stress and food choice

Stress and Food Choice: A Laboratory StudyGEORGINA OLIVER, PHD, JANE WARDLE, PHD, AND E. LEIGH GIBSON, PHD

Objective: This study investigated experimentally whether acute stress alters food choice during a meal. The studywas designed to test claims of selective effects of stress on appetite for specific sensory and nutritional categoriesof food and interactions with eating attitudes. Methods: Sixty-eight healthy men and women volunteered for a studyon the effects of hunger on physiology, performance, and mood. Eating attitudes and food preferences weremeasured on entry to the study. The stressed group prepared a 4-minute speech, expecting it to be filmed andassessed after a midday meal, although in fact speeches were not performed. The ad libitum meal included sweet,salty, or bland high- and low-fat foods. The control group listened to a passage of neutral text before eating the meal.Blood pressure, heart rate, mood, and hunger were measured at baseline and after the 10-minute preparatory period,when appetite for 34 foods and food intake were recorded. Results: Increases in blood pressure and changes in moodconfirmed the effectiveness of the stressor. Stress did not alter overall intake, nor intake of, or appetite for the sixfood categories. However, stressed emotional eaters ate more sweet high-fat foods and a more energy-dense mealthan unstressed and nonemotional eaters. Dietary restraint did not significantly affect appetitive responses to stress.Conclusions: Increased eating of sweet fatty foods by emotional eaters during stress, found here in a laboratorysetting, may underlie the previously reported finding that dietary restraint or female gender predicts stress-inducedeating. Stress may compromise the health of susceptible individuals through deleterious stress-related changes infood choice. Key words: stress, food choice, emotional eating, dietary restraint, appetite, nutrition.

ANOVA 5 analysis of variance; DBP 5 diastolic bloodpressure; DEBQ 5 Dutch Eating Behavior Question-naire; PANAS 5 Positive and Negative Affect Sched-ule; SBP 5 systolic blood pressure; STAI 5 State-TraitAnxiety Inventory.

INTRODUCTION

There is increasing evidence that stress may affecthealth not only through its direct biological effects butalso through changes in health behaviors that them-selves influence health (1, 2). Clearly, one such healthbehavior is food choice: that is, stress may lead to illhealth through unhealthy changes in diet as well asmore general effects on appetite (3).

Stress and diet associations are particularly com-plex. Stress is associated with biological changes thatmight be expected to reduce food intake, at least in theshort-term, such as adrenaline-induced glycogenoly-sis, slowed gastric emptying, autonomic shunting ofblood from gut to musculature, and activation of thehypothalamic-pituitary-adrenal axis (4, 5). Yet the ex-perimental results have been inconsistent. Animalstudies have produced evidence of both hyperphagiaand hypophagia in response to stress (57). Researchon everyday food intake in human subjects under low-

and high-stress conditions has also produced inconsis-tent results. Stress in the workplace has been associ-ated with higher energy intake in two studies (8, 9),examination stress has produced mixed results (10,11), and surgical stress, probably the most extremestressor examined, has been found to have no consis-tent effect (12). These varying results may be related tothe nature of the stressor; for example, mild stressorscould induce hyperphagia, and more severe stressors,hypophagia (7, 13).

Alternatively, there could be significant individualdifferences in responses to stress, with the study sam-ples varying in the proportions of the different re-sponse types. Pollard et al. (11) found that studentswho were high on anxiety and low on social supportwere more likely to show a hyperphagic response, andWardle et al. (9) found that dietary restraint levelsmoderated the response to work stress. An individualdifference model is supported by data from both pro-spective (14) and retrospective (15, 16) self-reportstudies, showing either increased, decreased, or nochange in eating during stress but with consistent ef-fects within individuals.

The importance of individual differences in the eat-ing response to stress has also been borne out by anumber of laboratory studies (13). Such studies typi-cally induce stress through one of a number of stan-dard procedures while assessing food intake, ostensi-bly as incidental to some other task, such as makingtaste ratings. A consistent pattern is that participantsscoring highly on a measure of dietary restraint eatmore under stress, whereas intake is the same or lowerin unrestrained eaters (1722).

This rather complex pattern of results suggests thatmore attention needs to be directed toward specifyingthe nature and intensity of the stress response, and the

From the Imperial Cancer Research Fund (ICRF) Health BehaviourUnit, Department of Epidemiology and Public Health, UniversityCollege London, London, United Kingdom.

Address reprint requests to: Professor Jane Wardle, ICRF HealthBehaviour Unit, Department of Epidemiology and Public Health,University College London, 2-16 Torrington Place, London WC1E6BT, United Kingdom. Email: [email protected]

Received October 18, 1999; revision received May 3, 2000.

853Psychosomatic Medicine 62:853865 (2000)

0033-3174/00/6206-0853Copyright 2000 by the American Psychosomatic Society

characteristics and motivational state of the partici-pants (eg, hunger, restraint, and emotional eating ten-dency). Furthermore, in these studies, usually only asingle food type is available, typically high in fatand/or sugar, such as ice cream. Thus, food intake hasbeen conflated with food choice. Understandingwhich foods are selected or avoided under stress is acrucial issue, both because it is necessary for theoret-ical interpretation of the mechanisms involved and forprediction of harmful effects of stress on health.

In contrast to the laboratory studies, self-reportedretrospective (15, 23) and prospective data (8, 9, 11)suggest that food choice does change under stress,with a tendency toward a relative increase in sugary,fatty (often snack-type) foods. Therefore, experimentaltests of effects of stress on eating should take intoaccount the sensory properties of foods.

Grunberg and Straub (24) extended the usual labo-ratory paradigm by providing participants with a rangeof foods differing in taste qualities (sweet, salty, andbland), although these were still snack foods presentedincidentally to the main task of viewing a film (usedfor stress induction). They found that men in thestressed group ate less than men in the control group.In women there were no significant differences, al-though stressed women did show a trend toward amodest increase in consumption of sweet and blandfoods with no change in intake of salty foods. Thesegender differences may have reflected differences indietary restraint, which is known to be higher inwomen (16, 25, 26), but unfortunately, as the authorsnoted, they did not include a measure of restraint. Theecological validity of Grunberg and Straubs (24) find-ings may also be limited by the fact that the amount offood eaten by their participants was very small (,20 gper person on average), whereas the variation wasrelatively high, suggesting that not all subjects werechoosing to eat.

