Tag Archives: hunger

Stock photo of a man trying to exaggeratedly open a jar of pickles.

Post-exercise hunger could thwart your efforts to lose weight

Exercise is the healthiest, most efficient way of losing those extra pounds. However, a new paper comes to show how physical activity can influence our appetite and desire to eat — and how best to manage these, if we want to lose weight.

Stock photo of a man trying to exaggeratedly open a jar of pickles.
Image credits Ryan McGuire.

Let’s face it — most of us have become a bit plump during the last year. Between the drop in physical activity as we quarantine in our homes and the comfort eating to soothe our troubled souls, it’s perfectly understandable. But most of us also harbor secret plans to shed the pounds once things quiet down.

A new paper could help us in that regard. Published by a team of researchers at the Technical University of Munich (TUM) and the University of Nebraska (USA), it details how people can feel the need to eat more food and faster after exercising. This, in turn, can sabotage our efforts of actually slimming down, and can make us give up on it entirely.

Food for thought

“In the sports context, we have the phenomenon of people overeating after physical activity,” said Prof. Köhler, Professor of Exercise, Nutrition, and Health at the Technical University of Munich. “People want to reward themselves and their bodies for being active. So we use a hypothetical experiment to find out why people eat more after exercise compared to when they don’t exercise.”

“Based on this study, we were able to show for the first time that certain characteristics, such as the amount and ‘urgency’ with which a person wants to eat, change over the course of physical exertion. These findings help us develop new interventions to optimize weight loss through exercise.”

The trial followed a randomized crossover structure involving 41 healthy participants (23 women, 18 men) between 19 and 29 years old with an average BMI of 23.7. They were randomly assigned to either a 45-minute exercise session or a 45-minute rest period. Either was performed during the participants’ first visit to the lab. Every participant was then asked to perform the other task upon their second visit.

After this, the real experiment would begin: the team wanted to see how exercise influenced the participants’ choices in regards to the amount and timing of food intake. Before the trials, participants filled out an electronic questionnaire that assessed how hungry or satiated they felt, had them pick between foods that differed in the time of consumption (i.e. immediately or delayed by preparation, for example), how much food they felt like eating (which they did by selecting the desired portions of each food item).

These preferences were recorded both for immediate and later consumption (i.e. they were asked to predict their food preference for four hours later). Then, the participants engaged in the exercise task, which consisted of 45 minutes of aerobic exercise on a bicycle ergometer. Upon completion, they were asked to fill the same questionnaire out a second time, and a third time half an hour later. Participants in the control (rest) group went through the same procedure, but with rest instead of exercise.

All in all, the team explains, exercise led to participants choosing a greater amount of food both immediately after the exercise and 30 minutes later, as reflected in their questionnaires. It also made them pick food that would be immediately available for consumption on both questionnaires.

“The actual results suggest that physical exertion can entice those who do sport to eat larger amounts of food more quickly after the training session,” says Prof. Köhler.

“Since weight loss is a main motivation for exercising for many, and failure to achieve the desired weight loss makes it likely to quit exercising, it could be a good strategy to think about what you want to eat afterwards before you start to exercise.”

The team is currently researching which strategies work best in improving the long-term effectiveness of training programs. But until they can pinpoint the most effective approach, just know that exercising will make you want to eat, a lot, and quickly. Keeping the reins on this can make or break your efforts to lose weight.

The paper “Exercise Shifts Hypothetical Food Choices toward Greater Amounts and More Immediate Consumption” has been published in the journal Nutrients.

Don’t make important decisions on an empty stomach

Credit: Pixabay.

Anyone who’s walked into a grocery store being hungry will tell that’s a very bad idea. Apparently, that’s not all. Making all sorts of important decisions on an empty stomach tends to make people settle for a small reward that arrives sooner than going the extra mile to reach a big reward at a later date, a new study found.

“We found there was a large effect, people’s preferences shifted dramatically from the long to short term when hungry,” said Dr. Benjamin Vincent, a psychologist at the University of Dundee in the United Kingdom. “This is an aspect of human behavior which could potentially be exploited by marketers so people need to know their preferences may change when hungry. “

Vincent and colleagues asked 50 participants questions relating to food, money, and other reward-based topics twice: when they were full and when they skipped a meal.

Quite unsurprisingly, hungry participants were more likely to settle for food incentives that arrived sooner. However, the researchers found that this tendency to settle for immediate but less satisfying rewards crossed over to other aspects of life, which were totally unrelated to food.

“People generally know that when they are hungry they shouldn’t really go food shopping because they are more likely to make choices that are either unhealthy or indulgent. Our research suggests this could have an impact on other kinds of decisions as well. Say you were going to speak with a pension or mortgage advisor – doing so while hungry might make you care a bit more about immediate gratification at the expense of a potentially more rosy future,” Vincent said in a statement.

When offered the choice between three different types of rewards, hungry participants generally preferred smaller hypothetical rewards that were awarded immediately rather than larger ones that would arrive later. When the participants had lunch, they were typically willing to wait 35 days to double the reward, but when hungry they grew too impatient being willing to wait only 3 days.

“This work fits into a larger effort in psychology and behavioral economics to map the factors that influence our decision making. This potentially empowers people as they may foresee and mitigate the effects of hunger, for example, that might bias their decision making away from their long term goals,” he added.

The findings, which were published in the journal Psychonomic Bulletin & Review, seem to concur those of a much more famous experiment, the so-called “marshmallow test” performed by Stanford psychologists in the 1960s. Put a marshmallow in front of a child, tell her that she can have a second one if she can go 15 minutes without eating the first one, and then leave the room. Whether she’s patient enough to double her payout is supposedly indicative of a willpower that will pay dividends down the line, at school and eventually at work.

The new study shows that hungry people will make more impulsive decisions even when their outcomes will do nothing to relieve hunger.

“You would predict that hunger would impact people’s preferences relating to food, but it is not yet clear why people get more present-focused for completely unrelated rewards,” Vincent.

“We hear of children going to school without having had breakfast, many people are on calorie restriction diets, and lots of people fast for religious reasons. Hunger is so common that it is important to understand the non-obvious ways in which our preferences and decisions may be affected by it.”

Fork.

The hunger hormone is involved in episodic memory in rats, new research finds

Ghrelin, the hormone that induces hunger, also seems to play a role in memory control.

Fork.

Image credits Christine Sponchia.

If you’re sitting in a restaurant keenly anticipating a delicious meal that will be served shortly, chances are you’ll feel hungry. That sensation is created by ghrelin, a hormone secreted in the stomach as you anticipate food. Ghrelin has been linked with the mediation of hunger signals between our gut and our brain, but new research at the Society for the Study of Ingestive Behavior suggests that the molecule might also play an important part in memory control.

Food for memory

“We recently discovered that in addition to influencing the amount of food consumed during a meal, the vagus nerve also influences memory function,” said Dr. Scott Kanoski, senior author of the study.

After its secreted, ghrelin binds to specialized receptors on the vagus nerve, which transmits signals between the gut and the brain. The team’s hypothesis was that ghrelin might also help the vagus nerve support memory formation.

Using a method called RNA interference, the team artificially reduced the amount of ghrelin receptor in the vagus nerve for a group of lab rats. The animals were then put through a series of memory tasks. The rats with reduced ghrelin signaling in the vagus nerve showed impaired performance in an episodic memory test compared to the control group. Episodic memory is the type of memory involved in remembering what, when, and where something occurred. For the rats, the test required remembering a specific object in a specific location.

A second part of the study looked at whether ghrelin signaling in the vagal nerve influences feeding behavior. They report that mice whose vagus nerve can’t receive signals from ghrelin ate more frequently than unaltered mice but consumed less food at each meal. The team says this might come down to deficits in episodic memory associated with impaired ghrelin signaling rather than feelings of hunger.

“Deciding to eat or not to eat is influenced by the memory of the previous meal,” says Dr. Elizabeth Davis, lead author on the study. “Ghrelin signaling to the vagus nerve may be a shared molecular link between remembering a past meal and the hunger signals that are generated in anticipation of the next meal.”

The team plans to expand their research to see if they can improve memory capacity in humans by manipulating ghrelin signaling between the gut and the brain.

