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Controlling satiety: how environmental factors influence food intake
Trends in Food Science & Technology 20 (2009) 271e277
Review
Controlling satiety: how environmental factors influence food intake Janna M. Smith* and Tanya L. Ditschun Senomyx Inc., 4767 Nexus Centre Drive, San Diego, CA 92121, USA (Neutrogena Corp., 5760 W. 96th Street, Los Angeles, CA 90045, USA. Fax: D1 310 216 5399; e-mail: [email protected]) The obesity epidemic is fueled by over-consumption of food. Increasing portion sizes have distorted perceptions as to what constitutes a normal meal size. Many environmental cues contribute to the growing portion norms such as restaurant meal size, economy sized grocery packages, and illusions produced from larger dishware and utensil sizes. This review examines factors contributing to portion distortion and the role of sensory-specific satiety (SSS) in consumption. It is proposed that SSS could be used to control food intake when used in conjunction with environmental cues, including portion control, avoiding distraction while eating, and variety of available foods.
Understanding sensory-specific satiety and its role in controlling food intake Over-consumption of food and lack of physical activity are directly related to the obesity epidemic facing society. Obesity is far-reaching, affecting the well-being of children and adults, rapidly changing our health needs and increasing the burden on our healthcare systems. Some food manufacturers have responded to consumer concerns about healthful eating by creating foods that are lower in sodium, sugar, and fats, yet these efforts are not enough to control the increasing rates of obesity and additional strategies are needed to counteract overeating. * Corresponding author. 0924-2244/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.tifs.2009.03.009
Sensory-specific satiety (SSS) is a condition we experience during the eating process that may be a possible strategy to combat overeating. Specifically, SSS is the decrease in the pleasure derived from continued consumption of a food (Rolls, 1984). This is an innate mechanism (Berthoud, Sutton, Townsend, Patterson, & Zheng, 2006; Rolls, 2005) which is strongest during the 2 h following consumption, and can affect liking ratings for over 24 h (Weenen, Stafleu, & Graaf, 2005). SSS combined with other consumption strategies such as limiting variety, exercising portion control, and overall awareness of environmental eating cues, may be the recipe to counteract overeating. In this review, several significant factors contributing to over-consumption of food are examined, and the use of SSS as an innate tool to controlling intake is explored. Factors affecting food intake Increased portion sizes have distorted perceptions as to what amount of food is ‘‘normal’’ or of appropriate size for consumption at a meal (Wansink and Van Ittersum, 2007). Together with an inability to adequately monitor or estimate caloric intake, the combination can result in over-consumption, which can be a significant contributor to obesity. This distortion of appropriate portion sizes can begin as early as 3 years of age (Savage, Fisher, & Birch, 2007). Both retail food and foodservice industries can share the blame; consumers have been shown to eat 30e50% more from larger-sized restaurant portions compared to smaller portions (Rolls, 2003), and 20e40% more from larger-sized packages than smaller packages (Wansink, 1996). While package size, serving size, and dishware size influence how much we eat, socioeconomic status and education level of the consumer have not been shown to aid in counteracting these influences. Even education about the propensity toward portion distortion cannot make one any less subject to this phenomenon (Wansink, Van Ittersum, & Painter, 2006). Portion control Portion control is perhaps one of the most important components, if not the most important component of weight loss, and many leading commercial diets advocate portion control as a weight loss tool. However, our consumption norms are gradually increasing (Wansink and Van Ittersum, 2007), thereby making it harder for consumers to exercise portion control. Portion distortion is everywhere: in our
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supermarket ‘economy’ sizes, in restaurant portions far beyond recommended serving sizes and caloric needs, and even in our dishware, which has increased in size to accommodate larger portions. These factors will be examined as to how they relate to perceptions of what is a normal amount of food to consume. Retail and foodservice serving sizes Marketplace portions have been increasing steadily, thus increasing our expectations of portion size. Restaurant portion sizes have increased significantly from when they were first introduced to their current sizes (Young and Nestle, 2003). In 1955 a soda from McDonald’s was 7 fl. oz. in volume. Today McDonald’s offers a 12 fl. oz. ‘‘child-sized’’ soda, a 42 fl. oz. Supersize and several different sizes in between. What used to be a ‘Large’ soft drink at Burger King in 1954 is now a ‘Small’ soft drink, at 16 fl oz. Foodservice portion sizes, including fast-food, non-fast-food franchise restaurants, and privately-owned restaurants, as well as individually packaged and ready-to-eat prepared foods have increased over the past 20 years (Schwartz and ByrdBredbenner, 2006). In 2003, Young and Nestle examined portion size in the US marketplace and compared it to federal standards developed by the US Department of Agriculture (USDA) and the Food and Drug Administration (FDA). The study found that products such as bagels and sodas exceeded the federal standard portion size by at least a factor of two, and some cookies were up to eight times the recommended portion size for that food item. They also found that fast-food chains offered portions that were 2e5 times larger than when their products were originally launched, supportive of increasing consumer expectations for portion sizes. Products such as these lead to portion distortion, thereby increasing consumption norms (Schwartz and Byrd-Bredbenner, 2006). These authors suggest that it is doubtful that portion sizes both in restaurants and packaged/prepared foods will decrease, and thus the consumer must make more considered choices to help regulate caloric intake.
74% more calories of juice or soft drink consumed. Similarly, in a second study, bartenders poured 27% more liquid into 12 oz. ‘tumbler’ glasses than into 12 oz. ‘highball’ glasses. The results also suggested that more experienced bartenders did not over pour as much as did less experienced bartenders, though they still had a tendency to pour more into short glasses than tall glasses of the same volumes. The tendency to pour more into the short glasses could manifest itself into consuming more than intended. Van Ittersum and Wansink (2007) also suggest that the size of plates, bowls, and spoons can contribute to a context effect known as the Delboeuf illusion (Fig. 2). The Delboeuf illusion, which is driven by the relative size of two concentric circles, is likened to the amount of empty space on a plate of food. For example, the same amount of food appears to be a smaller portion if it is served on large plate rather than a smaller plate. The same idea can be applied to other dishware and utensils.
Dishware and utensil sizes Further compounding the problem of larger consumption norms, dishware has increased in size, causing difficulty in estimating appropriate portion sizes. The verticalehorizontal illusion and the Delboeuf illusion contribute to these difficulties (Van Ittersum and Wansink, 2007; Wansink and Van Ittersum, 2003). The verticale horizontal illusion (Fig. 1), which affects liquid portion sizes, gives the impression that a tall, slender glass holds more liquid than a short, wide glass (Wansink and Van Ittersum, 2003). This illusion holds true for disbursement of liquids as well as consumption. This study demonstrated that both children and adults consumed more when drinking from a short, wide glass than from a tall, slender glass, even though they perceived the opposite to be true. In the study of children, this corresponded to an increase of
Fig. 2. An illustration of the Delboeuf illusion: the same amount of food appears to be a smaller portion if served on a larger plate rather than a smaller plate.
