help them lose weight, but it is better to choose healthier foods than to try to eat less, according to Penn State researchers.

    In a recent study, researchers measured how much participants ate when given meals that varied in portion size. Despite about one-third of participants having been trained in different strategies to manage food portions during a previous year-long weight loss trial, all participants ate more as portion sizes grew. Although the trained participants ate the same amount as the others, they tended to choose healthier foods and ended up consuming fewer calories overall.

    “The results show that choosing healthy, lower-calorie-dense foods was more effective and more sustainable than just trying to resist large portions of higher calorie options,” said Faris Zuraikat, graduate student. “If you choose high-calorie-dense foods but restrict the amount that you’re eating, portions will be too small, and you’re likely to get hungry.”

    Previous research has shown the power of the “portion size effect,” which is the tendency for people to eat more when larger portions are served and can result in people consuming more calories than they intended.

    The researchers designed an intervention to help people counteract this effect, in which participants were taught strategies to control food portions and eat healthier. Zuraikat said he and the other researchers wanted to see if this training was effective in helping people control portions.

    “We gathered a group of subjects who had extensive training on portion-control strategies to see if their response to increasing portion size of foods served at a meal differed from untrained individuals,” Zuraikat said. “We were also interested in whether those untrained individuals with overweight and obesity or normal weight differed in their response.”

    The researchers recruited three groups of women to participate in the study: 34 controls with overweight, 29 controls with normal weight, and 39 who had previously completed a one-year weight loss trial emphasizing portion-control strategies. All participants visited the lab once a week for four weeks. During each visit, the researchers provided the same foods but increased the portion size of the foods in a randomized order across weeks.

    Each meal consisted of foods with higher calorie density, like garlic bread, and lower calorie density, like salad. Foods were weighed before and after the meal to determine how much was eaten, and calorie intake was determined from these measures.

    The researchers found that when they were given larger portions, participants in all three groups ate more. For example, when the portion size was increased 75 percent, the average amount consumed went up 27 percent.

    However, the participants who received training consumed fewer calories overall than those who did not. Even though the participants in all three groups ate similar amounts of food, the participants who received training chose foods lower in calorie density.

    “All the groups were served the same meals, but their food choices differed. The participants who went through the training consumed more of the lower calorie-dense foods and less of the higher calorie-dense foods than the untrained controls,” Zuraikat said. “Consequently, trained participants’ calorie intake was less than that of the control groups, whose intake didn’t differ by weight status.”

    The researchers say the study — published in the journal Appetite — illustrates the strength of the portion-size effect while also suggesting easier, more sustainable strategies for managing calorie intake.

    “The study supports the idea that eating less of the higher-calorie-dense foods and more of the nutritious, lower-calorie-dense foods can help to manage hunger while consuming fewer calories,” said Barbara Rolls, professor and the Helen A. Guthrie Chair of Nutritional Sciences, Penn State. “You still have a full plate, but you’re changing the proportions of the different types of foods.”

    Liane S. Roe and Christine E. Sanchez, both of Penn State, were co-investigators in this study.

    The National Institute of Diabetes and Digestive and Kidney Diseases and the USDA supported this project.


  2. Study suggests marketing food as a “meal” rather than “snack” may help prevent overeating

    November 1, 2017 by Ashley

    From the University of Surrey press release:

    Marketing food as a ‘snack’ leads to increased consumption and continued overeating, a new study in the journal Appetite reports.

    In the first ever study of its kind, Professor Jane Ogden and her researchers from the University of Surrey examined the impact of labelling food products as ‘snacks’ or ‘meals’.

    During this innovative investigation, eighty participants were asked to eat a pasta pot which was either labelled as a ‘snack’ or a ‘meal.’ Each pot was presented as a ‘snack’ (eaten standing up from a plastic pot with a plastic fork) or a ‘meal’ (seated at a table from a ceramic plate and metal fork). Once consumed, participants were invited to take part in an additional taste test of different foods (animal biscuits, hula hoops, M&M’s and mini cheddars.)

