 Once again, I'm Van Hubbard and I'd like to welcome everybody to the third in the series of our NIDDK Clinical Nutrition and Obesity Lecture Series, which have been going on since December. This evening we are fortunate to have Dr. Barbara Rolls, who is from Johns Hopkins University, where she is professor at the Department of Psychiatry and Behavioral Sciences there. Soon she will be taking an appointment up at Penn State in this fall as well. She originally got her education at the University of Pennsylvania and then did her graduate studies over at Cambridge where she got her Ph.D. and then did a lot of work at Oxford University for up to the next 15 years before she returned to this country at Johns Hopkins. She's been active in a lot of the societies currently or has been president of the Society of Ingestive Behavior and will be talking to us tonight on the control of food intake. She has been responsible for some very interesting studies and is really a leader in this field. So I welcome Dr. Rolls. Thank you, Van. It's a pleasure to be here. I gave a very ambitious title, The Control of Food Intake, and it's a very complex subject and I'm certainly not going to be able to cover the whole of the control of food intake. Can I have the first slide, please? The first slide will show you my goals tonight, what I'm hoping to accomplish, which we'll start off talking about variety in the diet, which as we know is the number one dietary guideline is to eat more variety in your diet. And another important dietary issue is to restrict your fat intake. And I'm going to relate both of these to obesity. And I don't have any slides. Is it? Okay. Well, these are the 1985 USDA guidelines, which just reiterate what I said. This isn't working either. This is not my night, obviously. Should abandon technology. Does anyone have any idea what this thing does? Looks like it's plugged in. I don't know whether it switches on somewhere else. Maintaining a desirable body weight. So I'm going to start off with the variety in the diet. And this isn't working either. Why is that no surprise to me? Okay. Let's start right at the beginning and consider what we would do in a situation where we have foods that we like, but there's plenty of variety. Are we just going to eat one food, stick to the one we like the most? Or are we naturally going to eat a variety of foods? This is the classical data from Clara Davis taken back in the 20s. I don't think a study like this would ever get through an ethics committee now. She took newly weaned infants and gave them lots of pots of food so they could self-select their diet without any interference from the adult caretakers. And this is just a meal of one child or meals over a day. And this is what the child did. And this was quite typical of all of them. They had definite preferences. But you can see they don't just eat one food. They don't just stick to a single food no matter what. There was some pretty weird things here. And they ate them. They tried pretty much everything. So there seems to be a natural inclination to eat a variety of foods and not just stick to the favorite food. So what I want to consider first is why this happens. Why is it that we have a tendency to eat a variety of foods? Nothing is new in science. So start off by quoting Aristotle who said that flavors and smells of foods are pleasant when we're hungry, but when we're sated and not requiring to eat, they're not pleasant. And in the early 70s, French scientist Michel Cabanac really restated the same sort of idea that a given stimulus can induce a pleasant or unpleasant sensation depending on the subject's internal state. Now this relates to the palatability or how much we like particular foods. We don't always like a particular food equally. We'll probably like it more when we're hungry than when we're sated. So we some years ago did some experiments investigating how people respond to foods as they're eating them. This was new back then because this whole field developed out of the study of obesity. And most of the studies used solutions of sugar and what not. That's what Cabanac studies were based on. So to actually offer normal weight people real food was pretty revolutionary. So what we did was we had the people come to the lab at lunchtime and they would taste small samples of a variety of foods. This is just representative of a particular study. It would vary from study to study and they would rate how pleasant does this food taste, smell, appear, et cetera. And then they would be given a large portion of one of those foods and they would eat as much of it as they liked. And then after they finished eating, they would re-rate all of these foods including the one they've just eaten. And this is an experiment that we did in young teenagers. They were given as much of their favorite color of M&M to eat as they liked. And two minutes after they finished eating as much as they wanted, they re-rated all of these foods. And a change in the pleasantness rating means a negative change means the food was less pleasant after the meal. So you can see there's a very large decrease in the pleasantness of the M&M's that they've just eaten. And there was another color of M&M's that also not surprisingly decreased. And the other sweet foods also declined in pleasantness. But some of the non-sweet or savory foods actually increased in pleasantness. So we call this changing response to foods sensory specific satiety. And we think this relates back to the finding in the kids that Davis was studying. We think that this change in the palatability of a food as it's eaten helps to ensure that we eat a variety of foods. So as a particular food is eaten, it tastes less pleasant. But the taste of other foods, unless they're very similar to the food you've been eating, don't change very much. And your goal in a meal is to keep palatability high. That's the strategy that people adopt. So to keep palatability high, what you do is you switch from food to food. And you've taken a variety of foods and nutrients. We've done a whole lot of experiments investigating this phenomena. And this is a study in which we had the subjects eating cheese on crackers. And this is just to illustrate, first of all, that the change occurs rapidly. Here we tracked over the hour after they'd eaten as much cheese and crackers as they wanted. It peaks two minutes after eating. And then it gradually returns to baseline. So this is a short live phenomenon. It's a phenomenon that occurs within a meal to encourage consumption of variety within a meal. There's another phenomenon, a monotony effect with a food, which we're not studying. That's really why you tire of a food over time. So you don't want to eat the same food day after day. But that's not what we're talking about here. This is a short live phenomenon. And it occurs for all the different sensory properties of the food. Here you can see the cheese and crackers is declining more than all of the other foods that they've rated. Taste, texture, smell, and appearance. So when you don't like a food, you don't like anything about it after you've eaten as