Fig. 1. An illustration of vertical-horizontal illusion: a tall, slender glass appears to hold more volume than a short, wide glass even though both glasses hold the same volume.
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Van Ittersum and Wansink (2007) remind us that consumers, regardless of age and training, are susceptible to these types of illusions. A larger bowl or a larger spoon can fool even highly educated nutritional experts into taking larger portions. Wansink, Van Ittersum, and Painter (2006) used nutrition experts and graduate students from the Department of Food Science and Nutritional Science at the University of Illinois Urbana-Champaign to illustrate this problem. These subjects served themselves 31% more ice cream when given a large ice cream dish compared to a small ice cream dish. This corresponded to an average consumption of 127 more calories from the large bowl over the small bowl. This difference was exacerbated when providing subjects larger serving utensils as well; when provided a large bowl (34 oz.) and large spoon (3 oz.), subjects served themselves 57% more ice cream than those serving themselves from a small bowl (17 oz.) and small spoon (2 oz.) combination. Environmental cues from the larger consumption norms and larger package sizes can even impact unpalatable food. In 2005, Wansink and Kim found that moviegoers ate 33.6% more 2-week old stale popcorn from a large-sized container (240 g) than from a medium-sized container (120 g), despite the fact that they had just eaten dinner before the movie. In a similar study, test subjects ate 51% more popcorn from large-sized container than from medium-sized containers (Wansink and Park, 2001). These moviegoers had just finished lunch and were also eating stale popcorn. These studies suggest that portion size directly influences food intake, regardless of hunger level and taste preferences. Wansink and Van Ittersum (2007) recommend removing large packages, large servings, and large dinnerware from our everyday lives in an effort to counteract tendencies toward over-consumption. Using smaller serving spoons and containers, bowls, plates, glasses, and packages can assist in better controlling our portions. Simply being aware that the problem exists may not be enough to control our intake. Consumption of foods: awareness and convenience In addition to growing consumption norms and dishware illusions, other environmental distractions such as TV viewing can influence both food selection and intake. Blass et al. (2006) recruited 20 undergraduates to analyze the effect of TV watching on food intake. The students were split into two groups: one group ate pizza while watching TV or listening to opera music over two sessions, while the other group ate macaroni and cheese under the same conditions. Both groups ate significantly more food when they watched TV; the pizza group ate 36% more and the macaroni and cheese group ate 71% more than their respective opera-listening groups. The increase in caloric intake for both of these groups is substantial. Pizza-eaters watching TV tended to wait less time between helping themselves to another slice. With the macaroni and cheese group, the food
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was eaten at both a faster rate and for a longer period of time. It is possible that there is a lack of consumption awareness exhibited by consumers while watching TV. Eating while distracted could impair consumers’ abilities to monitor their food intake. Although listening to classical music may be less distracting than watching TV, Stroebele and de Castro (2006) found that listening to any type of music while eating was associated with greater food intake. Seventy-eight college students from Georgia State University recorded their environment and eating behaviors for one week. The students detailed their food choices, portion sizes, location of meal, time of day, meal duration, the friends they ate with, and if there was music present during the meal. If music was present, the music speed and volume were rated on 7-point scales. The researchers found that meal sizes with music were significantly greater than those without music (3008 kJ and 2561 kJ, respectively; p < 0.01). Perhaps the cause of greater amounts consumed was due to meal duration; meals were significantly longer with music than without (40.51 min and 29.25 min respectively; p < 0.05). Similarly, fluid intake was significantly greater with music than without (431 g and 338 g respectively; p < 0.05). Although Stroebele and de Castro’s results did not find significant differences due to music speed and volume, previous studies showed that music tempo increased drinking rate (McElrea and Standing, 1992) and loud music increased the amount consumed (McCarron and Tierney, 1989). Slow music is also not the answer to reducing food intake, as it was shown to increase meal duration and amount consumed (Caldwell and Hibbert, 2002). Whether it be music, TV, or even eating with friends, these distractions can influence the consumer’s ability to react to cues of satiety and fullness. Food accessibility may also be a factor contributing to greater consumption; the more accessible the food, the more that is consumed. Painter, Wansink, and Hieggelke (2002) examined consumption of chocolate candies under three conditions: where candies were visible and convenient, not visible but convenient, and visible but inconvenient. Participants ate the most candies when they were visible and convenient, and ate the least when they were visible but inconvenient. This demonstrates the tendency to eat more food when it is visible and within reach, two conditions that can be met while watching TV, for example. Combined, being unaware of the amount that we consume and consuming foods that are conveniently available can contribute to excessive food intake. Sensory-specific satiety as it relates to food intake The first portion of this paper analyzed the environmental cues that contribute to over-consumption. In this section, the body’s biological responses to food during and after consumption will be examined, specifically analyzing how SSS contributes to meal termination and how it may aid in portion control.