    Researchers found that those who had eaten pasta labelled as a ‘snack’ ate more at the taste test then when it had been labelled as a ‘meal.’ It was also found that those who ate the ‘snack’ standing up consumed more (50 per cent more total mass, sweet mass and total calories and 100 per cent more M&M’s) than those who had eaten the pasta sitting down at a table. This unique set of results demonstrate that when a food is labelled as a snack rather than a meal consumption is higher, particularly when standing rather than sitting.

    Researchers have attributed this to a combination of factors and believe that when eating a snack we are more easily distracted and may not be conscious of consumption. They also argue that memories for snacks and meals may be encoded differently in our subconscious and that we are unable to recall what we have eaten as a ‘snack.’

    Jane Ogden, Professor in Health Psychology at the University of Surrey, said: “With our lives getting busier increasing numbers of people are eating on the go and consuming foods that are labelled as ‘snacks’ to sustain them. What we have found is that those who are consuming snacks are more likely to over eat as they may not realise or even remember what they have eaten.

    “To overcome this we should call our food a meal and eat it as meal, helping make us more aware of what we are eating so that we don’t overeat later on.”

    Obesity is a growing problem in the United Kingdom with levels reported to have trebled in the last 30 years with 24.9 per cent of people now deemed obese, the highest levels in Europe. It is estimated that £16 billion a year is spent on the direct medical costs of diabetes and conditions related to being overweight or obese.


  3. Study examines how branding and prices influence children’s decisions about snack purchases

    August 15, 2017 by Ashley

    From the Tufts University, Health Sciences Campus press release:

    What determines how children decide to spend their cash on snacks? A new study shows that children’s experience with money and their liking of brands influenced purchase decisions — and that for some children, higher prices for unhealthy snacks might motivate healthier choices. The study is published in the journal Appetite.

    Besides parents, many actors such as schools, governments and food manufacturers influence and modify the consumption of energy-dense, nutrient-poor snack food among children through a multitude of venues such as parental guidance and restriction of such foods and snacks available to children at home, school programs (school lunch and vending machines), governmental mandates (taxation, nutrition education campaigns) and marketing messages.

    Researchers co-led by Professors Monika Hartmann from the University of Bonn and Sean Cash from the Friedman School of Nutrition Science and Policy at Tufts University studied the ways that children aged 8 to 11 use their own disposable income, predominantly an allowance provided by a parent, to purchase snack food on their own. In the study, they report that brand awareness was not necessarily aligned with preference of snack foods. Importantly, the extent of children’s experience with money influenced their purchase decisions, suggesting that higher prices for unhealthy snacks might be helpful in motivating at least those children that have experience with money to choose healthier options.

    The research took place in after-school programs in the Boston area with a sample of 116 children ages 8 to 11 years. The study consisted of a survey, two cognitive tests, and a discrete choice experiment (DCE). The participants were paid $2.00 each as compensation after completing the cognitive tests that they could then spend in the DCE part of the study.

    “We don’t know much about how kids spend their cash on snacks,” said corresponding author Sean Cash, Ph.D., economist and associate professor at the Friedman School of Nutrition Science and Policy at Tufts University. “It’s an understudied area. Currently, many children have their own disposable income, usually an allowance. They’re deciding how to spend that money on snacks, but we know very little about how they make those decisions.” This is especially true with respect to the extent to which children assess typical consumer tradeoffs regarding price and other food attributes.

    Cookies, apple slices, or yogurt

    The researchers presented a series of snack options to the children — cookies, apple slices, and tubes of yogurt. Each child was presented ten times with pairs of photographs of two snack items that differed by product type, price and brand. Each time they could select one of the two products or decide to make no choice.

    The child was told that at the end of the experiment, one choice would be drawn at random from the ten decisions the child made and the child would be obligated to purchase the chosen snack. The child had to pay the stated price of that choice, which ranged between $0.30 and $0.70, from the money previously earned in the study and they received the designated snack. This feature of the design made each choice more realistic for the kids. One group of snacks was from McDonald’s in order to test the importance of branding on children’s choices.

    Experience with money makes a difference

    Children made choices based primarily on food types (cookie, apple slices, yogurt). In the experiment, children most often chose the chocolate-chip cookies, with apple slices in second place. Other results were surprising.

