Zata Vickers - Dimensions of Satiety
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Dr. Zata Vickers is a professor in the Department of Food Science and Nutrition at the University of Minnesota. Her research encompasses the spheres of sensory evaluation of foods and of food acceptability. She has focused her research on such topics as crispness, astringency, sensory-specific satiety, long term acceptability of foods, using food to improve mood, and methods research related to topics such as palate cleansers and odor mixtures. She directs the Sensory Center at the University of Minnesota that provides sensory testing services to researchers within the University and to other Universities and private businesses. She also teaches an introductory course in Food Science and courses about the sensory evaluation of foods.
Transcript (Semi-automated, forgive typos!)
John: So Zata, thanks a lot for being on the show today.
Zata: Thank you.
John: So it's really actually a pleasure to meet you or to talk to you for the call here. It's kind of strange that we had never really met before we got started here on the show. I know several of your students. In fact, some of them have won the IFP student award. So I've always been a fan of yours. And one topic I'd like to kind of get started with I think is really interesting and it's maybe not fully appreciated is satiety. Could you tell our listeners, what about your research in the area of satiety?
Zata: Sure. So this is something that I haven't necessarily always been interested in, but I remember going to some conferences when I first started at the University of Minnesota and this was a Department of Food Science and Nutrition. And so some of those conferences were nutrition and they would talk about satiety and typically the speakers would be reporting how they measure blood glucose or glycolysis to kind of some blood-borne something. And after one of those, I was talking with some of my nutrition colleagues about, you know, what we thought the best way of measuring satiety was? And they were talking about like those two options and everything. And I said, well, if I had to measure satiety, I would just give people a line that said not hungry or for hunger. I would just give people a line that said not hungry at one end and very hungry at the other and ask them to put a mark on it. And they just laughed that, you know, and that was, you know, like the silliest thing imaginable. So anyway, so fast forward 30 some years later, and this young woman, Melinda Karalis, comes to do a PhD with me. And she knew some people at General Mills and interfaced with them. And when I asked her what she would really like to work on, she said she'd really like to work on measuring satiety or measuring fullness because the food industry was sort of, when she talked with people, they were really interested in being able to measure that after somebody ate their food. That's like 10 years ago or so. She was doing this work with me. But at that time, of course, the food industry wants to take their food and cut back the calories. And of course, they want to do it without affecting liking but they also want it to do it without affecting the fullness afterwards. They want to cut it back in a way that and then people would still maintain the fullness. So they should feel just as full after they eat it, or at least is not hungry after they eat it. And then hopefully that feeling of fullness would last longer and then within the food industry if they were making breakfast bars or something. So they had different formulations that, you know, is just one of these provide more satiety than the other. And how would they measure that? And that's a very different purpose than nutrition people really had for understanding satiety. So she decided that she wanted to work on that and that going in that literature reviews and seeing how people in the literature, how they would compare one food for another. And she said, you know, that you really can never tell that by looking at the literature because people are measuring different things. Sometimes measure hunger, sometimes they measure fullness, sometimes they measure appetite. Sometimes they measure desire to eat. Sometimes they are motivation. I mean, there were just all these different things that that people measured. So even if you got had a couple of cases where the food was staying the same, what they were measuring wasn't. And so with this sort of chaos, she decided that she really wanted to go back and take, you know, five giant steps back and better understand what these feelings of hunger and fullness were anyway. And so she started by having focus groups. And before people came to her focus group, she sent them out a little gift bag that had five different breakfasts in it. So like one of the breakfast was like carnation and some breakfast and another breakfast was two oranges and another was a little thing of oatmeal, instant oatmeal, and nothing was like a breakfast bar and some other things. And with the instructions that they were supposed to have one of those breakfasts, you know, on different days and then after they eat it, they're supposed to answer some questions that she had about, you know, how they felt and feelings of hunger and fullness. And then they came to the focus group. And she had four focus groups. So one was all guys, normal weight guys. One was normal weight women that were dieters because a lot of people that diet aren't overweight. Another group was normal weight women that were not dieters and another was overweight women. So