International Journal of (2001) 25, 365±372 ß 2001 Nature Publishing Group All rights reserved 0307±0565/01 $15.00 www.nature.com/ijo PAPER Night eating and nocturnal eating Ð two different or similar syndromes among obese patients?

C CeruÂ-BjoÈrk1*, I Andersson1 and S RoÈssner1

1Obesity Unit; Huddinge University Hospital, S-141 86 Huddinge, Sweden

OBJECTIVE: The main aim of this study was to identify subjects with (1) night eating syndrome (de®ned as morning , evening hyperphagia and ) and (2) nocturnal eating syndrome (de®ned as eating at night after having gone to bed). In the literature the differences and similarities between these two syndromes are not clear. SUBJECTS: One-hundred and ninety-four obese patients from an academic, clinical obesity unit. Mean BMI (Æ s.d.) was 40Æ 5kg=m2, age 44Æ 12 y and 76% were women. MEASUREMENTS: Questionnaires with multiple choices and open questions along with the Scale. RESULTS: Fourteen percent of the patients met the criteria for night eating and=or nocturnal eating syndrome. Night eating syndrome was manifest in 6% of the patients and nocturnal eating syndrome in 10%. Both the night eaters and the nocturnal eaters had more trouble getting to than the patients without night=nocturnal eating problems (P < 0.001 and P < 0.01). The nocturnal eaters also had more trouble staying asleep (P < 0.001). Morning anorexia was not typically found in nocturnal eaters. Being on long-term sick leave was more common among the nocturnal eaters (P < 0.01). CONCLUSION: Fourteen percent of the patients at our obesity unit met the criteria for night eating and=or nocturnal eating syndrome. There are clear similarities between night eating syndrome and nocturnal eating syndrome, but also differences. International Journal of Obesity (2001) 25, 365 ± 372

Keywords: food selection; night eating; nocturnal eating; obesity; sleeping problem

Introduction where 16 patients out of 25 (64%) met the criteria for night In 1955 Stunkard et al ®rst described night eating syndrome.1 eating syndrome. During the 45 y since then, few studies have been performed In 1990 `nocturnal eating syndrome' was described by the on the subject and many questions regarding the syndrome American Sleep Disorders Association in the International remain unanswered. Classi®cation of Sleep Disorders. The de®niton of this syn- The three criteria for `night eating syndrome' de®ned by drome is: `Frequent and recurrent awakenings to eat and Stunkard in 1996, are: morning anorexia, that is no appetite normal sleep onset following ingestion of the desired food'.9 for breakfast, evening hyperphagia, de®ned as 50% or more of This de®nition has also been used in some studies.10 ± 12 Such food intake after 7 pm and insomnia, ie trouble getting to studies suggest that there is little difference in the occurrence sleep and=or staying asleep.2 This de®nition of night eating of the two syndromes (Table 1). syndrome, or derivations of it, has been used in several Thus both night eating syndrome and nocturnal eating studies.3±8 A summary of the major prevalence studies per- syndrome have clear de®nitions. In the literature though, formed, indicates that the frequency of night eating syn- the differences between the two syndromes are not always drome varies from 8 to 27% among obese patients (Table 1). clear. In some articles the terms night eating and nocturnal The study performed by Stunkard in 19551 is an exception, eating are used synonymously.12 ± 14 In the International Classi®cation of Sleep Disorders, night eating is given as synonymous with, and as a key word to, nocturnal eating.9 The fact that night eating is something the obese patients *Correspondence: C CeruÂ-BjoÈrk, Obesity Unit, Huddinge University at our clinic rarely talk about, and the limited knowledge in Hospital, S-141 86 Huddinge, Sweden. the literature, made us realize that our knowledge about this E-mail: [email protected] Received 5 January 2000; revised 4 September 2000; problem is rather poor. Therefore our main aim in this study accepted 9 October 2000 was to clarify whether or not night eating is a problem to Night eating in obesity C CeruÂ-BjoÈrk et al 366 Table 1 Night eating and nocturnal eating syndrome in prevalence studies

Sample % n Author Reference Year

Night eating syndrome in obese patients 8 5=63 Adami et al 31999 Night eating syndrome in obese patients 27 30=111 Rand et al 51997 Night eating syndrome in obese patients 9 7=79 Stunkard et al 21996 Night eating syndrome in patients with BEDa 15 6=40 Stunkard et al 21996 Night eating syndrome in obese patients 15 26=174 Kuldau & Rand 4 1986 Night eating syndrome in obese patients 64 16=25 Stunkard et al 11955 Nocturnal eating syndrome in patients 6 7=120 Manni et al 11 1997 Nocturnal eating syndrome in obese patients 8 6=79 Greeno et al 10 1995

aBinge .