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Eating is a pleasurable activity, and the amount of pleasure that is obtained from eating may provide a key to how over-consumption can be controlled. Sensory-specific satiety (SSS) has been described as the decrease in the reward gained from intake of a specific food (Rolls, 1984). The degree of SSS can affect when a person terminates intake of a specific food (Hetherington, 1996), though the reward for consuming other types of foods will remain high (Rolls, 1984). Portion size, energy density, macronutrients, and variety may affect the feeling of being satiated. These conditions will be examined in relation to SSS. In general, SSS is rated as the difference between hedonic ratings of a test food consumed relative to the decrease in hedonic ratings for other uneaten foods. The reader is directed to specific citations for full details on calculation of SSS scores for individual research papers. Portion control and energy intake It has been hypothesized that consumption of small-portioned foods may help decrease overall intake when compared to consumption of large-portioned foods. Kral and Rolls (2004) review a number of previous studies that also support the theory that when larger portions are served to subjects, their energy intake increases due to increased consumption. Examining overall intake in relation to SSS may lead to some strategies for better controlling overconsumption. Weijzen, Liem, Zandstra, and de Graaf (2008) investigated the effect of portion sizes on SSS and overall intake. Subjects were asked to eat either nibble-sized (1.45 g) snacks or bar-sized (16.0 g) snacks ad libitum (both had equivalent energy density), and researchers measured subjects’ SSS and intake amounts. Motivational and hedonic ratings of both sizes of snacks decreased with consumption, indicating development of SSS. Subjects consumed 12% less of the nibble-sized snacks than bar-sized snacks under the controlled condition, and did not significantly differ in their SSS scores. The authors suggest that perhaps the subjects underestimated the size of the bars compared to the nibbles, which resulted in eating more of the bar snack. This reaffirms the earlier discussion about consumers ingesting more from larger-sized restaurant portions (Rolls, 2003) and retail packaged portions (Wansink, 1996), and thus controlling portion size can significantly impact food intake. The relationship between volume of food and energy intake and the impact on SSS can be more complex. Bell, Roe, and Rolls (2003) questioned whether SSS was affected by volume and/or energy content of a food. Subjects were asked to rate pleasantness before and after consumption of three different types of liquid foods. The foods were various combinations of volume (low or high) and caloric value (low or high). All samples contained the same macronutrient composition and were rated the same for initial palatability. Researchers found that both high and low energy density liquid foods had the same effect on
SSS when volume remained constant. However, when the food volume was doubled and energy density remained constant, subjects’ hedonic ratings of foods decreased significantly while SSS increased. As a result, volume may have more of an impact on termination of eating than energy density. Similarly, Miller, Bell, Pelkman, Peters, and Rolls (2000) found that development of SSS was similar for regular full-fat chips and olestra-containing chips after daily consumption over a 4-week period. So despite a difference in energy density and fat content for the two foods, SSS was not affected. These studies have examined portion size or energy density separately. A review of several studies confirms that when energy density and portion size are both increased within a meal, their effects independently increase energy intake (Kral and Rolls, 2004). It is suggested that decreasing energy intake while decreasing volume consumed in a meal’s first course can lead to decreased energy intake for the whole meal (Rolls, Roe, and Meengs, 2004). Again, this reveals a potential strategy for controlling overall food intake. While it is possible that consuming high volume and low energy density foods may result in satiation with consuming fewer calories, it is suggested that the relationship between consumption and energy density is quite complex, with many other psychological, physiological, and environmental influences involved. How distraction affects SSS Earlier in this discussion it was stated that environmental distractions, specifically TV viewing, play a significant role in over-consumption. Concrete explanations for this phenomenon still remain unclear. However, many hypotheses exist as to why distractions affect over-consumption of foods. One speculation applies the observation that individuals can ‘‘forget to eat’’ when engrossed in a task. Thus it is plausible that in the presence of food, distractions may limit an individual’s ability to monitor signals associated with satiety. In 2006, Brunstrom and Mitchell explored this hypothesis with two experiments. Initially, the researchers provided food to 88 females whom were either asked to sit in silence or distracted with a computer game. They found that the participants who sat in silence had rated larger differences in their desire to eat and fullness than the distracted participants. The second experiment used a similar method but asked participants to rate desire to eat, pleasantness, and intensity of two eaten to two uneaten foods before eating, immediately after, and at 5 and 10 min after eating. Non-distracted participants reported effects of SSS; their desire to consume the eaten food decreased while the uneaten food increased. Distracted participants maintained their desire to eat all foods and that desire remained at both 5 and 10 min after eating. The researchers speculate that distraction slows the development of SSS, which can lead to prolonged mealtimes or reduced time between meals and ultimately overeating. Therefore, regardless of the type of distraction during mealtime,
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such as TV viewing or playing a computer game, over-consumption is still the resulting effect. However, further investigations are suggested to understand the variety of distractions that lead to overeating. Variety of available foods Studies of SSS indicate that as a specific food is being consumed, interest level in continuing to eat that particular food declines. But what about alternative foods? Being satiated with one food may result in interest in or cravings for another. Gendall, Joyce, and Abbott (1999) have applied this idea to macronutrient content, and their work demonstrates that it can play an important role in food cravings, binge eating, and overall food intake. Some popular diet plans suggest reducing carbohydrate intake in an effort to lose weight. The results of Gendall and colleagues’ work may recommend against this type of low-carbohydrate diet for some individuals, as protein-rich meals may induce carbohydrate cravings. In this study, subjects were fed one of three meals differing in protein and carbohydrate content yet similar in energy content, fiber content, and total weight; the meals were described as protein-rich, carbohydrate-rich, and ‘‘mixed’’ meals. Results showed that after eating the protein-rich meal, subjects craved sweet carbohydrate-rich foods significantly more than after eating either the carbohydrate-rich or the mixed meals. Further, when permitted unlimited eating after the protein meal, subjects ate more energy-dense carbohydrate- and fat-laden foods. Thus, eating significant amounts of one type of macronutrient, such as protein, may not enable susceptible consumers to control cravings for another macronutrient, such as carbohydrates. This leads to questioning the long-term success of low-carbohydrate diet programs in maintaining a healthful lifestyle. While Gendall, Joyce, and Abbott (1999) are unable to determine if the effects in the study were due to SSS or other cognitive effects, a balanced diet of both protein and carbohydrates seems to fulfill nutritional needs and create the feeling of overall satiety. The effect of eating fat-rich meals in the context of a macronutrient was not examined in this study, and warrants further investigation. Although macronutrient-balanced diets have been shown to provide the feeling of satiety, subjects’ satiation was specific to the meal provided. In the real world, consumers have a wide variety of food choices even within a single category of products. Maier, Vickers, and Inman (2007) analyzed the development of SSS for various potato chips and found that liking, the desire for variety, and the desire for a food creating less SSS drove panelists’ subsequent potato chip choices. Participants were given one of six flavors of potato chips and ate an 80 g serving. At the end of each session, participants chose one of the six varieties of potato chip variety for additional consumption. Though liking of the flavor was a factor, it was also found that subjects chose additional consumption of varieties that were dissimilar to the one they had recently eaten. These results suggest