those are different things. So they came and she started off by just discussing having them, you know, tell her what they thought about these different breakfasts. How they felt after one breakfast and another one and started the discussion that way, and then she went on to probe more about other feelings of hunger and fullness. So she did that. And, of course, you know, good focus group style. She recorded those sessions and then she listened to them and made a transcript and then printed out the transcripts, arranged the transcript so they were little chunks, like a response was a chunk and then printed them out. So, like, you know, the guy focused group responses were on blue paper and the women that were dieters on green paper, you know, whatever. She color coded the papers and then she cut all of those phrases into their separate piece. So she had all the mounds of these strips of paper that she had. And she took over a conference room for a couple of days and she arranged these strips of papers and piles that were related. And it was kind of interesting because you could see, you know, the pile had all four different colors. It was something that everybody kind of thought. And the pile only contained blue was just the guys, and the pile just contained, you know, green, whatever it was, just the dieters and so forth. But, you know, but looking first off of that what was common for everybody. And so she came up with sort of what they called the themes. So her four themes were physical fullness. And that's what you might think it is. That's to the extent you feel stuffed or bloated. And there was also mental fullness and mental fullness is feelings like satisfaction or contentment after eating. So those are both fullness. So you have both physical, emotional...
John: Physical and mental fullness.
Zata: Those are two different themes. And then there was also physical hunger and mental hunger, which were another two themes. So physical hunger is probably what you would think it is. So that’s your stomach's rumbling or you have hunger pangs or something like that. And the mental hunger is you're thinking about food, your desires for food to the extent that it's interfering with your other things that you would like to think, think about. And one of the interesting things about that is that in Minnesota in 1944, when there was a professor of physiology here that did a starvation study and during World War II, and they recruited conscientious objectors, which were young men that did not want to go off and shoot the enemy with guns, but they were happy to serve their country in some other way. So they were the subjects in this starvation study. So he fed them so they kind of had to live with you, you know, someplace. And so he fed them 50 percent of their caloric needs. And of course, they measured bazillion things with the blood and strength and all that kind of stuff. But they didn't have rating scales that they didn't use rating scales. Instead, the guys kept diaries. And the big overwhelming thing they had in the diary was this obsession with food. They couldn't stop thinking about food. They were thinking about food all day long a day about what they were going to eat. And here we picked that up and are not starving people. And that's part of the mental hunger.
John: That's the much longer. Yeah.
Zata: And I always identify mental hunger is what I feel when after I've had a meal and I, you know, processed my dishes and then I go on to open the refrigerator door to see what's there that I might want to eat?
John: Yes, when I visit my parents’ house, though I'm not hungry, I go to the pantry. That might be addiction or something.
Zata: Yeah. And you might not say that you are hungry. I mean, how can you be hungry but that's a mental hunger sort of thing. So those were her four themes. And so that really formed the base of her understanding for how people felt.
John: Are their hunger and fullness are these opposite ends of the same scale or they actually independent?
Zata: Well, no, I wouldn't put them at opposite ends of the same scale. Simply because one of the things that was really enlightening to me at that time was what people had to say about the oranges? When they eat two oranges for breakfast, which I think is one more than most people would ever eat for breakfast. That they were physically full but mentally hungry. And so I thought, oh, so I would never after I heard, I would never use a scale that has fullness at one end and hunger at the other end because things can't be both.
John: Right. Nutritionally, you're still missing something even if you physically fall. Yeah.
Zata: So she took this background because her goal was to come up with a method for measuring feelings of hunger and fullness that the food industry could use. So she went back to all this literature and she took note of every skill that anybody had ever used in any questionnaire about that. And so that was like about almost 100 different rating skills that she picked up from the end that were measuring distinctly different things about hunger or fullness. All the other things that people didn't bother. Yeah, but a lot of skills. And she put that out as a questionnaire. She just, you know, edited them a bit so the language was right and they made sense on the scale. But she put that out and had about 200 people feel that questionnaire out just whenever they saw it and got it in any time of the day, no matter what they ate. We didn't ask anything else. We just asked that they were English, native English speakers. And then they felt that.
