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Food liking, familiarity and expected satiation selectively influence portion size estimation of snacks and caloric beverages in men
Appetite 55 (2010) 551–555
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Appetite journal homepage: www.elsevier.com/locate/appet
Food liking, familiarity and expected satiation selectively influence portion size estimation of snacks and caloric beverages in men§ Nina Brogden, Eva Almiron-Roig * Department of Clinical Sciences, University of Chester, Parkgate Road, CH1 4BJ Chester, United Kingdom
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 November 2009 Received in revised form 21 August 2010 Accepted 6 September 2010
We explored the relationship between three food attributes and portion size estimation. Twenty-seven men rated liking, familiarity and expected satiation (ES) of a chocolate bar, muffin, banana, cola, cornflakes, potato chips (crisps), hot chocolate drink and ice-cream, before estimating portion size when hungry and full. Portion estimates correlated with liking ratings in three foods (r = 0.53 to 0.28); with familiarity in two foods (r = 0.30, full only); and with ES in four foods (r 0.45). Across foods lower ES ratings tended to correlate with higher portion size estimates. Portion size estimation is influenced by food liking, familiarity and expected satiation. ß 2010 Elsevier Ltd. All rights reserved.
Keywords: Liking Familiarity Expected satiation Portion size estimation Hunger
Introduction Food familiarity and liking, together with expected fullness (expected satiation) are said to influence portion size selection, particularly in high energy density foods (Brunstrom & Rogers, 2009; Brunstrom, Shakeshaft, & Scott-Samuel, 2008). Due to the high energy content of such food, daily decisions about how much of it we consume can influence energy balance and body weight, and may promote obesity in the long-term (Ello-Martin, Ledikwe, & Rolls, 2005). Expected satiation (ES) is defined as the relative feeling of fullness that someone expects to experience after consuming different foods when compared on a calorie-for-calorie basis (Brunstrom & Rogers, 2009). ES develops upon exposure to a novel food, when an individual creates an association between the food’s sensory properties and its ability to promote satiation (Gibson & Brunstrom, 2007). On subsequent exposures, this learned association may influence portion size selection and thus determine subsequent energy intake (Brunstrom & Shakeshaft, 2009). As a result, learning and memory for expected satiation may be important in moderating portion sizes and eliciting energy
§ This work was supported by an internal Research Activity Exercise grant from the Faculty of Applied and Health Sciences, University of Chester, to EAR. The authors are grateful to Colin Sinclair for statistical advice; Sue Dunn, Juan M. Bravo and Helen Green for technical assistance; and to all the volunteers for their participation. * Corresponding author. E-mail address: [email protected] (E. Almiron-Roig).
0195-6663/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2010.09.003
compensation (Gibson & Brunstrom, 2007; Higgs, 2008). Such associations may be further modulated by the energy density of a food and a person’s appetite status (Kral, 2006; Yeomans, 2007). Familiarity and expected satiation may be interrelated. More familiar foods are expected to be more filling (Brunstrom, Shakeshaft et al., 2008). If expectations of fullness influence portion size selection (Brunstrom & Rogers, 2009) then more familiar foods may be chosen in smaller portions. On the other hand, liking has been associated with the selection of larger and more energetic portions of snack foods and popular dishes. However when comparing different foods on a calorie-for-calorie basis, expected satiation, not liking, is a better predictor of prospective portion size, that is, the amount of food (in kcal) considered large enough to stave off hunger until the next meal (Brunstrom & Rogers, 2009). Also, foods which are similarly liked such as chocolate bars and nuts elicit different prospective satiety responses under laboratory conditions (Brunstrom & Shakeshaft, 2009). The effects of liking and familiarity on portion size perception may be further modulated by appetite status. Based on existing research (Brunstrom, Rogers, Pothos, Calitri, & Tapper, 2008; Gibson & Brunstrom, 2007; Yeomans, 2007) we hypothesized that hunger, as opposed to fullness, may interact with or even override food preferences and associations between foods and expected satiation, eventually influencing portion size estimation. We have recently confirmed such an interaction in a controlled intervention where 27 young men rated the number of portion sizes of popular snack foods/drinks under full and hungry conditions (Brogden, Sinclair, & Almiron-Roig, 2009). On half of the occasions, subjects
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were asked to provide an ES rating for each item before estimating portions (to test if making an expected satiation judgment before making a portion size judgment influences portion size estimation). This design allows the separation of the effects of appetite status from those of expected satiation on portion size estimation in particular of foods/drinks that tend to be overconsumed (Brunstrom, Shakeshaft et al., 2008; Higgs, 2008). Mean portion size estimates in all items were smaller when participants were hungry compared with when they were full (p < 0.01 for all comparisons,) but there was no significant effect of the ES rating (present vs. absent) on mean portion size estimates (Brogden, 2009). As part of that intervention, we also explored the relationship between familiarity and liking with portion size estimation and appetite status, which we report in this paper. We hypothesized that for a given food, liking ratings would be inversely related to estimated portion size, because more of that food would need to be consumed to feel satisfied (Brunstrom & Shakeshaft, 2009). We also hypothesized that familiarity ratings would correlate positively with estimated portion size, due to past experience with the satiating effects of familiar foods (Brunstrom, Shakeshaft et al., 2008). Finally, based on recent data showing that expected satiation is a good predictor of portion size selection (Brunstrom & Rogers, 2009), the role of expected satiation as a predictor variable of portion size estimation was also explored.
