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Effects of fat content on fat hedonics: cognition or taste?
Physiology & Behavior 78 (2003) 247 – 253
Effects of fat content on fat hedonics: cognition or taste? Deborah Bowena,b,*, Pamela Greenb, Nancy Vizenora,b, Cathy Vua, Petra Kreutera, Barbara Rollsc a
Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA b University of Washington, Seattle, WA, USA c Pennsylvania State University, State College, USA
Received 20 February 2002; received in revised form 14 October 2002; accepted 1 November 2002
Abstract Understanding and perhaps overriding preferences for fat is important, given the relationship between higher dietary fat consumption and poorer health. We have examined the roles of potential mechanisms for differences in fat preference: actual fat content and expected fat content. The subjects were women (n = 192, ages = 50 – 69) recruited to a study of low-fat dietary change. Subjects were randomized to one of the four cells: participants received either a high- or low-fat milkshake at baseline, and half of each group was told that their milkshake was low in fat and the other half high in fat. Women who received a high-fat milkshake consumed more grams than women who received a low-fat milkshake. Women who expected low-fat shakes reported liking them more than those who expected high-fat milkshakes. These data indicate that both physiology and cognition play a role in determining consumption of high- and low-fat foods. D 2002 Elsevier Science Inc. All rights reserved. Keywords: Fat preference; Dietary fat; Taste
1. Introduction Fat is a preferred substance in general [1]. Understanding and perhaps overriding the consistent preference for and consumption of fat is important, given the relationship between dietary fat and health [2]. Consumption of a higher-fat diet has been linked to several chronic health problems, including cancer and cardiovascular diseases [3,4]. Reduction in daily fat consumption is the focus of several ongoing studies [5]. There is some evidence that reducing daily consumption of dietary fat causes a reduction in self-rated preference for fat [6]. Reduced preferences could help to maintain the reduced consumption, leading to reduced risk for disease [1]. The mechanisms that could be involved in a reduced selection of fat are unknown. We have chosen to examine the roles of three potential mechanisms for fat preference, based on the conceptual model described by Rozin and Vollecke [7]. In this formula* Corresponding author. Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue, N. MP900, Seattle, WA 98109, USA. Tel.: +1-206667-4982; fax: +1-206-667-7850. E-mail address: [email protected] (D. Bowen).
tion, preference is defined as the choice or selection of foods with a particular content, taste, or other quality. First, choice for a food has been shown to vary depending on the liking, or hedonic judgement of a food, and high-fat content of foods generally produces higher hedonic ratings [1]. Palatability is an important aspect of food choice and consumption, and certainly fat increases palatability [8]. Therefore, changing the fat content of the food may influence choice. According to this model, if we reduce the fat content of a food, we should find that individuals consume less of it. In this study, we manipulated the fat content of a food offering and asked individuals to taste it and rate its taste properties. We also measured amount consumed, to obtain a behavioral measure of choice. Second, previous research has examined the extent to which food selection may be modified by cognitions or labels attached to the foods [9,10]. Expected consequences of ingestion, for example, are important motivators of food choice, and the consequences of consuming high-fat foods are possibly a reason for avoidance. In a laboratory study, individuals ate more calories after a preload labeled ‘‘lowfat’’ than after an equicaloric preload labeled ‘‘high-fat’’ [11]. In a different study, when food was labeled ‘‘high-fat,’’
0031-9384/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 3 1 - 9 3 8 4 ( 0 2 ) 0 0 9 7 3 - 3
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subjects consumed less of it even though their hedonic ratings for ‘‘high-fat’’ food were higher than for food labeled ‘‘low-fat’’ [12]. These labels could alter the perceived health value of a food or class of foods, and therefore alter choices and hedonic judgements. Other studies have demonstrated the effects of labeling foods as to fat content on changing consumption [13– 15]. Therefore, we independently manipulated the label of high- or low-fat content to test this mechanism for determining preference and choice. Third, reports of gastrointestinal distress after eating highfat foods exist in individuals consuming lower amounts of daily dietary fat [6]. This association of high-fat foods with gastrointestinal distress could lead to decreases in liking and consumption. This finding leads us to the hypothesis that post-ingestional consequences of high-fat foods are distressing and could ultimately reduce choice of high-fat foods. We did not independently manipulate post-intestinal consequences in this study, but simply measured symptoms before and after consumption. We investigated the role of fat labels vs. fat content in a previous study of college students [16]. In this previous study, the actual fat content of the ice cream presented to subjects (high- vs. low-fat) and the expected fat content of the ice cream were independently manipulated to provide a balanced test of fat content vs. cognitions [17]. Consumption of the ice cream was higher when subjects expected high-fat ice cream than when subjects expected low-fat ice cream. Our data show the opposite pattern of Wardle and Solomons [12] above. We hypothesize that this difference is due to the characteristics of the participants. The subjects in our study were young (average age = 19), all recruited through an undergraduate subject pool. We concluded that, for this sample of young women, fat consumption was affected by label and that ‘‘high-fat’’ was a desirable quality. We wanted to extend our research and the findings of others to a sample of individuals that might identify ‘‘fat content’’ as particularly salient but with undesirable qualities. We conducted this study to better understand the effects of fat content and fat label on laboratory food consumption in a group that would likely have an interest in changing dietary habits and be aware of the health conditions associated with a high-fat diet. For the present study, we recruited subjects from the baseline period of an ongoing study of long-term dietary change in older, postmenopausal women, ages 50 – 79. We investigated the effects of label for high- and low-fat vs. actual fat content on consumption of high- and low-fat foods. We hypothesized that taste and label would affect both actual consumption and hedonic judgments. We hypothesized that these women would consume low-fat food more, compared to high-fat food, because of the potential for increased risk of nutritionally related disease in women aged 50 –79. We also measured hedonic judgements and fat taste judgements to determine the relationship between labeled and actual fat content to these judgements about taste. We hypothesized that the label of ‘‘high-fat’’ would cause
lowered hedonic judgements, again due to the characteristics of the women being tested.
