AWM: Eating Frequency and Patterns (2013)


de Zwaan M, Roerig DB, Crosby RD, Karaz S, Mitchell JE. Nighttime eating: A descriptive study. Int J Eat Disord. 2006; 39(3): 224-232.

PubMed ID: 16511835
Study Design:
Descriptive Study
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To collect descriptive data on participants who were selected using broad inclusion criteria for nighttime eating.

Inclusion Criteria:
  • Consumption of 50% or more of daily food intake in the evening (this could include supper)
  • Not feeling hungry at all or only a little hungry in the morning
  • Trouble getting to sleep or staying asleep at least once a month
  • Nocturnal eating at least once a month (getting up in the middle of the night to eat).
Exclusion Criteria:
  • Less than 18 years old
  • Pregnant or breast-feeding
  • Working night or evening shifts
  • Abusing alcohol or drugs
  • Physical illness influencing metabolism and food intake (e.g., insulin-dependent diabetes mellitus, untreated thyroid disease, cancer, any condition requiring a special diet)
  • Medication that might influence sleep or eating (e.g., diuretics, insulin, steroids; psychotropic medication was allowed if there was no clear temporal relation between onset of medication use and onset of nighttime eating).
Description of Study Protocol:


Newspaper advertisements that sought individuals who "eat large amounts of food in the evenings" and "get up during the night to eat." 


Descriptive study.


Respondents to newspaper were screened via telephone call. Those meeting inclusion criteria were mailed a consent form; once signed consent received, time for telephone interview was scheduled. Each participant was administered several instruments via one- to 1.5-hour telephone interview:

  • Night Eating Questionnaire (NEQ)
  • Night Eating Syndrome History and Inventory (NESHI)
  • Sleep Disorder Questionnaire (SDQ)
  • Eating Disorder Questionnaire (EDQ)
  • Structured Clinical Interview for diagnoses outlined in the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (SCID). 

Statistical Analysis

  • Descriptive statistical approach used
  • To compare groups, chi-square tests, T-tests, and analyses of variance (ANOVA) were used as appropriate
  • Cluster and latent class analyses considered, but sample size judged too small to conduct such analyses.
Data Collection Summary:

Timing of Measurements

Between January and December, 2002.

Dependent Variables

  •  Diagnosis of Night Eating Syndrome, using 1955 criteria
    • Eating 25% or more total daily calories consumed after the evening meal (81; 76.4%)
    • Morning anorexia with negligible food intake at breakfast (80; 75.5%)
    • Sleeplessness, at least until midnight more than half the time (70; 66%)
    • (Optional) Mood lower in the evening (17; 38.6%)
  • Diagnosis of Night Eating Syndrome, using 1999 criteria
    • 50% or more total daily calories consumed after last evening meal (48; 45.3)
    • Morning anorexia, even if participant eats breakfast (80; 75.5%)
    • Awakenings at least once a night (67; 63.2%)
    • Consumption of snacks during awakenings (61; 57.5%)
    • Repetition of the provisional criteria for three or more months (106; 100%)
    • Current Binge Eating disorder, rules out NES by 1999 criteria (9; 8.5%)
    • Current bulimia nervosa, rules out NES by 1999 criteria (4; 3.8%).

Independent Variables

  • Normal or obese BMI (mean BMI 30.8kg/m2)
    • BMI less than 25, normal (21; 19.8%)
    • BMI 40 or more, morbidly obese (12; 11.3%)                                            
  • Lifetime history of eating disorder
    • BED (15; 14.2%)
    • BN (6; 5.7%)
    • AN (2; 1.9%)
  • Psychiatric co-morbidity
    • Major Depressive Disorder (MDD) (59; 55.7%)
    • Bipolar I (3; 2.8%)
    • Dysthymia (current only) (12; 11.3%)
    • Anxiety disorders
      • Panic disorder (11; 10.4%)
      • Agoraphobia (1; 0.9%)
      • Social phobia (8; 7.5%)
      • Specific phobia (7; 6.6%)
      • OCD (6; 5.6%)
      • PTSD (19; 18.1%)
      • Generalized Anxiety Disorder (GAD; current only) (18; 17.5%)
  • Sleep disorders (N=92)
    • Restless legs (46; 50%)
    • Periodic limb movement disorder (PLMD) (30; 32.6%)
    • Bruxism (32; 34.8%)
    • Nightmares (35; 38%)
    • Sleepwalking (11; 12%)
    • REM Sleep behavioral disorder (25; 27.2%)
    • Confusional arousal (14; 15.2%)
    • Night Terrors (6; 6.5%)
    • Apnea (9; 9.8%).
Description of Actual Data Sample:
  • Initial N: 286 participants screened via telephone, 56 excluded, 230 accepted, 106 individuals returned signed consent for and scheduled for telephone interview
  • Attrition (final N): 106 individuals, 64.2% female
  • Age: Average 49.2 years
  • Ethnicity: 94% Caucasian
  • Other relevant demographics:
    • Six (5.7%) diagnosed with type 2 diabetes
    • 30 (28.3%) taking antidepressants
    • 29 (27.4%) taking prescription sleeping pills at least once a week at time of interview
  • Anthropometrics: Average BMI 30.8kg/m2 (SD=7.2), range 15.8 to 54.3kg/m2, 21 (19.8%) had BMI less than 25kg/m2 and 12 (11.3%) had BMI 40kg/m2 or more
  • Location: Neuropsychiatric Research Institute, Fargo, North Dakota.
Summary of Results:

