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Society and Food:Is there a connection between increasing portion sizes and obesity

Danielle Morrison

6 December 2010




            Over the past three years, “obesity has become a public health crisis in the United States” (Wang, Beydoun, Liang, Caballero, Kumanyika, 2008). This is an epidemic that can no longer be ignored. According to data recorded by U.S. Department of Health and Human services in 1977, the average adult male weighed 168 pounds and the average adult female weighed 143 pounds. In more recent data collected in 1996, the average adult male weighed 180 pounds while the average adult female weighed 155 pounds. The average weight of all males and females increased twelve pounds in just thirty years. The number of individuals classified as medically obese rose from 14% to nearly 30% in just thirty years (Centers for Disease Control, 2003).

            This increase in obese individuals over the last thirty years has been accompanied by an increase in portion and packaging sizes (Wansink, Painter, North, 2005). Experiments have shown that people eat more, on average, if a larger quantity of food is put in front of them and they will consume much more than they need to satisfy their dietary needs (Young, Nestle, 2002). This literature review will discuss whether larger food portions have contributed to the growing rate of obesity in this country.

Increased Portion Sizes

Patterns and Trends in Food Portion Sizes, 1977-1998 (Nielsen, Popkin, 2003)

            It was commonly accepted that “food portions [had] been increasing and that this increase [was] one factor contributing to the obesity epidemic in the United States” but there was very little data to confirm this (Nielsen, Popkin, 2003). The goal of this study was to produce empirical data showing the increase in food portions in the United States over the past thirty years.

This study used “nationally representative dietary intake data” to find patterns and trends in portion sizes (Nielsen, Popkin, 2003). This study compared portion sizes eaten inside and outside of the home also. Studies from 1977, 1989, and 1998 were included while calculating trends in data. These studies examined one day’s worth of food that was recorded by an in-home interviewer and two days’ worth of food that was self-recorded using 24-hour food recalls. Each record was taken approximately three days apart. The location of where the food was consumed was also taken into account when recording data in these interviews.

            The data from 1977, 1989, and 1998 that was compiled confirmed the “general consensus that there [was] a marked trend toward larger portion sizes in the United States” (Nielsen, Popkin, 2003). The portion sizes for all the foods examined, salty snacks, desserts, soft drinks, fruit drinks, French fries, hamburgers, cheeseburgers, pizza, and Mexican food, had all increased significantly. In just 19 years “the quantity of salty snacks increased by 93 kcal (0.6 oz), soft drinks by 49 kcal (6.8 oz), hamburgers by 97 kcal (1.3 oz), french fries by 68 kcal (0.5 oz), and Mexican dishes by 133 kcal (1.7 oz)” (Nielsen, Popkin, 2003).

There was not a significant difference in the portion of food consumed inside and outside of the home. After examining the kilocalories consumed in the study, it was clear that many Americans were consuming more than they needed to fulfill their dietary needs. Since approximately “10 kcal per day of unexpended energy [was] equivalent to an extra pound of weight per year,” it was easy to see why Americans were gaining weight with increased portion sizes (Nielsen, Popkin, 2003).

            Because a good portion of the data collected in this study was self-reported, the figures were probably not entirely accurate. The study estimates that many participants underreported their portion sizes. This would mean that portion sizes have increased more than documented. If this is true, the data would still support the conclusion that increased portion sizes have contributed to obesity in America.

Portion Sizes versus Food Intake

Portion size of food affects energy intake in normal-weight and overweight men and women (Rolls, Morris, Roe, 2002)

            This study looked at the effect that portion size had on an individual’s eating during a single meal. The goal of this study was to determine whether individuals ate more when they determined their portion size or when their portion size was determined for them. This study included fifty-one men and women who were recruited through advertisements in local university papers. The age of these individuals ranged from 21 years to 40 years old. These individuals were healthy, not using medication, not following a diet, not athletes in training, not pregnant or lactating, not allergic to any foods, and they ate three meals per day.

These participants were given a variety of tests to evaluate their dietary restraint, perceived hunger, and dis-inhibition. They were also given the Eating Attitudes Test to evaluate whether they had an eating disorder and the Zung Self-Rating Depression Scale and Depression Status Inventory to determine whether they showed signs of depression. Candidates who showed signs of eating disorders or depression were eliminated. A detailed demographics questionnaire was used along with measurements, weight, and height to determine the body mass index of each participant. Only participants with a body mass index of 20-28 were used. Another survey was used to determine which food the participants disliked. In order to provide more accurate results, the true nature of the experiment was not revealed to the participants. They were told the experiment had to do with lunch and taste.

They were served lunch one day a week for four weeks in the laboratory. Before each lunch, the subjects were given a questionnaire to insure that they had not eaten, drunk, or consumed medicine that affected appetite within a few hours before their meal. The 27 participants in the first group were given various amounts (500, 625, 750, or 1000 g) of macaroni and cheese along with carrot sticks, a snack-size milk chocolate bar, and water. They were required to eat the chocolate and carrots but were instructed to eat however much they wanted of the macaroni and cheese. During this meal, the subjects had to sit in cubicles and were not allowed to read or work while they ate. Food was measured before and after each participant ate. The second group of participants, which had 24 participants, did not receive food that was already on their plate. Instead, they served themselves from large serving dishes and were instructed to eat as much as they wanted. The meals were videotaped discretely so that the number of serving spoonfuls could be measured after the meal.