consider in group treatment at our clinic, or if it very rarely with those de®ned as nocturnal eaters and the obese patients occurs among our obese patients, and to clarify whether we in the day care hospital program. have to deal with two different syndromes or just one. This The information on frequency of sleeping problems and task was achieved by identifying subjects with night eating smoking habits among normal weight subjects has been syndrome as well as subjects with nocturnal eating syndrome taken from Statistic Sweden, a data base of 8935 subjects among the patients at our obesity unit. (Living conditions 96=97, Statistic Sweden, unpublished The second aim was to obtain further knowledge of data). the two syndromes as a base for future research, in particular We used SPSS and Statistica for statistical analysis. For with regard to potential clinical and therapeutical patient data and differences between the groups, we used the consequences. chi-square test, Fisher's exact test, the Mann ± Whitney U-test and the independent samples t-test. For correlation between night eating and morning anorexia we used Spearman's Methods rank correlation coef®cient. The study was approved by the In order not to exclude any kind of night eating behaviour at Hospital Ethical Committee. this early stage of our research we chose to construct a self- report questionnaire including questions about both the night eating syndrome and the nocturnal eating syndrome Results (Appendix, questions 1 ± 13). The subjects in this study had a BMI of 40Æ 5kg=m2 The de®nition of night eating used in this study is Stun- (meanÆ s.d.) and age 44Æ 12 y. Seventy-six percent were kard's de®nition: morning anorexia, evening hyperphagia women (n ˆ 147) and 24% were men (n ˆ 47). and insomnia.2 These criteria, however, do not seem to have been formally validated. We have de®ned morning anorexia as `no appetite in the morning', evening hyperphagia as `the Prevalence of night eating and nocturnal eating largest food intake occurring during a time period after 7 pm' syndrome and insomnia as `trouble getting to sleep and=or staying Thirty-three percent of the patients at our obesity unit had asleep'. The criteria we used for the de®nition of nocturnal morning anorexia, 31% had evening hyperphagia and 46% eating were `waking up at night and getting out of bed to eat' and=or `after having gone to bed, getting out of bed to eat or eating in bed'. One-hundred and ninety-four obese patients, referred to our obesity unit, answered the questionnaire. We excluded all patients working night shift=night time since it is known that shift work can cause a redistribution of food intake from day to night.15 In addition, patients participating in our day care hospital program during the period of April 1998 to March 1999 answered open questions about food choices as well as multiple choice questions about whether or not they con- sidered themselves night eaters (n ˆ 104) (Appendix, ques- tions 14 ± 17). Since January 1998 our day hospital program evaluation has included several behavioural and psychologi- cal questionnaires. We have compared the results of the Figure 1 Morning anorexia, sleeping problems and evening hyper- Binge Eating Scale16 (translation into Swedish: K Franson) phagia among obese patients (176 complete answers).

International Journal of Obesity Night eating in obesity C CeruÂ-BjoÈrk et al 367 had insomnia (Figure 1). A combination of all three criteria, signi®cant correlation between eating late at night (7 pm to ie night eating syndrome was found in 6% (Night). Nocturnal 4 am) and morning anorexia. eating syndrome (Nocturnal) was manifest in 10% of the subjects. When using both the de®nition of night eating and the de®nition of nocturnal eating syndrome we found Social factors that 14% met the criteria of one or both of the two syn- Signi®cantly more Nocturnal than Other were on long-term dromes. Among the group of the 19 Nocturnal, ®ve subjects sick leave, 32% vs 8% (P < 0.01), which was not the case for met the criterion `waking up at night and getting out of bed Night. We found no differences regarding occupation or civil to eat', six subjects met the criterion `after having gone to status. Among Night as well as Nocturnal and Other, the bed, getting out of bed to eat or eating in bed' and eight majority were gainfully employed or students. The patients subjects met both criteria. who were not gainfully employed or students were retired, When asking the question `Do you think that you have unemployed, on parental leave or on a long-term sick leave. problems with night eating?' we found that 67% of the Among all patients (Night, Nocturnal, Other) about a whole group answered yes for the time period 7 ± 10 pm third were single or a single parent (36=37=31%), while the and 14% answered yes for the time period after 10 pm majority lived with another adult (64=63=69%). (n ˆ 105). All Nocturnal and all Night but one, claimed that We found no difference in gender or BMI between the the night eating had contributed to their obesity. groups. There was no difference in age between the Noctur- nal and Other. Night were younger than Nocturnal and Other, 36 vs 44 y (P ˆ 0.0293). Among both Nocturnal and Night, as well as among Other, smoking was as common as Sleeping problems among Swedish people in general: smoking daily about 20%, Forty-six percent of the patients at our clinic stated that they smoking sometimes about 10%, nonsmokers about 70% had sleeping problems, which is signi®cantly more than the (Living conditions, Statistic Sweden, unpublished data). 15% among normal-weight Swedish people (P < 0.001) (Living conditions 96=97, Statistic Sweden, unpublished data). The prevalence of insomnia was signi®cantly higher Critical time periods among Nocturnal (n ˆ 19) compared with the other obese The answers to the question `When during day and night is it patients (Other; n ˆ 167, Table 2). More Nocturnal had trou- usually hardest to refrain from something you feel like ble getting to sleep, 63% vs 29% (P < 0.01) and more Noc- eating?' show that the most dif®cult period to refrain from turnal had trouble staying asleep, 74% vs 31% (P < 0.001). eating is from 7 to 10 pm (Figure 2a and b). Over 60% of both Among Night (n ˆ 11) more patients had trouble getting to Nocturnal, Night and Other had dif®culties during this sleep, 100% vs 29% (P < 0.001), but there was no difference period. The majority of Nocturnal (58%), and of Night in prevalence of trouble staying asleep. (55%) also had dif®culty refraining from eating between 10 pm and 1 am, compared to only 18% among Other (P < 0.001 and P ˆ 0.0101). There was also a signi®cant dif- ference between Nocturnal and Other, between 1 and 4 am, Morning anorexia 26% vs 0.6% (P < 0.001) and between 4 and 7 am, 11% vs The frequency of morning anorexia did not differ between 0.6% (P < 0.05). No Night claimed to have any problem Nocturnal and Other, and we did not ®nd a statistically refraining during this time period.

