Episode 15: Shaping Our Appetite

Peter Weng 0:09
2020 has truly been a turbulent year and brought forth a new set of challenges on how we live and how we communicate. And as such, we have needed to find ways to adapt and grow. we’ve adapted our podcast to be a live stream through zoom. We’ve brought a new co host onboard. So everyone please give a warm welcome to Reem hasnah, a graduate student from Sidra medicine in Qatar,

reem hasnah 0:31
it’s a pleasure for me to be the new member of the Gastronauts family. Hi everyone.

Peter Weng 0:37
And we are so excited to continue diving deep on gut brain matters and learning about the scientists Behind the Science. So come join me as we explore the steps that go into shaping a scientist on the Gastronauts podcast.

Hi, everyone, we would like to welcome you all to our sixth year of Gastronauts. For those of you who have been with us from the beginning, we would like to thank you all for your commitment. For those of you just tuning in, we are happy to have you join our community. Here at Gastronauts. Our ambition is to foster discussion and spread knowledge on gut brain matters. What started as a seminar series led by Dr. Diego Bohorquez in 2015, has now expanded into an international symposium and a podcast aimed at exploring the scientist Behind the Science. Today, we invite you to join us in thinking and talking about why we eat. My name is Peter and I along with Reem Hasnah will be your hosts. So without further ado, let’s introduce our speakers. Dr. Lisa Beutler is an assistant professor of medicine at Northwestern University Feinberg School of Medicine. She is a physician scientist aiming to study how the gut and brain communicate with each other to maintain body weight. Dr. Beutler received her MD and PhD from the University of Washington where she studied how input from NMDA receptors onto medium spiny neurons, inhibitory neurons in the basal ganglia are critical for learning and Dr. Richard pomodoros laboratory. She then proceeded to specialize clinically in endocrinology, and began studying how a subset of neurons in the hypothalamus these AGRP neurons are involved in regulating hunger in Dr. Zachary Knight’s lab, and she is currently studying how obesity affects the ability of these neurons to detect certain nutrients.

Dr. Anthony Sclafani is a professor of psychology at Brooklyn College at the City University of New York. He has had a truly distinguished career of over 50 years and studying the neurochemical circuits that govern learn taste preferences. He has served as the past president of both the Society of the study of adjusted behavior and the obesity society, and has authored over 300 publications. Dr. Sclafani began his research into ingestive behavior in Dr. Pete Grossman’s laboratory where he developed a wire knife to dissect neural pathways involved in an obesity syndrome generated from damage to the hypothalamus. From there he has pioneered studies that have helped answer how specific features of food promote appetite, and the brain reward systems that are activated from the consumption of palatable foods.

Sometimes eating is not a reward. So what do you think of this?

Dr. Anthony Sclafani 3:35
So that’s a very good question. I mean, one way to look at it is that the brain is basically turned on by food almost all the time. And if the food is satiating, then it generates signals that temporarily turn us off. Or if we accumulate too much fat, we have long term signals like leptin, that keeps our appetite somewhat limited. But when you look at the behavior of these shame, feeding animals, for example, whereas a normal rat, when food deprived, would drink, maybe 10 ml of a sugar solution, if you lead to sugar fall out of its stomach, in the 30 minute period, you test it and might drink 50 or 60 ml of the solution. So there’s no inhibition and it seems to be just permanently driving this reward system. You know, there are situations like with anorexia nervosa or with animals that hibernate and they show cyclic changes in their approach to food, that the brain may be turned off to food but it might be a good biological bet that if there’s food there, and it’s a nutritious and it tastes, we’ll eat it when you can.

Dr. Lisa Beutler 4:49
Food is certainly always rewarding to me.

reem hasnah 4:52
Me too.

Dr. Lisa Beutler 4:54
I think I think I overall agree with that. But I will say that one of the reasons why I got it To this field, I think there’s a there’s a few reasons why I was interested in studying feeding and setting obesity. One is very related to my medical school experience in my life experience with obese people and wanting to figure out why they were obese, because it just makes their life so much harder for something that is really not within their control. But the other reason that I really got into this is because I personally come from a family where about half of us are complete food maniacs, and the other half of us really, you know, eat to survive, you know, dinner at dinner, they eat because it’s like Time to eat dinner. And so they eat a small meal, and then they can stop. And so I think that there’s like, people are probably tuned differently as to how rewarding food is and to how far they will go. And I think, you know, kind of related to that, if you look at an average healthy, like 25 year old guy will go eat a burrito the size of his head, and feel really great afterwards and kind of learned nothing from the experience that maybe that’s overnutrition and not great. But you take that same person at the age of 40, or 50, or whatever, at some later age. And probably at some point part of the way through the burrito, they’re going to be like, Whoa, if I eat more than this, I’m gonna feel not great later. So I think that probably breaks maybe get put on more in general later in life and are also on at different levels and different people.

