Appetite 72 (2014) 106–113

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Appetite

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Research report

The role of emotional eating and stress in the influence of short sleep onfood consumption q

0195-6663/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.appet.2013.10.001

q Acknowledgments: The authors thank Leah LaPrate, Lauren Bernardo, AlbaneBajraktari, and Jaclyn Sheldon for their assistance in data collection and coding(Experiment 1). The authors are grateful for the funding provided by the WagnerCollege Office of the Provost.⇑ Corresponding author.

E-mail address: LNolan@wagner.edu (L.J. Nolan).

Julia S. Dweck, Steve M. Jenkins, Laurence J. Nolan ⇑Department of Psychology, Wagner College, 1 Campus Rd., Staten Island, NY 10301, USA

a r t i c l e i n f o

Article history:Received 16 August 2013Received in revised form 19 September 2013Accepted 4 October 2013Available online 19 October 2013

Keywords:Emotional eatingStressEating behaviorSleep deprivationSleep qualityBMI

a b s t r a c t

Short sleep duration is associated with elevated body mass index (BMI) and increased energy consump-tion. The present studies were conducted to determine what role emotional eating and stress might playin these relationships. The first was an exploratory questionnaire study in which sleep quality and dura-tion were measured in conjunction with the Dutch Eating Behavior Questionnaire in 184 women. Emo-tional and external eating scores were significantly higher in those who reported poor sleep quality (butwere not related to sleep duration). In a second study of 64 women who were provided with snacks in thelaboratory under stressed and control conditions, elevated food consumption was observed in those whoscored high on emotional eating and who reported short sleep (a significant stress � emotional eat-ing � sleep duration interaction) but not in those who reported poor sleep quality. No effects were foundin liking or wanting of food and few effects were found on appetite. BMI was not related to sleep durationor sleep quality in either study. The results suggest that the relationship between short sleep and elevatedfood consumption exists in those who are prone to emotional eating. An external stressor elevated con-sumption in normal sleepers to the level observed in short sleepers, however, it did not significantly ele-vate consumption in short sleepers. Future examinations of the effects of sleep duration and quality onfood consumption should examine emotional eating status.

� 2013 Elsevier Ltd. All rights reserved.

Introduction

Short sleep duration has been associated with elevated bodymass index (BMI, Gangwisch, Malaspina, Boden-Albala, &Heymsfield, 2005), disordered eating (Hicks & Rozette, 1986),emotional stress (Vgontzas et al., 2008), and neuroendocrinecontrol of appetite (Van Cauter et al., 2007). It is likely that thehigher BMI associated with short sleep is due to increased foodconsumption as there is little evidence for significantly reducedenergy expenditure (Chaput & Tremblay, 2012).

Cross-sectional studies using self-report questionnaires indicatelinear negative relationships between insufficient sleep and BMI inadults (Kohatsu et al., 2006; Wheaton et al., 2011) although therelationship is more mixed in adults than in children (Patel & Hu,2008). In children, short sleep duration is associated with concur-rent obesity and risk for elevated adult BMI (for a review, see Patel

& Hu, 2008). Chaput and Tremblay (2012) concluded that childrenand adolescents may be more vulnerable to the effects of shortsleep. However, long sleep (>8 h) may also increase risk for obes-ity; cross-sectional data show U-shaped relationships betweensleep duration and BMI (Chaput, Després, Bouchard, & Tremblay,2007; Gangwisch et al., 2005). These BMI changes may suggestchanges in energy consumption and/or expenditure.

Short sleep has been associated with increased energy con-sumption. In a 1-year longitudinal study of obese middle-agedadults, those who slept less reported higher daily energy consump-tion (Galli et al., 2013). Several studies have shown that an acutesevere restriction (by allowing up to 4 h of sleep except wherenoted) in sleep can elevate energy consumption (from snack inoverweight men and women limited to 5.5 h of sleep, Nedeltchevaet al., 2009; from breakfast in normal weight men, Brondel, Romer,Nougues, Touyarou, & Davenne, 2010; from daily intake in normaland overweight men and women, St-Onge et al., 2011) and in-crease hunger (in men, Brondel et al., 2010; Spiegel, Tasali, Penev,& Van Cauter, 2004) compared to those who slept 8–9.5 h. How-ever, the results of other studies are not consistent with these find-ings. For example, men subjected to 2 consecutive nights of 4 h ofsleep did not differ in breakfast and morning snack consumptionfrom when they experienced 2 consecutive nights of 8 h of sleep

Table 1Participant characteristics (mean ± SEM) and categorization of participants by sleepduration and BMI for both experiments.