2. Experimental methods 2.1. The Women’s Health Initiative We recruited our participants from the Women’s Health Initiative (WHI), a multicomponent set of research projects [5,18]. Its aim is to test methods of preventing common causes of morbidity and mortality among post-menopausal women. The major focus of this project is on cancer, cardiovascular diseases, and osteoporotic fractures. The WHI was initiated in 1992 and will be completed in 2007. Approximately 165,000 women aged 50 –79 years will be recruited nationwide at 40 WHI clinical centers and enrolled in either the three clinical trials (n = 64,500 women) or in the observational study (n = 100,000 women). The standard screening process for WHI included three separate visits; final eligibility determination and randomization were made on the third visit. Average follow-up will be approximately 9 years. The hypothesis for the randomized dietary trial within the WHI (DM) was that a low-fat, high fruit/vegetable/grain dietary plan would prevent breast and/or colorectal cancer and, secondarily, coronary heart diseases. Participants (n = 48,837) included in the DM met the criteria of having a daily caloric intake of more than 32% of energy from fat, living in the area for at least the following 3 years and willing to participate. Excluded were women with breast cancer or any other invasive cancer within the past 10 years, mastectomy, suspicion of poor dietary adherence, inability to complete a 4-day food record, having more than 10 meals out of home per week. Forty percent of the women involved in the DM were randomized to the intervention group, which followed the three nutritional goals: decrease of daily fat intake to less than 20% of total caloric intake (saturated fat intake to less than 7%), increase of fruits and vegetables to at least five servings per day and increase of grain products to at least six servings per day. This intervention program was delivered in groups, based on data from feasibility studies [19]. It included nutritional as well as psychological and behavioral strategies. 2.2. Design of the Taste Test Study The current study, called the Taste Test Study (TTS), was a research project to study the determinants of fat consumption and hedonic ratings in this sample of older women. The study session reported here was conducted at baseline, before randomization into the parent WHI DM study. The experimental design of the study was a 2 2 balanced placebo design [16] with two levels of actual fat content (high and low) and two levels of expected fat concentration (high and low) as the two factors. This study design allowed
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us to pit the cognitive explanation against the hedonic explanation for fat choice. Subjects were randomized to one of the four cells. Participants received either the highor low-fat milkshake, and were independently ‘‘informed’’ about the milkshake’s fat content (high or low) during both sessions. In this context, the ‘‘placebo’’ was the high-fat condition. 2.3. TTS subjects Subjects (n = 192) for this study were recruited from the Seattle Clinical Center intervention group participants from the WHI DM component. The average age of the TTS participants was 64 (S.D. = 10.2). A total of 91% were Caucasian, 74% had obtained a 4-year college degree, and 65% were married or living with a partner. During the second screening visit for the WHI, a diet technician informed the women about the possibility of taking part in the TTS by describing the study as one investigating whether dietary change affects women’s ability to taste foods. All participants were asked if they would consume dairy and chocolate products as part of the study. At the third screening visit, eligible participants were offered participation in the TTS and joined the WHI DM. If a woman was not eligible for DM, she was not eligible for the TTS. Women who participated in the TTS were randomized by the TTS staff to one of the four different drink/expectancies conditions of low- and high-fat milkshakes. Therefore, TTS women participated in their baseline taste session before any dietary sessions were conducted. However, these participants were screened for interest in dietary change and, therefore, had all expressed interest in and desire for a low-fat dietary plan. 2.4. Milkshakes During the taste session, we gave each participant a 16-oz chocolate-flavored milkshake and asked her to fill out a taste judgement questionnaire, consisting of 17 items about fat taste, flavor, and hedonic preferences. The ingredients for the milkshakes were as follows: Dreyer’s grand vanilla ice cream (high-fat shake only), Dreyer’s fat-free vanilla ice cream (low-fat shake only), whole milk, half and half (highfat shake only), nonfat milk (low-fat shake only), Hershey’s chocolate syrup, and Thicken Up (low-fat only, Sandoz). The nutritional composition of the milkshakes used in the present study is included in Table 1. The milkshakes were mixed on each laboratory session day and poured to fill 16-oz plastic cups. Weight and volume were approximately equal for the two milkshakes.
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Table 1 Nutrient composition of milkshakes Nutrient composition High-fat
Fat (g) Energy (kcal) Kcal from fat (%) Protein (g) Carbohydrate (g)
Low-fat
Per 100 g
Per shake
Per 100 g
Per shake
9.5 150.9 56.0 3.1 14.9
37.6 599.0 56.0 12.4 59.1
1.2 90.2 12.0 3.6 17.8
4.9 364.0 12.0 14.4 71.8
among the groups. Most of the participants (70%) had their visit at either 2:00 or 3:00 p.m. and, therefore, there was not enough variability to look at a time of day effect. At their scheduled appointment, the experimenter greeted each participant and led her to the interviewer room in the Fred Hutchinson Cancer Research Center. After filling out the consent form and the first symptom checklist, the experimenter introduced the taste test session with the verbal instructions: ‘‘Let me tell you a little bit about the study today. Some people who have participated in dietary studies, like the WHI, tell us that their sense of taste has changed during their participation. So today, we are going to have you taste one of the special milkshakes we have developed at Fred Hutchinson, and tell us what you think of it. Please fill out this rating sheet now, and let me know if you have any questions. I will be right back. Drink as much of the milkshake as you want. When you are done with the rating you can start on that packet of questionnaires.’’ Each participant then received the milkshake. Depending on her randomization, it was either a low- or high-fat milkshake, and she was either correctly or incorrectly informed about the fat content by the experimenter. To inform the participant, the experimenter said that the shake was a ‘‘low-fat, light’’ or a ‘‘rich, high-fat’’ drink. The appropriate phrase was used again in the next few sentences. The experimenter left the room for 5 min, returned to answer any questions about the sheets, and then left again for another 20 min. After filling out the taste sheet, the participant continued to complete a packet of the questionnaires. The participant was handed the second symptom checklist to complete and left alone again for 10 min. The experimenter took the shake from the participant at this time. If she needed more time to fill out the questionnaires, she was escorted to the WHI clinic waiting room where she could complete them. After the experiment, the participant was thanked for her participation.
3. Assessments 2.5. Procedure Laboratory sessions were scheduled with the third WHI screening visit, and the subjects refrained from eating for at least 2 h before the visit. All visits were scheduled between 11:00 a.m. and 3:00 p.m. Time of day of visit did not differ
Taste judgments were measured using a 17-item taste judgement sheet, which was filled out by the participant while consuming the milkshake. Each of the 17 items was rated on a 1 – 9 scale with adjective anchor points. The judgement list included fat taste items (creamy, oily, heavy,
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grainy) adapted from previous research [20,21] and a former study about fat and taste [22], items measuring flavor (sweet, tart, spicy, tasty) and hedonic preference judgment (appealing, pleasant, serve to guests, liking, satisfying when hungry), as well as single items (colorful, pleasant aroma, salty, and healthful). Consumption was measured by calculating the weight change of the milkshakes. Every milkshake was weighed before and after the laboratory session without the participants’ awareness. The weight difference score (before – after) was defined as our measure laboratory consumption. This procedure had been used in other research situations [16] as an estimate of preference. Self-reported symptoms were measured twice during the taste session: before and 25 min after the participant had consumed as much as they wanted of the milkshake. Symptom words literally included hungry, full, thirsty, comfortable, satisfied, nauseous, queasy, bloated, and sick. Each item was rated on a 1– 9 scale with adjective anchor points. This questionnaire was an adapted version of a questionnaire used [23] to assess GI symptoms in bulimic women. We used the Food Frequency Questionnaire (FFQ) as the main dietary assessment instrument for the WHI [24]. The WHI FFQ consisted of 124 food items or food groups, with 16 introductory questions (e.g., When you ate chicken, how often did you eat the skin?) used to refine nutrient calculations. There were nine categories of frequency responses which, for foods, range from never or less than once per month to six or more times per day. Portion size response options were ‘‘small,’’ ‘‘medium,’’ or ‘‘large,’’ based on the medium portion size printed on the questionnaire. The questionnaire was designed to be sensitive to fat-modified foods and food preparation methods, as well as to foods regionally and culturally consumed. The nutrient databases (from the University of Minnesota Nutrition Coordinating Center’s Nutrient Data System) and algorithms for FFQ analyses are described in detail elsewhere [25,26]. The FFQ was found to be moderately correlated with daily dietary food records in a sample of the WHI [27]. 3.1. Analyses Several of the taste items potentially measured similar tastes. Therefore, we first performed factor analysis of principal components with varimax rotation on the taste items to identify underlying constructs of the taste judgement items. We performed separate factor analyses for the fat taste items (creamy, grainy, oily, heavy) and the hedonic judgement items (appealing, pleasant, serve to guests, like, and satisfying). For both factor analyses, we set the eigenvalue at 1 or greater and included items if they loaded higher then 0.5 onto the factor and lower than 0.3 onto any other factor. We averaged the selected items to form scales for use in the subsequent analyses. We then examined the main outcomes: consumption, taste judgements, and hedonic ratings using analysis of variance. Finally, we examined the change in symptoms from before to after the taste test using a repeated
measures analysis of variance to determine any effects of actual and expected fat consumption on symptoms. All analyses are based on two-tailed tests.