Peter Weng 6:23
Do you think that sensing and ingesting behavior is altered with the aging process? So as we age, we tend to have new circuits new neuronal circuits or less of the effect of a specific sugar or a specific nutrients on our food preference?

Dr. Anthony Sclafani 6:41
That’s a good question. We certainly know with aging, the sensitivity of the olfactory system declines. And that could interfere with the appetite of elderly people. And unfortunately, many COVID patients have a lot of primarily odor, and that interferes with their attraction to food. We have not looked at aging animals for their post oral nutrient response. I think that’s an excellent question. And someone should write up an r1 application for that project.

Dr. Lisa Beutler 7:13
I totally agree. I think we don’t know from any of the models that we use, what aging does we just know, kind of from the human experience, and from mouse models, what Tony said about the olfaction going down? I think an interesting question is whether the homeostatic setpoint for body weight changes in aging people, does it get lower? Are we supposed to get skinnier? Does Britain think we should be skinnier when we’re older? Or do the negative consequences of eating too much just begin to alter our behavior? And hopefully in the coming years, we’ll find out the answer to that question.

Peter Weng 7:44
Has having a career in science of feeding altered your own food choices?

Dr. Anthony Sclafani 7:49
I’m not so sure I mean, I’ve been experimenting with some some recent developments in nutrition, there are these rare sugars called isomaltulose and allulose that have been promoted. Because I so multilocus is a sucrose type molecule that’s slowly digested. So it doesn’t produce a spike in blood glucose. And we’ve actually shown that mice will drink it. But they show let’s have a conditioning response to it. And allulose is a fructose molecule that’s not digested. It’s not metabolically use, you could buy cereal products that contain this fructose molecule that allows them to save the sugar, the cereal contains no sugar, because you can’t use it. And I’ve actually purchased the cereal. But it wasn’t particularly tasty to me. So I haven’t pursued that very much. But, you know, I’ve haven’t experimented with some products such as sweet taste inhibitors. But I’m not sure it really is changed my long term nutritional inputs.

Dr. Lisa Beutler 8:59
I think probably working in the field that I do, both in science and in medicine should have changed my eating behavior more than it has. But I think overall it has not. I think maybe if I’m being generous to myself, I would say that working in the feeding and in the obesity fields has at least made me try to focus on eating foods that I actually really love. And not eating foods simply because they’re available, but I still eat way too much.

reem hasnah 9:28
A question that I really want to ask you, Lisa. So as both we are females in science, how do you think your work might have been affected if you were in the field 50 years ago?

Dr. Lisa Beutler 9:40
Oh, man. I don’t know if I don’t know if I would have been in the field 50 years ago. To be honest, I don’t know how my life would have been different 50 years ago, but I’m very grateful to be doing science now. God I’ve not ever been asked quite this question. I will say that I count myself as someone who’s enormously privileged there are a large number of scientists and physicians in my family, my great grandmother on my dad’s dad’s side was a physician. And so I feel like I’ve experienced less barriers than many, many women. And many, many, certainly women of color have experienced and getting into science and medicine. So I want to start by just one expressing my gratitude and saying that I think that comparatively, I’ve had it fairly easy. But as I’ve transitioned to being a PA, and I have women trainees, I noticed the ways that they’re conditioned to behave differently than men still. And I’ve feel like I’ve worked to overcome some of that over the last 15 years. And my hope is that I can take my privilege and pay that forward to the next generation of women. Because I like if it had been 50 years ago, I may not have gone into science. And I hope that in another 50 years, it’s it’s easier still and more equitable still, for women and other groups.