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that, in turn, consumption of a dissimilar product could be greater than consumption of more of the same product. When applying this hypothesis to a real-life situation, one might expect a consumer to eat less food in general when fewer food choices are available. Raynor, Niemeier, and Wing (2006) demonstrated that limiting snack food variety and creating SSS were an effective weight loss tool during an 8-week study. Overweight test subjects participated in a weight loss intervention study, and were split into two groups: the first group was permitted to eat only one chosen snack food for the entire 8-week period, while the second group was permitted eat one snack per day but with no limit on the variety of choices for that snack. When consuming only one chosen snack food, hedonic ratings of the snack decreased over time whereas hedonic ratings did not change for the composite snack food. Weight loss was seen in both groups, but no significant difference was found; both groups were given caloric goals to meet for each day. Long-term SSS and monotony resulted from limiting snack food variety during the course of the study. As SSS is an innate characteristic (Rolls, 2005), individuals should use it to their advantage as a weight loss tool. In 2005, Weenen, Stafleu, and de Graaf used 25 women to measure post-prandial persistence of SSS. Subjects initially rated their appetite, then tasted and rated the pleasantness of cheese biscuits and pears in light syrup. Subsequently, subjects were given either the cheese biscuits or pears in light syrup to eat to satiety. The participants then tasted and rated both products at 0, 25, 50, 75, 100, and 125 min after eating. Subjects also took both products home to evaluate pleasantness for seven more days. Results showed that the food products eaten to satiety were significantly less liked 125 min after consuming. Furthermore, pleasantness ratings for the cheese biscuits eaten to satiety were significantly lower on days 2e7. Therefore, SSS can help prevent people from eating a specific food for 2 h and has lasting effects for days. This provides evidence that SSS is a possible weight loss tool because it prevents overeating by causing both short term and long-term satiety and lengthening the time between meals. However, because SSS is specific to only one food at a time, variety must be limited in order for SSS to be an effective solution to overeating. Some may wonder if SSS affects obese people differently than normal-weight individuals especially if it is a possible weight loss strategy. Snoek, Huntjens, van Gemert, de Graaf, and Weenen (2004) explored this idea and hypothesized that sensitivity to SSS differed between obese and normal-weight individuals. However, their research found the contrary. The study compared pleasantness scores of 21 obese to 23 normal-weight women before and after eating a test meal. All lunches induced SSS; the pleasantness scores for the eaten foods decreased equally in both the obese and normal-weight women. Although, the SSS was not significantly different between the two groups, the researchers did find a difference in residual
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hunger. Even though the obese women ate the same amount of food as the normal-weight women, and had a similar change in liking scores, the obese women had larger appetite ratings after eating their meals. This suggested that they still wanted more food, but the difference was in ‘‘wanting’’, not in ‘‘liking.’’ This reaffirms the earlier recommendation that SSS can and should be used as a weight loss tool, but it must be used in conjunction with limiting variety. When variety is available, subjects will simply eat more food, resulting in consuming more calories. Raynor and Epstein (2001) further solidified the consequences of food variety as it relates to SSS after they reviewed 39 studies that examined dietary variety, intake, and body composition. They concluded that variety increases food consumption and is associated with obesity. They name SSS as the cause of over-consumption when a variety of food is present. As a result, in order to utilize SSS as a weight loss tool, it is imperative that the diet remains monotonous and macronutrient-balanced. Since SSS in an innate quality to control food intake, it should be utilized to one’s advantage. Conclusions This review has examined many environmental and biological factors that cause over-consumption, which in turn contributes to the obesity epidemic. Because eating is an individual decision and act, physically controlling consumption is not a viable solution. However, awareness of environmental cues such as illusions, distractions, portion sizes, and variety may help consumers combat overconsumption. In addition, employing the theory of SSS by limiting food variety is a possible tactic for losing weight. This is an area which requires further investigation regarding its direct affect on obesity. Overall, the age-old recipe of expending more calories than are consumed is still the simplest solution for losing weight. References Bell, E. A., Roe, L. S., & Rolls, B. J. (2003). Sensory-specific satiety is affected more by volume than by energy content of a liquid food. Physiology and Behavior, 78, 593e600. Berthoud, H. R., Sutton, G. M., Townsend, R. L., Patterson, L. M., & Zheng, H. (2006). Brainstem mechanisms integrating gut-derived satiety signals and descending forebrain information in the control of meal size. Physiology and Behavior, 89, 517e524. Blass, E. M., Anderson, D. R., Kirkorian, H. L., Pempek, T. A., Price, I., & Koleini, M. F. (2006). On the road to obesity: television viewing increases intake of high-density foods. Physiology and Behavior, 88, 597e604. Brunstrom, J. M., & Mitchell, G. L. (2006). Effects of distraction on the development of satiety. British Journal of Nutrition, 96, 761e769. Caldwell, C., & Hibbert, S. A. (2002). The influence of music tempo and musical preference on restaurant patron’s behavior. Psychology and Marketing, 19, 895e917. Gendall, K. A., Joyce, P. R., & Abbott, R. M. (1999). The effects of meal composition on subsequent craving and binge eating. Addictive Behaviors, 24(3), 305e315.
Hetherington, M. M. (1996). Sensory-specific satiety and its importance in meal termination. Neuroscience and Biobehavioral Reviews, 20(1), 113e117. Kral, T. V. E., & Rolls, B. J. (2004). Energy density and portion size: their independent and combined effects on energy intake. Physiology and Behavior, 82, 131e138. Maier, A., Vickers, Z., & Inman, J. J. (2007). Sensory-specific satiety, its crossovers, and subsequent choice of potato chip flavors. Appetite, 49, 419e428. McCarron, A., & Tierney, K. J. (1989). The effect of auditory stimulation in the consumption of soft drinks. Appetite, 13, 155e159. McElrea, H., & Standing, F. (1992). Fast music causes fast drinking. Perceptual and Motor Skills, 75, 362. Miller, D. L., Bell, E. A., Pelkman, C. L., Peters, J. C., & Rolls, B. J. (2000). Effects of dietary fat, nutrition labels, and repeated consumption on sensory-specific satiety. Physiology and Behavior, 71, 153e158. Painter, J. E., Wansink, B., & Hieggelke, J. B. (2002). How visibility and convenience influence candy consumption. Appetite, 38, 237e238. Raynor, H. A., & Epstein, L. H. (2001). Dietary variety, energy regulation, and obesity. Psychological Bulletin, 127(3), 325e341. Raynor, H. A., Niemeier, H. M., & Wing, R. R. (2006). Effect of limiting snack food variety on long-term sensory-specific satiety and monotony during obesity treatment. Eating Behaviors, 7, 1e14. Rolls, B. J. (2003). The supersizing of America: portion size and the obesity epidemic. Nutrition Today, 38(2), 42e53. Rolls, B. J., Roe, L. S., & Meengs, J. S. (2004). Salad and satiety: energy density and portion size of a first-course salad affect energy intake at lunch. Journal of the American Dietetic Association, 104(10), 1570e1576. Rolls, E. T. (1984). The neurophysiology of feeding. International Journal of Obesity, 8(Suppl. 1), 139e150. Rolls, E. T. (2005). Taste, olfactory, and food texture processing in the brain, and the control of the food intake. Physiology and Behavior, 85, 45e56. Savage, J. S., Fisher, J. O., & Birch, L. L. (2007). Parental influence on eating behavior: conception to adolescence. Journal of Law, Medicine and Ethics, 35(1), 22e34. Schwartz, J., & Byrd-Bredbenner, C. (2006). Portion distortion: typical portion sizes selected by young adults. Journal of the American Dietetic Association, 106(9), 1412e1418. Snoek, H. M., Huntjens, L., van Gemert, L. J., de Graaf, C., & Weenen, H. (2004). Sensory-specific satiety in obese and normalweight women. The American Journal of Clinical Nutrition, 80, 823e831. Stroebele, N., & de Castro, J. M. (2006). Listening to music while eating is related to increases in people’s food intake and meal duration. Appetite, 47, 285e289. Van Ittersum, K., & Wansink, B. (2007). Do children really prefer large portions? Visual illusions bias their estimates and intake. Journal of the American Dietetic Association, 107(7), 1107e1110. Wansink, B. (1996). Can package size accelerate usage volume? Journal of Marketing, 60, 1e14. Wansink, B., & Kim, J. (2005). Bad popcorn in big buckets: portion size can influence intake as much as taste. Journal of Nutrition Education and Behavior, 37, 242e245. Wansink, B., & Park, S. B. (2001). At the movies: how external cues and perceived taste impact consumption volume. Food Quality and Preference, 12, 69e74. Wansink, B., & Van Ittersum, K. (2003). Bottoms up! The influence of elongation on pouring and consumption volume. Journal of Consumer Research, 30, 455e463. Wansink, B., & Van Ittersum, K. (2007). Portion size me: downsizing our consumption norms. Journal of the American Dietetic Association, 107(7), 1103e1106.