4. Results 4.1. Fat consumption The participants in this study consumed an average of 37% of daily energy as fat and a median of 38%, based on responses to the FFQ. There were no differences in percent of energy from fat for participants in the four study conditions. All participants did refrain from eating for at least 2.5 h before the laboratory sessions. For further analysis purposes, we divided participants into low-fat (fat consumption = 35%) and high-fat (fat consumption = 42%) categories, based on a median split of daily percent of energy from fat. 4.2. Identification of taste scales The fat taste analysis produced one scale composed of oily (loading = 0.80) and heavy (loading = 0.84). These items were subsequently averaged to form a single scale score. Creamy loaded highly onto a separate factor (loading = 0.84) and therefore was used in analysis as a single item. Grainy did not meet the loading criteria for either factor and was dropped from analysis. Together, the oily/heavy factor and the single item accounted for 73% of the variance. The Cronbach’s a for this scale was .59. The second factor analysis on the hedonic preference judgments items used the same technique and criteria as above. All five items loaded onto a single factor, accounting for 67% of the variance. Therefore, the following items were averaged to form the hedonic preference judgment scale: appealing (loading = 0.58), pleasant (loading = 0.67), serve to guest (loading = 0.69), like (loading = 0.84), and satisfying (loading = 0.56). The range of this scale was 2 – 9 with a X¯ of 6.7 and an S.D. of 1.64. The Cronbach’s a for this scale was .87. We performed a factor analysis on the symptom items to identify clusters of symptoms, using the same methodology as above. Three factors emerged from the nine items: GI distress (nausea, queasy, bloating, and sick, with loadings of 0.67, 0.73, 0.81, and 0.87), satiety (hunger, full, and thirsty, with loadings of 0.81, 0.63, and 0.57), and well-being (comfortable and satisfied, with loadings of 0.84 and 0.76). Together, these scales explained 59% of the variance. Each group of scale items was averaged to provide a single scale score for GI distress, satiety, and well being. The overall ranges, X¯, and standard deviations for GI distress, satiety, and well being were 1 – 9, X¯ = 1.4, S.D. = 1.2; 1 – 9, X¯ = 4.9, S.D. = 1.4; and 1– 9, X¯ = 6.1, S.D. = 2.4, respectively. The Cronbach’s a for these scales were .76, .45, and .55, respectively, for GI distress, satiety, and well being.
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4.3. Consumption and taste findings
Table 3 Ratings of fat taste for expected and actual milkshakes
Table 2 presents the consumption, and hedonic judgement measures in all participants (n = 192). The analysis of variance (ANOVA) showed that there was a significant main effect of actual drink on consumption ( F = 3.7, df = 1,188, P < .05). Women who received a high-fat milkshake consumed more than women who received a low-fat milkshake. The effect of expected drink on consumption was not significant ( F = 1.5, df = 1,188, P=.23). There was no interaction effect of expected drink vs. actual drink ( F = 0.0, df = 1,188, P=.99). In addition to the effect of labels vs. actual fat content, we analyzed the differences in consumption between participants who ate higher than the median daily fat consumption vs. lower than the median daily consumption. There were no differences in the amount consumed when the high- and low-fat daily consumption participants were compared. Participants reported liking the actual high-fat milkshakes better than the low-fat milkshakes ( F = 17.1, df = 1,188, P < .0001). A significant main effect of expected drink on hedonic preference was also identified ( F = 4.2, df = 1,188, P < .05). Women who expected low-fat shakes reported liking them more than those who expected high-fat milkshakes. There was no interaction effect of expected vs. actual drink ( F = 0.1, df = 1,188, P=.72). There were no effects of high- vs. low-fat daily consumption on hedonic judgements. The fat taste judgements creaminess and oiliness/heaviness are presented in Table 3. The ANOVA showed that women who received high-fat milkshakes found them to be creamier than those who consumed low-fat milkshakes ( F = 4.01, df = 1,188, P < .05). The effect of expected drink on creamy was not significant ( F = 0.3, df = 1,188, P < .57). There was no interaction effect of expected vs. actual drink on creamy taste ( F = 0.1, df = 1,188, P=.80). In contrast to the findings of actual/expected drink on creamy taste, there was a significant main effect of expected drink on oily/heavy judgements ( F = 6.0, df = 1,185, P < .02) and no effect of actual drink on oily/heavy judgements ( F = 0.1, df = 1,185, P=.74). All participants who expected
Creaminess ratingsa
Actual milkshake content High-fat (n = 105)
(b) Hedonic judgementsa Expected High-fat (n = 89) milkshake Low-fat (n = 103) content a
High-fat (n = 89) Low-fat (n = 103)
Oiliness ratingsa
Expected milkshake content
High-fat (n = 105)
Low-fat (n = 87)
5.7 * (0.4) 5.4 (0.3)
5.0 (0.7) 4.9 (0.4)
Actual milkshake content
High-fat (n = 86) Low-fat (n = 103)
High-fat (n = 102)
Low-fat (n = 87)
2.8y (0.2) 1.8 (1.0)
2.4 (0.4) 1.5 (0.8)
a
Scale range is 1 – 9, where 9 is high. * Main effect of actual milkshake significant; P < .05. y Main effect of expected milkshake significant; P < .05.
high-fat shakes found them to be oilier/heavier in taste than those who expected low-fat milkshakes. There was no significant interaction of expected vs. actual drink ( F = 2.1, df = 1,185, P=.15). There were no effects of high- vs. low-fat daily consumption on any fat intake measure. Table 4 shows the scores for the three symptom scales components before and after the taste test. There were no significant main effect differences for either of the two study conditions (expected and actual). The main effect of time was significant for ratings of GI distress, satiety, and well being ( F = 5.4, df = 1,186, P < .05; F = 177.8, df = 1,186, P < .01; F = 7.8, df = 1,186, P < .01 for GI distress, satiety, and well being, respectively). The interaction of time with actual fat content was significant for both reported satiety and well-being ratings ( F = 4.9, df = 1,186, P < .05 and F = 8.6, df = 1,186, P < .01 for satiety and well being, respectively). Participants who consumed high-fat shakes increased their ratings of satiety and well being from before to after consumption, relative to those who consumed low-fat shakes. Finally, the interaction of time with expected drink was significant for ratings of well being ( F = 3.9, df = 1,186, Table 4 Symptomsa (X¯, S.D.) reported before and after milkshake consumption
Table 2
(a) Amount of milkshake consumed (g) Expected High-fat (n = 89) milkshake Low-fat (n = 103) content
Expected milkshake content
Actual milkshake content
237.4 * (22.5) 257.6 (28.9)
6.8 * ,y (1.1) 7.2 (1.2)
Scale range from 1 to 9, where 9 is high. * Main effect of actual milkshake significant; P < .05. y Main effect of expected milkshake significant; P < .05.
Study conditions
Low-fat (n = 87) 204.5 (19.0) 225.2 (15.2)
5.8 (0.5) 6.3 (0.9)
Expected high/ actual high Expected high/ actual low Expected low/ actual high Expected low/ actual low a
GI distress
Satiety
Well being
X¯ (S.D.) *
X¯ (S.D.) * ,* *
X¯ (S.D.) * ,* * ,** *
Before
After
Before
After
Before
After
1.1 (0.2) 1.3 (1.0) 1.2 (0.4) 1.4 (1.3)
1.5 (1.4) 1.4 (1.2) 1.3 (0.6) 1.5 (1.4)
4.9 (1.6) 5.1 (1.5) 5.0 (1.5) 5.4 (0.8)
6.7 (1.5) 6.4 (1.2) 7.0 (1.4) 6.8 (1.3)
5.9 (2.5) 6.7 (2.3) 6.0 (2.3) 5.9 (2.4)
6.7 (2.1) 6.2 (2.0) 7.1 (1.7) 6.4 (2.0)
Scale range is 1 – 9, where 9 is high. * Main effect of time significant; P < .05. ** Interaction of time with actual milkshake significant; P < .05. *** Interaction of time with expected milkshake significant, P < .05.