Characteristic Experiment 1 Experiment 2

N 184 64Age (years) 18.6 ± 0.1 18.8 ± 0.4

DEBQEmotional 2.6 ± 0.1 2.5 ± 0.1External 3.0 ± 0.1 3.2 ± 0.1Restraint 3.0 ± 0.1 2.8 ± 0.1BMI (kg/m2) 22.7 ± 0.3 24.5 ± 0.6Underweight BMI 3.8% 1.6%Normal BMI 78.7% 64.1%Overweight BMI 13.1% 18.8%Obese BMI 4.4% 15.6%Sleep Durationa 7.3 ± 0.1 6.7 ± 0.1Short sleep 45.8% 71.9%Normal sleep 54.2% 28.1%

a N = 131 for sleep duration analysis in Experiment 1.

J.S. Dweck et al. / Appetite 72 (2014) 106–113 107

(Schmid et al., 2009), and male and female undergraduates whowere instructed to restrict their sleep to 4 h or less for 1 night re-ported (in food diaries) consuming fewer calories following thesleep deprivation than when they had normal sleep (Wells &Cruess, 2006).

Changes in food choice and eating behavior are associatedwith short sleep. Shorter sleep in children (Westerlund, Ray, &Roos, 2009) and fewer than 7 h of sleep in adults (Stamatakis &Brownson, 2008) are associated with consumption of fewer fruitsand vegetables and more energy-rich, nutritionally empty foods.Adolescents who report sleeping fewer than 8 h per night alsotend to eat more total calories (Garaulet et al., 2011), and moreenergy from fats rather than carbohydrates (Weiss et al., 2010).A preference for calories derived from fats over carbohydrateshas been observed in those experimentally restricted to 4 h ofsleep (St-Onge et al., 2011) and those who reported sleeping few-er than 7 h per day (Shi, McEvoy, Luu, & Attia, 2008). Not onlymay short sleepers eat differently, they differ from normativeduration sleepers in when they eat. Studies of college students(Hicks, Mc Tighe, & Juarez, 1986) and women (Kim, DeRoo, &Sandler, 2011) with short sleep (report fewer than 7 h per night)show a trend towards snacking rather than eating during conven-tional meal times. Increased snacking may be due to increasedtime for eating at later hours. Adults experimentally restrictedto no more than 5.5 h of sleep who were presented with snacksad libitum ate significantly more calories during the nighttimethan in the daytime (Nedeltcheva et al., 2009). Thus, there maybe an upregulation of appetite as mediated by the presence offood and modified eating patterns related to short sleep duration;studies of normal weight humans have reported high levels of theorexigenic hormone ghrelin and low levels of the anorectichormone leptin when restricted to 5 h of sleep (see Chaput &Tremblay, 2012 for review).

There has been little investigation of psychological variablesassociated with susceptibility to short sleep effects. Chaput,Després, Bouchard, and Tremblay (2011) examined the role of dis-inhibition (the loss of suppression of food consumption as mea-sured by the Three Factor Eating Questionnaire, TFEQ) in a largesample of adults in a 6-year longitudinal study and reported thatthose with high disinhibition scores experienced weight gains thatwere 2.5 times higher than those with low disinhibition scores.They also reported higher energy consumption. Perhaps sleepdeprivation results in a loss of inhibition of food consumption orincreases stress-related (emotional) eating in those who are proneto stress-related eating. The disinhibition factor of the TFEQ has asignificant emotional eating component (Hyland, Irvine, Thacker,Dann, & Dennis, 1989). Thus, two studies examining the relation-ship between sleep duration and quality and emotional eatingwere conducted.

The purpose of the first study was to examine whether there isan association between sleep duration and quality, BMI, and emo-tional and external eating. Emotional eating in particular has beenassociated with excessive (sometimes pathological) eating andobesity (Lindeman & Stark, 2001). Stress has been associated withboth emotional and external eating and it was expected that thesewould be associated with sleep disturbances. Following that, a sec-ond study was conducted in order to determine to what degreeemotional eating status, sleep duration, and sleep quality interactwith a stressor to influence actual food consumption. Because stu-dents commonly report short sleep (Buboltz et al., 2009), no exper-imental sleep manipulation was performed; the sleep patterns ofthe students were measured by self-report. While it would beinteresting to assign some students to short sleep, these manipula-tions are often more severe than what would be the ‘‘natural’’amount of deprivation and would be difficult to sustain outsideof the laboratory (Horne, 2008).

Experiment 1

Method

ParticipantsA sample of 184 undergraduate women volunteered to partici-

pate as one option to fulfill a course research requirement. Womenwere selected for study due to their higher rates of emotional eat-ing (van Strien, Frijters, Bergers, & Defares, 1986). Their anthropo-metric characteristics are presented in Table 1. When asked todescribe racial identification, 1.1% described themselves as Asian,2.7% as Black, 83.7% as White, 0.6% as Pacific Islander, 3.8% asmixed race, and 5.4% reported ‘‘other’’ or did not answer. On a sep-arate question, 5.0% described themselves as Latina.