J.M. Smith, T.L. Ditschun / Trends in Food Science & Technology 20 (2009) 271e277 Wansink, B., Van Ittersum, K., & Painter, J. E. (2006). Ice cream illusions: bowls, spoons, and self-served portion sizes. American Journal of Preventative Medicine, 31(3), 240e243. Weenen, H., Stafleu, A., & de Graaf, C. (2005). Dynamic aspects of liking: post-prandial persistence of sensory specific satiety. Food Quality and Preference, 16, 528e535.
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Weijzen, P. L. G., Liem, D. G., Zandstra, E. H., & de Graaf, C. (2008). Sensory specific satiety and intake: the difference between nibbleand bar-sized snacks. Appetite, 50(2e3), 435e442. Young, L. R., & Nestle, M. (2003). Expanding portion sizes in the US marketplace: implications for nutrition counseling. Journal of the American Dietetic Association, 103(2), 231e234.
Review
Controlling satiety: how environmental factors influence food intake Janna M. Smith* and Tanya L. Ditschun Senomyx Inc., 4767 Nexus Centre Drive, San Diego, CA 92121, USA (Neutrogena Corp., 5760 W. 96th Street, Los Angeles, CA 90045, USA. Fax: D1 310 216 5399; e-mail: [email protected]) The obesity epidemic is fueled by over-consumption of food. Increasing portion sizes have distorted perceptions as to what constitutes a normal meal size. Many environmental cues contribute to the growing portion norms such as restaurant meal size, economy sized grocery packages, and illusions produced from larger dishware and utensil sizes. This review examines factors contributing to portion distortion and the role of sensory-specific satiety (SSS) in consumption. It is proposed that SSS could be used to control food intake when used in conjunction with environmental cues, including portion control, avoiding distraction while eating, and variety of available foods.
Understanding sensory-specific satiety and its role in controlling food intake Over-consumption of food and lack of physical activity are directly related to the obesity epidemic facing society. Obesity is far-reaching, affecting the well-being of children and adults, rapidly changing our health needs and increasing the burden on our healthcare systems. Some food manufacturers have responded to consumer concerns about healthful eating by creating foods that are lower in sodium, sugar, and fats, yet these efforts are not enough to control the increasing rates of obesity and additional strategies are needed to counteract overeating. * Corresponding author. 0924-2244/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.tifs.2009.03.009
Sensory-specific satiety (SSS) is a condition we experience during the eating process that may be a possible strategy to combat overeating. Specifically, SSS is the decrease in the pleasure derived from continued consumption of a food (Rolls, 1984). This is an innate mechanism (Berthoud, Sutton, Townsend, Patterson, & Zheng, 2006; Rolls, 2005) which is strongest during the 2 h following consumption, and can affect liking ratings for over 24 h (Weenen, Stafleu, & Graaf, 2005). SSS combined with other consumption strategies such as limiting variety, exercising portion control, and overall awareness of environmental eating cues, may be the recipe to counteract overeating. In this review, several significant factors contributing to over-consumption of food are examined, and the use of SSS as an innate tool to controlling intake is explored. Factors affecting food intake Increased portion sizes have distorted perceptions as to what amount of food is ‘‘normal’’ or of appropriate size for consumption at a meal (Wansink and Van Ittersum, 2007). Together with an inability to adequately monitor or estimate caloric intake, the combination can result in over-consumption, which can be a significant contributor to obesity. This distortion of appropriate portion sizes can begin as early as 3 years of age (Savage, Fisher, & Birch, 2007). Both retail food and foodservice industries can share the blame; consumers have been shown to eat 30e50% more from larger-sized restaurant portions compared to smaller portions (Rolls, 2003), and 20e40% more from larger-sized packages than smaller packages (Wansink, 1996). While package size, serving size, and dishware size influence how much we eat, socioeconomic status and education level of the consumer have not been shown to aid in counteracting these influences. Even education about the propensity toward portion distortion cannot make one any less subject to this phenomenon (Wansink, Van Ittersum, & Painter, 2006). Portion control Portion control is perhaps one of the most important components, if not the most important component of weight loss, and many leading commercial diets advocate portion control as a weight loss tool. However, our consumption norms are gradually increasing (Wansink and Van Ittersum, 2007), thereby making it harder for consumers to exercise portion control. Portion distortion is everywhere: in our
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supermarket ‘economy’ sizes, in restaurant portions far beyond recommended serving sizes and caloric needs, and even in our dishware, which has increased in size to accommodate larger portions. These factors will be examined as to how they relate to perceptions of what is a normal amount of food to consume. Retail and foodservice serving sizes Marketplace portions have been increasing steadily, thus increasing our expectations of portion size. Restaurant portion sizes have increased significantly from when they were first introduced to their current sizes (Young and Nestle, 2003). In 1955 a soda from McDonald’s was 7 fl. oz. in volume. Today McDonald’s offers a 12 fl. oz. ‘‘child-sized’’ soda, a 42 fl. oz. Supersize and several different sizes in between. What used to be a ‘Large’ soft drink at Burger King in 1954 is now a ‘Small’ soft drink, at 16 fl oz. Foodservice portion sizes, including fast-food, non-fast-food franchise restaurants, and privately-owned restaurants, as well as individually packaged and ready-to-eat prepared foods have increased over the past 20 years (Schwartz and ByrdBredbenner, 2006). In 2003, Young and Nestle examined portion size in the US marketplace and compared it to federal standards developed by the US Department of Agriculture (USDA) and the Food and Drug Administration (FDA). The study found that products such as bagels and sodas exceeded the federal standard portion size by at least a factor of two, and some cookies were up to eight times the recommended portion size for that food item. They also found that fast-food chains offered portions that were 2e5 times larger than when their products were originally launched, supportive of increasing consumer expectations for portion sizes. Products such as these lead to portion distortion, thereby increasing consumption norms (Schwartz and Byrd-Bredbenner, 2006). These authors suggest that it is doubtful that portion sizes both in restaurants and packaged/prepared foods will decrease, and thus the consumer must make more considered choices to help regulate caloric intake.