The present study was designed to extend the workof Grunberg and Straub (24), including foods from thesweet, salty, and bland taste categories and high- andlow-fat examples within those sensory groups. Asidefrom replicating the work of Grunberg and Straub (24),analyzing effects by taste category may be importantbecause stress has been shown to affect taste percep-tion (27). A wider range of foods was provided torepresent the kinds of foods that might be eaten in bothmeals and snacks. Participants were tested when theywere moderately deprived of food and given a testmeal around midday to increase the likelihood of eat-ing beyond brief tasting.

Dietary restraint and emotional eating tendencieswere assessed as possible explanatory variables. Pre-vious studies that incorporated restraint used the Re-

straint Scale (28, 29) to measure such tendencies.However, that instrument does not clearly distinguishbetween cognitive restraint, which might be disruptedby stress; the tendency to overeat in the face of facili-tating cues; and the tendency to find relief from emo-tional stress through eating. Thus, the DEBQ was usedbecause it measures separate factors for dietary re-straint and emotionally and externally influenced eat-ing tendencies (30).

The literature suggests that women and restrainedeaters consume more calories and fat under stress (8, 9)and shift their food choices away from meal-typefoods, such as meat and vegetables, toward snack-typefoods (15). In contrast, men and unrestrained eatersshow either little difference or a reduction in foodintake under stress (12, 24). Therefore, we hypothe-sized that stress would elicit greater preference for,and consumption of, highly palatable, snack-typefoods, most especially in women and restrained andemotional eaters. In contrast, unrestrained, low emo-tional eaters (most likely to be men) were expected toshow no change or even a decrease in consumption inresponse to stress.

Finally, hunger state and appetite for specific foodswere assessed for potential mediation of effects ofstress on food intake. In particular, hunger was ex-pected to be lower in the stressed group and to benegatively correlated with biological signs of arousal,by means of which the impact of the stressor could begauged.

METHODS

Participants

Sixty-eight healthy, nonobese, nonsmoking volunteers (27 menand 41 women, students and staff of the University of London)agreed to participate in a study advertised as an investigation of theeffects of hunger on physiology, performance, and mood. Volun-teers were recruited through advertisements placed around the cam-pus and were paid UK5 ($7) on completion of the study. Partici-pants were allocated to either a stress or control condition, duringwhich they were provided with a buffet lunch in the laboratory. Thestudy design was approved by the Research Committee on Ethics ofUniversity College London.

Stress Manipulation

Anticipation of a speech performance was used as a stressor.Participants were told that they would be making a 4-minute speechthat would be recorded by video equipment set up prominently inthe laboratory and subsequently assessed. Written instructions forthe speech task, based on those used by Kapczinski et al. (31), weregiven. Participants were invited to select 1 of 10 controversial topicsfor their speech and to prepare notes for a period of 10 minutesbefore receiving a meal. The speech was scheduled to take placeimmediately after the meal, and participants were led to believe thatthe study was about hunger and its effect on performance and that

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854 Psychosomatic Medicine 62:853865 (2000)

they had been placed in a low-hunger condition that necessitatedthem eating a meal before making their speech. This ensured that theanticipatory stress created by the threat of public speaking wassustained while subjects were exposed to food but that there was noactive competing task to eating. Unknown to subjects at this stagewas that they were not required actually to perform the speech. Nomention of the speech task was made to participants in the controlcondition. Instead they were given a nonstressful task of comparableduration (10 minutes), which was to listen to a passage of emotion-ally neutral text (an excerpt from Under Milk Wood, Ref. 32). Theywere instructed to sit and relax while listening to the text, afterwhich, they were told, they would receive a meal. They were led tobelieve that the study was concerned with changes in physiologicalmeasurements before and after a meal.

Assessment of Impact of Stress Manipulation

Both physiological and psychological indices of arousal wereincluded, because desynchrony between self-reported anxiousmood and physiological measures of arousal has been well docu-mented (33). Blood pressure and heart rate were measured using aCopal digital sphygmomanometer UA-251 (baseline was an averageof two readings taken over a 3- to 5-minute period). A self-reportedmeasure of mood, the PANAS (34), was completed on arrival in thelaboratory (baseline) and after the 10-minute stress induction. At theend of the study, as part of the debriefing, participants were asked torate the perceived stressfulness of the study on a seven-point Likertscale (where 1 5 not at all stressful and 7 5 extremely stressful).

Assessment of Eating Behavior

Participants had been asked to refrain from eating for 4 hoursbefore the study to ensure a reasonably standardized level of depri-vation, resulting in a substantial intake from the meal. Ratings ofcurrent hunger (on a seven-point Likert scale, where 1 5 not at alland 7 5 extremely) were taken on arrival in the laboratory (base-line) and after the stress or control manipulation.

Two measures were used to assess the effect of the stress manip-ulation on eating behavior and food choice: 1) appetite for a range offoods immediately before eating the meal and 2) food intake duringthe meal. Foods had been selected on the basis of their nutrientcontent to represent three taste categories, sweet, salty, and bland,following the method of Grunberg and Straub (24). Within thesetaste categories, foods were additionally divided into low- and high-fat groups. A total of 34 foods were selected for the food preferencetasks (Table 1). Fifteen similarly categorized foods were provided forthe buffet meal (Table 2): 9 of these were represented by similarfoods among the 34 foods, but in addition, 3 bland high-fat spreadsand 3 sweet low-fat foods were chosen for appropriate use as smallportions and practicality for meal construction. To test the assump-tion that taste was related to nutrient content, 34 adults (not thosewho took part in the main study) were asked to rate the taste of eachof the 34 foods for sweetness, saltiness, and fattiness (where 1 5 notat all and 7 5 extremely). Perceptions of taste were found tocorrelate highly with actual nutrient content (sugar content andsweetness: r 5 0.84, p , .001; salt content and saltiness: r 5 0.76, p, .001; fat content and fatty taste: r 5 0.77, p , .001), thus validatingthe use of nutritional composition data to generate categories basedon taste.