The findings, “Vagal afferent ghrelin signaling promotes episodic memory and influences meal patterns in rats” have been presented at the 2019 Annual Meeting of the Society for the Study of Ingestive Behavior in Utrecht, Netherlands, in July.

Credit: Pixabay.

Why drinking alcohol gives you the munchies

Credit: Pixabay.

Credit: Pixabay.

Closing time at the bars usually sends scores of intoxicated men and women to the nearest diner or fast-food restaurant. In a new study, researchers at the Pennsylvania State University College of Medicine investigated what makes alcohol and high-fat junk food go so well together, finding that this union seems to be mediated by a shared brain circuit in the brain.

“Obesity and alcoholism, two of the most common chronic disorders in the United States, may be behaviorally linked as binge intake of palatable diets, such as diets high in fat, and binge alcohol intake may utilize the same neurocircuitry,” the researchers wrote.

The new findings agree with previous studies which found that alcohol consumption affects the same areas of the brain that control overeating.

For their study, the researchers experimented with three groups of adult male mice, each with different eating and drinking patterns. One group had unlimited access to a high-fat diet and had limited access to drinking water mixed with alcohol; the second group ate normal rodent food and had limited access to the same kind of alcoholic beverage as the first group; the third group had limited access to both high-fat foot and alcohol beverage. Over the course of eight weeks, the ratio of alcohol to drinking water was incrementally increased from 10% to 20%. Throughout the trial, all the animals were offered access to drinking water.

Animals in the third group, also known as the “binge diet”, had a weight-gain and weight-loss cycle associated with binge eating and drank more alcohol than water during their access period. The other groups consumed less alcohol than the binge diet group.

The results suggest that limited access to high-fat food promotes binge-like eating patterns, which also primes the brain for more alcohol consumption.

“Given the increasing rates of binge drinking and overall obesity rates in the U.S. in recent years, we think this new mouse model will be of critical importance in the near future,” wrote Caitlin Coker, MS, first author of the study which was presented at the American Physiological Society’s (APS) annual meeting at Experimental Biology 2019 in Orlando, Fla.

This wasn’t the first time that scientists have identified a link between alcohol consumption and eating behavior. Alcohol adds calories to your daily intake without offering much nutritive value in return. However, instead of filling you up and making you eat less, alcohol seems to have the opposite effect. For instance, one study identified the so-called apéritif effect, whereby consuming an alcoholic beverage (with 20 g of alcohol) before lunch led to an 11% increase in total food intake during the meal, and a 24% increase in high-fat savory foods.

Too much alcohol can lead to health problems, including being overweight. However, light to moderate alcohol intake can be healthy since its rich antioxidant content can offer protection against heart disease, diabetes, dementia, and more.

Hunger can be a pain in the butt. Credit: Pixabay.

Scientists find gut to brain connection that controls hunger — and switch it off

Hunger can be a pain in the butt. Credit: Pixabay.

Hunger can be a pain in the butt. Credit: Pixabay.

Researchers at the University of Pennsylvania have uncovered several mechanisms involved in either generating or suppressing hunger in mice. When mice were given a cocktail of hormones normally secreted during digestion, their hunger was satieted. This suggests that drugs acting upon these satiating mechanisms might prove to be highly useful against the world’s growing obesity epidemic, which is particularly problematic in the USA.

Don’t hate on hunger — it’s our friend

Have you ever stopped for a moment to realize that simply seeing or smelling food is able to temporarily satisfy your hunger? At least to a certain degree. Nicholas Betley and colleagues at the University of Pennsylvania demonstrated this concept in a previous paper. They showed how neurons that express agouti-related protein, or AgRP neurons, control the sensation of hunger. That their activity is suppressed upon eating as well as merely smelling or seeing food.

Hunger is one of the least pleasant bodily sensations out there, but such a sensation is no accident or freak of nature. Ultimately, hunger — as unpleasant and painful it can get — is there to save our lives from starvation. Essentially, AgRP neurons comprise ” a sensitive alarm system,” Betley explained, which can be turned off, or at least regulated, by nutrients.