74% more calories of juice or soft drink consumed. Similarly, in a second study, bartenders poured 27% more liquid into 12 oz. ‘tumbler’ glasses than into 12 oz. ‘highball’ glasses. The results also suggested that more experienced bartenders did not over pour as much as did less experienced bartenders, though they still had a tendency to pour more into short glasses than tall glasses of the same volumes. The tendency to pour more into the short glasses could manifest itself into consuming more than intended. Van Ittersum and Wansink (2007) also suggest that the size of plates, bowls, and spoons can contribute to a context effect known as the Delboeuf illusion (Fig. 2). The Delboeuf illusion, which is driven by the relative size of two concentric circles, is likened to the amount of empty space on a plate of food. For example, the same amount of food appears to be a smaller portion if it is served on large plate rather than a smaller plate. The same idea can be applied to other dishware and utensils.
Dishware and utensil sizes Further compounding the problem of larger consumption norms, dishware has increased in size, causing difficulty in estimating appropriate portion sizes. The verticalehorizontal illusion and the Delboeuf illusion contribute to these difficulties (Van Ittersum and Wansink, 2007; Wansink and Van Ittersum, 2003). The verticale horizontal illusion (Fig. 1), which affects liquid portion sizes, gives the impression that a tall, slender glass holds more liquid than a short, wide glass (Wansink and Van Ittersum, 2003). This illusion holds true for disbursement of liquids as well as consumption. This study demonstrated that both children and adults consumed more when drinking from a short, wide glass than from a tall, slender glass, even though they perceived the opposite to be true. In the study of children, this corresponded to an increase of
Fig. 2. An illustration of the Delboeuf illusion: the same amount of food appears to be a smaller portion if served on a larger plate rather than a smaller plate.
Fig. 1. An illustration of vertical-horizontal illusion: a tall, slender glass appears to hold more volume than a short, wide glass even though both glasses hold the same volume.
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Van Ittersum and Wansink (2007) remind us that consumers, regardless of age and training, are susceptible to these types of illusions. A larger bowl or a larger spoon can fool even highly educated nutritional experts into taking larger portions. Wansink, Van Ittersum, and Painter (2006) used nutrition experts and graduate students from the Department of Food Science and Nutritional Science at the University of Illinois Urbana-Champaign to illustrate this problem. These subjects served themselves 31% more ice cream when given a large ice cream dish compared to a small ice cream dish. This corresponded to an average consumption of 127 more calories from the large bowl over the small bowl. This difference was exacerbated when providing subjects larger serving utensils as well; when provided a large bowl (34 oz.) and large spoon (3 oz.), subjects served themselves 57% more ice cream than those serving themselves from a small bowl (17 oz.) and small spoon (2 oz.) combination. Environmental cues from the larger consumption norms and larger package sizes can even impact unpalatable food. In 2005, Wansink and Kim found that moviegoers ate 33.6% more 2-week old stale popcorn from a large-sized container (240 g) than from a medium-sized container (120 g), despite the fact that they had just eaten dinner before the movie. In a similar study, test subjects ate 51% more popcorn from large-sized container than from medium-sized containers (Wansink and Park, 2001). These moviegoers had just finished lunch and were also eating stale popcorn. These studies suggest that portion size directly influences food intake, regardless of hunger level and taste preferences. Wansink and Van Ittersum (2007) recommend removing large packages, large servings, and large dinnerware from our everyday lives in an effort to counteract tendencies toward over-consumption. Using smaller serving spoons and containers, bowls, plates, glasses, and packages can assist in better controlling our portions. Simply being aware that the problem exists may not be enough to control our intake. Consumption of foods: awareness and convenience In addition to growing consumption norms and dishware illusions, other environmental distractions such as TV viewing can influence both food selection and intake. Blass et al. (2006) recruited 20 undergraduates to analyze the effect of TV watching on food intake. The students were split into two groups: one group ate pizza while watching TV or listening to opera music over two sessions, while the other group ate macaroni and cheese under the same conditions. Both groups ate significantly more food when they watched TV; the pizza group ate 36% more and the macaroni and cheese group ate 71% more than their respective opera-listening groups. The increase in caloric intake for both of these groups is substantial. Pizza-eaters watching TV tended to wait less time between helping themselves to another slice. With the macaroni and cheese group, the food
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was eaten at both a faster rate and for a longer period of time. It is possible that there is a lack of consumption awareness exhibited by consumers while watching TV. Eating while distracted could impair consumers’ abilities to monitor their food intake. Although listening to classical music may be less distracting than watching TV, Stroebele and de Castro (2006) found that listening to any type of music while eating was associated with greater food intake. Seventy-eight college students from Georgia State University recorded their environment and eating behaviors for one week. The students detailed their food choices, portion sizes, location of meal, time of day, meal duration, the friends they ate with, and if there was music present during the meal. If music was present, the music speed and volume were rated on 7-point scales. The researchers found that meal sizes with music were significantly greater than those without music (3008 kJ and 2561 kJ, respectively; p < 0.01). Perhaps the cause of greater amounts consumed was due to meal duration; meals were significantly longer with music than without (40.51 min and 29.25 min respectively; p < 0.05). Similarly, fluid intake was significantly greater with music than without (431 g and 338 g respectively; p < 0.05). Although Stroebele and de Castro’s results did not find significant differences due to music speed and volume, previous studies showed that music tempo increased drinking rate (McElrea and Standing, 1992) and loud music increased the amount consumed (McCarron and Tierney, 1989). Slow music is also not the answer to reducing food intake, as it was shown to increase meal duration and amount consumed (Caldwell and Hibbert, 2002). Whether it be music, TV, or even eating with friends, these distractions can influence the consumer’s ability to react to cues of satiety and fullness. Food accessibility may also be a factor contributing to greater consumption; the more accessible the food, the more that is consumed. Painter, Wansink, and Hieggelke (2002) examined consumption of chocolate candies under three conditions: where candies were visible and convenient, not visible but convenient, and visible but inconvenient. Participants ate the most candies when they were visible and convenient, and ate the least when they were visible but inconvenient. This demonstrates the tendency to eat more food when it is visible and within reach, two conditions that can be met while watching TV, for example. Combined, being unaware of the amount that we consume and consuming foods that are conveniently available can contribute to excessive food intake. Sensory-specific satiety as it relates to food intake The first portion of this paper analyzed the environmental cues that contribute to over-consumption. In this section, the body’s biological responses to food during and after consumption will be examined, specifically analyzing how SSS contributes to meal termination and how it may aid in portion control.