minutes prior to the test, participants under conditions F and FES consumed a 737 kcal (3.1 MJ) breakfast pre-load, enough to induce satiety for 60 min (Brogden, 2009). The study protocol was approved by the Faculty of Applied and Health Sciences Research Ethics Committee, University of Chester. All participants provided written consent and were compensated £20 Sterling for participating. VAS ratings Before recruitment, participants rated liking and familiarity for the eight test foods/drinks on 100 mm VAS. Each VAS included a picture of the relevant food/drink and the prompt ‘‘how familiar are you with this food/drink?’’ (not familiar at all – extremely familiar); and ‘‘how much do you like this food/drink?’’ (not at all – very much). Liking and familiarity were defined respectively as how much a person liked or was familiar with the taste and feel of a food/drink in their mouth and stomach (Raudenbush & Frank, 1999; Yeomans, 2007). For the purpose of this study, cut-off values were set to 9 mm and 29 mm for a food/drink to be considered disliked or unfamiliar respectively. These were selected to include a sufficiently broad range of values but excluding low extremes, as subjects extremely unfamiliar/disliking the test foods would find it difficult to estimate portion size (Yeomans, 2007). Subjects also rated hunger and fullness on 100 mm VAS before the start of each test.
Methods Test foods This was a randomised cross-over trial involving 27 lean men recruited from the University of Chester campus (ages 18–45 years, BMI 18–27.9 kg/m2, non-dieting and non-smoking, with regular breakfast consumption). Exclusion criteria were as reported previously (Tsuchiya, Almiron-Roig, Lluch, Guyonnet, & Drewnowski, 2006). In addition, subjects who disliked or were unfamiliar with the study foods were excluded, as well as those scoring 9 on the disinhibition scale; or 10 on the cognitive restraint scale plus 7 on the hunger scale of the Three Factor Eating Questionnaire (Stunkard & Messick, 1985), as these individuals tend to respond to food cues differently from the general population (Brunstrom, Rogers et al., 2008; Yeomans, Tovey, Tinley, & Haynes, 2004). Participants attended the lab on four separate occasions spaced 5 days apart. At each session participants rated the number of portion sizes of eight foods/beverages displayed in front of them, after consuming breakfast (full conditions) or after an overnight fast (hungry conditions). On one of the full and one of the hungry conditions, participants were asked to rate the expected satiating power (ES) of each food before estimating portions. Thus, the four study conditions were: full, with ES rating absent (F); hungry, with ES rating absent (H); full, with ES rating present (FES); and hungry, with ES rating present (HES). The order of exposure to each condition was randomised across subjects (Williams, 1949). The ES rating consisted of a pre-piloted 100 mm visual analogue scale (VAS) question to which subjects responded under conditions FES and HES prior to portion rating: ‘‘how full do you think you would be after consuming this amount of food/drink?’’ (Brogden, 2009). In the context of this study, ES refers to the imagined sensation of fullness at the end of a meal and is comparable to ES measured using photographic stimuli (Brunstrom & Rogers, 2009). Prior to portion size estimation subjects were reminded that a portion was ‘‘the quantity of food/drink that you would consume on one eating or drinking occasion’’ (Schwartz & Byrd-Bredbenner, 2006). Subjects then rated portion sizes of test foods/drinks by responding in writing to the following question for each item: ‘‘how many portions of (item) do you think are in/on this (container type)?’’. Subjects were allocated 1 min to estimate and record the portion size of each test food/drink. Forty-five
Test foods/drinks were selected to represent items commonly consumed amongst university students and included: chocolate muffin; chocolate ice-cream tub; hot chocolate container; bottled cola; potato chips pack; king size chocolate bar; bowl of cornflakes (dry); fresh banana with skin (Table 1). All brand names were concealed before display. Each food/drink was presented in an individual booth, with the sequence randomised across sessions.
Table 1 Mean SEM (n = 27), liking, familiarity and expected satiation ratings for test foods/ drinks and mean SEM (n = 54) portion estimate under full (F) and hungry (H) conditions. Portion estimates data under the ES and non-ES rating conditions were pooled as the presence of the ES rating had no effect on portion estimates (Brogden, 2009). Expected satiation (100 mm VAS)
80.7 3.1*
88.4 3.5
a
92.3 2.3
85.3 2.6 76.4 3.8 53.2 5.2 39.3 4.5 45.3 4.7 35.7 3.8 59.4 5.0 38.2 3.6
(F) (H) (F) (H) (F) (H) (F) (H)
2.32 0.15 1.96 0.13 1.34 0.12 1.08 0.11 1.00 0.09 0.79 0.07 1.45 0.09 1.12 0.06
(F) (H) (F) (H) (F) (H) (F) (H)
63.5 4.8 49.0 4.0 54.4 4.6 37.1 4.4 79.6 3.8 69.4 3.2 65.2 4.3 54.6 4.8
(F) (H) (F) (H) (F) (H) (F) (H)
1.20 0.09 1.01 0.09 1.27 0.07 1.09 0.06 2.46 0.19 1.98 0.17 1.21 0.07 1.01 0.08
(F) (H) (F) (H) (F) (H) (F) (H)
Liking (100 mm VAS)
Ice-cream, tub (427 g, 5125 kJ) Chocolate bar (85 g, 1741 kJ) Fresh banana (80 g, 318 kJ) Hot chocolate, opaque container (473 ml, 2025 kJ) Muffin (140 g, 2372 kJ) Cola bottle (500 ml, 879 kJ) Potato chips, pack (150 g, 3125 kJ) Cornflakes, bowl, dry (63 g, 983 kJ) * a b c d
Portion size estimate (units)
Familiarity (100 mm VAS)
Item displayed
79.9 4.0
78.7 4.9
93.4 2.4
76.0 3.1
88.4 2.9
75.1 4.5
85.9 3.1
67.3 3.1
92.8 2.1
b
61.9 4.7
90.2 3.0
60.8 4.8
81.3 4.6c,d
Differs from cornflakes with p < 0.05. Trend, against cornflakes (p = 0.05). Trend, against ice-cream (p = 0.05). Trend, against banana (p = 0.05). Trend, against chocolate bar (p = 0.07).