much as you want. Another question, I mean, Kabanak stressed that it was your internal state, your need for nutrients that affected this response. And so an easy way to test that is to compare the response to high and low calorie foods. And here we had subjects eat as much as they wanted of a regular sugar sweetened pudding or the equivalent neutral sweetened pudding. And this is just showing the change in the rating of the high and low calorie puddings. And there's no difference. The calorie content did not affect the response in either subjects who knew what they were getting in terms of calories or those that didn't know. So it doesn't seem to be energy, which is why we tend to stress the sensory aspects of this phenomenon. So summarizing those experiments, and we didn't see any evidence that the changes in pleasantness of a food depended on its nutrients or its calories. The changes occurred rapidly before there was time for much absorption. And they generalized all the sensory properties of the food, taste, texture, smell, and appearance. And they also generalized the foods with similar tastes, so that, for example, consumption of one sweet food decreased the palatability of other sweet foods. This is a somewhat contentious statement to some nutritionists, but I think this work illustrates this. We eat foods, not just nutrients. The sensory characteristics of the foods are the primary influence on food selection. We've been interested in the clinical applicability of this kind of finding. And there's several situations that made us question whether sensory specific satiety might change in different groups. The elderly are a population which often have trouble getting sufficient nutrients. And they also often eat quite monotonous diets. And it was the monotonous diet that triggered us to think, perhaps they had some sort of problem with sensory specific satiety or experiencing the normal hedonic change to a food as they're eating it. Obviously, they have all kinds of other problems. They're isolated. They have denture problems and whatnot. But we wanted to know whether they would show normal sensory specific satiety. Because the first challenge was finding a food that they would all eat. They have so many dietary restrictions, we were going to do a pudding study, but we ended up using yogurt. That seemed to be something that all of these four age groups that we tested would eat freely. We tested in two different situations. We didn't know how to compare across age groups, because we couldn't assume that people of different ages would eat the same amount of yogurt if we just let them eat as much as they wanted. And if they didn't eat the same, it would be difficult to compare them. So we set it up. So we did an ad lib consumption test. And the same subjects also were given a fixed amount, about 300 grams. In fact, we had piloted this amount to see if it was appropriate. And our pilot work was so good that in this condition, they ate about 300 grams, all the different groups anyway. But I think that you can see quite strikingly in both types of tests. When you compare the change in the eaten food with the change in the uneaten foods, that this is typical sensory specific satiety, the difference between the eaten food and the uneaten food. We see it most clearly in the younger individuals. And as individuals age, sensory specific satiety has diminished. So at this point, there's no significant difference between the change in the liking for the food they've just eaten, and the uneaten foods, which they've tasted on the taste tray. And you can see when they had the fixed amount, this is very odd response. They actually showed a bigger decrease in their liking for the taste of the foods that they haven't eaten, than for the food that they just eaten, the yogurt. Now, I think this could be part of the explanation for why they eat monotonous diets. They can continue to eat the same food, and it's not becoming less pleasant. So they aren't encouraged to switch from food to food in the normal way. Another situation that we've tested is anorexia nervosa, where individuals restrict their intake, so they become very emaciated. This atypically is a male. Hopkins happens to specialize in male eating disorders. And also in bulimia nervosa, which is characterized by rapid consumption of very large quantities of food followed by purging. So we tested sensory-specific satiety in those clinical populations. And here again, you see in the control group, the typical change in the food that has been eaten, and the lack of change in the uneaten foods. And the bulimics, you see, are not showing sensory-specific satiety, and the anorexics are. And what this means or could mean is that the anorexics we found showed sensory-specific satiety after very small amounts of food. It only took in some of them a few bites, and they switched off liking the food. Now, this obviously could be part of why they limit their intake of food. I'm not saying this is the explanation of the eating disorders, but this certainly fits with their pattern of eating. And the bulimics who didn't show sensory-specific satiety in this situation also show behavior that fits with being able to eat large quantities of food. If you're not showing any change in your response to the food, you can just go on and sustain the binge. So I think that this sensory-specific satiety has been shown to be relevant in clinical populations. Leanne Birch at the University of Illinois has shown that it occurs in very young children, and there's evidence that you also see it in animals. So I think it's a very fundamental characteristic of our eating behavior, which helps to encourage consumption of a variety of foods. But providing a variety of foods may be the best way to ensure that a balance of nutrients is consumed, but if satiety-specific to the sensory properties of particular foods that have been eaten, you may get overeating when you have a wide variety of foods available. So that's another aspect of this that we've examined in a number of experiments, and this just summarizes some of the studies that we've done. Generally what we would do would be, again, invite subjects to the lab for lunch, and we would give them successive courses of different foods on one occasion. On another occasion, they get the same food repeatedly, and we compared the amount they consumed, either in the variety condition or in the single food condition. Usually the single food was their most preferred food, because that's the most stringent test to see if variety can enhance food intake. In one study, the foods were very different. Not only did they different sensory properties, but they had very different nutrients. We had a pretty weird selection of foods. I did these studies when I was in Britain, and we didn't have any cooking facilities in the lab. Sausages are the British bangers, believe it or not. Brits do just sit down and eat plates of sausages. This seems very peculiar in America, but in Britain it was perfectly normal. Anyway, we found that the subjects ate 60 percent more when they had the four different foods than when they had one of the foods throughout the meal. If we just had less variety in that we just changed the fillings in sandwiches and offered four successive courses, and compared to the favorite type of sandwich, we had a third more intake. If we had different flavors of yogurt, which also had different colors and texture, we had a 20 percent increase. This is my favorite, and I'm going to illustrate this in a minute. Different shapes of pasta, hoops and spaghetti and bows, 14 percent increase in intake if they had the three shapes and success, of course, as opposed to their favorite. Different flavors of sandwich fillings. Here we wanted to see if just flavor could affect intake. We had some pretty odd flavors because we had to have flavors where nothing else changed in these sandwiches. We got a 15 percent increase in intake, just changing flavors. These show really that the sensory properties without any nutrient differences can increase intake, changes in the sensory properties. But not all of them. It's quite good to have some negative results here, so it shows just giving people more food doesn't account for this. If we had three different flavors of chocolates, which are very distinctive, mint, coffee or orange, we didn't get any enhancement. Yogurts, which varied in flavor, but were all pink and the bits of fruit were fished out, so they didn't have textural differences, no effect. And color, differences in color. These were like M&M's, that Smarties in Britain, didn't increase intake. So it's clear that changes in sensory properties are affecting intake, and the variety in the sensory properties can enhance intake. But it's not just that color, et cetera, alone will have a powerful enough effect. This is the spaghetti that we used in our spaghetti experiment, uncooked, to get the 14 percent increase. Now I want to just tell you, I was unwittingly put into a natural experiment looking at sensory specific satiety. I attended a meeting in Italy, and we were invited to what was called on the program a pasta party. None of us knew what this was. We were bust off to the mountains, waited for the top pasta chef in Italy to come and cook for us. And this was apparently the Italians idea of a joke. We had 14 successive courses of pasta. They were all different, different shapes, different sauces. But believe me, we had pasta specific satiety. Even the hardiest people in the middle, that course eight, started giving up. And the host would make an announcement that the designer of Ferrari had designed this pasta. It was the most delicious pasta in Italy and everybody wanted it, and still nobody wanted pasta. So people are wandering around at this point. And then we get the dolce, the dessert. Everybody immediately flocks back to the table to eat. They had pasta specific satiety, but they still wanted their dessert at the end. And I think this illustrates that first of all, sensory specific satiety doesn't occur in isolation. You can get so full you don't want any more, regardless of how different the food is. I say that with qualification, though usually if you have a chocolate truffle at the end of a meal, you can fit it in. But in general, you just get physiological satiety and you don't want any more. Okay, so clearly variety can increase intake in a meal. And you can use this clinically in this way. If you want to increase appetite or encourage eating of a variety of foods, the sensory properties of the available food should be as varied as possible. So you can imagine situations, cancer patients, etc., where you'd want to try to apply this. To decrease appetite or keep intake low, the variety of foods available should be kept to the minimum needed for a balanced diet. And I think it's important to stress that because obviously a lot of diets are taken beyond that. One of the questions that we always wanted to ask was if you could put humans into a smorgasbord kind of situation, what would happen as they interacted with this very varied diet? Would they just keep responding to the variety or would they after a few days just tire of the variety and stop overeating? Very difficult to do those kinds of studies in humans. Obviously we're interested in the contribution of variety to obesity. We have done some studies in rats where we offered them either their normal child diet. We were politically correct. This was done some years ago. We were doing males and females way back before anybody else was. Sometimes the results differ in rats and in humans between sexes, but in this particular situation not. And what we did was we offered the rats in some situations high-fat palatable foods such as cookies or chocolate which didn't differ in their nutrient composition but which differed in their sensory properties. And if we offered them just one additional high fat palatable food on top of the chow they gained more weight. If they had successive variety of four different high-fat foods that didn't improve the weight gain much over the single food but if they had all four high-fat foods all the time in addition to these others you can see they really put on a lot more weight. And we did carcass analysis at this point and that weight was fat. So at least in the rats in this situation variety was making them eat over eat continually and contributing to the development of obesity. The practical aspects of this have been taken sometimes to the limit just after we published our first studies on this. Slimming magazine in Britain came out with this recommendation which was really quite unbelievable. They suggested that the way to control your appetite since variety can stimulate it is to get up in the morning and decide what you're going to eat and cook it all up into one big stew and that would be your food for the day. I think it would probably work. I think if you tried to eat any one food even if it was cream puffs you would lose weight because you would tire of it. In fact liquid diets part of the reason why they work is because of the monotony effect. But obviously nutritionally that's not a great idea. You have to have enough variety to get the proper nutrient balance but I think you need to be aware that variety can stimulate overeating and when people are trying to watch their weight they need to keep the variety of foods readily available to them down to the minimum required for healthy nutrition. I'm now going to switch to my other favorite topic and a great favorite. This actually was in a local color supplement last year which is really quite mind-boggling. I thought Madison Avenue really knew that fat was a big issue but apparently not. Dietary fat is is our national preoccupation at the moment. I don't think any one of us can get through a day without being told that we should cut down our dietary fat or if we go into a supermarket we're bombarded with messages now about fat. Low fat no fat reduced fat. What does it mean in terms of our intake? In spite of all these messages we're all finding it very difficult to cut back on our fat intake and that of course is because fat tastes good. It adds a lot of different things to food. It enhances flavor. It gives all kinds of textures to food. Creamy, crunch. It's very it's very complex but we're not doing a great job at getting fat intake down. And what I want to consider though is supposing we do supposing we manage to reduce our fat intake. Probably what we'll do is increase our consumption of carbohydrates. That's certainly what we're being told we should do and since I'm interested in hunger and satiety and the control of food intake I was interested in the question of whether carbohydrate and fat would satisfy hunger equally. And really there's not much data but there's certainly a lot of mystique about all of this. This is an article from the New York Times in the last year and I mean we have to believe it it's in the New York Times. It says it's as easy as the frozen glaugea commercial told us to eat an entire pint of ice cream all alone in one sitting. It's just as true with the box of cookies even a whole pie. Think how much easier it is to eat 1.5 ounces of potato chips than it is to eat 12 ounces of baked potato which has the same number of calories. That's because eating large quantities of fat does not make you feel satisfied or full. So that may be so but if you look in some of the standard nutrition textbooks they say that without fat foods are not satisfying that fat slows stomach emptying. You need fat to make you feel satisfied and full. So what is the real truth? What's going on? Now certainly fat and carbohydrate have a number of different properties which could affect hunger and satiety. This is just a list of some of them. Obviously fat has more calories per gram than carbohydrate. Less metabolic energy is used to store fat as body fat. Fat and carbohydrate cause similar stomach distention and empty from the stomach at the same rate. Now this is data based on monkeys and there isn't good data in humans but certainly the monkey data shows this. Fat may cause early release of satiety hormones. For example cholecystokinin is thought to affect satiety and fat is thought to release better than carbohydrate. Carbohydrates more rapidly absorbed than fat and carbohydrate causes rapid rises in blood glucose. So there are a number of reasons to suppose that these two nutrients might have quite different effects on hunger and satiety. So our approach to this was to try to develop foods that had the same protein content, had the same sensory characteristics. You need to control for sensory characteristics because people have preconceived ideas about fat and how it's going to make them feel. So we wanted to just look at physiologic effects of these nutrients, not worry about the cognitive or belief effects. I should say that we've done a study where we're labeling foods that are high and low fat or high and low calorie with some disparity between the actual calorie content and the fat message. People are responding to the fat message rather than the calorie message in the way the food affects their subsequent intake. So messages about fat are clearly having effects on our intake which we only partially understand. So in this study we controlled all of that out. These foods tasted the same, the subjects at the end of the study are given them to rate and they can't tell the difference between these in any systematic way and they certainly don't get systematic cues about the fat content. We gave males or females a fixed amount so we kept volume the same. What we varied in these yogurts which took about two years to develop by the way is very difficult food technology. They varied dramatically in their fat and carbohydrate content. You see here protein is the same. So not perfect. We can't get a food that's just fat or just carbohydrate and our philosophy is to use real foods but here we have these yogurt preloads. We give a fixed amount and then in this first study that I'm going to describe a half an hour after they had this fixed amount of yogurt they were given a self-selection meal like this. We're interested not only in the amount that subjects eat in these studies but whether they if for example if they've had a high fat preload do they avoid fat in the subsequent meal. So we have pairs of foods often in the studies. Here we have a raspberry sorbet versus a Haagen-Dazs chocolate ice cream or we have pretzels versus potato chips or salami versus turkey. So the people can adjust not only the amount they eat but the macronutrient composition of the diet and the first part of my talk was emphasizing how imprecisely intake is regulated. I mean you saw by just changing the variety in the meal people could eat as much as 60% more. I think this study on the other hand shows you that humans certainly have the capacity to adjust their intake to accommodate these calories in the preload. This is the baseline they got no preload in this so this is their intake without any of the yogurt and then this is the calories from the preload and this is how much they ate at lunch half an hour after these preloads and this show this is the percent of the calories in the preload that they compensated for in their lunch. These normal weight non-dieting weight preoccupied men overall showed 99% compensation for the calories in the preloads and you can see that it didn't matter whether the preloads were high or low in carbohydrate or fat the nutrient composition didn't matter. The calories certainly did. So we humans have the capacity to show caloric regulation. The fact that we often don't is because we're put in situations where palatability social factors etc override these physiologic controls. Now here this is a fascinating group nobody's ever studied this group before normal weight preoccupied men and they're just about the most aberrant group we've seen and it looks to me like they have a strategy of eating the same amount when they have a preload regardless of what's in it do very poorly at adjusting their intake. We've looked at normal weight women and restrained and unrestrained I won't show you those now this study is not quite finished yet so this is this is more than hot off the press. We're also interested in the obese and whether they can adjust intake because one possibility is that they are poor at caloric regulation and that's one reason why they have trouble with their body weight regulation. Well actually the obese unrestrained that means they're not really concerned about their body weight do pretty well but the restrained obese seem to have that same strategy that the obese are the restrained normal weight males had of eating the same amount so they really aren't showing physiologic regulation it appears that these restrained subjects and the normal weight restrained females were the same just have a strategy I've had a preload I can only eat so much in the meal and they don't really show physiologic adjustments. Okay well so far no differences between fat and carbohydrate though in any of these studies so I said that the two nutrients are absorbed and handled at different rates so one of the things that we investigated was that the time course of the effects of these nutrients on subsequent intake might be quite different so in this study we