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P < .05). Women who expected low-fat drink increased reports of well being from before to after, relative to those who expected high-fat drinks.
5. Discussion The findings of this study indicate that the fat content of a food provided in a laboratory setting does affect consumption and hedonic preference ratings. The direction of the consumption effect is similar to that of previous research (e.g., 12) but the effects for hedonic preference ratings were slightly different. In the previous study, subjects consumed less food with the label ‘‘high-fat,’’ but rated the actual ‘‘high-fat’’ foods as more preferred. This divergence of consumption and preference rating did not occur in the present study. In this study, women reported preference in the opposite direction for the label of fat content. Shakes labeled ‘‘low-fat’’ were rated as more preferred than drinks labeled ‘‘high-fat.’’ From these findings, we can speculate that high-fat foods might taste better, but that hedonic preference ratings are influenced by cognitive factors in this sample of women ready for dietary fat intervention. One possible explanation for differences in ratings from this study and previous research is the characteristics of the participants. Indeed, the response to the label of ‘‘low-fat’’ indicates some cognitive mechanism that controls hedonic judgements as well as taste judgments [28]. The women in this study were older, and in previous studies age has been associated with increasing concern about fat [29,30]. Also, all women in the present study were postmenopausal, and food consumption and taste preferences differ across the menstrual cycle [31]. Additionally, these women were recruited into a study to lower dietary fat. As such, dietary fat intake is highly relevant to these participants and probably seen as a negative label. We did not collect data on the labels assigned to low- and high-fat foods in the present study, nor did we in previous research. This potential explanation should be investigated in future research. These data, collected from a sample of older, postmenopausal women just randomized into an intensive dietary intervention trial for 10 years, were different from our previous research in college students. In that study [16], ‘‘high-fat’’ labeled food was consumed more, compared with ‘‘low-fat’’ labeled food. The procedures were similar between the two studies, even though slightly different foods were used (milkshakes vs. ice cream). The women in the present study were even slightly different in their ratings of high-fat food, when compared to the Wardle and Solomon participants, but these latter were not selected for interest in lowering fat. It is possible that younger, perhaps more weight-conscious women react differently to fat-related stimuli in laboratory settings, compared to older women. Pressures on younger women to be thin and to consume foods that promote thinness could act to disinhibit them from holding back. Perhaps older women, very motivated to eat
healthy foods, were more able to resist disinhibition. Therefore, these findings, together with others [12,28,29], indicate that taste and hedonics are dependent on the relevance and meaning of the food or category under observation. Again, this should be a topic of future research. The symptom measurements showed no main effects of consuming high- vs. low-fat foods (perceived or actual) on gastrointestinal symptoms distress. However, in this study, the time variable is, in essence, exposure to the food. Highfat shakes increased reports of satiety and well being, and expected low-fat food increased well being. GI symptoms did not differ over time by type of food. One conclusion to be made from these analyses is that consuming foods of varying fat content does not cause differing levels of gastrointestinal distress and, therefore, that post-ingestional symptoms are not likely to cause any decreased selection of high-fat foods. However, it could be true that post-ingestional GI distress symptoms only occur during times of dietary change, specifically fat reduction, and not during times of maintaining one’s typical dietary fat level. None of these women had started their intensive change program. Also, it could be true that symptoms occurred after longer time lapses in the postconsumption period. Or perhaps, symptomatic reactions to high-fat foods only occur after long periods of low-fat food consumption. We will be able to determine a time course for symptom experiences as we follow these women over time and across their participation in the intensive dietary intervention activities of the WHI. There are several design features of this study that limit the generalizability of the findings. First, the sample was composed of older, postmenopausal women. Certainly, age and hormonal status influence taste and eating, as might strong interest in learning how to eat healthy foods. Recent research by Roininen et al. [32] indicated that participants reported less concern about the health-related aspects of food and more concern about taste, compared with older participants in a large-scale survey. Each of these variables must be considered when comparing these findings to other studies. The sample does not represent women in the general public, as the WHI tends to be of higher socioeconomic status compared with the general public [5]. To the extent that fat taste is similar across socioeconomic status levels, we can make statements about other population groups, but the relationship between SES and reactions to fat consumption is unknown. Of course, in this study design, it is impossible to separate the effects of fat vs. energy. Future studies could manipulate this more carefully. The methods of measuring dietary fat choice and hedonic preference limit generalizability, in that we measured laboratory consumption in a very specific manner. Individuals did not choose among multiple foods, but ate only one food. Some of the Cronbach’s a’s for the scales were relatively low, pointing to the need to improve the taste measures. This study excluded large numbers of women, due to parent study requirements; therefore, generalization to a population-based sample is not possible. Finally, the fact that these women have been
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recruited to a study in which they may be asked to make major changes to their dietary habits may have influenced their responding. This must be considered when interpreting the data. Indeed, some of the women may have reported their answers in a false manner, because they wanted to represent themselves in a better light to the study investigators. This needs further exploration. In summary, the findings of this study have illuminated some basic effects of cognition and fat content in a sample of older women interested in dietary change. Older postmenopausal women interested in healthy eating consume more fat and rate high-fat foods as more preferred, compared with low-fat foods. Future research directions include similar investigations during times when individuals are making changes in their ongoing patterns and studies of these effects over longer periods of time.
Acknowledgements This work was supported by a grant (CA064327) from the National Cancer Institute. We gratefully acknowledge the thorough data management of Alithea Morasca.