N. Brogden, E. Almiron-Roig / Appetite 55 (2010) 551–555
Data management and statistical analysis Data were analyzed with SPSS for Windows, Version 16.0. (SPSS Inc., Chicago). Portion size estimates, expected satiation (ES), ES per unit of energy (ES/kcal), hunger, fullness, liking and familiarity ratings were treated as continuous data. ES/kcal was calculated dividing ES ratings (mm) by the energy content (kcal) of each displayed food. Because the presence of an ES rating had no influence on portion estimates in our study population (Brogden, 2009), results of portion estimates were pooled across the two ES conditions. Mean hunger, fullness, liking and familiarity ratings were compared using one-way repeated measures ANOVA with the Bonferroni correction, for analyses across conditions, and with paired t-tests or the Wilcoxon test for analyses across foods. The Pearson’s product-moment correlation test was used to investigate the relationship between liking, familiarity and ES ratings with portion size estimates within each food. Spearman’s rank correlation test was used for analyses across foods. The level of significance for all tests was set at <0.05.
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Table 2 Results of Pearson’s correlation test (n = 54). Pooled data were used as before (see Table 1). Variance (%) in portion estimates as explained by liking was: banana 26% (full) and 27% (hungry); cola 28% (full) and 12% (hungry); cornflakes 8% (full). For familiarity: cola 10% (full); ice-cream 9% (full). For ES/kcal, cornflakes 8% (full); chips and ice-cream 12% (full); hot chocolate 20% (hungry). Item
Condition
Liking vs. Portion estimate
Familiarity vs. Portion estimate
ES/kcal vs. Portion estimate
Chocolate bar
Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry
r = 0.01 r = 0.02 r = 0.07 r = 0.06 r = 0.51*** r = 0.52*** r = 0.53*** r = 0.35* r = 0.28* r = 0.16 r = 0.03 r = 0.05 r = 0.1 r = 0.23# r = 0.25# r = 0.06
r = 0.18 r = 0.16 r = 0.19 r = 0.09 r = 0.01 r = 0.09 r = 0.31* r = 0.24# r = 0.01 r = 0.05 r = 0.10 r = 0.15 r = 0.01 r = 0.08 r = 0.30* r=0
r = 0.04 r = 0.21 r = 0.03 r = 0.09 r = 0.05 r = 0.22 r = 0.26# r = 0.10 r = 0.29* r = 0.06 r = 0.35* r = 0.16 r = 0.26# r = 0.45** r = 0.35* r = 0.02
Muffin Banana Cola Cornflakes Potato chips Hot chocolate Ice-cream
Results *
Correlation is significant with p < 0.05. Correlation is significant with p < 0.01. *** Correlation is significant with p < 0.001. # Correlation shows a trend (i.e. 0.1 > p > 0.05). **
Participants All enrolled subjects (n = 27) completed the study. Mean (SEM) age and BMI were 24.9 (6.5) years and 23.3 (2.4) kg/m2. Mean (SEM) dietary restraint, disinhibition and hunger scores were 4.4 (3.8), 4.8 (2.2) and 6.3 (2.8) respectively. Appetite, liking and familiarity ratings ANOVA revealed a significant main effect of time on hunger [F(3.93, 102.23) = 145.63, p < 0.001] and fullness [F(3.71, 96.44) = 188.99, p < 0.001] confirming the effect of the intervention (Brogden, 2009). The most liked food was the ice-cream, whilst the least liked food were the cornflakes. The food rated as most familiar was the banana and the least familiar the cornflakes (Table 1). ANOVA identified a significant main effect of test food/ drink on mean ratings for liking and familiarity (F(7, 182) = 4.27, p < 0.001 and F(3.75, 97.56) = 4.09, p < 0.01 respectively). Pairwise comparisons confirmed higher liking ratings for the ice-cream (80.7 3.1) than for cornflakes (60.8 4.8) (p < 0.05). Mean liking also tended to be higher for the ice-cream compared with the potato chips (61.9 4.7) (p = 0.05) and for the chocolate bar (79.9 4.0) compared with the cornflakes (p = 0.05). No significant differences in familiarity ratings were detected between pairs of foods and drinks, except for a trend for the banana and for the chocolate bar (Table 1). Effects of liking and familiarity on portion size estimates Despite significant differences between liking ratings, the majority of portion estimates tended to fall within a much smaller range (Table 1). When looking at individual items, significant correlations between liking and portion estimates were detected for the banana and the cola (Table 2). Thus, individuals who liked the banana and the cola the most estimated these items in smaller portions than those individuals who liked them the least. A positive correlation was detected between liking and portion estimates for the cornflakes (full only). Thus individuals who liked the cornflakes the most estimated them in larger portion sizes than those individuals who liked them the least. Therefore, food/drink type affected the direction of the correlation. Also, liking ratings explained as little as 8% and as much as 28% of the variance in portion estimates, depending on food/drink type (Table 2).