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Eating is a pleasurable activity, and the amount of pleasure that is obtained from eating may provide a key to how over-consumption can be controlled. Sensory-specific satiety (SSS) has been described as the decrease in the reward gained from intake of a specific food (Rolls, 1984). The degree of SSS can affect when a person terminates intake of a specific food (Hetherington, 1996), though the reward for consuming other types of foods will remain high (Rolls, 1984). Portion size, energy density, macronutrients, and variety may affect the feeling of being satiated. These conditions will be examined in relation to SSS. In general, SSS is rated as the difference between hedonic ratings of a test food consumed relative to the decrease in hedonic ratings for other uneaten foods. The reader is directed to specific citations for full details on calculation of SSS scores for individual research papers. Portion control and energy intake It has been hypothesized that consumption of small-portioned foods may help decrease overall intake when compared to consumption of large-portioned foods. Kral and Rolls (2004) review a number of previous studies that also support the theory that when larger portions are served to subjects, their energy intake increases due to increased consumption. Examining overall intake in relation to SSS may lead to some strategies for better controlling overconsumption. Weijzen, Liem, Zandstra, and de Graaf (2008) investigated the effect of portion sizes on SSS and overall intake. Subjects were asked to eat either nibble-sized (1.45 g) snacks or bar-sized (16.0 g) snacks ad libitum (both had equivalent energy density), and researchers measured subjects’ SSS and intake amounts. Motivational and hedonic ratings of both sizes of snacks decreased with consumption, indicating development of SSS. Subjects consumed 12% less of the nibble-sized snacks than bar-sized snacks under the controlled condition, and did not significantly differ in their SSS scores. The authors suggest that perhaps the subjects underestimated the size of the bars compared to the nibbles, which resulted in eating more of the bar snack. This reaffirms the earlier discussion about consumers ingesting more from larger-sized restaurant portions (Rolls, 2003) and retail packaged portions (Wansink, 1996), and thus controlling portion size can significantly impact food intake. The relationship between volume of food and energy intake and the impact on SSS can be more complex. Bell, Roe, and Rolls (2003) questioned whether SSS was affected by volume and/or energy content of a food. Subjects were asked to rate pleasantness before and after consumption of three different types of liquid foods. The foods were various combinations of volume (low or high) and caloric value (low or high). All samples contained the same macronutrient composition and were rated the same for initial palatability. Researchers found that both high and low energy density liquid foods had the same effect on
SSS when volume remained constant. However, when the food volume was doubled and energy density remained constant, subjects’ hedonic ratings of foods decreased significantly while SSS increased. As a result, volume may have more of an impact on termination of eating than energy density. Similarly, Miller, Bell, Pelkman, Peters, and Rolls (2000) found that development of SSS was similar for regular full-fat chips and olestra-containing chips after daily consumption over a 4-week period. So despite a difference in energy density and fat content for the two foods, SSS was not affected. These studies have examined portion size or energy density separately. A review of several studies confirms that when energy density and portion size are both increased within a meal, their effects independently increase energy intake (Kral and Rolls, 2004). It is suggested that decreasing energy intake while decreasing volume consumed in a meal’s first course can lead to decreased energy intake for the whole meal (Rolls, Roe, and Meengs, 2004). Again, this reveals a potential strategy for controlling overall food intake. While it is possible that consuming high volume and low energy density foods may result in satiation with consuming fewer calories, it is suggested that the relationship between consumption and energy density is quite complex, with many other psychological, physiological, and environmental influences involved. How distraction affects SSS Earlier in this discussion it was stated that environmental distractions, specifically TV viewing, play a significant role in over-consumption. Concrete explanations for this phenomenon still remain unclear. However, many hypotheses exist as to why distractions affect over-consumption of foods. One speculation applies the observation that individuals can ‘‘forget to eat’’ when engrossed in a task. Thus it is plausible that in the presence of food, distractions may limit an individual’s ability to monitor signals associated with satiety. In 2006, Brunstrom and Mitchell explored this hypothesis with two experiments. Initially, the researchers provided food to 88 females whom were either asked to sit in silence or distracted with a computer game. They found that the participants who sat in silence had rated larger differences in their desire to eat and fullness than the distracted participants. The second experiment used a similar method but asked participants to rate desire to eat, pleasantness, and intensity of two eaten to two uneaten foods before eating, immediately after, and at 5 and 10 min after eating. Non-distracted participants reported effects of SSS; their desire to consume the eaten food decreased while the uneaten food increased. Distracted participants maintained their desire to eat all foods and that desire remained at both 5 and 10 min after eating. The researchers speculate that distraction slows the development of SSS, which can lead to prolonged mealtimes or reduced time between meals and ultimately overeating. Therefore, regardless of the type of distraction during mealtime,
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such as TV viewing or playing a computer game, over-consumption is still the resulting effect. However, further investigations are suggested to understand the variety of distractions that lead to overeating. Variety of available foods Studies of SSS indicate that as a specific food is being consumed, interest level in continuing to eat that particular food declines. But what about alternative foods? Being satiated with one food may result in interest in or cravings for another. Gendall, Joyce, and Abbott (1999) have applied this idea to macronutrient content, and their work demonstrates that it can play an important role in food cravings, binge eating, and overall food intake. Some popular diet plans suggest reducing carbohydrate intake in an effort to lose weight. The results of Gendall and colleagues’ work may recommend against this type of low-carbohydrate diet for some individuals, as protein-rich meals may induce carbohydrate cravings. In this study, subjects were fed one of three meals differing in protein and carbohydrate content yet similar in energy content, fiber content, and total weight; the meals were described as protein-rich, carbohydrate-rich, and ‘‘mixed’’ meals. Results showed that after eating the protein-rich meal, subjects craved sweet carbohydrate-rich foods significantly more than after eating either the carbohydrate-rich or the mixed meals. Further, when permitted unlimited eating after the protein meal, subjects ate more energy-dense carbohydrate- and fat-laden foods. Thus, eating significant amounts of one type of macronutrient, such as protein, may not enable susceptible consumers to control cravings for another macronutrient, such as carbohydrates. This leads to questioning the long-term success of low-carbohydrate diet programs in maintaining a healthful