Food Appetite Ratings. Photographs of each of the 34 foods werepresented one at a time. For each food, participants were asked,How much do you fancy eating some of this food at the moment?,and indicated their response on a scale from 1 (I definitely dontwant to eat this food at all at the moment) to 7 (Right now I really

want to eat this food). The appetite ratings had previously beenfound to show adequate test-retest reliability when administered to12 different adults on two occasions 30 minutes apart (mean r 50.83, p , .01). The ratings were completed after the stress (orcontrol) manipulations, immediately before the meal was served.The photographs were presented in random order to each subject tocontrol for possible order effects between sequentially presentedfoods.

Food Intake. Participants were allowed to eat freely for 15 min-utes from a buffet lunch consisting of, as far as was practicable, foodsfrom each of the taste categories described above (Table 2). Thefoods were weighed to the nearest 0.1 g before and after the meal todetermine the amount consumed.

Individual Difference Variables

A number of trait measures were completed before participation.Trait anxiety was assessed with the Trait scale of the STAI (35).Dietary restraint and the tendency to eat more when cognitive re-straint on eating is disrupted by psychological, sensory, or emo-tional challenges (sometimes labeled disinhibition) were assessedwith the Restraint, Emotional, and External Eating scales from theDEBQ (30). In addition, for each of the 34 foods listed in the appetiteratings, participants were asked to indicate how much they liked thefood in general. Responses were recorded on a Likert scale (where24 5 I really dislike this food and 14 5 I really like this food).

Procedures and Scheduling

The study was performed between 11:30 AM and 1:30 PM, thatis, at a time when a meal would usually be eaten. This is incontrast to the usual laboratory eating paradigms in which snackconsumption is measured without regard to meal times. On ar-rival at the laboratory, participants confirmed that they had eatennothing in the previous 4 hours, and baseline measures of bloodpressure, heart rate, mood (PANAS), and hunger were completed.Participants then received instructions for either the stress or controltask, according to their random allocation, and were left alone for the10-minute duration of the tasks. At the end of the 10-minute period,blood pressure, heart rate, and mood were reassessed in all subjects. Asecond hunger rating and the food appetite ratings were also com-pleted. Participants then received a meal with the foods presented onseparate plates on two trays, the position of the plates on the trays beingvaried for each participant. They were instructed that they could eatwhatever they wished from the selection and in whatever quantitiesthey desired, just as long as they ate something and were less hungry atthe end of the meal. The experimenter explained that they would be leftalone to eat for 15 minutes. At the end of the meal, the experimenterreturned, and the true nature of the study was explained. The debrief-ing included a rating of the perceived stressfulness of the study. Fi-nally, age, height, and weight were recorded.

Data Analysis

The main hypotheses were tested by ANOVAs; the interactionsbetween stress condition (group) and individual difference vari-ables, such as gender, restraint, and emotional eating, were of pri-mary interest. In most cases, there was an a priori prediction for thedirection of the interaction effect, and so an a level of 0.05 was takenas significant, despite quite large numbers of statistical tests. Unex-pected results that achieved this level of significance were inter-preted cautiously. Multiple comparison tests on the same dependent

STRESS AND FOOD CHOICE


variable were not required by this design. In addition, some rela-tionships between physiological and psychological variables wereassessed by using Pearsons product-moment correlation.

RESULTS

Participant Characteristics

The background characteristics of the group aresummarized in Table 3. Participants were between18 and 46 years old. The men were predictablyheavier (F(1,64) 5 117.17, p , .001) and taller (F(1,64)5 46.04, p , .001) than the women, but body mass indexdid not differ between the sexes. There were no differ-ences between groups randomized to the stress or control

condition on any of these measures. There were no sig-nificant group or gender differences in trait anxiety.

As expected, dietary restraint scores were signifi-cantly higher in women (F(1,64) 5 13.50, p , .001), andwomen scored higher than men on the emotional eatingscale (F(1,64) 5 4.99, p , .05), but there were no genderdifferences in external eating. There were no differencesbetween stress and control groups in dietary restraint,emotional eating, or external eating.

Ratings for liking of the foods to be used in thestudy showed that fatty sweet foods were most likedby the sample as a whole (see Table 3) and that saltylow-fat foods were the least liked. Men reported

TABLE 1. Foods Included in the Food Desirability Rating With Relevant Nutritional Compositiona

FoodCategory

FoodEnergy(kcal)

Sugars(g)

Fat(g)

Energy asFat (%)

Sodium(mg)

BlandLow fat Steamed rice 138 Trace 1.3 8.5 1

Boiled potatoes 72 0.7 0.1 1.3 7Bread (white) 217 3 1.3 5.4 530Raw carrot 35 7.4 0.4 10.3 25Raw tomato 17 3.1 0.3 15.9 9Steamed fish 83 0.0 0.9 9.8 65

High fat Avocado 190 0.5 19.5 92.4 6Fried cod in batter 247 Trace 15.4 56.1 160Unsalted peanuts 564 6.2 46.1 73.6 2Boiled egg 147 Trace 10.8 66.1 140Clotted cream 586 2.3 63.5 97.5 18Greek yogurt 115 2 9.1 71.2 71

SaltyLow fat Prawns 107 0 1.8 15.1 1590

Smoked salmon 142 0 4.5 28.5 1880Marmite (autolysed yeast extract) 172 0 0.7 3.7 4500Pretzels 381 0 3.5 8.3 1720Noodles and soy sauce 70 1.7 0.5 6.4 1424

High fat Cheddar cheese 412 0.1 34.4 75.1 670Crisps (potato chips, salted) 546 0.7 37.6 62.0 1070Dry-roasted peanuts 589 3.8 49.8 76.1 790Salami 491 Trace 45.2 82.9 980Frankfurters (hot dogs) 274 Trace 45.2 82.9 980Bacon 422 0.0 36.0 76.8 1990

SweetLow fat Honey 288 76.4 0.0 0.0 11

Boiled sweets (candies) 327 86.9 Trace Trace 25Lemon sorbet 131 34.2 Trace Trace 69Banana 95 20.9 0.3 2.8 1Meringue 379 95.4 Trace Trace 110

High fat Milk chocolate 529 56.5 30.3 51.6 120Vanilla ice cream 194 22.1 9.8 45.5 69Jam doughnut 336 18.8 14.5 38.8 180Fudge 441 81.1 13.7 28.0 160Chocolate-coated biscuit 524 43.4 27.6 47.4 160Sponge cake 459 30.9 26.3 51.6 350

a Nutrients per 100 g. Data from Holland et al. (51).