Significant correlations between familiarity ratings and portion size estimates were detected for the cola and the ice-cream under the full condition only (Table 2). Thus, when full, individuals who were most familiar with the cola and the ice-cream estimated these foods in smaller portion sizes than individuals who were least familiar. However, changes in familiarity ratings explained only a small proportion of the variance in portion estimates (up to 10%) (Table 2). This relationship was not observed under hungry conditions for either food/drink, although a trend in the same direction was detected for the cola. Additional analyses across foods (n = 8) revealed no significant associations between familiarity and portion estimates or between liking and portion estimates under any of the appetite conditions. Effects of expected satiation on portion size estimates Expected satiation ratings for each item are shown in Table 1. Significant correlations with portion size estimates were detected for the cornflakes, chips, hot chocolate and ice-cream, and a trend in the same direction was observed for the cola. Thus, individuals who rated these foods as more filling estimated the portions of such foods as larger than individuals who rated the same foods as less filling. This occurred when full only, except for the hot chocolate. Variations in ES explained between 8% and 20% of variations in portion estimates (Table 2). Across foods, ES/kcal correlated with portion estimates under the full condition [rho = 0.74 (p < 0.05)], and a similar trend was detected in the hungry condition [rho = 0.67 (p = 0.07)]. Thus, participants tended to assign smaller portions to some foods with high ES/kcal (banana, cola and cornflakes) and larger portions to some foods with lower ES/kcal (ice-cream, chips), however this did not occur for all foods (Fig. 1). Discussion We explored the effects of liking, familiarity and expected satiation (ES) on portion estimation using a convenient sample of 8 popular foods, evaluated by a panel of 27 men, under both hungry and full conditions. We detected significant negative associations
[()TD$FIG]
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Figure 1. Variation of portion size estimation with expected satiation (adjusted for energy content) under full conditions. Results of Spearman’s rank correlation are indicated. Each portion estimation point corresponds to the mean SEM of 54 individual ratings.
between liking and portion size estimates for the banana and the cola (the two most familiar items); and between familiarity and portion estimates for the ice-cream and the cola (full condition only). We also explored the extent to which expected satiation (ES) predicted changes in portion estimates. Significant positive correlations were detected for the cornflakes, chips, hot chocolate and ice-cream. Across foods, adjusted ES ratings correlated negatively with portion estimates under the full condition. Liking has been positively associated with the size of a satisfactory (satiating) portion (Brunstrom & Shakeshaft, 2009). Thus, we expected that within a given food, liking ratings and portion estimates would be inversely related. In other words, the more you like something, the more you could imagine eating of before being satisfied. We detected significant associations in such direction but only within certain foods (banana and cola). Liking has been tightly linked to palatability, which has been shown to positively influence energy intake in controlled laboratory studies (Yeomans, 2007). However Brunstrom and Rogers (2009) recently showed that expected satiation was a better predictor of meal size than expected liking. Foods with low expected satiation (not expected liking) were selected in larger portion sizes and regarded as less rewarding than other foods of equal caloric value. Thus, even for foods that are well liked, preference may not be a strong enough predictor of portion size selection. In agreement, we found no significant association between liking and portion size estimations across foods, however only a small number of foods were tested. While in the banana and the cola, liking ratings correlated with portion estimates under both appetite conditions, for the cornflakes, ice-cream and hot-chocolate this tended to occur selectively under hungry or full conditions only. It is possible that appetite status may interact with food type to modify the effects of liking on portion size estimates in certain foods (Gibson & Desmond, 1999; Yeomans, Weinberg, & James, 2005). In contrast to the liking results, our results for familiarity digress from previous findings (Brunstrom, Rogers et al., 2008; Brunstrom & Shakeshaft, 2009; Brunstrom, Shakeshaft et al., 2008). Since familiar foods are expected to be more filling than unfamiliar foods due to learned experiences, we hypothesized that familiarity ratings would be positively associated with portion size estimates (Brunstrom, Shakeshaft et al., 2008). Analyses within foods showed that as familiarity increased, portion estimates did not change significantly for most items, with the exception of cola and icecream, for which familiar subjects estimated portions as smaller than less familiar subjects. Across foods, no significant associations
were detected in any direction, which could be explained by the low variability in portion estimates and familiarity ratings in this dataset. In line with Brunstrom and Rogers (2009), changes in expected satiation ratings (adjusted for energy content) predicted (full) or tended to predict (hungry) changes in portion size estimation across foods. The low variability in portion size estimates mentioned above could also explain the lack of a stronger association between ES ratings and portion estimates especially when hungry. In addition, strong appetite feelings could potentially suppress the effects of past experiences when making decisions about foods. In agreement, correlations of ES/kcal within foods tended to be significant mostly under the full condition. Subjects who perceived the cornflakes, chips, hot chocolate and ice-cream portions as more filling, rated these portions as larger than subjects who found them less filling. This could be related to the actual volume displayed of these foods, which may be larger than what subjects normally consume, affecting participants’ perception of portion size and ES (Gibson & Brunstrom, 2007; Kral, 2006). We measured liking and familiarity only once prior to the test, under uncontrolled appetite conditions, and excluded participants who strongly disliked or were unfamiliar with the test foods. The exact effect of appetite status on liking and familiarity cannot be established from these data. However, despite the limited number of foods tested, subjects consistently rated portions as smaller when hungry than when full, irrespective of how filling they expected the foods to be (Brogden et al., 2009). These results support previous findings pointing to a possible dissociation between macronutrient composition, caloric value and portion size estimation (Brunstrom, Shakeshaft et al., 2008; Rolls, Roe, & Meengs, 2007). In order to reduce variability, we investigated non-restricted male eaters only, with a narrow BMI range. Whilst dietary learning seems to be predicted by levels of dietary restraint (Brunstrom & Mitchell, 2007) it is unclear how restraint and BMI may affect the relationship between liking and portion estimation. Further research is required to determine how liking and familiarity influence portion estimation of a wider range of foods and in other individuals. In conclusion, we have confirmed an association between liking and portion size estimation in some popular foods/drinks. Thus, for these foods, the more they were liked, the smaller their assessment of the portion size displayed. Also, for some foods, the more filling they were expected to be, the larger their portion estimation. The degree to which ES predicts changes in portion size estimation across different foods requires further investigation, but this is expected to follow an inverse relationship (Brunstrom & Rogers, 2009). Studies using a wider range of food items are necessary to elucidate which food attributes interact with liking/familiarity and ES to effect changes in portion size selection. Such information would be useful for developing behavioural interventions for weight loss and for the treatment of eating disorders (Gibson & Brunstrom, 2007).