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[11] Shide D, Rolls B. Information about fat content of preloads influences energy intake in healthy women. J Am Diet Assoc 1995;95(9):993. [12] Wardle J, Solomons W. Naughty but nice: a laboratory study of health information and food preferences in a community sample. Health Psychol 1994;13(2):180 – 3. [13] Solheim R. Consumer liking for sausages affected by sensory quality and information on fat content. Appetite 1992;19:285 – 92. [14] Caputo FA, Mattes RD. Human dietary responses to perceived manipulation of fat content in a midday meal. Int J Obes 1993;17:237 – 40. [15] Mattes RD. Fat preference and the adherence to a reduced-fat diet. Am J Clin Nutr 1993;57:373 – 81. [16] Bowen DJ, Tomoyasu N, Anderson M, Carney M, Kristal A. Effects of expectancies and personalized feedback on fat consumption, taste, and preference. JASP 1992;22:1061 – 79. [17] Marlatt GA, Rohsenow DR. Cognitive processes in alcohol use: expectancy and the balanced placebo design. In: Miller NK, editor. Advances in substance abuse, vol. 1. Greenwich, CT: TAI Press; 1980. [18] Behavioral Science Subcommittee NK. Women’s Health Initiative. Women’s Health Initiative: why now? What is it? What’s new? Am Psychol 1997;52:101 – 16. [19] Bowen D, Clifford CK, Coates R, Evan M, Feng Z, Fouad M, et al. The women’s health trial: feasibility study in minority populations: design and baseline description. Ann Epidemiol 1996;6:507 – 19. [20] Drewnowski A, Brunzell JD, Sande K, Iverius PH, Greenwood MRC. Sweet tooth reconsidered: taste responsiveness in human obesity. Physiol Behav 1985;35:617 – 22. [21] Drewnowski A, Greenwood MRC. Cream and sugar: human preferences for high-fat foods. Physiol Behav 1983;30:629 – 33. [22] Bowen DJ, Grunberg NE. Variations of food preference across the menstrual cycle. Physiol Behav 1990;47:287 – 91. [23] Broberg DJ, Dorsa DM, Bernstein IL. Nausea in bulimic women in response to a palatable food. J Abnorm Psychology 1990;99:183 – 8. [24] Tinker L, Burrows ER, Henry H, Patterson RE, Rupp JW, VanHorn L. The Women’s Health Initiative: overview of the nutrition components. In: Krummel D, Kris-Etherton P, editors. Nutrition and women’s health. Gaithersburg, MD: Aspen Publishers; 1996. p. 510 – 42. [25] Kristal AF, Shattuck AL, Williams A. Food Frequency Questionnaires for diet intervention research. Proceedings of the 17th National Nutrient Database Conference, International Life Sciences Institute, Baltimore, MD, Washington, DC, June 7 – 10; 1994. p. 110 – 25. [26] Kristal AF, Beresford SAA, Lazovich D. Assessing change in diet intervention research. Am J Clin Nutr 1994;59:185s – 9s. [27] Patterson RE, Kristal AR, Carter RA, Fels-Tinker L, Bolton MP, AgursCollins T. Measurement characteristics of the Women’s Health Initiative Food Frequency Questionnaire. Ann Epidemiol 1999;9:178 – 87. [28] Green P, Bowen DJ, Kestin M, Feng Z. Influences on food selection of women on low and high fat diets. J Appl Biobehav Res 1993;1: 174 – 98. [29] Bowen DJ, Meischke H, Tomoyasu N. Preliminary evaluation of the processes of changing to a low-fat diet. HER 1994;9:85 – 94. [30] Curry SJ, Kristal AR, Bowen DJ. An application of the stage model of behavior change to dietary fat reduction. HEQ 1992;7:97 – 105. [31] Bowen DJ, Grunberg NE. Variations in food preference and consumption across the menstrual cycle. Physiol Behav 1990;47:287 – 91. [32] Roininen K, Lahteenmaki L, Tuorila H. Quantification of consumer attitudes to health and hedonic characteristics of foods. Appetite 1999; 33:71 – 88.
Effects of fat content on fat hedonics: cognition or taste? Deborah Bowena,b,*, Pamela Greenb, Nancy Vizenora,b, Cathy Vua, Petra Kreutera, Barbara Rollsc a
Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA b University of Washington, Seattle, WA, USA c Pennsylvania State University, State College, USA
Received 20 February 2002; received in revised form 14 October 2002; accepted 1 November 2002
Abstract Understanding and perhaps overriding preferences for fat is important, given the relationship between higher dietary fat consumption and poorer health. We have examined the roles of potential mechanisms for differences in fat preference: actual fat content and expected fat content. The subjects were women (n = 192, ages = 50 – 69) recruited to a study of low-fat dietary change. Subjects were randomized to one of the four cells: participants received either a high- or low-fat milkshake at baseline, and half of each group was told that their milkshake was low in fat and the other half high in fat. Women who received a high-fat milkshake consumed more grams than women who received a low-fat milkshake. Women who expected low-fat shakes reported liking them more than those who expected high-fat milkshakes. These data indicate that both physiology and cognition play a role in determining consumption of high- and low-fat foods. D 2002 Elsevier Science Inc. All rights reserved. Keywords: Fat preference; Dietary fat; Taste
1. Introduction Fat is a preferred substance in general [1]. Understanding and perhaps overriding the consistent preference for and consumption of fat is important, given the relationship between dietary fat and health [2]. Consumption of a higher-fat diet has been linked to several chronic health problems, including cancer and cardiovascular diseases [3,4]. Reduction in daily fat consumption is the focus of several ongoing studies [5]. There is some evidence that reducing daily consumption of dietary fat causes a reduction in self-rated preference for fat [6]. Reduced preferences could help to maintain the reduced consumption, leading to reduced risk for disease [1]. The mechanisms that could be involved in a reduced selection of fat are unknown. We have chosen to examine the roles of three potential mechanisms for fat preference, based on the conceptual model described by Rozin and Vollecke [7]. In this formula* Corresponding author. Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue, N. MP900, Seattle, WA 98109, USA. Tel.: +1-206667-4982; fax: +1-206-667-7850. E-mail address: [email protected] (D. Bowen).
tion, preference is defined as the choice or selection of foods with a particular content, taste, or other quality. First, choice for a food has been shown to vary depending on the liking, or hedonic judgement of a food, and high-fat content of foods generally produces higher hedonic ratings [1]. Palatability is an important aspect of food choice and consumption, and certainly fat increases palatability [8]. Therefore, changing the fat content of the food may influence choice. According to this model, if we reduce the fat content of a food, we should find that individuals consume less of it. In this study, we manipulated the fat content of a food offering and asked individuals to taste it and rate its taste properties. We also measured amount consumed, to obtain a behavioral measure of choice. Second, previous research has examined the extent to which food selection may be modified by cognitions or labels attached to the foods [9,10]. Expected consequences of ingestion, for example, are important motivators of food choice, and the consequences of consuming high-fat foods are possibly a reason for avoidance. In a laboratory study, individuals ate more calories after a preload labeled ‘‘lowfat’’ than after an equicaloric preload labeled ‘‘high-fat’’ [11]. In a different study, when food was labeled ‘‘high-fat,’’
0031-9384/02/$ – see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 3 1 - 9 3 8 4 ( 0 2 ) 0 0 9 7 3 - 3
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subjects consumed less of it even though their hedonic ratings for ‘‘high-fat’’ food were higher than for food labeled ‘‘low-fat’’ [12]. These labels could alter the perceived health value of a food or class of foods, and therefore alter choices and hedonic judgements. Other studies have demonstrated the effects of labeling foods as to fat content on changing consumption [13– 15]. Therefore, we independently manipulated the label of high- or low-fat content to test this mechanism for determining preference and choice. Third, reports of gastrointestinal distress after eating highfat foods exist in individuals consuming lower amounts of daily dietary fat [6]. This association of high-fat foods with gastrointestinal distress could lead to decreases in liking and consumption. This finding leads us to the hypothesis that post-ingestional consequences of high-fat foods are distressing and could ultimately reduce choice of high-fat foods. We did not independently manipulate post-intestinal consequences in this study, but simply measured symptoms before and after consumption. We investigated the role of fat labels vs. fat content in a previous study of college students [16]. In this previous study, the actual fat content of the ice cream presented to subjects (high- vs. low-fat) and the expected fat content of the ice cream were independently manipulated to provide a balanced test of fat content vs. cognitions [17]. Consumption of the ice cream was higher when subjects expected high-fat ice cream than when subjects expected low-fat ice cream. Our data show the opposite pattern of Wardle and Solomons [12] above. We hypothesize that this difference is due to the characteristics of the participants. The subjects in our study were young (average age = 19), all recruited through an undergraduate subject pool. We concluded that, for this sample of young women, fat consumption was affected by label and that ‘‘high-fat’’ was a desirable quality. We wanted to extend our research and the findings of others to a sample of individuals that might identify ‘‘fat content’’ as particularly salient but with undesirable qualities. We conducted this study to better understand the effects of fat content and fat label on laboratory food consumption in a group that would likely have an interest in changing dietary habits and be aware of the health conditions associated with a high-fat diet. For the present study, we recruited subjects from the baseline period of an ongoing study of long-term dietary change in older, postmenopausal women, ages 50 – 79. We investigated the effects of label for high- and low-fat vs. actual fat content on consumption of high- and low-fat foods. We hypothesized that taste and label would affect both actual consumption and hedonic judgments. We hypothesized that these women would consume low-fat food more, compared to high-fat food, because of the potential for increased risk of nutritionally related disease in women aged 50 –79. We also measured hedonic judgements and fat taste judgements to determine the relationship between labeled and actual fat content to these judgements about taste. We hypothesized that the label of ‘‘high-fat’’ would cause
lowered hedonic judgements, again due to the characteristics of the women being tested.