“Being hungry can feel unpleasant, and these are the neurons that seem to mediate this,” Betley said in a statement. “Animals don’t like this stimulation. In the laboratory, we can turn these neurons on with the flash of a light. Interestingly, we found that animals will scamper to the other side of the room to turn off the light.”

The researchers experimented on genetically engineered so that calcium increased the fluorescence of a molecular reporter in the AgRP neurons. Because neuronal activity increases calcium levels, this allowed neural activity to be easily tracked as the rodents moved and performed various activities.

As the scientists previously noticed, AgRP neuron activity decreased rapidly and stayed low during and after eating. However, when the mice were presented with a strawberry-flavored, calorie-free gel, its sight and smell had no effect on the AgRP neurons. That’s because it is an unfamiliar food and therefore the rodents do not know to turn off their “hunger alarm”. When the rodents ate the calorie-free gel, activity in the AgRP neurons decreased — but only for about 200 seconds. Repeated trials with the calorie-free gel decreased this transient effect even further, the authors reported in the journal Cell Reports.

When the animals were given a calorie-containing gel, AgRP neuron activity declined and remained low. Upon subsequent exposures to the caloric gel, the mice’s AgRP neurons decreased activity in anticipation of the tasty treat, suggesting the rodents had learned to associate the smell and sight of the food with satiety.

The takeaway is that actual nutrients need to reach the stomach for hunger-causing neurons to stop firing. Moreover, the hunger reducing effect is dose-dependent on the calorie content.

“If they get the caloric kind first and then see the calorie-free kind, they predict the nutrients because the flavor is the same, the taste is similar. It takes 200 seconds for the animal to realize that whatever has hit its gut isn’t doing what it should be doing and the activity of those neurons comes back,” Betley said.

Fooling the brain the stomach’s fool

brain-stomach

Researchers have identified a connection between the brain and the gut that acts to satiate. Credit: University of Pennsylvania.

After the researchers were confident that it is nutrients that signal the brain to stop the hunger sensation, they next wanted to learn how it does so.

When mice were given hormones that are secreted during digestion — like cholecystokinin, peptide tyrosine and amylin, — AgRP neuron activity decreased dramatically in a dose-dependent manner. When low doses of these three peptides were combined, they acted synergistically, leading to a robust decrease in AgRP neuron activity.

These results suggest that any of these hormones or a combination of the three could help treat obesity in humans by suppressing hunger. Previously, when doctors individually administered these three hormones to human patients, it triggered nausea. However, the University of Pennsylvania researchers found no sign of malaise in mice that were given a cocktail of the three hormones. Betley thinks it’s because each hormone is given in low dose.

Next, Betley and colleagues will explore new ways to suppress AgRP neuron activity by looking for triggers that mimic the presence of nutrients in the gut.

“It would be interesting to see whether consuming smaller meals more frequently might lead to less activity in the neurons and thus less food intake overall,” Betley said. “Or maybe we can develop better combinations of foods or better ways of eating so we can avoid that 9 p.m. binge on Oreo cookies when you’ve had a really great diet all day.”

Always Gamble on an Empty Stomach: Hunger Is Associated with Advantageous Decision Making

Three experimental studies have shown that hunger improves strategic decision making; scientists argue that hungry people are significantly better at making decisions involving uncertain outcomes.

Hunger may help us make better decisions. Image via Where is my Doctor

We take decisions involving unknown outcomes every day. In real life, rationality often times means giving up a smaller, immediate reward, for a more consistent reward in the long run. However, many people engage in detrimental actions, just for the sake of the immediate reward. For example, many people would just have that hamburger or chocolate bar over a healthier meal. It’s this type of decision which puts our general well-being at risk.

“Many people tend to engage in this kind of disadvantageous choices, such as weight watchers who prefer a high caloric muffin for breakfast over a slim waist or business men preferring a night out at the casino over preparing next day’s meeting. Hot states like emotions or visceral drives have a bad reputation of compromising such self-control dilemmas by making people less patient to wait for the long-term benefits” researchers write in the study.