Peter Weng 11:01
These times have been really changing. And hopefully, we’re going to make a lot more progress in the coming years for both, I guess the diversity and inclusion efforts and thinking about the changes that we have in our society has also made me think about the technological advances and how things are developing at a blistering pace, really, some of the work that you Dr. Sclafani started out as were these course dissections and creating lesions in the hypothalamus. And now we can actually target really specific neuronal populations, through light or through chemicals. How do you leverage the implementation of these latest technologies against methods that you have developed in your laboratory that, you know, are tried and true? And how do you go about including or incorporating collaborative efforts for things like this?

Dr. Anthony Sclafani 11:44
Right, I am in total, or of the work that’s being done today, in manipulating the brain with the super sophisticated procedures when I was in graduate school 55 years ago, which by the way, I don’t recall how many women we had in our class, I think it was very few. At the time, we were manipulating the brain by putting a wire in the brain and passing electricity and destroying 1000s and 1000s of cells. My PhD advisor, was one of the first scientists to actually put drugs into the brain to manipulate the activity of chemospecific ways. But at that time, believe it or not, we were putting the drug in the brain in crystal form, we didn’t have the technique to inject solutions. So we just stuck a crystal at the end of a stainless steel tube. That’s how crude it was. So in my lab, I never developed these super sophisticated techniques, we were manipulating the gut, and lucky to be able to get shamed, feeding animals and self infusing animals. And that gave us a lot to keep us busy. But I just loved the work that’s being done today by both men and many women.

Dr. Lisa Beutler 13:00
Can I add something to that? Even even as like looking on a shorter timescale, I had basically a five year interruption and doing science between when I finished my graduate work. And when I started my postdoctoral research, because I was finishing my clinical training. And even in those five years between 2011 and 2016, I got back into science and was like, holy crap, this is really, really different than how I left it. I was pivoting fields as well. So that was certainly a component. But really, the actual tools and technologies available had just completely exploded in the last five years. And it was both, inspiring and terrifying. So I think that this is an exponential process. And we’ll see we’ll see how it continues going. But also, from my perspective, as a pretty Junior investigator, I learn so much by going back to some of the old literature, not like, you know, when when somebody brings me a paper and says this is really old, and it’s from 2001, or something like that. But really going back to when people were thinking and only had the tools to study the very most fundamental aspects of biology, or much more fundamental aspects of biology. I think you can learn a lot and save a lot of reinventing some wheels, and generate a lot of really cool questions by looking at these older studies.

reem hasnah 14:39
If you could offer your graduate students, any self advice of wisdom of what you gained throughout your expertise and throughout your career, what would it be and why?

Dr. Anthony Sclafani 14:49
Well,I think you have to be willing to change fields as needed and utilize the most latest techniques but one early experience that I had that was very instrumental. When I first came up with the idea that there was a Nā Pali Coast tatse, I submitted an NIH grant, it was rejected. And I resubmitted the grant, and it was rejected a second time. And in those days, the good old days, you could submit it a third time. And I submitted the grant a third time. And I think I worm him out, because I asked for four years of funding, but they only gave me two. And then, in those two years, I had already collected so much private, you know, private data, I finally had a breakthrough and showed convincing evidence. And they subsequently supported the grant for 30 years, and no, they had a problem, you know, getting funded. But if I gave up too soon, I don’t know where I would have been. So if you think you have a good idea, don’t give it up too soon. Give it a try couple of times,

Dr. Lisa Beutler 15:58
as a trainee, rather than focusing on the duration of your training, or how close or far you are, from your next goal. Focus on whether you like going to work everyday or not. Because if you like going to work on more days than you don’t like going to work, I think you’re probably doing something right. And this is a it’s a long path for all of us. So don’t get too too hung up on the number of years, you are from your next thing, just enjoy what you’re doing. And use that as your barometer for whether you’re doing the right thing.

Peter Weng 16:31
That’s really great advice.

reem hasnah 16:33
Yeah,

Peter Weng 16:33
I think that’s something I’ve been doing with myself lately. Like, how many days do I wake up? And I’m happy doing what I’m doing,

Dr. Lisa Beutler 16:38
right

Peter Weng 16:39
And if the answer is less than 50%, and maybe need to change my career path or something,

reem hasnah 16:44
maybe not change your career, change your team, the team plays a huge effect. So when you have a great team of people, and then you want to wake up every morning just to have coffee with them, and just talk science,

Peter Weng 16:57
where do you see the field of gut brand communication going in the future? And how do you want to be a part of this?