Dependent measuresThe Dutch Eating Behavior Questionnaire (DEBQ; van Strien

et al., 1986) was used to measure emotional eating (eating in re-sponse to aroused emotional states), external eating (eating in re-sponse to the presentation of food regardless of hunger), anddietary restraint (intentional control of food intake). The DEBQ iscomposed of 33 items, all based on a 5-point scale ranging from‘‘never’’ to ‘‘very often.’’ The test has high internal consistency withreliability between 0.80 and 0.95 and factorial validity (van Strienet al., 1986).

Sleep Measures: The Sleep Quality Index (SQI; Urponen,Partinen, Vuori, & Hasan, 1991), a validated brief questionnairecontaining 8 items to indicate the weekly frequency of varioussleep disturbances over previous 3 months, was used to measuresleep quality. Higher scores on this measure indicate poorer sleepquality: scores of 0 or 1 indicate good sleep quality, scores from 2to 8 indicate occasional sleep difficulties, and scores ranging from 9to 16 indicate poor sleep quality. The SQI has acceptable reliabilityof .71 in a US sample (Buboltz et al., 2009) and .74 in a Europeansample (Urponen et al., 1991). The Sleep Habits Questionnaire(SHQ; Lack, 1986) is composed of 9 questions about usual amountsof sleep, bedtimes, wake-up times, sleep latency, among othermeasures and was used to determine sleep duration. Sleepduration was calculated by subtracting the sleep latency fromthe difference between reported bedtime and wake time.

ProcedureAfter providing informed consent, participants were adminis-

tered the DEBQ and SQI/SHQ in counterbalanced order in smallgroups settings. Each participant was seated alone at a table to af-ford privacy. An additional questionnaire was administered to col-lect data on height, weight, age, sex, and ethnicity. While direct

108 J.S. Dweck et al. / Appetite 72 (2014) 106–113

measures are preferred, self-report of height and weight have beenshown to be valid proxy measures with a correlation of .97 withmeasured values in young adults (Kuczmarski, Kuczmarski, &Najjar, 2001) and in our laboratory (unpublished data). Partici-pants were debriefed as to the purpose of the study when theycompleted all questionnaires. All procedures were approved bythe Human Experimentation Review Board at Wagner College.Data were analyzed using SPSS (v. 15). Data were collected overa year at different points in the academic year (excluding finalsweek and first 3 weeks of each semester).

Results

Sleep characteristics of the sample are reported in Table 1. Themajority of participants reported occasional sleep problems(n = 137) and roughly equal numbers reported good (n = 21) andpoor (n = 26) sleep quality. Relationships between the variableswere not curvilinear and 1-tailed Pearson correlation coefficientswere computed. BMI was not correlated to sleep quality,r(182) = �.039, p = .604. Sleep duration could not be determinedfor participants who did not report sleep latency, so all analysesusing sleep duration is based on a subset of the sample (n = 131).A chi-square analysis revealed that the loss of these participantswas not from a particular subset (i.e., any particular BMI or sleepquality group, etc.) of the sample. BMI was not significantly corre-lated with sleep duration, r(129) = �.025, p = .389. Sleep durationand sleep quality were significantly weakly correlated,r(129) = �.176, p = .022. No relationships were found betweensleep duration and DEBQ scores. However, poorer sleep qualitywas associated with elevated emotional eating scores,r(182) = .210, p = .004, and elevated external eating scores,r(182) = .207, p = .005 (but not with restraint scores).

Discussion

Emotional and external eating scores were associated with poorsleep quality but not short sleep duration. However, these resultsdo not support those of other studies that higher BMI is associatedwith short sleep duration. While the sleep duration was varied, inthis sample fewer than half of the participants reported sleepingfewer than 7 h per night. Furthermore, only about 17% of the par-ticipants were overweight or obese. Thus, it is possible that therewere not enough participants with short sleep duration or highBMI in the sample to allow detection of a relationship betweenBMI and sleep duration. Nonetheless, the results indicated thatemotional and external eating tendencies were associated withpoor sleep quality.