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Contents lists available at ScienceDirect
Appetite journal homepage: www.elsevier.com/locate/appet
Food liking, familiarity and expected satiation selectively influence portion size estimation of snacks and caloric beverages in men§ Nina Brogden, Eva Almiron-Roig * Department of Clinical Sciences, University of Chester, Parkgate Road, CH1 4BJ Chester, United Kingdom
A R T I C L E I N F O
A B S T R A C T
Article history: Received 18 November 2009 Received in revised form 21 August 2010 Accepted 6 September 2010
We explored the relationship between three food attributes and portion size estimation. Twenty-seven men rated liking, familiarity and expected satiation (ES) of a chocolate bar, muffin, banana, cola, cornflakes, potato chips (crisps), hot chocolate drink and ice-cream, before estimating portion size when hungry and full. Portion estimates correlated with liking ratings in three foods (r = 0.53 to 0.28); with familiarity in two foods (r = 0.30, full only); and with ES in four foods (r 0.45). Across foods lower ES ratings tended to correlate with higher portion size estimates. Portion size estimation is influenced by food liking, familiarity and expected satiation. ß 2010 Elsevier Ltd. All rights reserved.
Keywords: Liking Familiarity Expected satiation Portion size estimation Hunger
Introduction Food familiarity and liking, together with expected fullness (expected satiation) are said to influence portion size selection, particularly in high energy density foods (Brunstrom & Rogers, 2009; Brunstrom, Shakeshaft, & Scott-Samuel, 2008). Due to the high energy content of such food, daily decisions about how much of it we consume can influence energy balance and body weight, and may promote obesity in the long-term (Ello-Martin, Ledikwe, & Rolls, 2005). Expected satiation (ES) is defined as the relative feeling of fullness that someone expects to experience after consuming different foods when compared on a calorie-for-calorie basis (Brunstrom & Rogers, 2009). ES develops upon exposure to a novel food, when an individual creates an association between the food’s sensory properties and its ability to promote satiation (Gibson & Brunstrom, 2007). On subsequent exposures, this learned association may influence portion size selection and thus determine subsequent energy intake (Brunstrom & Shakeshaft, 2009). As a result, learning and memory for expected satiation may be important in moderating portion sizes and eliciting energy
§ This work was supported by an internal Research Activity Exercise grant from the Faculty of Applied and Health Sciences, University of Chester, to EAR. The authors are grateful to Colin Sinclair for statistical advice; Sue Dunn, Juan M. Bravo and Helen Green for technical assistance; and to all the volunteers for their participation. * Corresponding author. E-mail address: [email protected] (E. Almiron-Roig).
0195-6663/$ – see front matter ß 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.appet.2010.09.003
compensation (Gibson & Brunstrom, 2007; Higgs, 2008). Such associations may be further modulated by the energy density of a food and a person’s appetite status (Kral, 2006; Yeomans, 2007). Familiarity and expected satiation may be interrelated. More familiar foods are expected to be more filling (Brunstrom, Shakeshaft et al., 2008). If expectations of fullness influence portion size selection (Brunstrom & Rogers, 2009) then more familiar foods may be chosen in smaller portions. On the other hand, liking has been associated with the selection of larger and more energetic portions of snack foods and popular dishes. However when comparing different foods on a calorie-for-calorie basis, expected satiation, not liking, is a better predictor of prospective portion size, that is, the amount of food (in kcal) considered large enough to stave off hunger until the next meal (Brunstrom & Rogers, 2009). Also, foods which are similarly liked such as chocolate bars and nuts elicit different prospective satiety responses under laboratory conditions (Brunstrom & Shakeshaft, 2009). The effects of liking and familiarity on portion size perception may be further modulated by appetite status. Based on existing research (Brunstrom, Rogers, Pothos, Calitri, & Tapper, 2008; Gibson & Brunstrom, 2007; Yeomans, 2007) we hypothesized that hunger, as opposed to fullness, may interact with or even override food preferences and associations between foods and expected satiation, eventually influencing portion size estimation. We have recently confirmed such an interaction in a controlled intervention where 27 young men rated the number of portion sizes of popular snack foods/drinks under full and hungry conditions (Brogden, Sinclair, & Almiron-Roig, 2009). On half of the occasions, subjects
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were asked to provide an ES rating for each item before estimating portions (to test if making an expected satiation judgment before making a portion size judgment influences portion size estimation). This design allows the separation of the effects of appetite status from those of expected satiation on portion size estimation in particular of foods/drinks that tend to be overconsumed (Brunstrom, Shakeshaft et al., 2008; Higgs, 2008). Mean portion size estimates in all items were smaller when participants were hungry compared with when they were full (p < 0.01 for all comparisons,) but there was no significant effect of the ES rating (present vs. absent) on mean portion size estimates (Brogden, 2009). As part of that intervention, we also explored the relationship between familiarity and liking with portion size estimation and appetite status, which we report in this paper. We hypothesized that for a given food, liking ratings would be inversely related to estimated portion size, because more of that food would need to be consumed to feel satisfied (Brunstrom & Shakeshaft, 2009). We also hypothesized that familiarity ratings would correlate positively with estimated portion size, due to past experience with the satiating effects of familiar foods (Brunstrom, Shakeshaft et al., 2008). Finally, based on recent data showing that expected satiation is a good predictor of portion size selection (Brunstrom & Rogers, 2009), the role of expected satiation as a predictor variable of portion size estimation was also explored.