2. Experimental methods 2.1. The Women’s Health Initiative We recruited our participants from the Women’s Health Initiative (WHI), a multicomponent set of research projects [5,18]. Its aim is to test methods of preventing common causes of morbidity and mortality among post-menopausal women. The major focus of this project is on cancer, cardiovascular diseases, and osteoporotic fractures. The WHI was initiated in 1992 and will be completed in 2007. Approximately 165,000 women aged 50 –79 years will be recruited nationwide at 40 WHI clinical centers and enrolled in either the three clinical trials (n = 64,500 women) or in the observational study (n = 100,000 women). The standard screening process for WHI included three separate visits; final eligibility determination and randomization were made on the third visit. Average follow-up will be approximately 9 years. The hypothesis for the randomized dietary trial within the WHI (DM) was that a low-fat, high fruit/vegetable/grain dietary plan would prevent breast and/or colorectal cancer and, secondarily, coronary heart diseases. Participants (n = 48,837) included in the DM met the criteria of having a daily caloric intake of more than 32% of energy from fat, living in the area for at least the following 3 years and willing to participate. Excluded were women with breast cancer or any other invasive cancer within the past 10 years, mastectomy, suspicion of poor dietary adherence, inability to complete a 4-day food record, having more than 10 meals out of home per week. Forty percent of the women involved in the DM were randomized to the intervention group, which followed the three nutritional goals: decrease of daily fat intake to less than 20% of total caloric intake (saturated fat intake to less than 7%), increase of fruits and vegetables to at least five servings per day and increase of grain products to at least six servings per day. This intervention program was delivered in groups, based on data from feasibility studies [19]. It included nutritional as well as psychological and behavioral strategies. 2.2. Design of the Taste Test Study The current study, called the Taste Test Study (TTS), was a research project to study the determinants of fat consumption and hedonic ratings in this sample of older women. The study session reported here was conducted at baseline, before randomization into the parent WHI DM study. The experimental design of the study was a 2 2 balanced placebo design [16] with two levels of actual fat content (high and low) and two levels of expected fat concentration (high and low) as the two factors. This study design allowed
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us to pit the cognitive explanation against the hedonic explanation for fat choice. Subjects were randomized to one of the four cells. Participants received either the highor low-fat milkshake, and were independently ‘‘informed’’ about the milkshake’s fat content (high or low) during both sessions. In this context, the ‘‘placebo’’ was the high-fat condition. 2.3. TTS subjects Subjects (n = 192) for this study were recruited from the Seattle Clinical Center intervention group participants from the WHI DM component. The average age of the TTS participants was 64 (S.D. = 10.2). A total of 91% were Caucasian, 74% had obtained a 4-year college degree, and 65% were married or living with a partner. During the second screening visit for the WHI, a diet technician informed the women about the possibility of taking part in the TTS by describing the study as one investigating whether dietary change affects women’s ability to taste foods. All participants were asked if they would consume dairy and chocolate products as part of the study. At the third screening visit, eligible participants were offered participation in the TTS and joined the WHI DM. If a woman was not eligible for DM, she was not eligible for the TTS. Women who participated in the TTS were randomized by the TTS staff to one of the four different drink/expectancies conditions of low- and high-fat milkshakes. Therefore, TTS women participated in their baseline taste session before any dietary sessions were conducted. However, these participants were screened for interest in dietary change and, therefore, had all expressed interest in and desire for a low-fat dietary plan. 2.4. Milkshakes During the taste session, we gave each participant a 16-oz chocolate-flavored milkshake and asked her to fill out a taste judgement questionnaire, consisting of 17 items about fat taste, flavor, and hedonic preferences. The ingredients for the milkshakes were as follows: Dreyer’s grand vanilla ice cream (high-fat shake only), Dreyer’s fat-free vanilla ice cream (low-fat shake only), whole milk, half and half (highfat shake only), nonfat milk (low-fat shake only), Hershey’s chocolate syrup, and Thicken Up (low-fat only, Sandoz). The nutritional composition of the milkshakes used in the present study is included in Table 1. The milkshakes were mixed on each laboratory session day and poured to fill 16-oz plastic cups. Weight and volume were approximately equal for the two milkshakes.
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Table 1 Nutrient composition of milkshakes Nutrient composition High-fat
Fat (g) Energy (kcal) Kcal from fat (%) Protein (g) Carbohydrate (g)
Low-fat
Per 100 g
Per shake
Per 100 g
Per shake
9.5 150.9 56.0 3.1 14.9
37.6 599.0 56.0 12.4 59.1
1.2 90.2 12.0 3.6 17.8
4.9 364.0 12.0 14.4 71.8
among the groups. Most of the participants (70%) had their visit at either 2:00 or 3:00 p.m. and, therefore, there was not enough variability to look at a time of day effect. At their scheduled appointment, the experimenter greeted each participant and led her to the interviewer room in the Fred Hutchinson Cancer Research Center. After filling out the consent form and the first symptom checklist, the experimenter introduced the taste test session with the verbal instructions: ‘‘Let me tell you a little bit about the study today. Some people who have participated in dietary studies, like the WHI, tell us that their sense of taste has changed during their participation. So today, we are going to have you taste one of the special milkshakes we have developed at Fred Hutchinson, and tell us what you think of it. Please fill out this rating sheet now, and let me know if you have any questions. I will be right back. Drink as much of the milkshake as you want. When you are done with the rating you can start on that packet of questionnaires.’’ Each participant then received the milkshake. Depending on her randomization, it was either a low- or high-fat milkshake, and she was either correctly or incorrectly informed about the fat content by the experimenter. To inform the participant, the experimenter said that the shake was a ‘‘low-fat, light’’ or a ‘‘rich, high-fat’’ drink. The appropriate phrase was used again in the next few sentences. The experimenter left the room for 5 min, returned to answer any questions about the sheets, and then left again for another 20 min. After filling out the taste sheet, the participant continued to complete a packet of the questionnaires. The participant was handed the second symptom checklist to complete and left alone again for 10 min. The experimenter took the shake from the participant at this time. If she needed more time to fill out the questionnaires, she was escorted to the WHI clinic waiting room where she could complete them. After the experiment, the participant was thanked for her participation.