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liking fatty bland and fatty salty foods significantlymore than women (F(1,64) 5 6.65, p , .02 for fattybland foods; F(1,64) 5 15.12, p , .001 for fatty salty

foods). There were no significant differences in gen-eral food preferences between stress and controlgroups.

TABLE 3. Characteristics of Participantsa

Stress Group Control Group

Men Women Men Women

N 14 20 13 21Age (y) 25.6 6 4.8 26.5 6 7.0 26.9 6 6.7 25.3 6 4.2Body weight (kg) 70.9 6 8.8 58.5 6 8.7 76.3 6 9.4 59.7 6 7.8Height (m) 1.80 6 0.07 1.63 6 0.7 1.82 6 0.06 1.66 6 0.05Body mass index 21.7 6 2.2 22.0 6 2.5 23.1 6 2.6 21.7 6 2.3Psychological indices

Trait anxiety (STAI) 40.9 6 10.7 44.2 6 8.7 42.1 6 11.2 42.3 6 10.8Self-esteem (Rosenberg) 21.3 6 4.8 22.2 6 3.9 22.5 6 4.6 23.0 6 5.7

Measures of eating behavior (DEBQ)Dietary restraint 2.15 6 0.89 2.49 6 0.81 1.66 6 0.60 2.79 6 0.85Emotional eating 2.18 6 0.71 2.59 6 0.86 2.50 6 1.08 3.07 6 0.91External eating 3.09 6 0.62 3.21 6 0.49 3.33 6 0.51 3.37 6 0.53

General food-liking scoresBland

Low fat 1.57 6 0.81 1.82 6 0.96 2.01 6 0.52 1.84 6 1.15High fat 1.78 6 0.60 0.96 6 1.10 1.32 6 1.03 0.81 6 1.20

SaltyLow fat 0.96 6 1.64 1.82 6 1.14 1.37 6 1.23 0.47 6 1.54High fat 1.92 6 0.89 0.73 6 1.58 1.88 6 0.90 0.56 6 1.43

SweetLow fat 1.37 6 0.96 1.27 6 1.29 1.62 6 1.24 1.36 6 1.31High fat 1.99 6 1.25 2.08 6 1.27 2.50 6 0.87 1.61 6 1.79

a Data are mean 6 SD.

TABLE 2. Compositiona of Test Meal Given to Participants

FoodCategory

FoodEnergy(kcal)

Carbohydrate(g)

Sugars(g)

Protein(g)

TotalFat(g)

Sodium(mg)

Quantity Provided

BlandLow fat White bread 252 48.5 1.6 9.6 2.2 500 5 rolls (200 g)

Raw carrot 35 7.9 7.4 0.3 0.6 25 100 gRaw tomato 17 3.1 3.1 0.3 0.7 9 1 ( 80 g)

High fat Peanut butter 592 12.5 6.5 23.6 49.7 400 70 g (2 35-g jars)Flora (soft margarine) 739 1.0 1.0 0.2 81.6 800 50 g (5 10-g packets)Butter 737 Trace Trace 0.5 81.7 750 35 g (5 7-g packets)

SaltyLow fat Marmite (autolysed yeast

extract)172 1.8 0.0 39.7 0.7 4500 24 g (3 8-g packets)

High fat Cheddar cheese 412 0.1 0.1 25.5 34.4 700 100 g (grated)Salted crisps (potato chips) 557 49.9 0.4 4.5 37.7 600 30 gSalted peanuts 600 8.6 3.8 29.0 50.0 500 200 g

SweetLow fat Mandarin 35 8.0 8.0 0.1 0.9 2 2 medium (300 g)

Grapes 60 15.4 15.4 0.4 0.1 2 100 gStrawberry jam 265 66.0 66.0 0.4 0.1 Trace 70 g (2 35-g jars)

High fat Cake (cherry, slices) 407 50.9 34.2 3.9 20.8 80 100 g (3 slices)Chocolate biscuits 493 66.5 28.5 6.8 24.1 450 70 g (4 biscuits)

a Nutrients per 100 g. Data from Holland et al. (51).



Effectiveness of the Stress Manipulation

At baseline, there were no differences between thestress and control groups in heart rate, SBP, or DBP(see Table 4). Men in both groups had significantlyhigher SBP (F(1,64) 5 25.98, p , .001) and DBP(F(1,64) 5 4.28, p , .05) than women. The change inheart rate after the stress manipulation did not reachsignificance (group-by-time interaction: F(1,64) 52.82, p , .10; Table 4). SBP increased over time (frombaseline to after stress) in the stressed group and de-creased in the control group (group-by-time interac-tion: F(1,64) 5 14.41, p , .001; Table 4). The patternwas the same for men and women. DBP decreased inthe control but not in the stress group (group-by-timeinteraction: F(1,64) 5 4.42, p , .05).

There were no significant differences between stressand control subjects in positive or negative affectscores at baseline. Negative affect scores were log-transformed to produce a normal distribution. As pre-dicted, subjects in the stress group showed a signifi-cant increase in negative affect from baseline, whereasthose in the control group showed a reduction in neg-ative affect relative to baseline (group-by-time interac-tion: F(1,64) 5 11.77, p , .001). For positive affect, thecontrol group showed a decrease, whereas in thestressed group positive affect remained constant

(group-by-time interaction: F(1,64) 5 10.00, p , .01).Gender had no effect on affect scores.

Overall, the manipulation achieved significant ifmodest differences between groups in both physiolog-ical and psychological indices of stress (Table 4). Thiswas borne out by the post hoc subjective ratings ofperceived stress. Participants in the stressed grouprated their experience as significantly more stressful(mean rating 5 4.26, SD 5 1.4) than the control group(mean rating 5 1.62, SD 5 1.0) (F(1,64) 5 69.12, p ,.01). This between-group difference applied to bothmen and women.