minutes prior to the test, participants under conditions F and FES consumed a 737 kcal (3.1 MJ) breakfast pre-load, enough to induce satiety for 60 min (Brogden, 2009). The study protocol was approved by the Faculty of Applied and Health Sciences Research Ethics Committee, University of Chester. All participants provided written consent and were compensated £20 Sterling for participating. VAS ratings Before recruitment, participants rated liking and familiarity for the eight test foods/drinks on 100 mm VAS. Each VAS included a picture of the relevant food/drink and the prompt ‘‘how familiar are you with this food/drink?’’ (not familiar at all – extremely familiar); and ‘‘how much do you like this food/drink?’’ (not at all – very much). Liking and familiarity were defined respectively as how much a person liked or was familiar with the taste and feel of a food/drink in their mouth and stomach (Raudenbush & Frank, 1999; Yeomans, 2007). For the purpose of this study, cut-off values were set to 9 mm and 29 mm for a food/drink to be considered disliked or unfamiliar respectively. These were selected to include a sufficiently broad range of values but excluding low extremes, as subjects extremely unfamiliar/disliking the test foods would find it difficult to estimate portion size (Yeomans, 2007). Subjects also rated hunger and fullness on 100 mm VAS before the start of each test.
Methods Test foods This was a randomised cross-over trial involving 27 lean men recruited from the University of Chester campus (ages 18–45 years, BMI 18–27.9 kg/m2, non-dieting and non-smoking, with regular breakfast consumption). Exclusion criteria were as reported previously (Tsuchiya, Almiron-Roig, Lluch, Guyonnet, & Drewnowski, 2006). In addition, subjects who disliked or were unfamiliar with the study foods were excluded, as well as those scoring 9 on the disinhibition scale; or 10 on the cognitive restraint scale plus 7 on the hunger scale of the Three Factor Eating Questionnaire (Stunkard & Messick, 1985), as these individuals tend to respond to food cues differently from the general population (Brunstrom, Rogers et al., 2008; Yeomans, Tovey, Tinley, & Haynes, 2004). Participants attended the lab on four separate occasions spaced 5 days apart. At each session participants rated the number of portion sizes of eight foods/beverages displayed in front of them, after consuming breakfast (full conditions) or after an overnight fast (hungry conditions). On one of the full and one of the hungry conditions, participants were asked to rate the expected satiating power (ES) of each food before estimating portions. Thus, the four study conditions were: full, with ES rating absent (F); hungry, with ES rating absent (H); full, with ES rating present (FES); and hungry, with ES rating present (HES). The order of exposure to each condition was randomised across subjects (Williams, 1949). The ES rating consisted of a pre-piloted 100 mm visual analogue scale (VAS) question to which subjects responded under conditions FES and HES prior to portion rating: ‘‘how full do you think you would be after consuming this amount of food/drink?’’ (Brogden, 2009). In the context of this study, ES refers to the imagined sensation of fullness at the end of a meal and is comparable to ES measured using photographic stimuli (Brunstrom & Rogers, 2009). Prior to portion size estimation subjects were reminded that a portion was ‘‘the quantity of food/drink that you would consume on one eating or drinking occasion’’ (Schwartz & Byrd-Bredbenner, 2006). Subjects then rated portion sizes of test foods/drinks by responding in writing to the following question for each item: ‘‘how many portions of (item) do you think are in/on this (container type)?’’. Subjects were allocated 1 min to estimate and record the portion size of each test food/drink. Forty-five
Test foods/drinks were selected to represent items commonly consumed amongst university students and included: chocolate muffin; chocolate ice-cream tub; hot chocolate container; bottled cola; potato chips pack; king size chocolate bar; bowl of cornflakes (dry); fresh banana with skin (Table 1). All brand names were concealed before display. Each food/drink was presented in an individual booth, with the sequence randomised across sessions.
Table 1 Mean SEM (n = 27), liking, familiarity and expected satiation ratings for test foods/ drinks and mean SEM (n = 54) portion estimate under full (F) and hungry (H) conditions. Portion estimates data under the ES and non-ES rating conditions were pooled as the presence of the ES rating had no effect on portion estimates (Brogden, 2009). Expected satiation (100 mm VAS)
80.7 3.1*
88.4 3.5
a
92.3 2.3
85.3 2.6 76.4 3.8 53.2 5.2 39.3 4.5 45.3 4.7 35.7 3.8 59.4 5.0 38.2 3.6
(F) (H) (F) (H) (F) (H) (F) (H)
2.32 0.15 1.96 0.13 1.34 0.12 1.08 0.11 1.00 0.09 0.79 0.07 1.45 0.09 1.12 0.06
(F) (H) (F) (H) (F) (H) (F) (H)
63.5 4.8 49.0 4.0 54.4 4.6 37.1 4.4 79.6 3.8 69.4 3.2 65.2 4.3 54.6 4.8
(F) (H) (F) (H) (F) (H) (F) (H)
1.20 0.09 1.01 0.09 1.27 0.07 1.09 0.06 2.46 0.19 1.98 0.17 1.21 0.07 1.01 0.08
(F) (H) (F) (H) (F) (H) (F) (H)
Liking (100 mm VAS)
Ice-cream, tub (427 g, 5125 kJ) Chocolate bar (85 g, 1741 kJ) Fresh banana (80 g, 318 kJ) Hot chocolate, opaque container (473 ml, 2025 kJ) Muffin (140 g, 2372 kJ) Cola bottle (500 ml, 879 kJ) Potato chips, pack (150 g, 3125 kJ) Cornflakes, bowl, dry (63 g, 983 kJ) * a b c d
Portion size estimate (units)
Familiarity (100 mm VAS)
Item displayed
79.9 4.0
78.7 4.9
93.4 2.4
76.0 3.1
88.4 2.9
75.1 4.5
85.9 3.1
67.3 3.1
92.8 2.1
b
61.9 4.7
90.2 3.0
60.8 4.8
81.3 4.6c,d
Differs from cornflakes with p < 0.05. Trend, against cornflakes (p = 0.05). Trend, against ice-cream (p = 0.05). Trend, against banana (p = 0.05). Trend, against chocolate bar (p = 0.07).