John: To avoid any compounds.
Zata: Yeah. And so are things that people want. And they could also for all of those, they could say if they didn't understand something. And so she then took that she got rid of the ones that had a reasonable number of people saying that they didn't understand what it meant. And then the others with the ratings that they had and put it through factor analysis. Actually, she did a lot of hand sorting of this and sort of old fashioned ways of doing it. And then at the end, I said, well, you know what, if you're going to publish this, we need to, like, do what everybody else would do as a factor analysis. And of course, it gives you exactly the same result, because it's just, you know, whether you do it by hand or whether you get software to do it. So we have software for the final version. And very reassuringly, what you saw for the first big four factors were mental fullness, mental hunger, physical fullness, physical hunger, those. And then the fifth factor was liking. And we developed quite a bit as to how we would do that. But a lot of people, when they were measuring hunger and fullness and had asked about liking and it came out as a factor with quite a bit of weight. So from that and those skills that fit into those, where she developed what we now call the five factors satiety questionnaire. And so that was the questionnaire. And then in the course, next thing you want to do is just this give you the information that you want. So can you validate it and say so? She did about three experiments to validate it. I'll pretty much just go through one. But validation is sort of a combination is does it tell you the same things that more traditional methods tell you. And by the time she was this far along, some group of people have published. What if you're measuring hunger and satiety? The questions you should ask and there were six or seven of those questions in that papers that if you're measuring those, that you should ask those questions. So we already had those questions. So they were part of and actually in this five factor satiety questionnaire, there are about 50 questions in that which a lot of people would say, like, I don't know, people can answer that many questions. Well, we pay our participants. People can answer 50 questions, especially if you're paying them to do that. So she needed to test it to see how it would work. And the first study that she did was we wanted to get two things that we knew were going to be different in the feelings that people had after. And we got those out of the focus groups that was the oranges and the oatmeal. Those had strikingly different responses in the discussions and people felt quite different after those. And so she's going to use this questionnaire to measure satiety, hunger and fullness things after eating oranges and after eating oatmeal. So one of the issues you have when you're going to feed people things is how much of it they're going to eat, because that's certainly going to affect how hungry than full you are. And in most of the more traditional studies, the satiety they would match foods for calories, which makes tons of logical sense. By then, Barbara rolls out of her lab. She had done a couple of studies where she pretty effectively showed that people based there sort of expected feelings of hunger and fullness on the volume, not on the thing, so she had some wonderful studies where she showed that if you like, if you make a soup and then you dilute it. So but you served the same amount and you dilute that soup like half. And if you serve the same amount and you give it to people and ask them to measure, you know, how hungry or full, whatever it is, they give the same ratings because they you know, they thought and you can also sort of whip of food. So if you like, make a mousse out of something instead of a dense, but if you match the volumes, they will find them to be equal. So we needed to match volumes of oranges, cut up oranges with oatmeal. And the very different because oatmeal is sort of a solid, you know, when you say dense, densing and oranges. You have all the space between the pieces of the oranges. So how do you know that you have the same volume? And, you know, if you're a food scientist, you can measure volume in these things. But that's not what we need. We need it for other people thought they were the same. So there's a little mini study that goes on. So she has the bowl with the oatmeal in it and then she has an empty bowl that same thing and a whole bunch of oranges and orange pieces. And then she asked the people to fill that second bowl up. So there's the same amount of oranges that there is of oatmeal. And she had several different people did that and found sort of the average weight. So that's how I decided how much oranges we would serve for that. And then for the study, people would come and they would come twice for breakfast. One time they would have oatmeal. One time they would have oranges. And half the people at oatmeal's first and half the people had oranges first. And so when they would come, they would, first of all, answer the not quite 50 questions because we didn't need to ask them any questions about their feelings after they ate that food. But we asked most of the 50 questions beforehand. So they answer all those questions and then we would give them the bowl of oatmeal or the bowl of orange and we would ask them to eat it. And then when they were done, we would ask them to answer the 50 questions. And then as they left, we