Dr. Lisa Beutler 17:04
I think I see it as really turning into more than just one field. I don’t know that I consider gut brain communication to be a totally unified field. My focus is on body weight maintenance. Tony’s focus is on development of taste preference. Are those two things related? Yes, but Tony’s built, and I’m building an independent career on two aspects of this thing that are completely different. I think that the direction that I’m probably overall most excited about and hope to contribute to is understanding how genetics lead to differences that promote or protect from obesity, why body weight maintenance succeeds in some people and fails and others is what keeps me up at night. And I think that the way we’re going to ultimately understand that from a gut brain perspective, is to really drill down the molecular aspects of this genetic aspects of this,

Dr. Anthony Sclafani 18:04
we need much more translation in our research. Because while it’s very easy to condition, a mouse in rakk, with intragastric confusions, it’s much more difficult to demonstrate food learning and adults, adult humans, although children seem to learn much, much more readily, there’s something missing. And part of it is the complexity of the human environment and the foods that we eat. But there may be differences in how rapid humans form development, you know, developmental responses to gi changes. So some of our experiments have been have to be safely translated to human work and see how we can understand the difference between humans and rodents in this regard, because it’s easy to make animals obese and maybe prevent them becoming from obese obviously, in a clinical situation, it’s much more difficult.

Peter Weng 19:01
Yes,certainly, a lot of the goals with regards to obesity are not particularly for mice would be great if we never had any obese mice. But we want to translate this impact to humans in the socially complicated diseases like obesity and anorexia. What is the biggest barrier to communicating this information to the public?

Dr. Anthony Sclafani 19:19
Well, it’s very difficult. Every week, you’ll read the New York Times The Washington Post or some magazine, and they’ll highlight a recent study that came out and it sounds like you know, it’s the best thing since whitebread was invented. And it turns out they overhype the results. So the results were based on a small group size or some cases it’s based on limited number of human subjects in an experiment. So it’s very difficult for the news media, I think, to do a good job in presenting the data because they’re always looking for the hottest headline too, and then people they don’t pay attention to it. Because the story keeps changing. So now we have, you know, artificial sweeteners cause overweight, sugar causes overweight. But what should people do? They don’t know what to do.

Dr. Lisa Beutler 20:10
I think that overhyping is a huge, huge issue. And I think some people respond by not listening. But I think that unfortunately, some fraction of the population might respond by listening too much, and get really fixated on ideas that were sold to them as being potentially like a really great cure, but are either not practicable or not going to be effective, and it leads to kind of recurrent disappointment, and really doesn’t help anyone. And I think another another problem with communicating to the public is just that, you know, this is my job. And it’s really, really hard to stay on top of the amount of literature that’s coming out on this. And for somebody who doesn’t do this as their career, and even for the media to keep up on the literature as it really is, I think, is probably borderline impossible.

Peter Weng 21:03
Yeah, I think I’ve talked to some friends who are not really in the scientific fields. And a lot of times, they’ll be like, Oh, I thought we cured that disease already. And it’s just like, No, we’ve just learned more and more about it. But there’s still a lot of work to be done, to transition a bit about our communication to the public communication amongst scientists. And I really want to thank you both for participating in this new experimental seminar type format. And I’m curious to hear how you felt the dissemination of scientific knowledge has changed over the past 20 to 50 years, from an era before PowerPoint presentations, Dr. Sclafani to a time of now we have these virtual conferences, what principles have enabled the presentation to be so memorable or having a long lasting impact? And how do you think these types of presentations or dissemination of knowledge will continue to evolve?

Dr. Anthony Sclafani 21:53
Well, I think these new methods are very effective. We used to take as a weeks to prepare our slides for a slide talk. Now we could do everything almost instantaneously include the latest data, when I was a graduate student at the University of Chicago, we literally had to go to the library, and look in index medicus, or psych abstracts to find out what the research was today, on your telephone, you could look up PubMed and find out what the latest news is. But the latest news doesn’t always tie back to the oldest studies. So you know, you have to be very careful and looking at what’s the latest brightest thing and try and put everything in context. But as far as communication wise, I’m, I just love these new forms of communication.