Key Findings

Association Between 1955 and 1999 Diagnoses of NES

Criteria for 1995 Diagnosis of NES Met Criteria for 1999 Diagnosis of NES Met Criteria for both 1955 and 1999 Diagnosis of NES Met Statistical Significance of Agreement Between Old and New Criteria
31 14 8 χ2=6.067, P=0.014
29.2% 13.2% 7.5%  

Association between Independent variables and NES

Variable Association with 1955 Criteria for NES Significance Association with 1999 Criteria for NES

Lifetime history of major depressive disorder

59, 55.7%


χ2 = 4.160, p-0.041

No difference

Not significant

Other independent variables No significant association with NES symptoms

Other Findings

  • Participants with BMI less than 25kg/m2 did not differ from participants with BMI more than 30kg/m2 on any of the night eating symptoms, nor did they differ for mean age and gender
    • 60% of obese participants reported being overweight before night eating began, and there was no significant difference in age of onset of night eating between normal and overweight participants
  • Participants with a lifetime history of eating disorder did not differ from participants without a lifetime history of eating disorders in any of the night eating symptoms. Participants with history of ED:
    • Had higher prevalence of major depressive disorder (80% vs. 50% χ2=7.244, P=0.27)
    • Were more likely to report current sleepwalking (20% vs. 8%, χ2=7.244, P=0.027)
    • Were more likely to report current confusional arousal (35% vs. 8.1%, χ2=12.616, P=0.002)
    • Women more likely to have history of ED (85% vs 59%, χ2=4.659, P=0.031)
    • Participants with eating disorder significantly younger (42.7 years vs. 50.7 years, T=2.514, P=0.013)
  • Nocturnal eating (eating when waking during the night) occurred an average of twice a night among participants meeting full 1999 criteria, and almost all awakening was accompanied by eating
  • Participants who met full criteria for either diagnostic construct at breakfast and lunch significantly less often compared with those who did not meet full criteria for either diagnostic construct
  • Participants who met 1955 criteria reported significantly less control over evening eating than those who did not meet full criteria (42.9 vs. 62.7, T=2.685, df=95, P=0.009)
  • Nocturnal eating episodes: 14 participants without any nocturnal eating episodes were excluded, final sample for this analysis of N=92 (31 men and 61 women)
    • On a scale of zero to 100, self-reported average amount of control over nocturnal eating episodes was 41.4 (range zero to 100)
      • 41 participants (44.5%) reported no or just a little control
      • 32 (34.8%) reported complete or very much control over nocturnal eating episodes
      • 80% with nocturnal eating reported consuming 25% or more and 46% reported consuming 50% or more of daily food intake after the evening meal
      • Average age of onset of nocturnal eating was 33.2 years with 20 (21.7%) reporting onset at less than 19 years
      • Nocturnal eating was not associated with purging behavior
      • 16 participants (17/5%) reported they were completely (N=1), mostly (N=5) or partially (N=10) unaware of nocturnal eating episode
      • Only 15 (16.3%) indicated that they woke up specifically to eat; 33 (35.9%) woke to use bathroom, 24 (26.1%) woke due to insomnia and 20 (21.7%) woke for other reasons
      • Nocturnal eating episodes were consistent throughout week for 76.1% participants; 17.4% reported improvement on weekends and days off; 3.3% reported worsening on weekends and days off
      • Most participants had never consulted a physician for nocturnal eating [N=80 (87%)].
Author Conclusion:
  • This descriptive study confirms some of the observations made by other researchers and has many faces and names [Night Eating Syndrome (NES), Nocturnal Eating/Drinking Syndrome (NEDS), Sleep Related Eating Disorders (SRED)]. It remains unclear if these are related or distinct syndromes, whether night eating is a disorder of arousal or circadian rhythm or whether it can be perceived as an eating disorder.
  • The purpose of this study was not to offer a definitive method of classifying NES but, instead, using a community sample, to demonstrated that the criteria sets that are being used by different groups (obesity researchers, sleep researchers) overlap and do not overlap in noteworthy ways, and that the current systems are inadequate. The study points out areas of obvious weakness in the current systems that people are using. Most likely, the participants in our and other samples represent a heterogeneous group of participants, with different mechanisms being responsible for their night eating behavior.
Funding Source:
University/Hospital: Neuropsychiatric Research Institute, Fargo, North Dakota
Reviewer Comments:
  • This study gave little information on what is associated with NES, and a lot of information about what was not associated with NES, based on a small sample, with no healthy control group. The sample was self-selected and less than one half of participants who qualified actually participated; it is unclear if results would generalize to all participants with nighttime eating problems.
  • The only independent variable that was found to be statistically significantly related to NES was Major Depressive Disorder. The study showed a variety of associations between the different independent variables, and described variations among symptoms within the criteria for NES.
  • The most important information from this study was that there is not agreement among researchers as to criteria (let alone names) for Night Eating Disorders. Before this night eating problems can be well researched, there needs to be agreement on diagnostic criteria. This is definitely an area that needs more research.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? N/A
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? N/A
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? N/A
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? No
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? ???
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? N/A
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? N/A
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes