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Richard mattes' research explores the mechanisms contributing to obesity, focusing on food intake, satiety, and metabolism. He examines cultural influences on food portions, individual food units, and snacking behaviors, as well as the effects of macronutrient content and taste sensitivities on hunger and satiety. Mattes also investigates the role of metabolism and taste sensitivities in intake, particularly in relation to peanut consumption and the glycemic response.
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Contributions of Appetite, Metabolism and Taste Sensitivities In Human Obesity: A Review of Richard D. Mattes’s Research Rebecca Dover Fall 2006
A critical literature review submitted in partial fulfillment of the requirements for the senior research thesis.
Abstract Richard Mattes has done considerable research in an attempt to discover the mechanisms contributing to obesity and weight loss. Obesity is a growing trend in America that leads to health problems and death. The research of Richard Mattes offers insight into the contributing factors of obesity, and possible preventative and intervening techniques. Mattes exposes cultural increases in food portions, individual food units, and snacking behaviors that may lead to increased energy intake. Increasing energy intake without increasing physical activity can lead to positive energy balance, which leads to weight gain. Mattes also looks at different food forms, such as solids versus liquids, and their effects on satiety. As solids had more satietal value, and chewing was a hypothesized reason, Mattes also investigated the effects of chewing gum on satiety. He also experimented with various macronutrient contents of food items, as well as with effects of glycemic index on the glycemic response. Richard Mattes’s research also examined metabolic responses that affect weight. He compared fructose and glucose and their utilization after exercise. He also studied the use of peanuts and peanut oil as monounsaturated fat sources to improve lipid profiles in the blood and decrease risks for cardiovascular disease. In the area of taste sensitivities, Mattes researched taste sensations as a possible predictor of salt sensitivity, which can lead to high blood pressure. He also tested the effects of oral fat stimulation on the postprandial lipid response and cholesterol. Mattes’s research has helped to create a vast understanding of the body’s utilization and regulation of consumed substances.
stigmatization and discrimination in many situations. Research that identifies possible contributing factors for obesity is valuable because of the high impact that obesity is having on the United States population. (AOA, 2006). Dietary intake is one factor that may contribute to obesity when a positive energy balance is reached. Energy balance refers to the gross energy intake after energy (calorie) consumption, expenditure, and storage. By increasing energy intake without increasing physical activity, a positive energy balance is reached. Several factors may contribute to feeding behaviors that increase dietary intake. The culture in which an individual grew up or now lives can affect feeding behaviors. Food portions, size of individual food units, and convenience of packaging and availability are culturally specific characteristics that may increase positive energy balance (Devitt and Mattes, 2004). Characteristics of individual food items may also promote positive energy balance. For example, liquids have been shown to have less impact on satiety than solid foods, in some studies (Mattes, 2005). The macronutrient content and Glycemic Index, a property of foods that helps to predict the postprandial blood glucose response, are also factors that affect hunger and satiety, which in turn corresponds with dietary intake (Alfenas and Mattes, 2005). Besides studying appetitive variables that contribute to positive energy balance, Richard Mattes has also researched the influence of metabolism and taste sensitivities on intake. One area that Dr. Mattes has particularly explored is the effect of peanut consumption on lowering cholesterol and heart disease. He also has researched the substrate utilization of different sugars. In order to more completely understand metabolic effects on intake, metabolic processes must be explained.
Thermogenesis is the process of generating energy, or heat, by increasing the metabolic rate above normal. This can occur in response to exercise, specific nutrition, or nutritional supplements. It also occurs when the body is exposed to cold temperatures. Different macronutrients affect thermogenesis at varying rates. Proteins have a higher thermogenic rate than fats and carbohydrates, meaning that they increase metabolism more. Another concept of metabolism related to positive energy balance is the Glycemic Response. The Glycemic Response occurs after the ingestion of foods, and is determined by the Glycemic Index of the food, a property of carbohydrate containing foods. The Glycemic Response refers to how quickly the body is able to increase blood glucose levels. If a food can quickly raise blood glucose levels, it has a high Glycemic Response. Richard Mattes has proposed and researched the ability of foods with a lower Glycemic Response to maintain satiety longer and thus decrease intake (Alfenas and Mattes, 2005). Richard Mattes is perhaps most interested in intake as it related to sensory characteristics of foods. More specifically, his research focuses on taste sensitivities that affect feeding behaviors. The gustatory system is a chemical sensory system. The process of taste begins when a chemical tastant on the tongue enters the outer taste pore of a taste bud and interacts with the apical end of a taste receptor cell to stimulate neurotransmitter release onto afferent taste nerves. These nerves collectively represent three cranial nerves that innervate different sections of the tongue and carry signals to the brain. While there are five identified tastes: salty, sour, bitter, sweet, and umami, Dr. Mattes has done considerable research examining a possible taste of fat. He has also
high glycemic load may result in increased intake at the next meal, when compared to a meal with a low glycemic load. Richard Mattes, along with Rita C.G. Alfenas P.h.D., (2005), sought to repeat these results, while also controlling for macronutrient composition of the meals, meal duration, energy density, rheology, and palatability, which are all possible confounds of previous studies. However, a more natural setting was also sought, as lack of generalization of lab settings has inhibited other studies. Rather than presenting either all low or all high glycemic loads, Mattes and Alfenas presented mixed meals. They also presented foods with different nutrient content, such as high protein, different types of fats, and varying levels of carbohydrates, to note effects of different nutrients on the glycemic response, and subsequently on food intake. In addition, the study consisted of two 8-day experimental periods, which is longer than previous studies, in order to examine any adaptation effects to multiple low or high glycemic load meals (Alfenas and Mattes, 2005). Seventy-nine foods were selected for similar micronutrient composition and published glycemic index values. These values were then confirmed with non-study subjects by testing the glycemic responses to each food. Forty-eight foods remained in the study. Subjects were placed into either low or high glycemic index groups. Before each 8-day session, each group had a variety session where they ate a combination of three foods for each meal, all of which corresponded to their glycemic index group. They then selected their favorite food from each meal, and ate only that food for their meals during the experimental sessions. They were allowed to eat as much as they wanted, and amount eaten was covertly measured. Blood sampling and appetite questionnaires were completed before eating, as well as 30, 60, and 120 minutes after breakfast and lunch.
The appetite questionnaires consisted of labeled magnitude scales inquiring about hunger, desire to eat, and fullness. Blood glucose levels were measured using capillary blood as oppose to venous blood, because glucose changes are more reliable in the capillaries. Nutrient content, palatability, and energy density were similar between groups (Alfenas and Mattes, 2005). The results did not show a significant difference in glycemic or insulin responses after breakfast or lunch, between groups or over the 8 day time period. There was also no significant difference in hunger, fullness, or desire to eat. Therefore, Mattes’s and Alfenas’s data does not support a difference in appetite resulting from a high or low glycemic load meal, even over a long period of time. Mattes and Alfenas attribute the lack of results to the possible confound of meal duration, which can affect the glycemic and insulin responses. However, if this were to be controlled, ecological relevance would be lessened. (Alfenas and Mattes, 2005) In this study, Richard Mattes attempted to improve upon previous studies, but reproduce their findings. However, when he controlled for confounding variables, the results did not support the glycemic load of meals as a predictor for appetite and food intake. His results show that appetite, although only one possible factor of weight gain, is difficult to predict as a means of increased intake. Self-reporting as a means of collecting data can also be faulty, and create varying results, as seen here. Mattes explores this issue in another study. Richard Mattes examined the problem of self-reporting in humans in a study designed to discover why people tend to under record their dietary intake during research studies. Other studies have shown that under recording occurs because people
include placing an X on a figure of a human body in the areas where pain is felt during hunger. These methods create population data for hunger experiences, but do not produce data for the individual. Mattes and his colleagues sought to create a more finely tuned scale to more accurately measure the subjective feeling of hunger among individuals (Friedman et al, 1999). The study was divided into 2 experiments. The first experiment asked subjects to specifically describe feelings of hunger. The subjects were not food deprived, but rather were asked to imagine hunger. They then outlined on a human figure the areas that were associated with hunger pains. The second experiment asked subjects to fast for 22 hours and to complete hunger questionnaires at various times throughout the day, as well as the body outline. They were then given either a low or high fat meal and given the questionnaires and body outline again. After eating a meal of their own choice later, they repeated the data collection process once more. The outlined areas from the figures were cut out and weighed for both groups (Friedman et al, 1999). The first group, who had imagined hunger sensations, reported abdominal pains and headaches for extreme hunger. The second group did not vary after either low or high fat meals, implying that nutrient content does not affect satiety after fasting. The hunger pains as reported in the questionnaires did not change significantly throughout the day of fasting. However, the area of body circled increased throughout the day, implying that hunger questionnaires may not provide complete data on hunger sensations. The scale utilized in this experiment could improve data that relies on hunger questionnaires, and hunger questionnaires should not be used alone as sources of data (Friedman et al, 1999).
Along with the effects of glycemic load on appetite and intake, Richard Mattes, along with Amy A. Devitt (2004), has studied the effects of the size of food units and energy density. Portion sizes have been continuously rising since the 1970’s, and along with them, energy intake. This suggests that positive energy balance occurs because of intake, a voluntary action, and not solely on physiological, metabolic processes. Food packaging has also become more convenient, with hand held items increasing. The size of the individual food unit is a likely determinant of the size of the portion that the individual will ingest. Therefore, if the food unit sizes were to decrease culturally in the United States, portion size and intake might decrease as well. However, smaller food units could potentially increase intake. For example, a person may only consume one customary-portioned cheeseburger, even if several are presented, but if several small- sized cheeseburgers, the individual may feel that they can eat more, and consume more than if they had eaten the larger food unit. In addition, food unit size could have little to do with positive energy balance. Some studies show that individuals tend to consume consistent gram weights of food. Therefore, positive energy balance could be a result of the energy density of certain foods, eaten in similar portion sizes to less energy dense foods (Devitt and Mattes, 2004). Devitt and Mattes used smaller than customary portion sizes to study portion effects on gram weight intake and energy consumption. They hoped to discover whether intake was monitored physiologically, by gram weight of intake, or culturally, by food unit size and fat content. Meals were given to subjects over a four-day time period. Each day meals varied on energy density and food unite size. Appetite and desire to eat were measured after each meal, as well as the amount consumed. However, the results were
stable during periods of diet manipulation, when compared to baseline levels, then dietary compensation was estimated to have taken place (Mattes et al, 1988). The most significant compensation occurred for caloric dilution as opposed to supplementation. In other words, when subjects were given low calorie meals, they compensated by eating more throughout the day, despite being unaware of the type of meal they were ingesting. When subjects ingested the high calorie meal, they usually did not compensate by ingesting fewer calories throughout the day, but rather ate the same amount that they consumed during baseline. If subjects had continued in this pattern, weight gain would most likely have occurred, because subjects ingested more calories, per day, than at baseline (Mattes et al, 1988). This study appears to show that people tend to eat as much as they can. When they do not have enough calories, they will eat more, but when they do have enough calories, they still eat more. For some foods, nutritional value is difficult to assess, and this study shows that the body does not have a foolproof physiological mechanism to assess energy intake. The increased compensation during caloric dilution emphasizes the survival technique involved in dietary compensation as well. In times of hunger or energy need, the body can discern differences in caloric content. In times when ingestion is unimportant, perhaps this mechanism becomes inactive because it is not needed. While food unit size and portion size are culturally determined factors that may predict intake, different fat sources are nutritional factors that may affect satiety, and consequently, intake. While fat has high energy density (i.e. calorie content) and palatability, it has weak satiety impact and a small oxidative response, resulting in its
tendency to be stored. However, individual fatty acids may have different oxidative rates and satiety effects. The saturation of fat may also affect satiety. Mattes and Alfenas (2003) conducted an experiment to discover the different satietal properties of fat sources high in monounsaturated fatty acids (MUFA’s) and those high in polyunsaturated fatty acids. Subjects ate muffins similar in taste and appearance, but containing different types of fat. Appetite questionnaires and feeding records were kept and used as data. While Mattes’s previous research has shown the inaccuracies of these methods, this study involved plastic containers and detailed instructions on how to measure food intake, to increase the accuracy of the feeding records (Alfenas and Mattes, 2003). When the fat free muffins were consumed, higher hunger ratings were found than for the muffins containing the various fats, suggesting that fat has a satietal impact. However, the fat free muffins contained less total energy, which could have decreased satiety. No significant differences were found between the different types of fats, although the predicted impact on satiety was PUFAs > MUFAs > SFAs (saturated fatty acids). Mattes’s study challenges the notion that different fatty acids have different satietal impacts, although fat free foods should still result in less energy consumption due to having fewer total calories than fat containing muffins. The effects of fat content on satiety are still unclear, but appear not to be an adequate predictor for hunger or fullness (Alfenas and Mattes, 2003). Another physical aspect of a food item that could affect satiety is whether or not the ingested substance is a solid food or a liquid, such as a beverage. Solid foods have been shown to satisfy the appetite more than liquids, possibly due to the action of chewing. However, beverages such as sodas, beer, wine, and milk are consumed often,