gave them a little timer that was set to buzz in an hour and buzz again in two hours and a paper questionnaire. And they could go back to wherever they were wanted to go. And when the timer rang for an hour, they needed to fill out that question again, 50 questions just so they told us how what their feelings were for all those questions. And then when it buzzed after two hours, they came back to the lab and they again filled out the questionnaire probably online and rated again those 50 questions. And then we told them, I said, well, thank you so much for not eating in the last two hours because we didn't allow them to eat. They were told not to eat the last and the last two hours. And they said because you you're probably really hungry now. So we have some snacks for you. And so we gave each person their own personal little tray and a bunch of different kinds of different foods. And we had fixed them so they couldn't really put them in their pocket to take them away. then we have pre-weight each of those things in there and then when they left, we weight them again to see how much they weigh because there's ratings you have and there's also the behavior how much do you eat after.
John: Right. It's kind of covert measurement.
Zata: So what she found is, you know, going back to the needing to validate it, did we find the same information that the traditional methods found? Because we had those seven questions and yes, we found those seven questions were quite thing. The sort of good news or impressive thing was that we found other information. And that was especially about like the mental fullness is that you had the oatmeal, you were mentally more full and interesting so when you compare the oatmeal and oranges, if you look at all the traditional ratings, which were how hungry you are, what's your appetite for? You know, is that there was no difference between the oatmeal and the oranges. But we did pick up differences. We looked at the mental fullness and we did pick up differences in mental hunger and not only at the right after, but those persisted over those two hours. And they ate more food afterwards if they'd had the oranges. So that was somewhat pretty, and she did a couple of other foods as well and a couple other studies like that. And so we were pretty comfortable afterwards that we were, that if you used her five factors satiety scale you would get at least the information that was recommended that, you know, from those 6-7 of the things, plus you would get the mental hunger and the mental fullness information which you were not getting from those other scales. And another study that she had done at that time was to look at differences in liking. When she done that with a smoothie and other people had used smoothies, milkshakes, study differences and liking for that and they look at the impact of differences on liking on satiety, hunger, fullness, whatever it was. So she wanted to do that, too and what a lot of these people did was they add a cumin to their smoothie or milkshake and that's how they made it last light. So without thinking a whole lot about this, we added cumin to a smoothie and then people came and they had the regular smoothie at one time and the cumin smoothie at another time. And again, balance that out. Well, when she went and started looking at her data is that some of the people liked the smoothie with cumin better than they like the smoothie without cumin. And so, of course, you go back to the earlier studies where they did that and they never even measured liking they just had the fun. They assume, they said we have a difference in liking. We have the smoothie when she's going. Well, you know, some people actually like the cumin better and some people like them equally. So in order to really look at the difference and liking, we had to sort of throw out those people. And then we didn't have that many left. And the study was no longer balanced. So we never published it at that time. But a few years later, I had another grad student, Mitchel Maddis, that came and she was working with me with my sensory center coordinator for a couple of years. And I asked Mitchel, can you redo Melinda's study with the smoothies and just fix everything that was wrong with that. And so the main thing that was wrong was she didn’t get the liking right. Adding cumin doesn't really, you know, change liking for everybody. So he did pre-tasting and he was going to change liking by adding quinine, which he did. But for each person that was going to be in the study, they came to pre-taste and they tasted smoothies that differed in the amount of quinine and rated how well they liked them. And then he set for each person individually a level of quinine that we would put in their smoothie that would drop their liking about 20 percent of the scale length. So that would be hopefully that was sort of as good as we could get equally disliked or trying to maintain. In the final analysis there, you know, the liking shifted it around. But everybody like the smoothie without quinine better than they like. So he made that change and then redid the study and actually he found pretty much the same thing that moment. He found is that there was a distinct differ in the mental fullness or the mental hunger. So better like smoothies produce more mental fullness and that was the case from right afterwards and up to two hours later, and if you had the better like smoothie, you did not eat as much off of your mini buffet as you did at the less like smoothie.