N. Brogden, E. Almiron-Roig / Appetite 55 (2010) 551–555
Data management and statistical analysis Data were analyzed with SPSS for Windows, Version 16.0. (SPSS Inc., Chicago). Portion size estimates, expected satiation (ES), ES per unit of energy (ES/kcal), hunger, fullness, liking and familiarity ratings were treated as continuous data. ES/kcal was calculated dividing ES ratings (mm) by the energy content (kcal) of each displayed food. Because the presence of an ES rating had no influence on portion estimates in our study population (Brogden, 2009), results of portion estimates were pooled across the two ES conditions. Mean hunger, fullness, liking and familiarity ratings were compared using one-way repeated measures ANOVA with the Bonferroni correction, for analyses across conditions, and with paired t-tests or the Wilcoxon test for analyses across foods. The Pearson’s product-moment correlation test was used to investigate the relationship between liking, familiarity and ES ratings with portion size estimates within each food. Spearman’s rank correlation test was used for analyses across foods. The level of significance for all tests was set at <0.05.
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Table 2 Results of Pearson’s correlation test (n = 54). Pooled data were used as before (see Table 1). Variance (%) in portion estimates as explained by liking was: banana 26% (full) and 27% (hungry); cola 28% (full) and 12% (hungry); cornflakes 8% (full). For familiarity: cola 10% (full); ice-cream 9% (full). For ES/kcal, cornflakes 8% (full); chips and ice-cream 12% (full); hot chocolate 20% (hungry). Item
Condition
Liking vs. Portion estimate
Familiarity vs. Portion estimate
ES/kcal vs. Portion estimate
Chocolate bar
Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry Full Hungry
r = 0.01 r = 0.02 r = 0.07 r = 0.06 r = 0.51*** r = 0.52*** r = 0.53*** r = 0.35* r = 0.28* r = 0.16 r = 0.03 r = 0.05 r = 0.1 r = 0.23# r = 0.25# r = 0.06
r = 0.18 r = 0.16 r = 0.19 r = 0.09 r = 0.01 r = 0.09 r = 0.31* r = 0.24# r = 0.01 r = 0.05 r = 0.10 r = 0.15 r = 0.01 r = 0.08 r = 0.30* r=0
r = 0.04 r = 0.21 r = 0.03 r = 0.09 r = 0.05 r = 0.22 r = 0.26# r = 0.10 r = 0.29* r = 0.06 r = 0.35* r = 0.16 r = 0.26# r = 0.45** r = 0.35* r = 0.02
Muffin Banana Cola Cornflakes Potato chips Hot chocolate Ice-cream
Results *
Correlation is significant with p < 0.05. Correlation is significant with p < 0.01. *** Correlation is significant with p < 0.001. # Correlation shows a trend (i.e. 0.1 > p > 0.05). **
Participants All enrolled subjects (n = 27) completed the study. Mean (SEM) age and BMI were 24.9 (6.5) years and 23.3 (2.4) kg/m2. Mean (SEM) dietary restraint, disinhibition and hunger scores were 4.4 (3.8), 4.8 (2.2) and 6.3 (2.8) respectively. Appetite, liking and familiarity ratings ANOVA revealed a significant main effect of time on hunger [F(3.93, 102.23) = 145.63, p < 0.001] and fullness [F(3.71, 96.44) = 188.99, p < 0.001] confirming the effect of the intervention (Brogden, 2009). The most liked food was the ice-cream, whilst the least liked food were the cornflakes. The food rated as most familiar was the banana and the least familiar the cornflakes (Table 1). ANOVA identified a significant main effect of test food/ drink on mean ratings for liking and familiarity (F(7, 182) = 4.27, p < 0.001 and F(3.75, 97.56) = 4.09, p < 0.01 respectively). Pairwise comparisons confirmed higher liking ratings for the ice-cream (80.7 3.1) than for cornflakes (60.8 4.8) (p < 0.05). Mean liking also tended to be higher for the ice-cream compared with the potato chips (61.9 4.7) (p = 0.05) and for the chocolate bar (79.9 4.0) compared with the cornflakes (p = 0.05). No significant differences in familiarity ratings were detected between pairs of foods and drinks, except for a trend for the banana and for the chocolate bar (Table 1). Effects of liking and familiarity on portion size estimates Despite significant differences between liking ratings, the majority of portion estimates tended to fall within a much smaller range (Table 1). When looking at individual items, significant correlations between liking and portion estimates were detected for the banana and the cola (Table 2). Thus, individuals who liked the banana and the cola the most estimated these items in smaller portions than those individuals who liked them the least. A positive correlation was detected between liking and portion estimates for the cornflakes (full only). Thus individuals who liked the cornflakes the most estimated them in larger portion sizes than those individuals who liked them the least. Therefore, food/drink type affected the direction of the correlation. Also, liking ratings explained as little as 8% and as much as 28% of the variance in portion estimates, depending on food/drink type (Table 2).