Table 2 The frequencies of different characteristics between Night and Other, and between Nocturnal and Other

Patients with night Patients with nocturnal eating syndrome (n ˆ 11) eating syndrome (n ˆ 19) Other patients (n ˆ 167)

Trouble getting to sleep (%) 100***a 63**b 29 Trouble staying asleep (%) 55 74***b 31 Morning anorexia (%) 100***a 37 29 Long-term sick leave (%) 9 32**a 8 Gainfully employed or student (%) 55 53 69 Single or single parent (%) 36 37 31 Gender (male=female) (%) 18=82 11=89 26=74 BMI (kg=m2)384040 Age (y) 36, P ˆ 0.0293c 44 44

***P < 0.001; **P < 0.01. Only statistically signi®cant differences are shown. aFisher's exact test. bThe chi-square test. cThe independent-samples t-test.

International Journal of Obesity Night eating in obesity C CeruÂ-BjoÈrk et al 368 Table 3 Food choices during the evening and the night among obese patients; obese outpatients (n ˆ 104)

Sandwiches 50% Sweets 45% Food dishes 20% Nonalcoholic beverages 30%a Alcoholic beverages 11% Snacks 14% Fruit 14% Others 21%

In several cases two or more food groups were mentioned. aThe beverages include drinks with and without energy.

Discussion This study is based on a rather short, self-report question- naire that we constructed and which is not yet properly validated. This is an obvious weakness of the study. The questionnaire was ®rst tested in a smaller group of patients (40 patients not included in the study) and thereafter recon- structed. A strength of the study is that all patients who were asked to answer the questionnaire did so. Answering the questionnaire was totally voluntary and did not in any way affect the patient's treatment. (The person asking the patients to answer the questionnaire was not a member of the treatment team.) Compared to other studies (Table 1) we found a rather low frequency of night eating syndrome among our patients (6%). One reason for this might be a question of interpreta- tion of Stunkard's de®nition of the syndrome. For example, Figure 2 Dif®cult periods to refrain from eating during day and night as reported by obese patients (a) Nocturnal, n ˆ 19; Other, n ˆ 167. Fish- evening hyperphagia, de®ned by us as `the largest food intake er's exact test. *P < 0 05, ***P < 0.001. (b) Night, n ˆ 11; Other, n ˆ 167. occurring during a time period after 7 pm' was de®ned by Fisher's exact test. *P < 0.05. In several cases two or more periods were Rand et al as `excessive evening eating'5 and by Kaldau et al as mentioned. `eating on and off throughout the evening without enjoy- ment'.4 We also believe there is a cultural explanation. In Sweden, dinner is served earlier than in many other coun- In the morning and until the early afternoon, from 7 am tries. For the majority of the Swedish people dinner time is to 4 pm, there was no difference between the groups. Until around 6 pm (A Marmur, E Callmer, L-E Holm, G Wilsby, 4 pm the majority did not have great dif®culty refraining Applied Nutrition, unpublished data). This is probably why from eating. Between 4 and 7 pm fewer patients among only 20% of the patients at our unit claimed that they had a Night had problems refraining compared to Other, 9% vs food dish after 7 pm, when answering the question `What do 48% (P < 0.05). you usually eat at night?' A study by Adami et al showed that According to the results of the Binge Eating Scale, Night in Italy, a country with a Mediterranean eating style, 70% of and Nocturnal had binge eating problems to the same extent the people had dinner after 8 30 pm.17 as Other, median score 22 (range 13 ± 31) vs median score 18 The nocturnal eating syndrome was found in 10% of the (range 1 ± 37). subjects. This is a sleep-related eating disorder, not related to any speci®c time of night. When both de®nitions were used together we found a total group of 27 patients (14%). Food selection Perhaps this number is closer to the true picture of the The most commonly selected food item at night was sand- night eating problem among the obese patients. In addition, wiches, chosen by 50% of the subjects (Table 3). There was the answers to the question `Do you think that you have no difference between Night and Nocturnal and Other problems with night eating?' support the idea that night= regarding food choices at night, but we did ®nd a gender nocturnal eating is not uncommon (67% for the time period difference. More men than women chose alcoholic beverages 7 to 10 pm and 14% for the time period after 10 pm). Thus at night, 29% vs 3% (P < 0.001) and women tended to choose even for Other, the time period between 7 and 10 pm is a chocolate to a greater extent, 10% vs 0% (P ˆ 0.074). period when it is dif®cult to refrain from eating. This is