John: And they would consume the whole smoothie?
Zata: They had to consume the whole smoothie.
Zata: Because otherwise they wouldn't know how much they, because you have to measure the intake for that.
John: So they have equal amount of smoothie, but they're more mentally full when they like the smoothie and then they eat less later?
John: Very interesting.
Zata: Yeah. I just love that result because it’s sort of my personal eating philosophy where, you know, you might as well take the good stuff.
John: There's a lot of choice for that.
Zata: You know, you'll be more content, more satisfied, you'll be more, you know, whatever all those things, if you eat the good stuff and if you eat stuff that's just okay.
John: Yeah. Well, this has been fascinating, Zata, because as you know, there's a lot of machine learning that goes on trying to model liking. But it looks like that if you're trying to really understand the kind of consumer appreciation for food, especially, you know, we talk about hunger and fullness, kind of some of the primary reasons people eat food. It seems like it's a lot more complicated than liking and then you need maybe these more robust measures.
Zata: Yeah, and I think that was one of the really big findings out of her focus group, was that, you know, hunger and fullness is complex. It's not a simple scale. You can't do it with one scale on hunger. You can't do it with one scale that's hungry at one end and full at the other end, because if you've got the oranges, you’re physically full and mentally hungry. So where do you put your mark on the scale?
John: Yeah, well, life is one big multi-objective optimization problem. And that's what it sounds like too is a multi-objective optimization problem. This has been great, Zata. So, amazingly we are now almost out of time. So I do want to get your kind of, this has been very fascinating though, and very enlightening for me and for our listeners as well. So do you have any advice that you would give to young sensory scientist? I mean, to your students often go on to very successful careers. I mean, what do you do to help your students to prepare so that when they do go into industry or academia, how do you help them to kind of get off on the right foot as they begin their careers?
Zata: Well, I'm pretty limited in how I can help them because I haven't, you know, I don't have a successful industry career. So one thing they need to do is meet people that do have those and get to know them and hear what people are really looking for. My contribution is much more fundamental. You know, just what is your objective? Can you state that clearly? Does that suggest a particular test design? If you do that test, will you do that? The answer to that? How will you know the answer to that? You know, what data analysis are you going to know? Usually there's going to be some number that you're going to come up with if it's bigger than this and ta-da. And if it's smaller than that then ta-da. And if it's the same size and ta-da and a lot of things kind of reduce down to that. But I think a lot of ways I just work on thinking skills. And then otherwise my advice to people and sometimes you can't follow it, but, you know, everybody does sort of follow it for their life as a whole is find something to work on that you're really interested in. Because then you'll be happy to work at it for longer than you can work on something you're not interested in. And you’d be interested to hear more about it. You'll like to meet other people that are interested in that as well. And I suppose it's to have your job be more than a job, you know, if that's what it's going to be. So, that's my advice to people as for heaven's sake, find something you're interested in. Life is just too short to have a job and be working on things that you don't care about and you're really not interested in.
John: I totally agree with that. That's an excellent advice. So now, finally, if someone wants to reach out to you, what's the best way for people to get in contact you?
Zata: Yeah, my email is the best thing so email@example.com and if you can't remember that, you can always just Google my name and that's how I find out other people's emails.
John: Sounds good. Alright, Zata, this has been a real pleasure. Thank you very much for being on the show today.
John: Okay, it's been great. Thanks a lot. Okay, that's it. Hope you enjoyed this conversation. If you did, please help us grow our audience by telling your friend about AigoraCast and leaving us a positive review on iTunes. Thanks.
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