    “What we found is that brand awareness was not a key factor in purchasing the snacks. What mattered more is a child’s like or dislike the brand,” said first author Monika Hartmann, Ph.D., who was a visiting scholar at the Friedman School while the study was being conducted. She is based at the Institute of Food and Resource Economics at the University of Bonn.

    The other important result was a distinct dichotomy with respect to how price affected the children’s purchase decision. Children who were used to receiving an allowance from their parents paid attention to the price, whereas those who had little experience handling money generally did not. This result supports research that suggests experience with cash is an important aspect of learning what prices mean.

    “Overall, the literature on children’s price responsiveness and brand awareness is scarce,” the authors wrote in their article. “The former is especially true for younger children (elementary school).” At the same time, they observed that children spend a considerable amount of money on snacks while childhood incidence of chronic dietary-related disease (type-2 diabetes, coronary artery disease, and obesity) is high and increasing around the world.

    The authors point out that this is a small study, regionally biased, and with limited choices within the experiment. They suggest further research to explore the efficacy of using price and presentation (e.g., packaging, branding) as additional tools in the fight against the growing incidence of chronic disease among children. Their work was supported by a grant from the German Research Foundation (DFG) with additional support from the U.S. Department of Agriculture’s National Institute of Food and Agriculture.


  4. Study explains why food looks even better when dieting

    April 22, 2017 by Ashley

    From the Hiroshima University press release:

    Over recent decades, our understanding of hunger has greatly increased, but this new discovery turns things on their head. Up until now, scientists knew that leptin — a hormone released by fatty tissue, reduces appetite, while ghrelin — a hormone released by stomach tissue makes us want to eat more. These hormones, in turn, activate a host of neurons in the brain’s hypothalamus — the body’s energy control center.

    The discovery of NPGL by Professor Kazuyoshi Ukena of Hiroshima University shows that hunger and energy consumption mechanisms are even more complex than we realized — and that NPGL plays a central role in what were thought to be well-understood processes.

    Professor Ukena first discovered NPGL in chickens after noticing that growing birds grew larger irrespective of diet — suggesting there was more to energy metabolism than meets the eye. Intrigued, the researchers at HU performed a DNA database search to see if mammals might also possess this elusive substance. They found that it exists in all vertebrates — including humans.

    In order to investigate its role, if any, in mammals, Professor Ukena’s team fed three groups of mice, on three distinct diets, to see how NPGL levels are altered. The first set of mice was fed on a low-calorie diet for 24 hours. The second group was fed on a high-fat diet for 5 weeks — and the third lucky group was fed on a high-fat diet, but for an extended period of 13 weeks.

    The mice fed on a low calorie diet were found to experience an extreme increase in NPGL expression, while the 5-week high-fat-diet group saw a large decrease in NPGL expression.

    Further analysis found that mice possess NPGL, and its associated neuron network, in the exact same locations of the brain as those regions already known to control appetite suppression and energy use.

    Professor Ukena proposes that NPGL plays a vital role in these mechanisms — increasing appetite when energy levels fall and reducing appetite when an energy overload is detected — together, helping to keep us at a healthy and functioning weight, and more importantly alive!

    As NPGL levels greatly increased in mice exposed to a low calorie diet, Professor Ukena believes it is an appetite promoter, working in opposition to appetite suppressing hormones such as leptin. Backing this hypothesis up, it was found that mice directly injected with NPGL exhibited a voracious appetite.

    Interestingly NPGL levels, which plummeted in the 5-week-long high-fat-diet mice — fell back to normal levels in mice who gorged themselves for the longer period of 13 weeks.

    It is proposed that exposure to high-fat diets for long periods of time lead to insensitivity to leptin’s appetite-suppressing effects, and so NPGL — even at normal levels — leads to weight gain and obesity, showing that the body can only do so much to keep our weight in check.

    Professor Ukena says that further study is required to understand the interaction of previously known appetite mechanisms with this new kid on the homeostasis block. It does seem however, that we still have a lot to learn about appetite, hunger, and energy consumption. It is hoped that this study into mammalian NPGL adds another piece to the puzzle.

    What is certain — but you knew this already — is that dieting is difficult. The discovery and study of mammalian NPGL helps explain why, and provides a plausible excuse for those whose good intentions fall short.