just took the high fat and the high carbohydrate yogurts that I showed in the slide of the composition of the preloads and we had the subjects eat them with varying time delays between the yogurt and getting lunch so again we have our no load condition which is our baseline intake and then the high carbohydrate high fat loads at different times and again you can see no significant difference between the two nutrients at any time we were predicting that the carbohydrate would get into the system and have an early effect and the fat would come in later with a delayed satiety effect but we haven't seen that and we didn't see any differences any consistent differences this is with a hundred and eighty minute time delay we had the subjects track their ratings of their hunger over time and no systematic differences in ratings of hunger between the carbohydrate and fat so from these studies and we didn't find any evidence to support the hypothesis that fat is either more or less satiating than other macronutrients and subsequent food and macronutrients selection wasn't affected by the macronutrient content of the loads so this implies that consumption of low fat foods could aid in reducing overall fat intake I'll come back to that because we don't where as we see caloric adjustments following these loads we don't see adjustments of macronutrients so when they've had the high fat load they don't adjust their fat intake or similarly with carbohydrate well those were single meal manipulations and obviously one wants to know what happens over a longer period of time even even a whole day would be better than looking at a meal perhaps so at Hopkins we have what's called a programmed environment this was an environment that was built by NASA really to study effects of long-term isolation for the space program I think they decided that people were not going to get on very well prolonged isolation in small groups so the NASA money pretty well disappeared from this and it's now very useful for drug studies and food intake studies is you can put people into this environment for three or four weeks at a time and the advantage is that you can accurately measure everything that the subjects are consuming in this kind of situation we pre-way all the food that goes in we weigh it when it comes out we also look at all the trash and assess that and they also key in what they're eating we have three different checks on their intake in this kind of situation it's interesting they tend to under report by about 15% so even in a situation where it's clear that all their behaviors being monitored their assessment of their own food intake is out by about 15% which is one reason why you need to go to this extent put people in here to get the accurate data what you can't do though is run very large numbers of subjects because it's very expensive so we in these studies have run groups of three at a time for a total of six subjects and in the first experiment that I'm going to describe we were again interested in comparisons of fat and carbohydrate and in this situation we used normal commercially available foods and we manipulated lunch by 400 kilo calories we had four different conditions a high carbohydrate low carbohydrate condition and a high fat and a low fat condition so the high calorie conditions were 800 kilo calories and the low were 400 and the subjects again this was a covert manipulation the subjects couldn't tell what they were getting and they didn't know that there were differences in fat and carbohydrate and we did some counterbalancing of the conditions across groups but with an n of six you can't do a complete design okay so apart from the required lunch these subjects could eat over the rest of the day from a very wide selection of foods including high fat foods low fat foods and this is their total caloric intake with the test lunch so their total caloric intake they had each condition for three days at a time was not significantly different across these conditions so again no difference between the fat and carbohydrate and we found here's lunch we found a very rapid compensation for the caloric difference at lunch the 400 kilo calories by dinner time which was their next big meal there was no longer any significant difference between the groups in caloric intake and this shows the macronutrient intake across the entire day and this includes the test lunch so not surprisingly then in the high fat condition they're taking in more total fat if you took the lunch out the nutrients would be the same across conditions so they don't adjust their macronutrient intake to accommodate the differences in nutrients in the lunch so in this study then these normal weight meals compensated for the 400 kilo calorie reduction in these test lunches and they maintained a constant energy intake over the three days of each manipulation period and we didn't find any differences between the responses to the reduction in fat or carbohydrate and the compensation took place rapidly and it was seen on the first day of the manipulation so there was no learning involved it was a quick response of course we've already seen that these normal weight males are our best compensators so these kinds of studies have not been extended to other populations and it's not clear that they would be applicable for example to dieters or to obese individuals well in a study that just came out in this month's American Journal of Clinical Nutrition we took this further and decided we wanted to manipulate fat and carbohydrate to a greater extent so we had a lot more conditions in here we had low medium and high carbohydrate and fat conditions we also had a baseline condition and we manipulated breakfast lunch and afternoon snack and they could eat as much else as they wanted over the rest of the day so they could ask for extra at these meals and they could eat whatever they wanted it at dinner or between meals so they had plenty of opportunity to compensate for differences between conditions the conditions varied between 700 and 1700 calories so we varied up to 52% of their normal daily intake carbohydrate or fat this just shows the experimental design again six subjects normal weight men and they had baseline at the beginning and end and then two days on each condition okay here's our our baseline intake so that's what we're comparing to and this is the intake in the the planned occasions as we call them the required meals the breakfast lunch and snack and this is their voluntary intake over the rest of the day and you can see if you compare total intakes to baseline intake stays within 15% of baseline the only condition which differed significantly from baseline was the low carbohydrate condition which was the least energy dense it had a lot of drinks there was a lot of volume of food there they they didn't eat enough to make up for the reduced calorie foods that they were eating again when you look at the macronutrient intakes this is over the rest of the day without the planned occasions very constant so they're not adjusting macronutrients so here when you put the planned occasions in macronutrient