It is possible that one mechanism for increased eating and po-tential eventual weight gain in those with sleep disturbances iseating induced by the stress that results from sleep deprivationor poor sleep quality each of which produces similar physiologicalchanges as external stressors. Indicators of stress such as activa-tion of the hypothalamic–pituitary–adrenal (HPA) axis and in-creased cortisol secretion are associated with sleep deprivationand poor sleep quality (Balbo, Leproult, & Van Cauter, 2010). In-deed, Vgontzas et al. (2008) found that obese participants withpoor sleep quality reported higher stress than those without sleepproblems, and chronic emotional stress was a stronger predictorof sleep duration than BMI. Stress may also be the underlyingcause of both poor sleep quality and elevated tendencies towardfood consumption. In order to determine the role of stress in therelationship between sleep variables and eating behavior, a sec-ond experiment utilizing an experimentally induced stressorwas conducted.

Experiment 2

Method

ParticipantsA sample of 66 undergraduate women participated in the study

as one option to fulfill a course research requirement. They weretold that snacks would be served and those with dietary restric-tions were not permitted to enroll. Two participants were not in-cluded in the final sample since they did not eat 3 of the 6 foodsused in the conditions tested. Thus, all analyses were performedon a sample of 64 women. No member of this sample had partici-pated in Experiment 1.

Anthropometric and demographic measuresHeight and weight were measured (using a stadiometer and

digital scale, respectively) to determine BMI; participant character-istics are presented in Table 1. When asked to describe racial iden-tification, 3.1% described themselves as Asian, 4.7% as Black, 87.5%as White, and 3.1% as mixed race. On a separate question, 10.9% de-scribed themselves as Latina.

Independent and predictor variablesStressor: Participants were asked to solve an unsolvable Sudoku

puzzle (obtained from The Book of Impossible Sudoku by P. Mutton)to induce stress. The method is effective in inducing stress andstress-related food consumption in women (Habhab, Sheldon, &Loeb, 2009) due to ego-threat (negative self-referent information)which can induce emotional eating (Wallis & Hetherington, 2004).

Sleep quality and duration: The Pittsburgh Sleep Quality Index(PSQI; Buysse, Reynolds, Monk, Berman, & Kupfer, 1989) was usedto assess participants’ sleep habits during the previous month. ThePSQI is composed of 19 items and classifies sleep into seven cate-gories including sleep quality, sleep duration, and habitual sleepefficiency. The test has good reliability with a Cronbach’s alphaof 0.83 and a test–retest reliability of 0.85 (Buysse et al., 1989).In analyses including sleep duration, the participant’s report ofsleep duration (not time in bed) was used.

Dependent measuresEating styles: The DEBQ was used to measure emotional and

external eating and dietary restraint.Food measurement and presentation: Participants were pre-

sented with a tray containing 6 snacks: cookies (33 g, Linden’s BiteSize Chocolate Chippers), cheese (58 g, Cello variety pack, sliced),chocolate candies (38 g, M&M plain), jelly beans (43 g, Jelly Bellyvariety), crackers (17 g, Ritz plain), and celery sticks (28 g). Theywere also provided a cup of water (approximately 200 mL). Eachsnack food was pre-weighed and placed in a tray compartment.Each compartment was filled so that all appeared equally fulland location of each food in the tray was alternated. Post consump-tion, each snack item was weighed again and the difference inweight computed to determine the amount of each food con-sumed. Energy consumption was calculated from product nutritionlabels.

Appetite questionnaires: Participants rated their appetite (hun-ger, fullness, quantity of food they thought they could presentlyeat, and desire to eat) on a 100 mm visual analog scale (VAS;Aitken, 1969) which has been shown to be a valid and reliablemethod for the measurement of subjective appetite (Blundellet al., 2010). After consuming the foods, participants were askedto rate their appetite again. Wanting for and liking of each foodwas assessed during a taste test; each food was sampled and desireto consume that food and pleasantness of that food ‘‘right now’’while in the mouth was rated on a VAS. Participants were also

J.S. Dweck et al. / Appetite 72 (2014) 106–113 109

asked to report how much time had passed since they had lasteaten any food.

Stress: As a manipulation check, stress was measured using theState-Trait Anxiety Inventory for Adults (STAI; Spielberger,Gorsuch, Lushene, Vagg, & Jacobs, 1983). The STAI differentiatesbetween trait anxiety and state anxiety with 40 items regardinghow participants generally feel (trait) and how they feel at thismoment (state). Only participants’ state anxiety was measured totest for effects of the stressor between conditions. The STAI hasstrong internal consistency, with correlations of 0.86–0.92 for traitanxiety and 0.83–0.92 for state anxiety.

Physiological arousal: Tonic electrodermal activity in response toparticipants’ stress was measured by galvanic skin response (GSR;Biopac Systems, Goleta, CA). It was used to determine whetherthere were differences in arousal for sleep duration and emotionaleating groups.