  5. Gates of serotonin: Cracking the workings of a notorious receptor

    April 25, 2016 by Ashley

    From the Ecole Polytechnique Fédérale de Lausanne media release:

    brain scanEPFL scientists have elucidated for the first time how a notoriously elusive serotonin receptor functions with atom-level detail. The receptor transmits electrical signals in neurons and is involved in various disorders, meaning that the discovery opens the way for new treatments.

    Serotonin is a major neurotransmitter, regulating mood, appetite, sleep, memory, learning, and other functions by binding to dedicated receptor proteins. Serotonin receptors have been researched for decades, but details about their structure and function are hard to come by. EPFL scientists have now made the first ever computer simulation of a notoriously elusive serotonin receptor that is involved in fast signal transmission in neurons and plays a central role in disorders such as schizophrenia, chemotherapy nausea, irritable bowel syndrome, anxiety, and seizures. The work is published in the journal Structure.

    The 5-HT3 receptor (5-HT stands for 5-hydroxytryptamine, the technical name of serotonin) is the third member of a family of serotonin receptors. It is made up of five proteins that form a tube-like channel through the cell membrane. When serotonin binds to the receptor, a gate opens up and allows positively charged ions of sodium, potassium or calcium to flow through the channel. This changes the electrical balance between the inside and outside of the neuron, and an electrical signal is transmitted across the cell membrane.

    In our central and peripheral nervous system such “neurotransmitter-gated” receptors with ion channels like 5-HT3 are critical for signaling between neurons. However they have been notoriously difficult to study with traditional tools of structural biology. But in a 2014 Nature paper, the lab of Horst Vogel at EPFL published the first ever, high-resolution and complete 3D structure of the 5-HT3 receptor.

    Now, Vogel’s lab has followed up with a complete computer simulation of 5-HT3 that reveals the motions of each atom across microseconds and at atomic, sub-nanometer resolution. This so-called “molecular dynamics simulation” uses the structure of 5-HT3 receptor that Vogel’s lab uncovered in 2014 to accurately depict the structural changes that 5-HT3 undergoes inside a cell membrane after serotonin binds and activates it to open its ion channel. To make sure that they were not looking at random structural changes of the receptor itself, the researchers also ran simulations of the receptor without the ligand.

    “Our 2014 paper delivered the architecture of the 5-HT3 neuroreceptor with atomic detail,” says Horst Vogel. “But that was a static structure that did not explain how the receptor functions as a gated transmembrane ion channel to transmit electrical signals across the cell membrane.”

    Specifically, Vogel’s team wanted to know how a ligand, e.g. serotonin, that binds to the part of 5-HT3 outside of the cell, can open the ion channel’s gate, which is buried inside the cell’s membrane six nanometers away — a considerable distance in the world of molecules.

    With this degree of accuracy, the researchers feel confident that the simulation delivers a realistic description of how the 5-HT3 receptor works. Beyond that, it also acts as a blueprint for the function of neurotransmitter-gated, ion-channel receptors in general.

    The data can help us understand how neuronal signals are transmitted at an atomic scale,” says Vogel. “This would hold enormous potential for future drug development and treatment of disorders linked to these receptors, including schizophrenia, anxiety, nausea, and others.”


  6. Study identifies key shift in the brain that creates drive to overeat

    May 3, 2013 by Ashley

    From the Indiana University press release via EurekAlert!:

    brain scanA team of American and Italian neuroscientists has identified a cellular change in the brain that accompanies obesity. The findings could explain the body’s tendency to maintain undesirable weight levels, rather than an ideal weight, and identify possible targets for pharmacological efforts to address obesity.

    The findings, published in the Proceedings of the National Academy of Sciences Early Edition this week, identify a switch that occurs in neurons within the hypothalamus. The switch involves receptors that trigger or inhibit the release of the orexin A peptide, which stimulates the appetite, among other behaviors. In normal-weight mice, activation of this receptor decreases orexin A release. In obese mice, activation of this receptor stimulates orexin A release.

    The striking finding is that you have a massive shift of receptors from one set of nerve endings impinging on these neurons to another set,” said Ken Mackie, professor in the Department of Psychological and Brain Sciences in the College of Arts and Sciences at IU Bloomington. “Before, activating this receptor inhibited the secretion of orexin; now it promotes it. This identifies potential targets where an intervention could influence obesity.”

    The work is part of a longstanding collaboration between Mackie’s team at the Gill Center for Biomolecular Science at IU Bloomington and Vincenzo Di Marzo’s team at the Institute of Biomolecular Chemistry in Pozzuoli, Italy. Both teams study the endocannabinoid system, which is composed of receptors and signaling chemicals that occur naturally in the brain and have similarities to the active ingredients in cannabis, or marijuana. This neurochemical system is involved in a variety of physiological processes, including appetite, pain, mood, stress responses and memory.

    Food consumption is controlled in part by the hypothalamus, a portion of the brain that regulates many essential behaviors. Like other important body systems, food consumption is regulated by multiple neurochemical systems, including the endocannabinoid system, representing what Mackie describes as a “balance of a very fine web of regulatory networks.”

    An emerging idea, Mackie said, is that this network is reset during obesity so that food consumption matches maintenance of current weight, not a person’s ideal weight. Thus, an obese individual who loses weight finds it difficult to keep the weight off, as the brain signals the body to eat more in an attempt to return to the heavier weight.

    Using mice, this study found that in obesity, CB1 cannabinoid receptors become enriched on the nerve terminals that normally inhibit orexin neuron activity, and the orexin neurons produce more of the endocannabinoids to activate these receptors. Activating these CB1 receptors decreases inhibition of the orexin neurons, increasing orexin A release and food consumption.

    This study identifies a mechanism for the body’s ongoing tendency to return to the heavier weight,” Mackie said.

    The researchers conducted several experiments with mice to understand how this change takes place. They uncovered a role of leptin, a key hormone made by fat cells that influences metabolism, hunger and food consumption. Obesity causes leptin levels to be chronically high, making brain cells less sensitive to its actions, which contributes to the molecular switch that leads to the overproduction of orexin.

     


  7. Study suggests association between dietary nutrients and sleep patterns

    February 18, 2013 by Ashley

    From the Perelman School of Medicine at the University of Pennsylvania press release via ScienceDaily:

    sleeping_couple“You are what you eat,” the saying goes, but is what you eat playing a role in how much you sleep? Sleep, like nutrition and physical activity, is a critical determinant of health and well-being.

    With the increasing prevalence of obesity and its consequences, sleep researchers have begun to explore the factors that predispose individuals to weight gain and ultimately obesity.

    Now, a new study from the Perelman School of Medicine at the University of Pennsylvania shows for the first time that certain nutrients may play an underlying role in short and long sleep duration and that people who report eating a large variety of foods — an indicator of an overall healthy diet — had the healthiest sleep patterns.

    The new research is published online, ahead-of-print in the journal Appetite.

    “Although many of us inherently recognize that there is a relationship between what we eat and how we sleep, there have been very few scientific studies that have explored this connection, especially in a real-world situation,” said Michael A. Grandner, PhD, instructor in Psychiatry and member of the Center for Sleep and Circadian Neurobiology at Penn.

    “In general, we know that those who report between 7 — 8 hours of sleep each night are most likely to experience better overall health and well being, so we simply asked the question “Are there differences in the diet of those who report shorter sleep, longer sleep, or standard sleep patterns?”

    To answer this question, the research team analyzed data from the 2007-2008 National Health and Nutrition Examination Survey (NHANES) sponsored by the Centers for Disease Control and Prevention. NHANES includes demographic, socioeconomic, dietary, and health-related questions.

    The sample for the survey is selected to represent the U.S. population of all ages and demographics. For the current study, researchers used the survey question regarding how much sleep each participant reported getting each night to separate the sample into groups of different sleep patterns. Sleep patterns were broken out as “Very Short” (<5 h per night), “Short” (5-6 h per night), “Standard” (7-8h per night), and “Long” (9 h or more per night). NHANES participants also sat down with specially trained staff who went over, in great detail, a full day’s dietary intake.