composition of the diet each day very dramatically according to the foods that we required them to eat so then this study showed that the subjects again showed caloric compensation total caloric intake remained within 15% of the baseline across all the conditions only under the low carbohydrate condition was caloric intake less than under the control conditions caloric intake under the high fat condition was less than under the high carbohydrate condition we found in the high fat condition there was a prolonged suppression of intake into the evening we didn't look at nausea but it's possible that the high fat they didn't feel very good after eating all that fat was minimal evidence for compensation for the macronutrient content of a required occasion so again no macronutrient composite compensation so all of these different studies are really leading to very similar conclusions well so far most of the manipulations that I've talked about have really involved substituting carbohydrate for fat most of the low fat foods that are currently available in the marketplace are using carbohydrate fat substitutes things like maltodextrins to mimic the fatty taste but we are on the verge of a revolution I can tell you virtually every food company in this country has some type of fat substitute we've already seen the introduction of Simplas which is the protein based fat substitute made by NutriSuite and Simple Pleasures ice cream and that relies on the protein molecules sort of sliding easily across one another and giving a sort of fatty slimy feel but there are other kinds there are more carbohydrate fat substitutes coming the protein ones fat different versions of fat that aren't absorbed and talking about that I don't know how many of you read science news but this came on my desk today in an honor of Valentine's Day I'll have to tell you what this says for all our concern about staying slim and reducing dietary fat it's hard to imagine giving or worse getting a box of low calorie low fat chocolates for Valentine's Day and then it goes on to conclude it's all this business about inherent preferences for sugar and fat and all and so it ends so chocolate lovers take heart undoing millions of years of evolution will not be easy and neither will tricking the palette with substitute fats and artificial sweeteners it may be a long time before anyone devises a low calorie low fat chocolate that lets one savor a Valentine's gift without guilt for now we might as well enjoy those sweets and eat healthier next week well this is coming it's coming in a few weeks this is the Milky Way too and it has 25 percent fewer calories the entire reduction is in fat it's using a novel fat substitute called capronin which is made up of medium chain and very long chain triglycerides which are not readily absorbed so they only have three to five calories per gram it's delicious I like it better than the real Milky Way I wish I had enough to share it all with you but this article is obviously not up to date even though it's this week's this this is potentially the biggest change we'll ever see in our diets because things like this this is Alastra are coming and this isn't this isn't the only non-caloric fat substitute that's currently being developed Frito lay has one best foods has one Arco has one this is the one that's further along the furthest along in the approval process none of them are yet approved for consumption but Alastra is basically a sugar molecule with fatty acid strung around the outside so it feels like fat but it can't be hydrolyzed so it's not absorbed so it goes through unabsorbed when they first produced it they had some problems with what they euphemistically called anal leakage it's like taking castor oil if it's not absorbed it has to come out but they've now changed the melting point so it comes out as a solid I have tasted that Procter and Gamble potato chips completely fat free potato chips no fat at all that taste and feel just like the real thing so if you think that isn't revolutionary I don't know what is potentially our diets can be changed radically and we know almost nothing about what these fat substitutes do to food intake I'm going to tell you about a study that we did which was sponsored by Procter and Gamble and at the same time as we did our study there was a parallel study done in Britain by Blundell and Burley also sponsored by Procter and Gamble and Leanne Burchett Illinois has done a study in kids and there's one long-term study that was done years ago with an earlier version of Alestra you know beast subjects done by Glick that is the sum total of our knowledge of how these fat substitutes are going to affect our intake and one reason why more studies are not being done is the FDA does not require efficacy they only require safety so they they do not require food companies to have any knowledge of the effects these fat substitutes will have on intake so having said all that it's a great tool for studying the regulation of fat intake because you can simply remove fat and stick a left in its place it has the same volume the same feel as real fat so you don't have to worry about balancing out with other nutrients when you're doing your manipulation you simply remove fat and you end up with a product that's indistinguishable from the full fat version so in the study that we did which was an acute study in normal weight non-dieting men again we manipulated breakfast and we had two different levels of Alestra that we introduced into this breakfast so we had three different calorie levels and this is the breakfast it was biscuits that Procter and Gamble made this was a double-blind study so we didn't know what we were giving the subjects and they didn't know what they were getting and then it had a spread like margarine which was made either with real margarine or with Alestra and marmalade or jam coffee the subjects had to eat the breakfast and then we fed them in the lab self-selection lunch similar to the one that you saw before and a self-selection dinner and they tracked their hunger and fullness over the day and this is the total caloric intake over the testing here is breakfast and by design of course the calorie levels at breakfast were different across conditions lunch time they didn't make up the calorie difference now we missed you saw in our other studies there was an early compensation at half an hour in this study they weren't allowed to eat again until lunch and we may have missed the early compensation I think there may be two different things going on here in terms of regulation of calories after you eat an early response and a later response when the foods are metabolized so anyway no difference at lunch but then at dinner time in the low calorie condition the 36 gram electric condition they ate significantly more dinner so they ended up again eating the same calories over the day and then over the rest of the day evening snacks and next day breakfast intakes the same so the Alestra had no effect on daily caloric intake in this population of subjects again as in the other studies they don't adjust their macronutrient intake to