Food Intake: Effects of Gender and Stress

Gender Differences. Men ate significantly moreweight of food (F(1,64) 5 6.03, p , .02) and had ahigher total energy intake (F(1,64) 5 11.07, p , .001)than women (Table 5), as would be expected from theirsignificantly higher body weights and consequentlygreater daily energy requirements. Controlling for en-ergy requirements (covariate F(1,63) 5 5.77, p , .02)removed this gender effect (for grams: F(1,63) 5 1.16;for kilocalories: F(1,63) , 1; both NS), and so esti-mated energy requirement was included as a covariatein subsequent analyses involving total amounts of food

TABLE 4. Effectiveness of the Stress Manipulation: Physiological and Psychological Indices


Men Women Men Women

Mean SD Mean SD Mean SD Mean SD

Physiological indicesHeart rate (beats/min)

Baseline 65.6 9.4 68.2 12.4 63.9 8.7 71.6 13.7T1 66.0 11.2 71.4 11.6 62.9 9.4 69.1 12.8Change 0.4 10.0 3.3 8.2 21.0 8.5 22.5 7.8

SBP (mm Hg)Baseline 129.1 15.5 113.1 13.0 132.2 14.6 114.8 10.8T1 130.4 14.5 114.2 13.7 124.5 10.1 108.4 8.7Change 1.3 10.2 1.1 9.2 27.7 6.9 26.4 8.2

DBP (mm Hg)Baseline 82.6 10.9 75.1 9.5 81.5 10.1 79.2 8.5T1 81.6 11.4 80.9 13.8 81.2 10.7 76.9 6.8Change 21.0 4.9 5.8 7.4 20.3 6.3 22.3 8.4

Psychological indicesPositive affect

Baseline 28.6 6.5 28.6 5.3 33.4 5.6 30.2 5.9T1 27.6 6.5 29.3 5.3 29.9 6.6 26.9 5.6Change 20.9 2.9 0.7 5.5 23.5 2.9 23.3 3.9

Negative affectBaseline 14.2 4.3 14.5 5.0 12.9 2.4 12.3 2.8T1 15.7 5.1 16.6 6.4 12.4 2.5 10.7 1.1Change 1.5 3.5 2.1 6.1 20.5 1.9 21.6 2.6

Perceived stressfulness of manipulation 4.1 1.5 4.4 1.4 1.7 0.9 1.6 1.0

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eaten. However, analyses involving measures of selec-tion of different food sensory categories were not ad-justed for energy requirements. Daily energy require-ments were estimated on the basis of publishedfigures.1 This resulted in mean (SD) daily energy re-quirements of 3031.0 (236.9) kcal/d for the men and2172.6 (185.1) kcal/d for the women (sex difference:F(1,64) 5 284.6, p , .001). Both men and womenconsumed about one-third of their daily caloric re-quirements from the food presented, suggesting thatthis eating episode could realistically be considered ameal rather than merely a snack.

Stress Effects. There were no significant main ef-fects of stress group on weight of food consumed, totalenergy intake, or energy density of the meal (kcal/g),nor were there any interactions between group andgender (Table 5). Total intake was also analyzed interms of the main macronutrients (carbohydrate, fat,and protein) and for starch and sugar separately, butno significant effects were found (data not shown).

To examine intake in relation to choice from thefood sensory categories (sweet, salty, and bland), theamount of food eaten from each category, includinghigh- and low-fat levels, was calculated (Table 5).Four-factor repeated-measures ANOVA of intake (g)

with food category and fat level as within-subjectsfactors, and group and gender as between-subjects fac-tors, revealed a number of significant effects (withe-corrected F values adjusted for sphericity where nec-essary). There was no significant main effect or anyinteractions involving stress group (Table 5). However,intake differed by food category (F(2,128) 5 67.47, p ,.001), fat level (F(1,64) 5 116.76, p , .001), and gender(F(1,64) 5 6.03, p , .02). Furthermore, food categoryinteracted with gender (F(2,128) 5 3.28, p , .05) andfat level (F(2,128) 5 194.55, p , .001), and all of thesefactors interacted (F(2,128) 5 6.94, p , .001). There-fore, effects of fat level and gender were analyzedwithin each food category by two-factor ANOVA. Re-sults for energy intake were essentially similar and soare not presented here.

Bland Foods. Men ate significantly more bland foodthan women (F(1,66) 5 11.69, p , .001), although thisdifference was more apparent for low-fat than high-fatbland foods (F(1,66) 5 9.57, p , .01) (Table 5). Thismay not be surprising given that the high-fat blandfoods were spreads, which were consumed in muchsmaller amounts than the low-fat bland foods (bread,carrots, and tomatoes) (F(1,66) 5 381.17, p , .0001).

Salty Foods. Men ate significantly more salty foodsthan women (F(1,66) 5 4.48, p , .05). This effect wasindependent of fat level, although the one low-fat saltyfood available, yeast extract (Marmite spread), waseaten in far smaller amounts than the high-fat saltyfoods (F(1,66) 5 135.12, p , .0001).

Sweet Foods. Unlike bland and salty foods, men didnot eat any more sweet foods than women (F(1,66) , 1;

1 Estimated daily energy requirements were calculated, using pub-lished equations, from basal metabolic rate, which is dependent onage, sex, and weight, multiplied by physical activity level (PAL)(36). Because no data were available for activity levels, moderatelevels were assumed for both occupational and nonoccupationalactivity in both men (PAL 5 1.7) and women (PAL 5 1.6).