After the meal, subjects were given visual analogue scales to access their level of hunger and satiety immediately before and after eating. Subjects who did not like the taste of the entrée were excluded from the results on that day. Subjects who always finished their plate were also taken into consideration when calculating results. Before leaving the experiment on the last day, subjects completed another questionnaire about what they thought the purpose of the study was and if they noticed differences in the test days.

The results of this experiment showed “that increasing portion size of macaroni and cheese [affected] food intake in adults during a single meal” (Rolls, Morris, Roe, 2002). In general, the participants ate more if more food was put on their plate. This study also found that “portion size influences the development of hunger and satiety” (Rolls, Morris, Roe, 2002). Subjects ate more before they reached satiation if they were offered larger portions. Both groups of adults, the ones who had food given to them and the ones who served themselves, overate if there was more food present on the plate or on the large serving dish. This study confirmed that both men and women overate when they were given large portion sizes but did identify characteristics of more susceptible people.

This study seemed very well done. Throughout the course of the study, questionnaires were given to insure that the participants complied with the strict guidelines of the experiment. Individuals who could have altered the results significantly, such as consistent “plate cleaners” and individuals with depression or eating disorders were discovered and eliminated from the final data (Krassner, Brownell, Stunkard, 1979) but this study was unable to determine why larger portion sizes affected food intake.

Why do larger portion sizes cause overeating?

Bottomless Bowls: Why Visual Cues of Portion Size May Influence Intake (Wansink, Painter, North, 2005)

            This study examined why individuals ate more when they were given larger portion sizes. Before the experiment, this study did a questionnaire. The study examined visual cues that individuals used to determine whether they were full. They found that over 54% of adults felt as though they needed to clean their plates before they stopped eating. Other individuals said that they needed “to eat one-half or three-quarters of what they [were] served” before they felt full. Most individuals used visual cues automatically without any conscious effort (Wansink, Painter, North, 2005).

            This study discovered that it was very difficult for the participants to accurately determine how much that had eaten without a visual cue. When an individual used visual cues, they used food levels instead of satiation to determine when they should stop eating. It was also discovered that food levels influenced their feelings of satiation. Through these findings, researchers determined that influencing visual cues would affect food intake.

            After the questionnaire, the researchers hypothesized that “altering a visual cue of how much [was] eaten would influence intake” (Wansink, Painter, North, 2005). They also wondered whether this would be reflected in consumption estimates and satiation” (Wansink, Painter, North, 2005). A self-refilling bowl was used to eliminate visual cues. This experiment consisted of 39 men and 15 women ranging from 18-47 years old, who had a mean BMI of 24.9 kg/m2. The mean age was 22.5 years old so most of the participants were young, especially because they were recruited from a large university.

            Participants were recruited through flyers and told that they were going to be eating a soup-only lunch and then answering a questionnaire. Subjects were put in groups of four to serve as a distraction and a means of creating familiar groups. The participants would eat less cautiously if they knew the individuals that they were sitting with. Some participants were given self-refilling bowls while others were given normal bowls. Theoretically, all of the participants should have eaten around the same amount of food because they were in the same social situation.

            The participants were not told what the true goal of the experiment was before they participated. They were given different colored bowls, blue and green, and asked questions about the color of the bowls. This was to make them think that the experiment had something to do with food intake and color. Each person was told to “enjoy the new recipe of tomato soup” without moving the bowl from its place on the table (Wansink, Painter, North, 2005). After 20 minutes, the participants were given a questionnaire that asked them to judge how much they thought they ate. They were also asked questions to determine how full they were after consumption. Questions about hunger were not asked before the experiment because the researchers believed that it would affect their results. They made sure to select a random group of people so that hunger levels would vary.

            The amount of soup remaining was weighed and the data was recorded. The researchers’ original hypothesis was confirmed in the results collected. Individuals with self-refilling bowls ate “14.7 vs. 8.5 ounces” of soup that individuals with normal bowls ate (Wansink, Painter, North, 2005). In the questionnaire after the experiment, 61% of the participants “agreed with the statement ‘I always try to clean my plate (or bowl) at home’” (Wansink, Painter, North, 2005). The group with the normal bowls estimated that they had eaten “32.2 calories fewer than they actually ate” (Wansink, Painter, North, 2005). Even though the group with the self-refilling bowls had eaten significantly more, they estimated that they “had eaten 140.5 calories fewer than they actually ate” (Wansink, Painter, North, 2005). This difference was due to the second group’s inability to rely on visual cues.

            Overall, this study showed that “a visual cue or consumption norm [could] influence how much one [expected] to consume and how much one eventually [consumed]” (Wansink, Painter, North, 2005). This study showed the importance of knowing portion sizes without having to rely on visual cues. It seemed to be a reliable study minus the fact that they could not survey the participants about satiation and hunger before the experiment and compare the results afterwards. They had to depend on averages. Also, there were a lot more males than females, which could have influence the results. This experiment was also tested with a “calorically dilute food” instead of a “calorically dense food” so they had to assume that the results were the same for all types of food (Wansink, Painter, North, 2005). This may or may not have been true.


            These three studies showed that portion sizes had indeed increased over the last thirty years and the rates of obesity had increased also. They showed that individuals ate more when they were given larger portion sizes and they underestimated their total intake. Because unconsumed calories contribute to weight gain, it was reasonable to connect increased food intake to weight gain. The studies also showed that the consumption of larger portion sizes was a general trend that seemed to be very common for Americans as a whole. Specific genders and races were not excluded from this trend. The last experiment showed that most individuals had no concept of how much they were eating unless they knew the size of the bowl and relied on visual cues to guestimate their intake. These studies confirmed that increased portion sizes in America have probably contributed to obesity among its citizens.


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