ProcedureAll procedures were approved by the Human Experimentation

Review Board at Wagner College. A repeated-measures design (uti-lizing counter-balanced order and random condition assignment)was employed in which participants were experimentally stressedunder one condition but not the other. Each session tested one par-ticipant at a time and was scheduled as an afternoon ‘‘snack’’ be-tween 12:30 and 6 PM. Participants were tested at the same timeon non-consecutive days always within the same week. Studentshave similar schedules on alternate days (e.g. the same class meet-ings on Mondays and Wednesdays with others scheduled on Tues-days and Thursdays) so this scheduling also served to somewhatcontrol for eating and activities patterns. Data were collected overan 18-month period (excluding the first month of each semesterand the final examination period).

Upon arrival at the laboratory, the participant provided in-formed consent (first session) and was escorted to a test room.During the first session only, regardless of condition, the PSQIand DEBQ were administered. When the stress condition was thefirst session, GSR leads were placed on the participant’s non-dom-inant hand prior to administration of the questionnaires, and shewas instructed to limit movement of that hand as much as possi-ble. When the stress condition occurred in the second session,the GSR leads were placed on the participant’s hand just prior tothe administration of the Sudoku task.

Next, the participant was provided written instructions on howto solve Sudoku puzzles and then asked to solve the provided puz-zle (at which time GSR recording began). To further induce ego-threat, she was told that most people were able to complete it inapproximately 10 min. After allowing 12 min to solve the puzzle,the experimenter entered the room and stated that more than10 min had passed and that the puzzle did not need to be com-pleted. The STAI was then administered and the GSR leads wereremoved.

Each participant was then presented with the tray of snacks andcup of water and asked to rate her appetite and then sample eachfood following the written taste test procedure. She was also in-formed that she could eat as much or as little of the food as shewished upon completion. The participant could indicate that shewas finished at any time, but after 10 min, if she had not exitedthe test room, the experimenter entered the room to determinewhether she was finished. By allowing participants to eat for aslong a time as desired, the time taken to complete the snack couldbe used as an additional dependent variable. The duration of thesnack period was measured, and the post-snack appetite question-naire was then administered.

The non-stress condition followed the same procedure with theexception of the GSR leads and Sudoku task. After completing thePSQI, DEBQ, and STAI, the participants were presented with the

snack tray and water. Participants’ height and weight were mea-sured after the final appetite questionnaires in the second sessionregardless of the condition.

Participants were debriefed as to the purpose of the study viaemail after all data collection was completed. This was done tomaintain the integrity of the study, to ensure that participantswho completed the sessions would not disclose the full nature ofthe study to future potential participants.

Statistical analysesAll statistical analyses were conducted (unless otherwise sta-

ted) using SPSS (v. 15). Means are reported ± SEM.

Results

Replication of Experiment 1In this sample, like in Experiment 1, there were no significant

correlations between BMI and sleep duration, r(62) = .004,p = .486, or sleep quality as measured by PSQI, r(62) = .019,p = .440. Furthermore, there was also no significant relationshipbetween sleep duration and DEBQ scores. However, unlike inExperiment 1, there were no significant correlations between sleepquality and emotional eating, r(62) = .145, p = .126, or external eat-ing, r(62) = �.122, p = .168. The correlation coefficient for the rela-tionship between sleep quality and emotional eating was similar invalue to that found in experiment 1. As in Experiment 1, poor sleepquality was significantly associated with short sleep duration,r(62) = �.632, p = .000.

Manipulation checkThe STAI score in the stress condition (M = 41.00 ± 1.25) was

significantly higher than in the control condition(M = 35.88 ± 1.29), t(63) = 3.51, p = .001, d = .51. While it is likelythat the Sudoku puzzle was an effective stressor, the presence ofthe polygraph may have contributed as a stressor since it wasnot present in the control condition.

Eating and sleep characteristicsIn order to test whether emotional eating status interacted with

the stressor to affect food consumption, participants were dividedinto emotional eating groups using criteria suggested by van Strienet al. (2013) where high emotional eaters scored above 2.6 and lowemotional eaters scored below 1.8 (those in-between were classi-fied as moderate emotional eaters). Since only 12 participantsscored below 1.8, they were grouped with the moderate emotionaleaters (low/moderate, n = 36; high, n = 28).

The participants reported a mean sleeping duration below 7 hper night over the month prior to testing. Most individuals in thisage group require 8–9 h of sleep (Dement & Vaughan, 1999). Inaddition, the mean global PSQI score of the sample suggested that,on average, the students had poor sleep quality (M = 6.5 ± .36). Ascore >5 is indicative of likely poor sleep quality (Buysse et al.,1989) and it was used as a criterion to create two groups, thosewho reported poor (n = 36) and good (n = 28) sleep quality, so thatits potential interaction with the stressor on food consumptioncould be evaluated.