Dr. Lisa Beutler 22:45
And I think that’s something that stayed consistent. I mean, I don’t I can’t speak from experience from 20 or 30 years ago. But something that has stayed the same, at least at the level of the literature, and as long as I’ve been on in science, is that whatever the technology is, that is used to disseminate new scientific stories, the key to doing so successfully is to tell a story. And the science that I read, and the science that sticks with me, and the presentations that stick with me, are those that really succeed in telling a story and answering the why, and then proceeding logically through the how and what it showed. And in fact, that’s how I came to be in neuroscience, which is a field that I when I was younger I swore I would never go into.

reem hasnah 23:29
For people who are considering to be a part of this field, what advice do you give them for young scientists, graduate students, or just high school students that might have listened to us?

Dr. Anthony Sclafani 23:42
My advice is, it’s to me. It’s been an exciting way of life. I spent 50 years or more in the laboratory. I was fortunate, however, to be funded, a little nervous if I was in a new student, what the funding situation is going to be. But it’s, it’s, you know, it’s exploration. Science is just wonderful to increase your understanding of the universe.

Dr. Lisa Beutler 24:10
As a young investigator, I am nervous about the funding situation and where my career is gonna be in five years. But as I alluded to, before, I like going to work every day like I look forward to going into the lab and seeing my students and talking to them and talking to my technician. And that’s I can’t think of a better barometer for choosing a career than that. And I guess my other advice, which I think is easier advice to give than probably to take, but something that I would advise young scientists or young people thinking they want to get into scientists is to not be afraid to reach out to us because as you can probably tell, we really love talking about what we do and answering questions and talking to young scientists and young people who want to do science is one of the highlights of what I get to do. So if you’re curious, send an email. If we don’t respond, send another email, we won’t get mad at you. And just keep at it and keep trying to get your your foot into the door. Like I said, that’s easier for me to say than to do. And that also comes from a fair amount of privilege. But hopefully, if this can get to some ears, that were reluctant to actually send an email because they don’t want to be a bother because they don’t know if it’s appropriate. It is, and do it.

Dr. Anthony Sclafani 25:28
I agree.

reem hasnah 25:29
Thank you, guys. A huge thank you from the gastronorm family to the audience who attended today’s episode, your presence matters the most to us. Also, we would like to thank our speakers, Dr. Buetler, and Dr.Sclafani, who gave us from their precious time to share with us their science and knowledge. A final remark. I’m really thankful and excited to be the newest member of the gastronorm family, and to be co hosting these episodes with Peter. See you in our next episode. Stay tuned. Thank you, everyone.

Dr. Anthony Sclafani 26:02
Thank you. It was a pleasure.

Peter Weng 26:03
Thank you all.

Dr. Lisa Beutler 26:04
Thank you very much.

reem hasnah 26:10
Dr. buechler. And Dr. Sclafani taught us many fascinating things. But the major highlights of this podcast is what we eat shapes how we eat, and that different nutrients activate different receptor and as a consequence, different pathways. Also, in this episode, we received a great advice that in science never stopped trying and keep on going, knock many doors and send too many emails. with that. I want to thank you all so much for listening, and we’ll see you on the next episode. For more of our contents, you can follow us on the new Twitter account gutbrainmatters, or visit our website thinkgastronauts.com the Gastronauts podcast would be impossible without our incredible team. Meredith is our producer and team music composer. And the special thanks to the founders of Gastronauts Dr. Diego Bohorquez, and the Bohorquez laboratory.

Jan 2021 – Piali Sengupta & Brian Gulbransen

The Gut That Moves Us

We kicked off the new year with a virtual discussion with Dr. Piali Sengupta & Dr. Brian Gulbransen on January 12, 2021.

Dr. Sengupta received her PhD from MIT, where she studied pheromone signaling in yeast Brent Cochran’s laboratory. She then did her post-doc at UCSF, where she identified genes that encode how olfactory receptors are encoded in C. elegans with Cori Bargmann. She was later recruited to Brandeis University in 1996. Dr. Sengupta is currently a professor of Biology at Brandeis University and was recently elected as an AAAS fellow in 2019 for her pioneering work on the molecular genetics of chemical communication and thermosensation in C. elegans.Her lab work has two primary research focuses: one is the cilia squad, which is focused on the mechanisms by which cilia form and function, and the other is the axis of taxis: which is aimed at uncovering how thermal and chemical stimuli are sensed by C. elegans

Dr. Gulbransen received his Ph.D. from the University of Colorado Health Science Center, where he studied chemoreceptor cells. He is currently an associate professor in the physiology department at Michigan State University. The focus of his lab is to understand how inflammation in the nervous system (neuroinflammation) leads to long-term changes in gastrointestinal function with a particular focus on the intercellular communication between glia, neurons and immune cells.