lifestyle. While Gendall, Joyce, and Abbott (1999) are unable to determine if the effects in the study were due to SSS or other cognitive effects, a balanced diet of both protein and carbohydrates seems to fulfill nutritional needs and create the feeling of overall satiety. The effect of eating fat-rich meals in the context of a macronutrient was not examined in this study, and warrants further investigation. Although macronutrient-balanced diets have been shown to provide the feeling of satiety, subjects’ satiation was specific to the meal provided. In the real world, consumers have a wide variety of food choices even within a single category of products. Maier, Vickers, and Inman (2007) analyzed the development of SSS for various potato chips and found that liking, the desire for variety, and the desire for a food creating less SSS drove panelists’ subsequent potato chip choices. Participants were given one of six flavors of potato chips and ate an 80 g serving. At the end of each session, participants chose one of the six varieties of potato chip variety for additional consumption. Though liking of the flavor was a factor, it was also found that subjects chose additional consumption of varieties that were dissimilar to the one they had recently eaten. These results suggest
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that, in turn, consumption of a dissimilar product could be greater than consumption of more of the same product. When applying this hypothesis to a real-life situation, one might expect a consumer to eat less food in general when fewer food choices are available. Raynor, Niemeier, and Wing (2006) demonstrated that limiting snack food variety and creating SSS were an effective weight loss tool during an 8-week study. Overweight test subjects participated in a weight loss intervention study, and were split into two groups: the first group was permitted to eat only one chosen snack food for the entire 8-week period, while the second group was permitted eat one snack per day but with no limit on the variety of choices for that snack. When consuming only one chosen snack food, hedonic ratings of the snack decreased over time whereas hedonic ratings did not change for the composite snack food. Weight loss was seen in both groups, but no significant difference was found; both groups were given caloric goals to meet for each day. Long-term SSS and monotony resulted from limiting snack food variety during the course of the study. As SSS is an innate characteristic (Rolls, 2005), individuals should use it to their advantage as a weight loss tool. In 2005, Weenen, Stafleu, and de Graaf used 25 women to measure post-prandial persistence of SSS. Subjects initially rated their appetite, then tasted and rated the pleasantness of cheese biscuits and pears in light syrup. Subsequently, subjects were given either the cheese biscuits or pears in light syrup to eat to satiety. The participants then tasted and rated both products at 0, 25, 50, 75, 100, and 125 min after eating. Subjects also took both products home to evaluate pleasantness for seven more days. Results showed that the food products eaten to satiety were significantly less liked 125 min after consuming. Furthermore, pleasantness ratings for the cheese biscuits eaten to satiety were significantly lower on days 2e7. Therefore, SSS can help prevent people from eating a specific food for 2 h and has lasting effects for days. This provides evidence that SSS is a possible weight loss tool because it prevents overeating by causing both short term and long-term satiety and lengthening the time between meals. However, because SSS is specific to only one food at a time, variety must be limited in order for SSS to be an effective solution to overeating. Some may wonder if SSS affects obese people differently than normal-weight individuals especially if it is a possible weight loss strategy. Snoek, Huntjens, van Gemert, de Graaf, and Weenen (2004) explored this idea and hypothesized that sensitivity to SSS differed between obese and normal-weight individuals. However, their research found the contrary. The study compared pleasantness scores of 21 obese to 23 normal-weight women before and after eating a test meal. All lunches induced SSS; the pleasantness scores for the eaten foods decreased equally in both the obese and normal-weight women. Although, the SSS was not significantly different between the two groups, the researchers did find a difference in residual
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hunger. Even though the obese women ate the same amount of food as the normal-weight women, and had a similar change in liking scores, the obese women had larger appetite ratings after eating their meals. This suggested that they still wanted more food, but the difference was in ‘‘wanting’’, not in ‘‘liking.’’ This reaffirms the earlier recommendation that SSS can and should be used as a weight loss tool, but it must be used in conjunction with limiting variety. When variety is available, subjects will simply eat more food, resulting in consuming more calories. Raynor and Epstein (2001) further solidified the consequences of food variety as it relates to SSS after they reviewed 39 studies that examined dietary variety, intake, and body composition. They concluded that variety increases food consumption and is associated with obesity. They name SSS as the cause of over-consumption when a variety of food is present. As a result, in order to utilize SSS as a weight loss tool, it is imperative that the diet remains monotonous and macronutrient-balanced. Since SSS in an innate quality to control food intake, it should be utilized to one’s advantage. Conclusions This review has examined many environmental and biological factors that cause over-consumption, which in turn contributes to the obesity epidemic. Because eating is an individual decision and act, physically controlling consumption is not a viable solution. However, awareness of environmental cues such as illusions, distractions, portion sizes, and variety may help consumers combat overconsumption. In addition, employing the theory of SSS by limiting food variety is a possible tactic for losing weight. This is an area which requires further investigation regarding its direct affect on obesity. Overall, the age-old recipe of expending more calories than are consumed is still the simplest solution for losing weight. References Bell, E. A., Roe, L. S., & Rolls, B. J. (2003). Sensory-specific satiety is affected more by volume than by energy content of a liquid food. Physiology and Behavior, 78, 593e600. Berthoud, H. R., Sutton, G. M., Townsend, R. L., Patterson, L. M., & Zheng, H. (2006). Brainstem mechanisms integrating gut-derived satiety signals and descending forebrain information in the control of meal size. Physiology and Behavior, 89, 517e524. Blass, E. M., Anderson, D. R., Kirkorian, H. L., Pempek, T. A., Price, I., & Koleini, M. F. (2006). On the road to obesity: television viewing increases intake of high-density foods. Physiology and Behavior, 88, 597e604. Brunstrom, J. M., & Mitchell, G. L. (2006). Effects of distraction on the development of satiety. British Journal of Nutrition, 96, 761e769. Caldwell, C., & Hibbert, S. A. (2002). The influence of music tempo and musical preference on restaurant patron’s behavior. Psychology and Marketing, 19, 895e917. Gendall, K. A., Joyce, P. R., & Abbott, R. M. (1999). The effects of meal composition on subsequent craving and binge eating. Addictive Behaviors, 24(3), 305e315.
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Weijzen, P. L. G., Liem, D. G., Zandstra, E. H., & de Graaf, C. (2008). Sensory specific satiety and intake: the difference between nibbleand bar-sized snacks. Appetite, 50(2e3), 435e442. Young, L. R., & Nestle, M. (2003). Expanding portion sizes in the US marketplace: implications for nutrition counseling. Journal of the American Dietetic Association, 103(2), 231e234.