TABLE 5. Effect of Stress, Gender, and Sensory Category on Food Intakea

Intake Category


Men Women Men Women


Total food intake 378.9 135.6 310.7 110.6 391.8 140.6 316.6 94.4Total energy intake (kcal) 884.4 402.2 686.9 282.3 922.5 293.1 637.3 203.6Energy density of intake (kcal/g) 2.31 0.51 2.26 0.64 2.45 0.74 2.09 0.63Bland foods

All 204.2 74.6 155.3 60.2 217.8 72.0 154.6 63.7Low fat 189.1 70.3 142.3 51.2 200.8 75.9 142.5 64.5High fat 15.0 11.7 13.0 13.9 17.0 13.0 12.1 10.8

Salty foodsAll 57.1 44.3 44.3 32.2 60.4 28.8 39.5 25.0Low fat 2.4 6.4 0.5 1.7 1.5 2.5 0.8 1.4High fat 54.7 45.1 43.8 32.2 58.8 28.8 38.7 25.4

Sweet foodsAll 117.7 96.2 111.1 95.4 113.6 84.6 122.5 73.1Low fat 72.4 67.5 76.1 76.9 75.1 72.2 92.2 68.4High fat 45.3 49.6 35.0 41.3 38.5 34.3 30.2 29.5

a Units are grams except where indicated.



Table 5). Both men and women ate significantly moreweight of low-fat than high-fat sweet foods (F(1,66) 520.44, p , .001, no interaction).

Effects of Dietary Restraint on Intake

A median split of restraint scores was used to dis-tinguish restrained and unrestrained eaters. Genderwas included as a covariate because there were signif-icantly more female than male subjects in the high-restraint group (x2 5 4.98, p , .05).

There were no significant differences in intake (aseither weight or energy) between restrained and unre-strained eaters and no interaction between restraintlevel and stress condition (F values , 1, except thegender covariate, which had values of F(1,63) 5 5.23,p , .05 for grams and F(1,63) 5 9.82, p , .01 for kcal;results were not qualitatively different without genderas a covariate; see Table 6). Analyses grouping foodintake in terms of energy density of overall intake(Table 6), sensory categories, and percentage of energyfrom carbohydrate, protein, and fat (data not shown)all failed to reveal any significant effects of restraint orstress or any interactions involving these factors.

Effects of Emotional Eating on Intake

Restrained eaters scored significantly higher on theemotional eating subscale of the DEBQ (t(66) 5 3.23, p, .01), and women were also more emotional eatersthan were men (t(66) 5 2.26, p , .05) (Table 3). Thus,although gender might mediate the interaction be-tween restraint and emotional eating, effects of thelatter could give a clearer indication of individual dif-ferences in eating responses to stress. Again, genderwas included as a covariate in these analyses.

Subjects were divided, on the basis of a mediansplit, into high and low emotional eaters (ie, emo-tional eaters and nonemotional eaters). No signifi-cant effects of stress condition or any interaction withemotional eating status were seen when total intakewas analyzed in terms of either weight or energy eaten(group effect and group-by-emotional eating interac-

tion, all F values , 1; see Table 7). Gender was asignificant covariate here for both grams of food eaten(F(1,63) 5 7.18, p , .01) and energy intake (F(1,63) 512.33, p , .005).

Unlike total intake, the energy densities of the mealseaten varied by stress condition and emotional eatingstatus (stress-by-emotional eating interaction: F(1,63)5 6.17, p , .02; Table 7). In the stress group, theenergy density of high emotional eaters intake wassignificantly greater than that of low emotional eaters(t(32) 5 2.22, p , .05), whereas among control subjectsthe high emotional eaters ate less energy-dense mealson average (t(32) 5 1.45, NS). Gender was not a signif-icant covariate for energy density (F(1,63) 5 1.56, NS;Table 7), possibly reflecting the fact that variation inenergy density results from different choices ratherthan differences in overall intake.

Effects of stress and emotional eating, and any in-teractions with fat level, were investigated separatelyfor intake of each food sensory category by using three-factor repeated-measures ANOVA. Intakes of blandand salty foods were unaffected by these factors.

Sweet Foods. Gender was not a significant covariatefor intake of sweet foods, and so subsequent analysesdid not include gender. Overall, weight of intake ofsweet low-fat foods (fruit and jam) was higher thanintake of high-fat foods (cake and chocolate biscuits)(F(1,64) 5 18.66, p , .001), although the reverse wastrue for energy intake (F(1,64) 5 35.12, p , .001),reflecting the far greater energy density of the sweethigh-fat foods (Table 7). There were no main effects forstress group or emotional eating, but there were three-way interactions between fat level, group, and emo-tional eating (grams: (F(1,64) 5 3.53, p , .07; kcal:(F(1,64) 5 5.05, p , .05), which were examined furtherby separate analyses for low- and high-fat sweet foods.

High emotional eaters were found to eat almosttwice the weight of sweet fatty foods on average thandid low emotional eaters in the stress group (t(32) 51.78, p , .05, one-tailed test; Table 7); in contrast,among controls, high and low emotional eaters did notdiffer significantly in their intake of sweet fatty foods(t(32) 5 0.78). Although this interaction just failed to

TABLE 6. Effect of Dietary Restraint and Stress on Overall Food Intake

Intake Category


Low Restraint High Restraint Low Restraint High Restraint


Total food intake (g) 312.7 123.9 365.0 122.6 364.0 142.6 326.7 87.9Total energy intake (kcal) 730.3 357.2 806.2 339.8 799.9 327.5 692.9 209.1Energy density of meal eaten (kcal/g) 2.33 0.59 2.24 0.60 2.24 0.68 2.22 0.72

G. OLIVER et al.


reach significance for grams eaten (stress-by-emotionaleating interaction: F(1,64) 5 3.60, p 5 .06), the effecton energy intake was significant (F(1,64) 5 4.26, p ,.05) for the group-by-emotional eating interaction,again with high emotional eaters eating nearly twicethe energy intake of low emotional eaters amongstressed subjects (Figure 1). In comparison, no effectsof emotional eating or stress were seen for intake ofsweet low-fat foods (Table 7).

Analyses of separate macronutrient intake did notreveal any significant effects of stress or emotionaleating or any interactions for amount or percentage ofenergy eaten.

Effects on Hunger

Men and women did not differ in their hunger ratingrecorded at baseline, nor were there significant differ-ences between participants allocated to the stress andcontrol groups. For the sample as a whole, initial hun-ger ratings were reasonably high (mean rating 5 4.87,SD 5 1.23, of a maximum 7), so a substantial intakecould be expected during the meal.