    This included everything from the occasional glass of water to complete, detailed records of every part of each meal. With this data, the Penn research team analyzed whether each group differed from the 7-8 hour “standard” group on any nutrients and total caloric intake.

    They also looked at these associations after controlling for overall diet, demographics, socioeconomics, physical activity, obesity, and other factors that could have explained this relationship. The authors found that total caloric intake varied across groups. Short sleepers consumed the most calories, followed by normal sleepers, followed by very short sleepers, followed by long sleepers.

    Food variety was highest in normal sleepers, and lowest in very short sleepers. Differences across groups were found for many types of nutrients, including proteins, carbohydrates, vitamins and minerals. In a statistical analysis, the research team found that there were a number of dietary differences, but these were largely driven by a few key nutrients. They found that very short sleep was associated with less intake of tap water, lycopene (found in red- and orange-colored foods), and total carbohydrates, short sleep was associated with less vitamin C, tap water, selenium (found in nuts, meat and shellfish), and more lutein/zeaxanthin (found in green, leafy vegetables), and long sleep was associated with less intake of theobromine (found in chocolate and tea), dodecanoic acid (a saturated fat) choline (found in eggs and fatty meats), total carbohydrates, and more alcohol.

    Overall, people who sleep 7 — 8 hours each night differ in terms of their diet, compared to people who sleep less or more. We also found that short and long sleep are associated with lower food variety,” said Dr. Grandner.

    What we still don’t know is if people altered their diets, would they be able to change their overall sleep pattern? This will be an important area to explore going forward as we know that short sleep duration is associated with weight gain and obesity, diabetes, and cardiovascular disease. Likewise, we know that people who sleep too long also experience negative health consequences. If we can pinpoint the ideal mix of nutrients and calories to promote healthy sleep, the healthcare community has the potential to make a major dent in obesity and other cardiometabolic risk factors.”

    Other authors for Penn include Nicholas J. Jackson and Jason R. Gerstner, PhD. This research was supported grants from National Institutes of Health (T32HL007713, 12SDG9180007 and P30HL101859).


  8. Study looks at how appetite cells in brain respond to fasting

    February 8, 2012 by Sue

    From the Cell Press press release via EurekAlert!:

    There are two key cell types in the brain that are central to the regulation of feeding behaviors, agouti-related peptide (AgRP)-expressing neurons and proopiomelancortin (POMC)-expressing neurons. Previous work has shown that the AgRP neurons promote feeding and weight gain, while the POMC cells have been linked with appetite suppression and weight loss. Now a new study published by Cell Press in the February 9 issue of the journal Neuron uncovers a neural pathway that links fasting with activation of AgRP neurons. The research provides valuable insight into the complex mechanisms that control food seeking behavior.

    “Given their critical roles in feeding behaviors, there is great interest in understanding the factors that regulate the activity of AgRP and POMC neurons,” says senior study author, Dr. Bradford B. Lowell, from Beth Israel Deaconess Medical Center and Harvard Medical School. “However, although both types of neurons receive abundant excitatory and inhibitory inputs, the influence of these upstream signals has not received much attention.”

    Dr. Lowell and colleagues analyzed the impact of excitatory inputs on AgRP and POMC neurons by manipulating NMDA receptors (NMDARs) in each cell type. These receptors receive inputs from the major excitatory neurotransmitter in the brain. Interestingly, only mice lacking NMDARs on their AgRP neurons, and not those lacking NMDARs on their POMC neurons, exhibited altered body weight and food intake. Thus, this type of excitatory information is only critical for the function of AgRP neurons.

    Importantly, the researchers also discovered that fasting, which is known to activate AgRP neurons and promote both food seeking and energy conservation, was associated with an increase in excitatory inputs and an increase in the number of dendritic spines on the AgRP neurons. Dendritic spines are physical protrusions on the neuron that receive incoming signals. These fasting-induced changes in AgRP neurons were also dependent on the presence of NMDARs.

    Taken together, the results suggest that excitatory information received by NMDARs plays a critical role in regulating the connectivity of AgRP neurons and governing the cellular and behavioral response to fasting. “The next step will be to identify the neurotransmitters and hormones that modulate the excitatory inputs to AgRP neurons, and the mechanisms by which this modulation occurs,” concludes Dr. Lowell. “This is likely to provide a better understanding of how various factors control feeding behavior.”