accommodate the differences in nutrients in the test foods so what that meant over the entire test day was that when they had the Alestra they had ate significantly less fat over the day a bit more protein and significantly more carbohydrate so just by manipulating the fat content of the one meal we're getting intakes adjusted in the right direction towards the dietary recommendations well you might think that this fat substitute would produce some peculiar effects on hunger and fullness and whatnot and we didn't find any signs of that we tracked hunger and fullness over the 24 hours so we're no consistent significant differences between conditions in either hunger or fullness so from this study then we conclude that the energy intakes between the conditions over the 24 hour period didn't differ significantly in this group of lean non-dieting males and substitution of fat with Alestra led to a dose dependent reduction in daily fat intake we had a reciprocal increase in carbohydrate intake so we didn't see that a fat specific compensation followed consumption of Alestra and there weren't any significant differences in ratings of hunger and fullness between conditions so it didn't alter the cyclical pattern of hunger and satiety that occurs throughout the day the study conducted in Leeds had virtually identical findings and the study that Leanne Burch did in young kids was very similar as well so that's what we know about the fat substitutes I really think we need more information one of the questions that I think is most interesting and key in this field is in particularly a view of our findings supposing your caloric intake stays the same but you reduce the percentage of calories from fat in the diet what's going to happen or what happens with long-term consumption of low fat diets are you going to lose weight this is a study that was conducted at Cornell and that group interprets their data quite differently from the way we interpret ours fact when Dave Levitsky talks about this data he talks about the imprecision of caloric compensation in humans you've seen that we've seen a lot of precision in our data what he did in his study was he fed subjects for 11 weeks a diet that had 35 to 40 percent of its calories from fat and then for another 11 weeks 20 to 25 percent of its calories from fat and he looked at changes in body weight food intake etc and he found that well both groups lost weight but the group that had the reduced fat diet even though they could eat as much as they wanted of these reduced fat foods lost weight so he's interpreted this to imply that as long as you're eating a low-fat diet you can eat as much as you like and you're going to lose weight I think that that's fine I mean that's a that's certainly a possibility but how do you get the people to stick to it in real life in his study the people couldn't eat any foods that had more than 20 percent fat most of us when we're surrounded by high-fat foods don't do that so what about the other issue of isochloric diets which are lower in fat and their impact on body weight there there isn't actually a lot of good data surprisingly even though most weight loss programs now are advocating low-fat this is a study that sort of addresses that this was an experiment in which they fed people high-fat diets 37% fat for four weeks and then they kept them on a low-fat diet for weeks 5 to 24 and they're trying to keep body weight constant and so what this is showing is how much energy the subjects had to eat to maintain body weight on the low-fat diet here's base the baseline at the beginning and they had to increase their consumption of food of calories on the low-fat diet so this perhaps implies that if you reduce the percentage of calories from fat over the long term there may be some weight reduction there's some cancer studies coming out now that are showing a similar sort of finding so I'm going to conclude now the results of these studies overall then which the fat content was reduced were variable in terms of caloric compensation showing partial to complete compensation for decreasing calories our studies we saw good compensation but in the Levitsky studies and perhaps if you get very low levels of fat you have to eat a lot of volume to make up the calories you will get some decrease in total energy intake but I think it has to be a big fat reduction before you're going to get to that point we did see the compensation for fat was incomplete so all of our studies there was a reduction in daily fat intake with consuming the low-fat foods and I think that's really the best news out of all of this that if people do choose low-fat versions of foods instead of high-fat versions they will decrease the percentage of calories from fat in their diets so then I think as the more palatable low-fat foods become available it should become easier to reduce the percentage of calories from fat in the diet I say this is pure speculation because we don't know and certainly some nutritionists now are arguing that giving foods with fat substitutes and fat mimetics is simply encouraging us to continue to like fatty foods and it won't result in any permanent change in our fat consumption we don't know that we simply don't have any answers there's no no research I think what happens with a lot of these foods the fat substitutes reduce fat foods is going to depend on the motivation of an individual if somebody is on a diet and is choosing a low-fat food instead of a high-fat food and watching their calories over the rest of the day then it may be a useful tool for weight control because it gives them some alternative foods I think this last slide sums up what I think a lot of people are doing with these foods this is trying not to think of light ice cream as the perfect vehicle for hot fudge I think that's the problem with this that's what a lot of us do at these foods thank you very much yeah we haven't done that we've we've just been concerned with adjustments of energy intake and most of the studies with the preloads for example be very quick within half an hour before the foods would be fully metabolized and utilized but I agree with you I mean we need a whole energy balance kinds of studies the thing is people that do regulation of intake don't usually do regulation of output so we don't know the whole energy equation just the how many calories it takes to process but that many high-carbohydrate carbon high-carbohydrate foods are like potatoes and they're very hard to eat as much calories and potatoes well sure that's what I was alluding to if you get a very low energy density diet you're probably not going to be able to eat enough to make up and so in that situation you probably will get a reduction in daily energy intake as well whatever did you put in the yogurt and increase the carbohydrate so much it was maltose mostly yeah no I mean this stuff is formulated it had well we we have some aspartame in the low carbohydrate version and we use multidextrins and other tricks of the trade we had a someone from your play come and spend quite a bit of time with us formulating this is better than most of the