3. Assessments 2.5. Procedure Laboratory sessions were scheduled with the third WHI screening visit, and the subjects refrained from eating for at least 2 h before the visit. All visits were scheduled between 11:00 a.m. and 3:00 p.m. Time of day of visit did not differ
Taste judgments were measured using a 17-item taste judgement sheet, which was filled out by the participant while consuming the milkshake. Each of the 17 items was rated on a 1 – 9 scale with adjective anchor points. The judgement list included fat taste items (creamy, oily, heavy,
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grainy) adapted from previous research [20,21] and a former study about fat and taste [22], items measuring flavor (sweet, tart, spicy, tasty) and hedonic preference judgment (appealing, pleasant, serve to guests, liking, satisfying when hungry), as well as single items (colorful, pleasant aroma, salty, and healthful). Consumption was measured by calculating the weight change of the milkshakes. Every milkshake was weighed before and after the laboratory session without the participants’ awareness. The weight difference score (before – after) was defined as our measure laboratory consumption. This procedure had been used in other research situations [16] as an estimate of preference. Self-reported symptoms were measured twice during the taste session: before and 25 min after the participant had consumed as much as they wanted of the milkshake. Symptom words literally included hungry, full, thirsty, comfortable, satisfied, nauseous, queasy, bloated, and sick. Each item was rated on a 1– 9 scale with adjective anchor points. This questionnaire was an adapted version of a questionnaire used [23] to assess GI symptoms in bulimic women. We used the Food Frequency Questionnaire (FFQ) as the main dietary assessment instrument for the WHI [24]. The WHI FFQ consisted of 124 food items or food groups, with 16 introductory questions (e.g., When you ate chicken, how often did you eat the skin?) used to refine nutrient calculations. There were nine categories of frequency responses which, for foods, range from never or less than once per month to six or more times per day. Portion size response options were ‘‘small,’’ ‘‘medium,’’ or ‘‘large,’’ based on the medium portion size printed on the questionnaire. The questionnaire was designed to be sensitive to fat-modified foods and food preparation methods, as well as to foods regionally and culturally consumed. The nutrient databases (from the University of Minnesota Nutrition Coordinating Center’s Nutrient Data System) and algorithms for FFQ analyses are described in detail elsewhere [25,26]. The FFQ was found to be moderately correlated with daily dietary food records in a sample of the WHI [27]. 3.1. Analyses Several of the taste items potentially measured similar tastes. Therefore, we first performed factor analysis of principal components with varimax rotation on the taste items to identify underlying constructs of the taste judgement items. We performed separate factor analyses for the fat taste items (creamy, grainy, oily, heavy) and the hedonic judgement items (appealing, pleasant, serve to guests, like, and satisfying). For both factor analyses, we set the eigenvalue at 1 or greater and included items if they loaded higher then 0.5 onto the factor and lower than 0.3 onto any other factor. We averaged the selected items to form scales for use in the subsequent analyses. We then examined the main outcomes: consumption, taste judgements, and hedonic ratings using analysis of variance. Finally, we examined the change in symptoms from before to after the taste test using a repeated
measures analysis of variance to determine any effects of actual and expected fat consumption on symptoms. All analyses are based on two-tailed tests.
4. Results 4.1. Fat consumption The participants in this study consumed an average of 37% of daily energy as fat and a median of 38%, based on responses to the FFQ. There were no differences in percent of energy from fat for participants in the four study conditions. All participants did refrain from eating for at least 2.5 h before the laboratory sessions. For further analysis purposes, we divided participants into low-fat (fat consumption = 35%) and high-fat (fat consumption = 42%) categories, based on a median split of daily percent of energy from fat. 4.2. Identification of taste scales The fat taste analysis produced one scale composed of oily (loading = 0.80) and heavy (loading = 0.84). These items were subsequently averaged to form a single scale score. Creamy loaded highly onto a separate factor (loading = 0.84) and therefore was used in analysis as a single item. Grainy did not meet the loading criteria for either factor and was dropped from analysis. Together, the oily/heavy factor and the single item accounted for 73% of the variance. The Cronbach’s a for this scale was .59. The second factor analysis on the hedonic preference judgments items used the same technique and criteria as above. All five items loaded onto a single factor, accounting for 67% of the variance. Therefore, the following items were averaged to form the hedonic preference judgment scale: appealing (loading = 0.58), pleasant (loading = 0.67), serve to guest (loading = 0.69), like (loading = 0.84), and satisfying (loading = 0.56). The range of this scale was 2 – 9 with a X¯ of 6.7 and an S.D. of 1.64. The Cronbach’s a for this scale was .87. We performed a factor analysis on the symptom items to identify clusters of symptoms, using the same methodology as above. Three factors emerged from the nine items: GI distress (nausea, queasy, bloating, and sick, with loadings of 0.67, 0.73, 0.81, and 0.87), satiety (hunger, full, and thirsty, with loadings of 0.81, 0.63, and 0.57), and well-being (comfortable and satisfied, with loadings of 0.84 and 0.76). Together, these scales explained 59% of the variance. Each group of scale items was averaged to provide a single scale score for GI distress, satiety, and well being. The overall ranges, X¯, and standard deviations for GI distress, satiety, and well being were 1 – 9, X¯ = 1.4, S.D. = 1.2; 1 – 9, X¯ = 4.9, S.D. = 1.4; and 1– 9, X¯ = 6.1, S.D. = 2.4, respectively. The Cronbach’s a for these scales were .76, .45, and .55, respectively, for GI distress, satiety, and well being.
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4.3. Consumption and taste findings
Table 3 Ratings of fat taste for expected and actual milkshakes
Table 2 presents the consumption, and hedonic judgement measures in all participants (n = 192). The analysis of variance (ANOVA) showed that there was a significant main effect of actual drink on consumption ( F = 3.7, df = 1,188, P < .05). Women who received a high-fat milkshake consumed more than women who received a low-fat milkshake. The effect of expected drink on consumption was not significant ( F = 1.5, df = 1,188, P=.23). There was no interaction effect of expected drink vs. actual drink ( F = 0.0, df = 1,188, P=.99). In addition to the effect of labels vs. actual fat content, we analyzed the differences in consumption between participants who ate higher than the median daily fat consumption vs. lower than the median daily consumption. There were no differences in the amount consumed when the high- and low-fat daily consumption participants were compared. Participants reported liking the actual high-fat milkshakes better than the low-fat milkshakes ( F = 17.1, df = 1,188, P < .0001). A significant main effect of expected drink on hedonic preference was also identified ( F = 4.2, df = 1,188, P < .05). Women who expected low-fat shakes reported liking them more than those who expected high-fat milkshakes. There was no interaction effect of expected vs. actual drink ( F = 0.1, df = 1,188, P=.72). There were no effects of high- vs. low-fat daily consumption on hedonic judgements. The fat taste judgements creaminess and oiliness/heaviness are presented in Table 3. The ANOVA showed that women who received high-fat milkshakes found them to be creamier than those who consumed low-fat milkshakes ( F = 4.01, df = 1,188, P < .05). The effect of expected drink on creamy was not significant ( F = 0.3, df = 1,188, P < .57). There was no interaction effect of expected vs. actual drink on creamy taste ( F = 0.1, df = 1,188, P=.80). In contrast to the findings of actual/expected drink on creamy taste, there was a significant main effect of expected drink on oily/heavy judgements ( F = 6.0, df = 1,185, P < .02) and no effect of actual drink on oily/heavy judgements ( F = 0.1, df = 1,185, P=.74). All participants who expected
Creaminess ratingsa
Actual milkshake content High-fat (n = 105)
(b) Hedonic judgementsa Expected High-fat (n = 89) milkshake Low-fat (n = 103) content a
High-fat (n = 89) Low-fat (n = 103)
Oiliness ratingsa
Expected milkshake content
High-fat (n = 105)
Low-fat (n = 87)
5.7 * (0.4) 5.4 (0.3)
5.0 (0.7) 4.9 (0.4)
Actual milkshake content
High-fat (n = 86) Low-fat (n = 103)
High-fat (n = 102)
Low-fat (n = 87)
2.8y (0.2) 1.8 (1.0)
2.4 (0.4) 1.5 (0.8)
a
Scale range is 1 – 9, where 9 is high. * Main effect of actual milkshake significant; P < .05. y Main effect of expected milkshake significant; P < .05.
high-fat shakes found them to be oilier/heavier in taste than those who expected low-fat milkshakes. There was no significant interaction of expected vs. actual drink ( F = 2.1, df = 1,185, P=.15). There were no effects of high- vs. low-fat daily consumption on any fat intake measure. Table 4 shows the scores for the three symptom scales components before and after the taste test. There were no significant main effect differences for either of the two study conditions (expected and actual). The main effect of time was significant for ratings of GI distress, satiety, and well being ( F = 5.4, df = 1,186, P < .05; F = 177.8, df = 1,186, P < .01; F = 7.8, df = 1,186, P < .01 for GI distress, satiety, and well being, respectively). The interaction of time with actual fat content was significant for both reported satiety and well-being ratings ( F = 4.9, df = 1,186, P < .05 and F = 8.6, df = 1,186, P < .01 for satiety and well being, respectively). Participants who consumed high-fat shakes increased their ratings of satiety and well being from before to after consumption, relative to those who consumed low-fat shakes. Finally, the interaction of time with expected drink was significant for ratings of well being ( F = 3.9, df = 1,186, Table 4 Symptomsa (X¯, S.D.) reported before and after milkshake consumption
Table 2
(a) Amount of milkshake consumed (g) Expected High-fat (n = 89) milkshake Low-fat (n = 103) content
Expected milkshake content
Actual milkshake content
237.4 * (22.5) 257.6 (28.9)
6.8 * ,y (1.1) 7.2 (1.2)
Scale range from 1 to 9, where 9 is high. * Main effect of actual milkshake significant; P < .05. y Main effect of expected milkshake significant; P < .05.