In order to determine whether sleep duration interacted withthe stressor to affect food consumption, participants were dividedinto short (<7 h/night, n = 46) and normal (P7 h/night, n = 18)sleepers. Seven hours is a common criterion used to define shortsleep as sleep durations higher than 7 are associated with optimalBMI (Adámková et al., 2009).

Role of previous food consumption and BMI in snack consumptionThe time since food was last eaten prior to arrival at the labora-

tory was measured in a subset of the sample (n = 41). The amount

110 J.S. Dweck et al. / Appetite 72 (2014) 106–113

of energy consumed in the snack was not significantly related totime since last ate. There was no significant difference in time sinceeaten between the 2 conditions reflective of the similarity in sche-dule for the 2 test days, t(40) = .638, p = .527. BMI was not signifi-cantly correlated to the amount of food consumed in the stress,r(64) = .155, p = .222, or control, r(64) = .082, p = .518, conditions.BMI was also not correlated with emotional eating. Thus, neithertime since last ate nor BMI were included as predictors in subse-quent analyses.

Food consumption and sleep durationTo examine whether the effect of the stressor on snack con-

sumption interacts with emotional eating and sleep duration, a3-way mixed 2 � 2 � 2 factorial design ANOVA (with stressor aswithin-subjects factor and emotional eating and sleep durationas between-subjects factors) was performed. The stressor did ele-vate food consumption (M = 151.78 ± 11.41 kcal) over control lev-els (M = 133.87 ± 12.11 kcal), F(1,60) = 16.447, p = 000, partialg2 = .215. However, there was no main effect of emotional eating,F(1,60) = .748, p = .391, partial g2 = .012, or sleep duration,F(1,60) = .115, p = .736, partial g2 = .002. There were significant 2-way interactions between stress and both sleep duration and emo-tional eating (p < .01 for each). Finally, the results revealed thepresence of a 3-way interaction between stress, emotional eatingand sleep duration, F(1,60) = 5.519, p = .022, partial g2 = .084.While there was no effect of stress or sleep duration on the amountof food consumed in the group of low to moderate emotional eat-ers, short sleep predicted higher consumption in high emotionaleaters in the control condition. Consumption in the stress condi-tion was higher in the normal sleep group but did not differ inthe short sleep group, suggesting that short sleep elevated con-sumption to stress condition levels (see Fig. 1).

To test whether the effects were present in each food tested, theconsumption of each of the 6 foods was analyzed in the same fash-ion (see Table 2 for energy consumption from each food). A 3-wayinteraction was found for cookie consumption, F(1,56) = 5.339,p = .025, partial g2 = .087, but not for any of the other foods. Signif-icant 2-way interactions present for the other foods revealed nopatterns in selective changes in one food over another. Thosewho reported short sleep tended to eat more cheese, jelly beans

Fig. 1. Mean energy consumption in stress (dashed line) and control conditions (solid lirepresent standard error.

and celery while normal sleepers tended to eat more crackers,cookies and chocolate.

Food consumption and sleep qualityTo examine whether an interaction occurred between sleep

quality, emotional eating, and stressor, a similar analysis was per-formed. There were no significant interactions with PSQI scores inthe 3-way ANOVA, F(1,60) = .914, p = .343, partial g2 = .015. Therewere also no 2-way interactions. Due to lack of interaction be-tween PSQI and other factors, no analyses of individual foods wereconducted.

Snack durationIt is possible that the amount of time the participants spent eat-

ing contributed to amount of food consumed; thus, the role of thestressor, emotional eating, and sleep duration on snack durationwas examined. Snack duration was measured in 42 of the partici-pants and was found to be positively correlated with total energyconsumption in both the control, r(40) = .862, p = .000, andstressed conditions, r(39) = .764, p = .000. A repeated measures t-test revealed a non-significant difference between snack durationin the control (M = 4.22 ± .25 min) and stressed(M = 4.05 ± .23 min) condition, t(40) = �1.022, p = .313. In orderto analyze the role of snack duration in the amount of energy con-sumed in the emotional eating and sleep duration conditions in thefull sample, missing values were estimated using the multipleimputation method (Rubin, 1987). While there was a tendencyfor the participants to eat for a shorter period of time under thestress condition, a 3-way ANOVA revealed no significant 3-wayor 2-way interactions between stress condition, snack duration,emotional eating, or sleep duration for 5 imputed sets of scores(datasets created using NORM 2.03; Schafer, 1997). Furthermore,there remained no main effect of stress on snack duration. Thus,it is likely that there was no effect of the stressor on snack durationand that snack duration did not account for difference in energyconsumption observed.