mechanisms that prevent satiety after the consumption of a beverage must be discovered. It is also important to know if low satiety of a liquid meal replacer or beverage may promote increased energy intake, in an attempt to become satiated. Richard Mattes examined this topic in his research on the satietal effects of ethanol. Ethanol makes up about 4-6% of U.S. per capita energy consumption. (Mattes,
because they are ingested so quickly. They also reduce gastric fill more quickly than solid foods. Finally, chewing has been implicated as a possible satietal influence, and is lacking in beverages. Alcohol, similar to other beverages, does not decrease the amount eaten, and even increases it, a possible problem for the liquid meal replacement industry. (Mattes, 1996) Richard Mattes conducted further research involving the behavior of chewing as it relates to appetite, while also relating it to cultural phenomena such as increased snacking. In the previous study, Mattes examined high calorie, low satiety characteristics of beverages. However, an answer to the problem of increased beverage consumption would be to introduce an item with high oral satiety, or ability to satisfy the desire to eat, with minimum calories. Sweetened chewing gum was his item of choice. Sweetened chewing gum provides early oral satiety, and studies using unflavored gum show that chewing gum increases satiety in general. Other studies have also shown sweet chewing gum’s potential to reduce the desire to eat something sweet. Mattes sought to discover an influence of chewing gum on overall appetite and intake (Julis and Mattes, 2006). Subjects were divided into two group. One group was allowed to chew gum for 20 minutes when they experienced a craving for something sweet. They could not have a sweet item until another craving occurred. The second group had a fixed time for chewing their gum, set at 2 hours after a meal. They then waited for a craving to occur, and could not eat anything until they had waited for 20 minutes. Regular hunger logs were kept in each group (Julis and Mattes, 2006). Chewing gum did not significantly alter appetite or intake within either group. Therefore, sweetened chewing gum does not appear to have an effect on satiety or the
activity logs were kept. Both groups lost significant amounts of weight. The difference between groups was significant as well, but only moderately. Both groups lost weight, but both were also placed on restrictive diets. Because their weight loss was congruent with their dieting, HCA can not be concluded to have affected satiety or weight loss. Instead, it is likely that the subjects simply adhered to their diets, perhaps because they were subjects in a study and had heightened awareness of their eating behaviors. The effects of HCA cannot be expunged though, because it was not tested at varying levels or on varying individuals. Subjects were moderately overweight, and HCA has been shown to affect obese individuals more than lean individuals. Low doses have also been shown to be more effective than high doses, and so more research involving different levels of HCA might yield more conclusive results. (Mattes and Bormann, 2000) In addition to his research concerning possible appetitive variables of weight loss, Richard Mattes has also studied weight management after a period of weight loss as it relates to appetite. The issue of sustained weight loss is of high importance due to the tendency of individual who have lost weight to regain the weight after a period of time. One reason for this may be individual differences in responses to a sustained decrease in energy intake. Mattes attempts to determine characteristics of individuals that may help to predict sustained weight maintenance after the initial weight loss period. Such characteristics include time spent in food acquisition, preparation, and consumption, in an attempt to draw conclusions about an individual’s preoccupation with food. Other factors include dietary motivation and concern over health (Mattes, 2002). The study involved a weight loss period followed by a maintenance period. If weight gain occurred, return to the weight loss regimen was required. It took place over a
period of 64 months, during which time questionnaires regarding the aforementioned variables were administered. Subjects were classified as maintainers, rebounders, and nonresponders in accordance with their weight loss and maintenance (Mattes, 2002). Nonresponders spent significantly more time shopping for food and eating. They also spent less time preparing their food, so they could have been eating more convenience foods. Finally, nonresponders ate with fewer people than the other two groups. Rebounders exhibited less dietary restraint than maintainers, while maintainers showed more flexibility in their eating behaviors. Maintainers also appear to have more awareness of sensory cues relating to fullness and satiety than rebounders. These findings are important to the study of obesity because they reflect individual characteristics that may affect a person’s ability to lose and/or maintain weight. By increasing knowledge of individual differences as related to weight loss, research can become more accurate as it accounts for these differences in subjects (Mattes, 2002). Richard Mattes’s research has focused heavily on appetitve variables as a purported factor of weight gain. Nutritional aspects of foods and beverages were examined, as well as physical aspects of foods, such as solids vs. liquids. Mattes’s hypotheses were formed from previous research studies and knowledge in his field. The inconclusive nature of many of his findings is representative of the many variables that determine satiety, and on an even bigger scale, weight loss and maintenance.
Metabolism In addition to researching appetite and its relation to obesity, Richard Mattes has also done considerable research into metabolic processes. Sometimes, these processes are