commercially available we I mean we make it all ourselves well we saw the best in the normal weight unweight preoccupied men and the women did pretty well the most typical obese group was the group at the bottom of the panel the obese restrained the obese unrestrained are pretty atypical those are obese who just don't care about their body weight so the obese restrained did very badly and that they they they tend to restrict and they tend not to adjust of course this is a lab situation too and so that that's often a problem in these kinds of studies but I think one hypothesis that we'd like to test further is that they are impaired in their ability to adjust their intake to calories from whatever nutrient and also I think they do rely more on cognitions they have a mindset this is what I'm allowed to eat then of course they they break the rules and they want you know this what the Canadians Paul Avian Herman called what the hell effect where they break their diet and so then they just go ahead and and binge and that's quite typical which they didn't they don't tend to do in this situation interesting I I guess I said that it was caloric compensation in those men and I was challenged on that when I presented this a few weeks ago by a colleague who said it compi caloric compensation because the calories won't yet be recognized as calories by the body because it was too quick it's a half an hour after they started eating the load and I had admitted that I didn't know what the mechanism was it seemed way too quick to me but it's it's been something we've seen in three or four different studies now and I said well I don't know what it is do you know what it is and he said yes he thought it was volume we controlled for volume so I don't know how they're doing it's very intriguing and I think it's one of the things we need to sort out was how people can do it that well that that was one of the biggest surprises to me of any of these studies that intake was adjusted so well in any group in these studies really don't know what they are so I mean choosing in terms of are you questioning them with regard to at least their perceptions yeah at the end they rate all the different yogurts for how fatty they think it is sweetness plus a whole lot of different questions and then they're not usually consistent differences between them that would anyway relate to their intake so it's really a covert manipulation but as I mentioned briefly one of the things I think we need to investigate more is how the messages about fat are affecting intake and people's responses to foods because what's happening now with a lot of the low fat foods is they're still pretty high calorie for example simple pleasures ice cream is an example of that I mean they they've gotten the fat down but they've put an awful lot of carbohydrate in and that's where I would say we're finding that people are responding to the message when there's a disparity in reducing intake according to the message rather than the actual calorie content of the food but need to do more on that milky way bars are interesting milky way two will be the same size as milky way one looks like it yeah don't you think people object to that and what they'd really like is a bigger well it's interesting because that's that's another question that we don't know I mean supposing you buy this repeatedly are you gradually going to learn that it's not very satisfying and want more or are you just going to stop buying it because it's not very satisfying we don't know there's never been any studies of repeat consumption of these kinds of things you know I think it's it's more likely to happen that you're going to eat more if you have a big bag of potato chips and you know I mean you've got the message that it's lower in calories and lower in fat and you also have the opportunity to learn how satisfying it is that's one of the determinants of human food intake is your previous experience with a food so as you repeatedly eat this what's going to happen nobody knows but these things are providing great tools for those was working in this field because we can dissociate now sensory and physiologic factors and fat and see what happens possibly although we I mean we've never really looked at the question of repeat consumption of the same food and learning about foods which I think is an interesting possibility it's something also that may be impaired in obesity it may be that our normal way people would do well and the obese wouldn't so I haven't been a lot of studies on the obese just just the one that we mentioned delivery of a different portion size and I haven't impact on overall intake there've been a few and most of them have not ever been published we did some and David Booth in England did some and generally portion size can affect intake the bigger the portion size the more you eat but again no long-term studies to see if that would persist which one would need to do but it's it's interesting because portion size clearly in something like this determines how much you eat you eat the whole thing and if you go to a food company and say well how did you decide what the portion was going to be it's usually just well that's what the industry says the portion should be and for a bag of potato chips it's just historic there's no rational reason we looked at their smell their ability to smell using the University Pennsylvania smell identification test which is a 40 item multiple choice and our elderly subjects did show the typical decline in ability to smell but when we tried to relate that to the change and sensory specifics of time looking at the subjects that weren't paired and we couldn't find any relationship that's not to say it doesn't exist but these the elderly subjects rated the foods the same initial palatability so there weren't there weren't differences like that that make it look like that's the only explanation well there are pain we're hoping that somebody's going to come up with a nice easy taste test like the smell test but generally it's it's smell anyway that's more important in food intake than taste but it would be nice to do that and I really think it would be nice to see how the lack of sensory specific satiety affects actual food intake in a varied meal situation and we're planning to do that we hope to videotape them eating and see how they switch from food to food and how much they eat in a varied meal versus a moment on this one that kind of thing once again I'd like to thank Barbara I think she did a very good job in compensating compensating for some of the troubles that we were showing her at the beginning but so compensation works in various ways and again I'd like to remind you that there are some evaluation forms on the back table and there's also information that can be filled out if you want to be put on a mailing list if you haven't done so in the past for the future lectures the next lecture will be on March 25th and entitled nutrition and the injury stress response in the hospitalized patient by Bruce Bistrian from Harvard Medical School thank you for coming and hopefully we'll see you all again next month