Appetite measuresThere were no significant differences between hunger, desire to

eat, estimated quantity of food that could be eaten, or fullness

ne) for short and normal sleepers categorized by emotional eating score. Error bars

Table 2Mean (±SEM) energy consumed (kcal.) in each condition for each food.

Food Sleep High emotional eating Low/moderate emotionaleating

Control Stress Control Stress

Cookies Normal 29.29 ± 5.54 54.95 ± 14.93 43.62 ± 9.15 44.10 ± 6.41Short 36.60 ± 6.17 40.05 ± 6.23 39.87 ± 6.87 39.96 ± 6.59

Crackers Normal 25.67 ± 6.25 45.67 ± 2.45 26.41 ± 5.42 25.45 ± 4.66Short 34.23 ± 5.78 35.48 ± 4.69 25.00 ± 4.13 23.04 ± 3.31

Chocolate Normal 16.50 ± 5.67 50.00 ± 20.37 21.60 ± 7.38 28.45 ± 14.88Short 28.95 ± 11.55 29.59 ± 10.09 15.39 ± 3.30 14.61 ± 3.45

Cheese Normal 16.46 ± 5.72 37.37 ± 13.26 41.71 ± 14.15 37.17 ± 13.02Short 48.13 ± 9.99 63.65 ± 10.80 32.16 ± 7.15 30.09 ± 5.60

Jelly beans Normal 5.25 ± 0.95 8.75 ± 2.77 11.61 ± 2.66 15.14 ± 4.91Short 12.13 ± 2.12 12.77 ± 2.32 16.18 ± 3.77 18.62 ± 6.85

Celery Normal 0.51 ± 0.12 0.68 ± 0.21 0.74 ± 0.14 0.64 ± 0.16Short 0.63 ± 0.13 0.74 ± 0.18 0.53 ± 0.08 0.47 ± 0.06

J.S. Dweck et al. / Appetite 72 (2014) 106–113 111

between the stressed and control conditions. In both conditions,pre-snack hunger strongly predicted the amount of energy con-sumed: stressed, r(62) = .334, p = .007, and control, r(62) = .333,p = .007.

The observed changes in food consumption could be related tochanges in appetite, motivation to eat, and/or changes in likingand/or wanting for food. The participants were not, on average,very hungry or very full before and after the snack. Furthermore,there was no significant change in hunger from before snack(stressed: M = 39.98 ± 3.18; control: M = 42.44 ± 3.51) to aftersnack (stressed: M = 39.38 ± 3.22; control: M = 39.62 ± 3.35),t(63) = .282, p = .779 and t(63) = 1.213, p = .230 for stressed andcontrol groups respectively. However, in the stressed conditionthere was a significant elevation in fullness from before(M = 46.95 ± 3.34) to after the snack (M = 55.08 ± 3.12),t(63) = �2.957, p = .004. The trend in the control condition wassimilar but not statistically significant, t(63) = �1.752, p = .085.

To examine whether the effect of the stressor on appetite rating(both before and after eating the snack) interacts with emotionaleating and sleep duration, a 3-way mixed 2 � 2 � 2 factorial designANOVA (with stressor as within-subjects factor and emotional eat-ing and sleep duration as between-subjects factors) was per-formed. There were no 3-way interactions for any of the pre- orpost-eating appetite measures.

The same analysis was performed on ratings of the pleasantnessand desire to consume the food when present in the mouth. No dif-ferences in desire or pleasantness ratings or interactions were ob-served for any of the foods.

PsychophysiologyNo relationship was found between GSR (peaks per minute of

tonic response) and DEBQ measures. There was no significant dif-ference in GSR between emotional eating or sleep duration groups.

Discussion

Naturally occurring short sleep is associated with elevated en-ergy consumption in emotional eaters. When stressed, energy con-sumption in emotional eaters was elevated over control levels innormal sleepers, but in short sleepers the amount of energy con-sumed in the control condition was as high as it was in the stressedcondition. Thus, it appears that those in the short sleep conditionate similar higher amounts of energy over normal sleepers regard-less of presence of external stressor. Short sleep may produce aneffect on eating that is equivalent to the ego-threat produced bythe stress condition. It also suggests that, in the snack paradigmused here, there is a ceiling to how much food is consumed when

stressed and there is no additive effect of short sleep and ego-threat.

These findings lead us to a conclusion similar to that of Chaputet al. (2011); the effect of sleep deprivation on food consumptionmay depend on characteristics of the participants. Had we notmeasured emotional eating, we may not have observed any rela-tionship between these levels of sleep deprivation and food con-sumption. No clear patterns in individual foods emerged. St-Ongeet al. (2011) reported elevated fat consumption after only 4 h ofsleep (the different cheeses ranged in fat from 65% to 74% of en-ergy). However, the higher-fat foods in the present study werenot selected more by short sleepers in the present study. Further-more, there was no pattern when comparing the snacks in regardto sweet or savory categorization.