Significant correlations between familiarity ratings and portion size estimates were detected for the cola and the ice-cream under the full condition only (Table 2). Thus, when full, individuals who were most familiar with the cola and the ice-cream estimated these foods in smaller portion sizes than individuals who were least familiar. However, changes in familiarity ratings explained only a small proportion of the variance in portion estimates (up to 10%) (Table 2). This relationship was not observed under hungry conditions for either food/drink, although a trend in the same direction was detected for the cola. Additional analyses across foods (n = 8) revealed no significant associations between familiarity and portion estimates or between liking and portion estimates under any of the appetite conditions. Effects of expected satiation on portion size estimates Expected satiation ratings for each item are shown in Table 1. Significant correlations with portion size estimates were detected for the cornflakes, chips, hot chocolate and ice-cream, and a trend in the same direction was observed for the cola. Thus, individuals who rated these foods as more filling estimated the portions of such foods as larger than individuals who rated the same foods as less filling. This occurred when full only, except for the hot chocolate. Variations in ES explained between 8% and 20% of variations in portion estimates (Table 2). Across foods, ES/kcal correlated with portion estimates under the full condition [rho = 0.74 (p < 0.05)], and a similar trend was detected in the hungry condition [rho = 0.67 (p = 0.07)]. Thus, participants tended to assign smaller portions to some foods with high ES/kcal (banana, cola and cornflakes) and larger portions to some foods with lower ES/kcal (ice-cream, chips), however this did not occur for all foods (Fig. 1). Discussion We explored the effects of liking, familiarity and expected satiation (ES) on portion estimation using a convenient sample of 8 popular foods, evaluated by a panel of 27 men, under both hungry and full conditions. We detected significant negative associations
[()TD$FIG]
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Figure 1. Variation of portion size estimation with expected satiation (adjusted for energy content) under full conditions. Results of Spearman’s rank correlation are indicated. Each portion estimation point corresponds to the mean SEM of 54 individual ratings.
between liking and portion size estimates for the banana and the cola (the two most familiar items); and between familiarity and portion estimates for the ice-cream and the cola (full condition only). We also explored the extent to which expected satiation (ES) predicted changes in portion estimates. Significant positive correlations were detected for the cornflakes, chips, hot chocolate and ice-cream. Across foods, adjusted ES ratings correlated negatively with portion estimates under the full condition. Liking has been positively associated with the size of a satisfactory (satiating) portion (Brunstrom & Shakeshaft, 2009). Thus, we expected that within a given food, liking ratings and portion estimates would be inversely related. In other words, the more you like something, the more you could imagine eating of before being satisfied. We detected significant associations in such direction but only within certain foods (banana and cola). Liking has been tightly linked to palatability, which has been shown to positively influence energy intake in controlled laboratory studies (Yeomans, 2007). However Brunstrom and Rogers (2009) recently showed that expected satiation was a better predictor of meal size than expected liking. Foods with low expected satiation (not expected liking) were selected in larger portion sizes and regarded as less rewarding than other foods of equal caloric value. Thus, even for foods that are well liked, preference may not be a strong enough predictor of portion size selection. In agreement, we found no significant association between liking and portion size estimations across foods, however only a small number of foods were tested. While in the banana and the cola, liking ratings correlated with portion estimates under both appetite conditions, for the cornflakes, ice-cream and hot-chocolate this tended to occur selectively under hungry or full conditions only. It is possible that appetite status may interact with food type to modify the effects of liking on portion size estimates in certain foods (Gibson & Desmond, 1999; Yeomans, Weinberg, & James, 2005). In contrast to the liking results, our results for familiarity digress from previous findings (Brunstrom, Rogers et al., 2008; Brunstrom & Shakeshaft, 2009; Brunstrom, Shakeshaft et al., 2008). Since familiar foods are expected to be more filling than unfamiliar foods due to learned experiences, we hypothesized that familiarity ratings would be positively associated with portion size estimates (Brunstrom, Shakeshaft et al., 2008). Analyses within foods showed that as familiarity increased, portion estimates did not change significantly for most items, with the exception of cola and icecream, for which familiar subjects estimated portions as smaller than less familiar subjects. Across foods, no significant associations
were detected in any direction, which could be explained by the low variability in portion estimates and familiarity ratings in this dataset. In line with Brunstrom and Rogers (2009), changes in expected satiation ratings (adjusted for energy content) predicted (full) or tended to predict (hungry) changes in portion size estimation across foods. The low variability in portion size estimates mentioned above could also explain the lack of a stronger association between ES ratings and portion estimates especially when hungry. In addition, strong appetite feelings could potentially suppress the effects of past experiences when making decisions about foods. In agreement, correlations of ES/kcal within foods tended to be significant mostly under the full condition. Subjects who perceived the cornflakes, chips, hot chocolate and ice-cream portions as more filling, rated these portions as larger than subjects who found them less filling. This could be related to the actual volume displayed of these foods, which may be larger than what subjects normally consume, affecting participants’ perception of portion size and ES (Gibson & Brunstrom, 2007; Kral, 2006). We measured liking and familiarity only once prior to the test, under uncontrolled appetite conditions, and excluded participants who strongly disliked or were unfamiliar with the test foods. The exact effect of appetite status on liking and familiarity cannot be established from these data. However, despite the limited number of foods tested, subjects consistently rated portions as smaller when hungry than when full, irrespective of how filling they expected the foods to be (Brogden et al., 2009). These results support previous findings pointing to a possible dissociation between macronutrient composition, caloric value and portion size estimation (Brunstrom, Shakeshaft et al., 2008; Rolls, Roe, & Meengs, 2007). In order to reduce variability, we investigated non-restricted male eaters only, with a narrow BMI range. Whilst dietary learning seems to be predicted by levels of dietary restraint (Brunstrom & Mitchell, 2007) it is unclear how restraint and BMI may affect the relationship between liking and portion estimation. Further research is required to determine how liking and familiarity influence portion estimation of a wider range of foods and in other individuals. In conclusion, we have confirmed an association between liking and portion size estimation in some popular foods/drinks. Thus, for these foods, the more they were liked, the smaller their assessment of the portion size displayed. Also, for some foods, the more filling they were expected to be, the larger their portion estimation. The degree to which ES predicts changes in portion size estimation across different foods requires further investigation, but this is expected to follow an inverse relationship (Brunstrom & Rogers, 2009). Studies using a wider range of food items are necessary to elucidate which food attributes interact with liking/familiarity and ES to effect changes in portion size selection. Such information would be useful for developing behavioural interventions for weight loss and for the treatment of eating disorders (Gibson & Brunstrom, 2007).
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