  9. Study points to physiological reasons why looking at food makes people feel hungry

    January 19, 2012 by Sue

    From the Max Planck Institute press release:

    Max Planck researchers have proven something scientifically for the first time that laypeople have always known: the mere sight of delicious food stimulates the appetite. A study on healthy young men has documented that the amount of the neurosecretory protein hormone ghrelin in the blood increases as a result of visual stimulation through images of food. As a main regulator, ghrelin controls both eating behaviour and the physical processes involved in food metabolism. These results show that, in addition to the physiological mechanisms for maintaining the body’s energy status, environmental factors also have a specific influence on food consumption. Thus, the pervasive presence of appetising food in the media could contribute to weight increase in Western populations.

    Warning: “Avoid looking at pictures of appetising food as it will make you hungry!” Dieticians could be making recommendations along these lines in the future. It has long been known that, in addition to the physiological regulatory circuits for the maintenance of a sufficient energy status for the body, external stimuli like smell or the sight of food also influence our feelings of hunger and our resulting eating behaviour. The danger that the exposure to such images will result in the consumption of food that is not needed to maintain the body’s energy status is particularly high in our advertising-dominated society.

    In a study involving healthy male subjects, Axel Steiger and his research group at the Max Planck Institute of Psychiatry investigated the molecular processes for the control of food consumption. They examined the specific physiological reaction of the test subjects to images showing either delicious food or non-edible objects. The concentrations of different hormones in the blood such as grehlin, leptin and insulin, which play a role in the regulation of food consumption, were measured. The researchers actually observed that the concentration of grehlin in the blood increases specifically in response to visual stimulation with food images.

    “The findings of our study demonstrate, for the first time, that the release of ghrelin into the blood for the regulation of food consumption is also controlled by external factors. Our brain thereby processes these visual stimuli, and the physical processes that control our perception of appetite are triggered involuntarily. This mechanism could prompt us to eat a piece of cake just two hours after breakfast,” says Petra Schüssler, a scientist at the Max Planck Institute. She thus recommends that individuals with weight problems should preferably avoid looking at images of appetising food.

     


  10. Study suggests short walk can cut chocolate consumption by half – even in stressful situations

    December 7, 2011 by Sue

    From the University of Exeter press release:

    A 15-minute walk can cut snacking on chocolate at work by half, according to research by the University of Exeter. The study showed that, even in stressful situations, workers eat only half as much chocolate as they normally would after this short burst of physical activity.

    Published in the journal Appetite, the research suggests that employees may find that short breaks away from their desks can help keep their minds off snacking.

    In the study, 78 regular chocolate-eaters were invited to enter a simulated work environment, after two days abstinence from chocolate snacking. Two groups were asked to take a brisk 15-minute walk on a treadmill and were then given work to complete at a desk. One group was given an easy, low-stress task, while the other was asked to complete a more demanding job. The other two groups were asked to have a rest before completing the same tasks as the first two groups. Again, half were given an easier task and the remainder a more challenging one. Chocolate was available in a bowl on the desk for all participants as they carried out their work.

    Those who had exercised before working consumed on average half the amount of chocolate as the others: around 15 grammes, compared with 28 grammes. 15 grammes is equivalent to a small ‘treat size’ or ‘fun size’ chocolate bar.

    The difficulty of the task made no difference to the amount of chocolate they ate, which suggests that stress did not contribute to their cravings for sweet snacks.

    Lead researcher Professor Adrian Taylor of Sport and Health Sciences at the University of Exeter said: “We know that snacking on high calorie foods, like chocolate, at work can become a mindless habit and can lead to weight gain over time. We often feel that these snacks give us an energy boost, or help us deal with the stress of our jobs, including boredom. People often find it difficult to cut down on their daily treats but this study shows that by taking a short walk, they are able to regulate their intake by half.”

    Exercise is known to have significant benefits for mood and energy levels and has potential for managing addictions. Professor Taylor and his colleagues at the University of Exeter have previously shown that exercise can curb cravings for chocolate but this is the first study to show a reduction in consumption.