International Journal of Obesity Night eating in obesity C CeruÂ-BjoÈrk et al 369 important to keep in mind when discussing changes of food Our clinical experience is that talking about nocturnal habits with the patients. activity is a sensitive issue and that eating in the dark can be Nearly 50% of the patients at our clinic had sleeping a very shameful activity, which is not easily admitted. To ®nd problems of some kind. Among the Night and Nocturnal out more about this behaviour and to ®nd answers to the the problem was even more common. This suggests that questions why?, when?, how? what?, we believe the open there is a need for greater awareness of the importance of interview is an appropriate method, which will also be the sleeping problems in the design of the obesity unit's routines next step in night eating research at our unit. There is also a for diagnosing and managing obese patients. need for futher research on observation of sleep and eating In obesity treatment we ®nd it important to note gender relationships in a laboratory setting with neuroendocrine differences when discussing food choices with the patients. measures, which so far has been performed only in one In this group, more men than women consumed alcoholic study.8 beverages in the evening, while women tended to choose Night eating and nocturnal eating patterns have clear chocolate to a higher extent. In a former study at our unit we similarities, but also show differences in appearence. Our also found gender differences in food preference; men chose opinion is that there is more to unite the two syndromes alcoholic beverages more often than women did and women than there are differences between them. The majority of chose sweets more often than men did.18 We also found that these patients had sleeping problems; it was signi®cantly sandwiches were perceived to have contributed to the devel- harder for them to refrain from eating later at night and all opment of obesity by 40% of the patients at our unit. In the but one claimed that their eating at night had contributed to present study sandwiches were the most commonly chosen their obesity. We believe that the differences between the food item at night among the obese patients. Sandwiches are groups found in this study are not wide enough to cause any common in Swedish diet19 and obese men were found to trouble in a joint treatment program. have a higher energy intake from sandwiches than normal- By including both night and nocturnal eating syndrome weight men.20 Our data on night eating supports the notion in one criterion, we believe that there would be improved that sandwiches are a great problem to our patients, which chances of an effective treatment program by an increased has to be taken into consideration when giving advice on cooperation between clinics specialized in obesity, eating food choices. Only 30% of the subjects mentioned a drink disorders and sleeping disorders. We also believe that by when answering the question about what they consume at using two separate criteria there would be a greater risk of night. Our clinical experience is that patients tend to forget some patients being excluded even though they may have what they drink with the food, for example with the evening night eating problems. sandwiches. Not more than 37% of Nocturnal in this study experi- Acknowledgements enced morning anorexia. This implies that by using Stun- This study was supported by grants from Resource Center for kard's de®nition of night eating we exclude the majority of Eating Disorders. the nocturnal eaters in this group. On the other hand, the de®nition of nocturnal eating used in this study includes some patients who may not have References a very high energy intake at night. The nocturnal eating 1 Stunkard AJ, Grace WJ, Wolff HG. The night-eating syndrome. syndrome refers to an eating pattern rather than to the Am J Med 1955; 19: 78 ± 86. 2 Stunkard A, Berkowitz R, Wadden T, Tanrikut C, Reiss E, Young L. amount of food consumed. Therefore, in some cases, noc- and the night-eating syndrome. 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International Journal of Obesity Night eating in obesity C CeruÂ-BjoÈrk et al 372

International Journal of Obesity