Nov 2020 – Dylan Dodd & Mary Estes

Learning To Co-Exist With Humans: A Microbe’s Story

On November 3, 2020, we held a virtual conversation with Dr. Dylan Dodd and Dr. Mary Estes.

Dr. Dylan Dodd is an Assistant Professor at Stanford University. He received training as a physician scientist at the University of Illinois in Urbana-Champaign. His PhD work in Professor Isaac Cann’s laboratory looked at the molecular mechanisms for energy capture by gut bacteria. He then worked in Dr. Sonnenberg’s laboratory, where he studied how gut bacteria contribute to small molecules that impact host physiology. He has leveraged his research to co-found a company that engineers bacteria to modulate the immune system and his research group’s focus is to uncover the chemistry underlying host-microbe interactions in the gut. 

Dr. Mary Estes is a Professor of Virology and Microbiology in the Department of Medicine at Baylor College of Medicine. She is a member of the National Academy of Sciences, the past president of the American Society for Virology, a fellow of the American Association for the Advancement of Science, and has authored over 400 articles, She is a molecular virologist whose research is focused on understanding viral (rotavirus and norovirus) infections of the gastrointestinal tract. Her research group’s focus is to study how the viral proteins interact with receptors of the intestinal cells.

Oct 2020 – Michael Krashes & Yulong Li

Tracking Behavior One Molecule At A Time

On October 6, 2020, we held our second virtual conversation with Dr. Michael Krashes and Dr. Yulong Li.

Dr. Krashes is a Section Chief at the NIDDK. He received his Ph.D. from the University of Massachusetts Medical School, his work focused on memory circuits and odor memory processing in Drosophila. His lab currently focuses on how the brain brings together information sensed from its external environment and its own internal states, including memory, to guide eating behavior (the study of neural circuits that guide the behavior of obtaining food).

Dr. Li is a Professor at the School of Life Sciences in Peking University. He received his Ph.D. at Duke University, where he utilized single molecule techniques to understand the role of specific proteins in neurotransmitter release. He then pursued a post-doc at Stanford University in the laboratory of Richard Tsien, where he developed a genetically-encoded pH probe to monitor activity-dependent release of neurotransmitters. His lab has expanded on his previous work and developed advanced imaging probes to untangle the exact chemical signals neurons are using to communicate. Dr. Li’s lab has used these probes to identify new receptors and neurotransmitters and characterize their role in specific neural circuits.

Sep 2020 – Lisa Beutler & Anthony Sclafani

We eat because we need, because we want: find out why

On September 8, 2020, we opened our 2020-2021 season with a virtual conversation with Dr. Lisa Beutler and Dr. Anthony Sclafani. We will be posting the podcast and recordings soon!

Dr. Beutler is an Assistant Professor of Medicine at Northwestern University Feinberg School of Medicine. She is a physician scientist aiming at how the gut and brain communicate with each other to maintain body weight. Dr. Beutler received her MD and PhD from the University of Washington, where she studied how input from NMDA receptors onto medium spiny neurons (a type of inhibitory cell in the basal ganglia) is critical for learning in Dr. Richard Palmiter’s laboratory. She then proceeded to specialize clinically in endocrinology and began studying how a subset of neurons in the hypothalamus (AgRP) neurons are involved in regulating hunger in Dr. Zachary Knight’s lab and is currently studying how obesity affects the ability of these neurons to detect certain nutrients.  

Dr. Sclafani is a Professor of Psychology at Brooklyn College at the City University of New York. He has had a truly distinguished career of over 50 years in studying the neurochemical circuits that govern learned taste preferences. He has served as the past-president of both the Society for the Study of Ingestive Behavior and the Obesity Society and has authored over 300 publications. Dr. Sclafani began his research into ingestive behavior in Dr. Pete Grossman’s laboratory where he developed a wire knife to dissect neural pathways involved in an obesity syndrome generated by damage to the hypothalamus that elicited overeating. From there he has pioneered studies that have helped to answer how specific features of food promote appetite and the brain reward systems that are activated from the consumption of palatable foods.