Hunger showed no significant change from baselineto after stress, nor was there any differential effect inthe two groups; thus, there was no support for theprediction that stress affected hunger at the group level(data not shown). Data from the stress group alonewere examined for evidence that greater physiologicalarousal was linked with lower hunger. A significant(negative) correlation emerged with heart rate in a

partial correlation controlling for gender (r 5 20.21, p, .05), with a higher heart rate being associated withlower hunger. There were no significant associationsfor hunger with blood pressure.

The association between rated hunger and desire toeat specified foods was examined using mean appetiteratings across all the 34 foods. This showed that hun-ger was positively correlated with appetite for thefoods (r 5 0.42, p , .001).

Desire to Eat Bland, Salty, and Sweet Foods

In the analyses of rated appetites for the three foodsensory categories, general preference for foods in thatcategory (based on the liking ratings made at the startof the study) was included as a covariate to assessappetite independently of variation due to differencesin general liking. General preference ratings were con-sistently significant covariates for the rated desires toeat bland, salty, and sweet food (bland: F(1,65) 512.57, p , .001; salty: F(1,65) 5 10.22, p , .01; sweet:F(1,65) 5 12.82, p , .001). When analyzing for effectsof restraint and emotional eating on desire for foods,gender was not a significant covariate (largest F 51.63), and so it was excluded from those analyses.

Gender. No significant main effects were found, buta group-by-gender interaction was seen for sweet foods(F(1,63) 5 4.28, p , .05), and in an unexpected direc-tion, with appetite for sweet foods being increased bystress in men but not in women (stressed vs. controlmen: mean (SD) 5 3.57 (1.09) vs. 2.76 (1.10), F(1,24) 5

TABLE 7. Effect of Emotional Eating Status, Stress, and Sensory Category on Food Intakea

Intake Category


Low EmotionalEating

High EmotionalEating

Low EmotionalEating

High EmotionalEating


Total food intake 327.1 119.0 357.7 134.9 307.1 75.9 369.0 134.4Total energy intake (kcal) 687.4 330.2 898.8 341.3 735.9 224.4 752.9 308.7Energy density of meal (kcal/g) 2.11 0.60 2.55 0.46 2.44 0.55 2.10 0.74Bland foods

All 172.6 69.8 180.0 72.4 151.6 46.1 195.6 82.0Low fat 160.0 64.0 164.1 64.6 136.1 42.6 182.5 83.9High fat 12.6 11.8 15.9 14.8 15.4 13.2 13.1 11.0

Salty foodsAll 45.5 41.1 56.1 31.5 42.9 27.0 50.3 29.0Low fat 1.4 5.3 1.1 2.3 0.7 1.4 1.3 2.1High fat 44.1 41.2 55.0 31.8 42.2 27.5 49.0 28.9

Sweet foodsAll 109.0 86.3 121.6 109.4 112.6 68.0 123.0 82.8Low fat 80.0 71.4 65.7 75.2 73.9 68.7 93.0 70.4High fat 28.9 33.8 55.9 55.2 38.7 33.4 30.0 30.1

a Units are grams except where indicated.



4.64, p , .05; stressed vs. control women: mean (SD) 53.32 (1.09) vs. 3.63 (1.10), F , 1; all means wereadjusted for the effect of the general liking covariate).In contrast, among unstressed control subjects, womendesired to eat sweet foods more than men (F(1,31) 54.58, p , .05). This effect was independent of fat level(group-by-gender-by-fat level interaction, F , 1). Noeffects of gender or group, nor any interactions, wereseen on appetite for either bland or salty foods (datanot shown).

Restraint. No significant effects of restraint, or anyinteractions with stress, on desire to eat foods werefound (data not shown). This was the case for all foodsensory categories.

Emotional Eating. The only notable effect was that,for salty foods only, stressed high emotional eatersexpressed greater appetite than low emotional eaters,whereas control subjects did not differ (stress-by-emo-tional eating interaction: F(1,63) 5 4.22, p , .05; mean

(SD) desire to eat for high vs. low emotional eaters:stressed group, 4.58 (0.90) vs. 3.62 (0.91), respectively;control group, 3.73 (0.93) vs. 3.71 (0.90), respectively).

DISCUSSION

There was no evidence here of a general hypophagiceffect of stress on men nor any stress-induced hy-perphagia specifically in women, contrary to the find-ings of Grunberg and Straub (24). Previous studies ofstress and eating typically gave snack-type foods tononfood-deprived subjects, with eating being pre-sented as an incidental activity while performing amore central task. The present study is unusual inexplicitly providing mildly food-deprived participantswith a meal to overcome the problem of low intake thatencumbered earlier studies and in incorporating awider range of foods to allow more valid assessment offood choice.

However, stress did increase intake of sweet fattyfoods in emotional eaters. In addition, women scoredmore highly on emotional eating than men, as is typi-cally found (30). Thus, Grunberg and Straubs (24) sexdifference in the appetitive response to stress may infact have been mediated by a difference in emotionaleating.

The cake and chocolate biscuits preferred here bystressed emotional eaters are typically eaten as snacks.There is evidence that snack consumption may bemore susceptible to stress than meals (15, 37). Suchfoods may be preferred during stress through learningthat small energy-dense snacks are more easily in-gested and digested when gut activity is suppressed bysympathetic arousal. In comparison, a naturalisticstudy of the impact of surgical stress on food intakefound no effect of stress on meal intake or composition(12).

Unlike a number of previous studies (1820, 38,39), the present study did not reveal a significant in-fluence of dietary restraint on eating behavior understress, although there was a trend toward greater con-sumption of sweet foods by highly restrained stressedsubjects. In this study, restraint was measured usingthe restraint scale of the DEBQ, which contains itemspertaining only to dietary restraint and thus is not ameasure of vulnerability to dietary disinhibition,whether through emotional relief or other reasons. Incontrast, the Restraint Scale (28, 29), which has beenfound to discriminate eating responses to stress (20,38), paradoxically contains only 1 item (of 10) thatexplicitly refers to dietary restraint; the remainingitems addressing weight fluctuation, preoccupationwith food, tendency to binge when eating alone, andfeeling guilty after overeating. The psychometric rele-

Fig. 1. Effect of emotional eating status and stress manipulation onintake (kcal) of sweet fatty foods. Data are mean 1 SE. *t(32)5 1.85, p , .05, one-tailed test, for greater intake by highemotional eaters in the stressed group vs. the control group(independent t test; see text for details of significantANOVA interaction). Intakes among low emotional eatersdid not differ between groups.