The observed change in energy consumption may not be due tochanges in liking/wanting as measured by VAS. Lack of effect onliking and wanting is consistent with Brondel et al. (2010) who re-ported no effects on olfactory liking of foods and wanting for thosefoods after sleeping only 4 h. Furthermore, the changes in con-sumption may not be due to increased hunger or desire to eat ordecreased fullness as measured by VAS. This is consistent withthe findings of St-Onge et al. (2011) who reported no effects of4-h of sleep on hunger or fullness in the men and women tested.However, it is inconsistent with those of Brondel et al. (2010)who reported elevated hunger prior to breakfast and dinner insleep-deprived men.

General discussion

The results of these two studies indicate that emotional eatingis related to measures of sleep quality (when measured by theSQI, not PSQI) and interacts with sleep duration to predict eating.For moderately short sleep durations, the amount of food con-sumed may depend on an individual’s sensitivity to stressors andthe degree to which eating occurs in the presence of stress.

The results do not point clearly to whether it is sleep durationor sleep quality that has the more important role in energy con-sumption and potential weight gain. Experiment 2 provided onlya partial replication of Experiment 1. In both samples, no relation-ship was found between sleep deprivation or sleep quality andBMI. In Experiment 1, sleep quality was significantly weakly asso-ciated with DEBQ and in Experiment 2 it was not (although itwould have been had the sample been as large as in Experiment1). The difference in results may depend on the measure of sleepquality used, as different scales were used in Experiments 1 and2. For example, in SQI scoring, a significant number of participantsare identified as having some sleep problems over the past3 months while the PSQI scoring creates a dichotomy based onone prior month. Furthermore, the differences may depend on de-gree of short sleep duration or severity of poor sleep quality in thesample; in Experiment 1, the participants were not as likely to becategorized as short sleepers as those who participated in Experi-ment 2. The percentage of participants in Experiment 2 with poorsleep quality was similar to that measured (by PSQI) in other stud-ies of college students (Lund, Reider, Whiting, & Prichard, 2010). Inthe test of actual eating behavior, it was sleep duration that pre-dicted consumption, not sleep quality (measured by PSQI). It is un-known whether SQI would have predicted food consumption had itbeen used in Experiment 2. Finally, differences in the sample char-acteristics may be due to the perceived attractiveness of the stud-ies to a potential volunteer. Experiment 2 offered free snacks toparticipants but required 2 visits to the lab while experiment 1 of-fered no snacks but only 1 test session was required (and less re-search credit was awarded).

There was no significant role for dietary restraint in eitherstudy. This finding is consistent with that of Chaput et al. (2011)

112 J.S. Dweck et al. / Appetite 72 (2014) 106–113

who found no interaction between sleep duration and restraint (asmeasured by the TFEQ) on energy consumption.

The present studies have important limitations. It is not possi-ble to determine whether emotional eating or sleep duration havea causal effect in the design utilized in this study. The stressmanipulation did elevate food consumption in emotional eaters.Because the test meal in this study is a snack, the amount of energyconsumed is small. Yet, if increased snacking were to be sustainedover a significant period of time, weight gain would be likely. It isnot known whether the interactions reported here produce an in-crease in snacking periods or would increase food consumption inmeals; however, in either scenario there might be considerable ele-vation in energy consumption in this subset of people. However,there is some evidence to suggest that food consumption in a snackmay be more sensitive to stress than it is in a meal (Oliver &Wardle, 1999). No attempt was made to control for possible effectsof menstrual cycle on sleep quality, appetite, or food consumption.Finally, the response of men (whose food consumption may bemore sensitive to positive emotional experience than an ego-threat; Macht, Roth, & Ellgring, 2002; Nolan, Halperin, & Geliebter,2010) and older women to short sleep and stress may not followthe pattern observed in young women in the present researchdesign.

The results of the present study suggest that mild short sleepmay influence energy consumption. Sleep deprivation may act asa stressor and elevate food consumption in those prone to emo-tional eating. Additional stressors appear to not elevate consump-tion further in a short duration snack period although it waseffective in elevating consumption in those who report sleepingmore than 7 h per night. The results also suggest that changes inenergy consumption associated with short sleep depend on charac-teristics related to approaches to food consumption that may notbe strongly related to subjective appetite. Finally, while no rela-tionship was found between sleep variables and BMI in these sam-ples, university students who are sleep deprived and are emotionaleaters, may be setting unhealthy patterns which may elevate BMIas they age as suggested by Chaput et al. (2011).

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