Study conditions
Low-fat (n = 87) 204.5 (19.0) 225.2 (15.2)
5.8 (0.5) 6.3 (0.9)
Expected high/ actual high Expected high/ actual low Expected low/ actual high Expected low/ actual low a
GI distress
Satiety
Well being
X¯ (S.D.) *
X¯ (S.D.) * ,* *
X¯ (S.D.) * ,* * ,** *
Before
After
Before
After
Before
After
1.1 (0.2) 1.3 (1.0) 1.2 (0.4) 1.4 (1.3)
1.5 (1.4) 1.4 (1.2) 1.3 (0.6) 1.5 (1.4)
4.9 (1.6) 5.1 (1.5) 5.0 (1.5) 5.4 (0.8)
6.7 (1.5) 6.4 (1.2) 7.0 (1.4) 6.8 (1.3)
5.9 (2.5) 6.7 (2.3) 6.0 (2.3) 5.9 (2.4)
6.7 (2.1) 6.2 (2.0) 7.1 (1.7) 6.4 (2.0)
Scale range is 1 – 9, where 9 is high. * Main effect of time significant; P < .05. ** Interaction of time with actual milkshake significant; P < .05. *** Interaction of time with expected milkshake significant, P < .05.
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P < .05). Women who expected low-fat drink increased reports of well being from before to after, relative to those who expected high-fat drinks.
5. Discussion The findings of this study indicate that the fat content of a food provided in a laboratory setting does affect consumption and hedonic preference ratings. The direction of the consumption effect is similar to that of previous research (e.g., 12) but the effects for hedonic preference ratings were slightly different. In the previous study, subjects consumed less food with the label ‘‘high-fat,’’ but rated the actual ‘‘high-fat’’ foods as more preferred. This divergence of consumption and preference rating did not occur in the present study. In this study, women reported preference in the opposite direction for the label of fat content. Shakes labeled ‘‘low-fat’’ were rated as more preferred than drinks labeled ‘‘high-fat.’’ From these findings, we can speculate that high-fat foods might taste better, but that hedonic preference ratings are influenced by cognitive factors in this sample of women ready for dietary fat intervention. One possible explanation for differences in ratings from this study and previous research is the characteristics of the participants. Indeed, the response to the label of ‘‘low-fat’’ indicates some cognitive mechanism that controls hedonic judgements as well as taste judgments [28]. The women in this study were older, and in previous studies age has been associated with increasing concern about fat [29,30]. Also, all women in the present study were postmenopausal, and food consumption and taste preferences differ across the menstrual cycle [31]. Additionally, these women were recruited into a study to lower dietary fat. As such, dietary fat intake is highly relevant to these participants and probably seen as a negative label. We did not collect data on the labels assigned to low- and high-fat foods in the present study, nor did we in previous research. This potential explanation should be investigated in future research. These data, collected from a sample of older, postmenopausal women just randomized into an intensive dietary intervention trial for 10 years, were different from our previous research in college students. In that study [16], ‘‘high-fat’’ labeled food was consumed more, compared with ‘‘low-fat’’ labeled food. The procedures were similar between the two studies, even though slightly different foods were used (milkshakes vs. ice cream). The women in the present study were even slightly different in their ratings of high-fat food, when compared to the Wardle and Solomon participants, but these latter were not selected for interest in lowering fat. It is possible that younger, perhaps more weight-conscious women react differently to fat-related stimuli in laboratory settings, compared to older women. Pressures on younger women to be thin and to consume foods that promote thinness could act to disinhibit them from holding back. Perhaps older women, very motivated to eat
healthy foods, were more able to resist disinhibition. Therefore, these findings, together with others [12,28,29], indicate that taste and hedonics are dependent on the relevance and meaning of the food or category under observation. Again, this should be a topic of future research. The symptom measurements showed no main effects of consuming high- vs. low-fat foods (perceived or actual) on gastrointestinal symptoms distress. However, in this study, the time variable is, in essence, exposure to the food. Highfat shakes increased reports of satiety and well being, and expected low-fat food increased well being. GI symptoms did not differ over time by type of food. One conclusion to be made from these analyses is that consuming foods of varying fat content does not cause differing levels of gastrointestinal distress and, therefore, that post-ingestional symptoms are not likely to cause any decreased selection of high-fat foods. However, it could be true that post-ingestional GI distress symptoms only occur during times of dietary change, specifically fat reduction, and not during times of maintaining one’s typical dietary fat level. None of these women had started their intensive change program. Also, it could be true that symptoms occurred after longer time lapses in the postconsumption period. Or perhaps, symptomatic reactions to high-fat foods only occur after long periods of low-fat food consumption. We will be able to determine a time course for symptom experiences as we follow these women over time and across their participation in the intensive dietary intervention activities of the WHI. There are several design features of this study that limit the generalizability of the findings. First, the sample was composed of older, postmenopausal women. Certainly, age and hormonal status influence taste and eating, as might strong interest in learning how to eat healthy foods. Recent research by Roininen et al. [32] indicated that participants reported less concern about the health-related aspects of food and more concern about taste, compared with older participants in a large-scale survey. Each of these variables must be considered when comparing these findings to other studies. The sample does not represent women in the general public, as the WHI tends to be of higher socioeconomic status compared with the general public [5]. To the extent that fat taste is similar across socioeconomic status levels, we can make statements about other population groups, but the relationship between SES and reactions to fat consumption is unknown. Of course, in this study design, it is impossible to separate the effects of fat vs. energy. Future studies could manipulate this more carefully. The methods of measuring dietary fat choice and hedonic preference limit generalizability, in that we measured laboratory consumption in a very specific manner. Individuals did not choose among multiple foods, but ate only one food. Some of the Cronbach’s a’s for the scales were relatively low, pointing to the need to improve the taste measures. This study excluded large numbers of women, due to parent study requirements; therefore, generalization to a population-based sample is not possible. Finally, the fact that these women have been
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recruited to a study in which they may be asked to make major changes to their dietary habits may have influenced their responding. This must be considered when interpreting the data. Indeed, some of the women may have reported their answers in a false manner, because they wanted to represent themselves in a better light to the study investigators. This needs further exploration. In summary, the findings of this study have illuminated some basic effects of cognition and fat content in a sample of older women interested in dietary change. Older postmenopausal women interested in healthy eating consume more fat and rate high-fat foods as more preferred, compared with low-fat foods. Future research directions include similar investigations during times when individuals are making changes in their ongoing patterns and studies of these effects over longer periods of time.
Acknowledgements This work was supported by a grant (CA064327) from the National Cancer Institute. We gratefully acknowledge the thorough data management of Alithea Morasca.
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