Hungry for gain

The fact that humans tend to make irrational decisions, especially under physical and emotional stress is well documented – and we’ve likely all experienced it at one point or another. The clearest example is sexually aroused people, who engage in more impulsive decision making about sexual encounters, even when they are aware of the potential negative outcomes. Also, when we get really hungry, we tend to forget about our weight loss objectives. So even though opting for a small reward when a bigger one is available is generally regarded as self-control failure, many people do it. But a new study reviewing three social experiments revealed that surprisingly, people can be better at taking decisions when they are hungry.

Studies 1 and 2 demonstrated that participants with more hunger or greater appetite made more advantageous choices in the Iowa Gambling Task compared to sated participants or participants with a smaller appetite. The Iowa gambling task or (IGT) is a psychological task thought to simulate real-life decision making. It was introduced by researchers at the University of Iowa. Participants are presented with 4 virtual decks of cards on a computer screen. They are told that each time they choose a card they will win some game money. Every so often, however, choosing a card causes them to lose some money. The goal of the game is to win as much money as possible.

The Iowa Gambling Task. Image via Wiki Commons.

 

In these studies, the Iowa Gambling Task took a slightly different form. 30 students (9 male, 21 female, average age 22) were instructed to refrain from eating and drinking (except water) from 11 pm in the evening prior to their session. Upon arriving at the lab the next morning, they were given a 200 ml yogurt to ensure minimum satiation, and were then asked to play the game. The second and third experiment replicated the first one, also working on eliminating possible sources of error or mislead.

The results were pretty clear – when participants were hungry (rated their hunger 5 out of 5), they tended to make better decisions.

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“This series of studies set out to test the hypothesis that hot [in this case – hunger] states may benefit, rather than compromise, advantageous decision making insofar it concerns complex decisions with uncertain outcomes. Based on the notion that intuition and emotions may improve this specific category of decisions, we argued that hot states, which are known to make people more reliant on their feelings, improve their decisions”.

Another intriguing result of the study was that people in a hot state do not only perceive those objects as bigger that are generally (money) or specifically (food when one is hungry) regarded as rewarding, but also the neutral object of a circle. It seems likely that hot state like hunger affects the perception of all kinds of objects and makes us better at seeing how we can use objects to achieve our goals. In the end, hunger may make us more impulsive, but that’s not necessarily a bad thing.

“Our findings bear important implications for theorizing about the role of hot states in decision making. It may be, as suggested in the foregoing, that hot states in general, and hunger and appetite in particular, do not necessarily make people more impulsive but rather make them rely more on their gut feeling which benefits complex decisions with uncertain outcomes. Alternatively, it may be that hot states do increase impulsivity but that impulsivity is not necessarily bad”, researchers conclude.

Journal Reference: Denise de Ridder, Floor Kroese, Marieke Adriaanse, Catharine Evers. Always Gamble on an Empty Stomach: Hunger Is Associated with Advantageous Decision Making. Published: October 23, 2014. DOI: 10.1371/journal.pone.0111081. 

Incredible waster; half of Earth’s food is wasted

It’s hard to believe that about half of the food produced on our planet is wasted, especially when about a quarter of Earth’s inhabitants are suffering from hunger; this, my friends is the wonderful world we live in. Not a world without resources, but a world in which we do not know how to use the resources which are given to us.

Just a few days ago, the Stockholm International Water Institute, the UN Food and Agriculture Organization, and the International Water Management released a paper in a join effort, called “Saving Water: From Field to Fork – Curbing Losses and Wastage in the Food Chain”. The work itself is really interesting, but probably the most interesting and shocking fact is that half of the food produced worldwide is wasted, and that includes water too.

“As much as half of the water used to grow food globally may be lost or wasted,” says Dr. Charlotte de Fraiture, a researcher at IWMI. “Curbing these losses and improving water productivity provides win-win opportunities for farmers, business, ecosystems, and the global hungry.” – Environment News Service

Also, this is not an exception in the developed countries which know should know how to deal with their resources better.

The paper points out that the food crisis which is ever present in today’s world is not just caused by over population and other external causes, but by some internal causes as well.

“Inefficient harvesting, transport, storage and packaging make a considerable dent in the potential availability of food. Additional and significant losses and wastage occur in food processing, wholesale, retail and in households and other parts of society where food is consumed.”