G. OLIVER et al.


vance of labeling such a questionnaire as measuringrestraint has been discussed in detail elsewhere (30,40, 41), but such a multifaceted instrument does notallow clear interpretation of the psychological mecha-nisms by which stress could be influencing food con-sumption and choice. In any event, it cannot be con-cluded from that measure that a critical factor inresponding to stress is the tendency to restrain intake,and we find no support for such a conclusion. Further-more, the Disinhibition scale of the Three-FactorEating Questionnaire (41) (overeating elicited by so-cial, sensory, and emotional cues) discriminates be-tween women who report eating more during stressand those who do not (16), whereas the restraint-spe-cific scale of that instrument did not predict stress-induced eating.

In comparison, the emotional eating scale of theDEBQ used here specifically defines individuals whohave a tendency to eat more during negative emotionalstates (ie, emotion-induced disinhibition) (42). Justsuch an emotional eating effect was observed here:High emotional eaters ate more sweet, fatty, and thusenergy-dense foods under stress. Thus, this study pro-vides some evidence that a stress-induced change infood choice is a measurable behavioral phenomenon,at least in this laboratory environment, not just a sub-jective phenomenon confined to self-report measures.These results are particularly important because theincreased eating is confined to certain foods, espe-cially those that current health recommendations sug-gest should be limited. In contrast to intake, rateddesire to eat the various categories of foods was lessaffected by stress, although desire to eat salty foodswas specifically greatest in stressed emotional eaters.Even so, the increased desire to eat sweet foods whenstressed seen here in men but not in women (irrespec-tive of emotional eating status) is contrary to the (in-take) results of Grunberg and Straub (24). These effectson desire for food sensory categories require replica-tion and should be interpreted cautiously.

Why might some individuals be more susceptible tounhealthy shifts in food choice when under stress?The effect is not dependent on gender per se, but theemotional eaters were more likely to be female. Froman intervention perspective, it will be important tounderstand how emotional eating tendencies develop.This characteristic has been discussed extensivelyelsewhere (13, 30), but its origin remains poorly un-derstood. One consideration is that an initial experi-ence of eating highly palatable energy-dense foodswhen upset may become habitual by reinforcementthrough sensory, nutritional, and neurohormonalroutes (43, 44).

A recent study provides some support for this mod-

el: Markus et al. (45) found that neurotic (stress-prone) subjects were protected from depressed moodand raised cortisol induced by a psychological stressortask after eating a carbohydrate-rich/protein-poorbreakfast and lunch but not after a carbohydrate-poor/protein-rich diet. In stable subjects, mood was de-pressed and cortisol increased equally after either diet.This result was interpreted as improved coping after adiet-induced increase in the supply of precursoramino acids to serotonin synthesis. That is, the carbo-hydrate-rich/protein-poor diet specifically allowsgreater uptake of the precursor amino acid tryptophaninto the brain. The implication is that neurotic orstress-prone individuals may be particularly sensitiveto dietary effects on brain pathways influencing moodand stress coping. Furthermore, to learn to self-med-icate through eating in this manner would most likelyrequire ingestion of unusually low-protein foods inisolation (46), as might be achieved by snacking onsweet and fatty foods when hungry. Also, within thistheoretical framework, dietary restraint, found to bepositively correlated with emotional eating or disinhi-bition here and elsewhere (16, 30, 41), may predisposean individual to learning such a dietary-induced reliefof dysphoria; that is, dieting has been shown to lowerplasma tryptophan levels in women and to sensitizeserotoninergic function (47).

An alternative neurohormonal mechanism forstress-induced preferential selection of sweet fattyfoods is suggested by evidence that such highly palat-able foods can themselves relieve stress through re-lease of endogenous opioids (44, 48).

The effects of stress on hedonic reactions to, andperception of, taste also need consideration. For in-stance, Dess and Edelheit (27) found that stresschanged peoples perception of saccharins bitternessand sweetness, as it does in rats (6), but the direction ofchange depended on aspects of temperament such astrait arousability, pleasure (net affective valence), anddominance. Despite no suggestion of gender differ-ences (27), it could be fruitful to determine the rela-tionship of these traits to emotional eating tendencies.

As with any laboratory study carried out in thisarea, the impact of the stressor on the participants islikely to be less severe than is the case for real eventsoccurring in a nonexperimental setting without ethicalconstraints. Caution is required in generalizing fromthese results to less controlled situations in daily life.Even so, anticipation of public speaking is known to bea fearful stimulus to students (49); actual performancemight have led to subjects eating while in a relievedrather than stressed state. Here, certainly, subjects inthe stress group rated their experience as significantlymore stressful than did subjects in the control group,



but this was in response to the question asked duringthe debriefing session, and so answers may have beeninfluenced by demand effects. Nevertheless, on thepremise that stress-induced changes in food choicemight actually help to alleviate stress, group differ-ences in the perceived stress level reported after themeal may have been less than would be the case with-out a meal. It should be noted that the (presumablyadaptational) decrease from baseline in physiologicalarousal among control subjects is a well-recognizedphenomenon in psychophysiological research (50):Far from vitiating the use of stress and controlgroup labels, it illustrates the justification for such acontrol group. The combination of this difference be-tween groups in changes in physiological measuresand the evidence of greater physiological and psycho-logical arousal in the stressed group justifies thestressed vs. control group comparisons.

Despite the limitations described, this study isunique in its assessment of the effect of stress on foodchoice in the laboratory by presenting, in the form ofan explicit meal, a range of foods varying in nutritionalcomposition, taste and textural qualities, and dietaryroles (ie, snack foods and meal foods). Susceptibleindividuals were found to select less healthy foodsunder stress, supporting the proposition that stressmay damage health in part through unhealthy foodchoice. However, the variety of foods was limited, andso caution is needed in interpreting which propertiesof the foods are critical to the effect. The findingsdeserve replication and extension, for instance, underdifferent stress conditions and eating contexts, to-gether with further characterization of vulnerabletraits (51).

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