LASA side studies

Nutrition and Food-related Behaviour study 2014-2015 (side study)

Filename: LASAxxxx (to be determined)

 

Contact: Liset Elstgeest, Marjolein Visser

 

Background

Lifestyle plays a major role in health and disease. Unhealthy diets and physical inactivity are amongst the most important causes of major non-communicable diseases, such as cardiovascular disease, obesity, diabetes mellitus type II and certain cancers (1). In contrast, a good nutrient status and a healthy food intake, including high intakes of fruit, vegetables, fish and wholegrains, are associated with health benefits (2-4) and lower mortality risk (5, 6). More recently, a link between diet and mental health has been suggested, such as depression and cognition (7-10). As diet is a modifiable risk factor, it plays an important role in the prevention of these diseases. With data on diet, many determinants and outcomes in relation to food(-related behaviour) can be studied.

 

Dietary data within LASA

Qualitative information on specific diets, use of fruits, vegetables and dairy products, and number of eating moments during the day was obtained at some regular waves in the first LASA cohort (waves B, C, D and E, see documentation on Diet and food consumption). Further, quantitative information on dietary intake (fruit, vegetables, fish, alcohol) and eating habits was collected from 1058 respondents in the Lifestyle side study in 2007. More recently, the Nutrition and Food-related Behaviour study has collected quantitative data on respondents’ complete nutritional intake as well as food-related behaviour. This extensive study was conducted between the fall of 2014 and spring of 2015 as part of the European Union project called MooDFOOD: a Multi-country cOllaborative project on the rOle of Diet, FOod-related behaviour, and Obesity in the prevention of Depression (http://www.moodfood-vu.eu).

 

Measurement instruments in LASA

The Nutrition and Food-related Behaviour study consisted of a questionnaire and, in a subgroup, multiple 24-hour dietary recalls.

 

Questionnaire

The questionnaire consisted of a semi-quantitative food frequency questionnaire (FFQ), questions on food-related behaviour (such as emotional eating, overeating, meal skipping, snacking, food preparation, sustainability and mindful eating), and questions on body weight, weight change in the past 6 months, depressive symptoms and undernutrition (see Table 1).

 

The questionnaire was available in a paper version and online version. The variable ‘vrlversie’ indicates which version the respondent has completed. During the development, the questionnaire was pilot tested for understandability and duration of completion (18 persons in total: 7 on paper, of which 2 persons out loud, and 11 online).

 

Table 1: Content of the questionnaire

 

Section

Topic

Subtopic

Heading in questionnaire (in Dutch)

No. of items

 

0

General

Date + person of completion

Date of birth + gender

Datum + invuller

Geboortedatum + geslacht

2

2

1

Food frequency questionnaire

Eating pattern

Food intake

A. Voedingspatroon

B. Voedingsmiddelen

10

76

2

Food-related behaviour

Weight(loss) and appetite

Mindful eating

Meals and snacks

 

Interoceptive awareness of hunger and satiety

Alexithymia

Binge eating

Eating styles

Problems food intake

Use of amenities

Food products for older adults

Dietary recommendations

C. Gewicht

G. Eten met aandacht

H. Maaltijdgebruik en tussendoortjes

I. Honger en verzadiging

 

J. Gevoelens

K. Eetbuien

L. Eetgedrag

M. Problemen voedingsinname

N. Gebruik voorzieningen

O. Voedingsmiddelen voor ouderen

P. Voedingsadviezen

13

25

8

 

4

 

12

1

20

10

7

5

 

8

3

 

Sustainability

Sustainable behaviour

Q. Duurzaamheid

6

4

Mental health

 

Change in sleep and change in appetite

Depressive symptoms

Mental health problems

D. Slaap en eetlust

 

E. Stemming

F. Psychische problemen

2

 

20

3

 

Two datasets are available: Food Frequency Questionnaire (‘FFQ’, sections 0 and 1, file xxxx, under construction) and Food-related Behaviour (‘FRB’, sections 0, 2, 3 and 4, file xxxx, under construction). Below, the subtopics are described.

 

Eating pattern (A. Voedingspatroon)

Ten questions are asked about meal preparation, frequency of meals, type of meals, and following a specific diet or regime.

 

Food intake (B. Voedingsmiddelen)

The Dutch version of the FFQ of the HELIUS Study (Amsterdam Medical Center; AMC) is used. This FFQ was developed by the AMC, the National Institute for Public Health and the Environment (RIVM) and Wageningen University. It consists of 76 questions about 238 food items and asks for consumption during the past 4 weeks. A nutrient database was constructed based on the Dutch Food Composition Table (Nederlands Voedingsstoffenbestand (NEVO)) 2011 (11). Each food item in the FFQ was linked to one or more foods of the nutrient database to calculate the intake of macro- and micronutrients (see Table 2). More information on the development of the FFQ can be found in Beukers et al. (12).

 

Next to the original FFQ items, the following information on food intake is available in the FFQ dataset:

 

  • Cleaned frequency of consumption of each food item in number of times per day in the past 4 weeks (‘NXX_freq’). For this cleaned frequency, it was assumed that if the frequency question - question a - was missing, the food item was not eaten in the past 4 weeks.
  • Consumption of each food item in grams per day (variables ‘hvhXXXX’).
  • Food groups: foods were categorized into 17 major food groups based on the Dutch Food Consumption Surveys (DFCS), which were originally based on EPIC-Soft classification (‘groepX’) (13). In addition, foods were categorized into 10 groups according to the ‘Richtlijnen Voedselkeuze 2011’ from the Netherlands Nutrition Centre (‘groepXrvk’) (14).
  • Total intake of energy and nutrients per day (see Table 2).
  • Several ‘inconsistency variables’ (in Dutch: foutvariabelen): additional variables were computed to indicate inconsistencies in respondents’ answers (see also below under ‘Recommendations and remarks FFQ’).

 

Weight (loss) and appetite (C. Gewicht)

Current body weight is asked (C1) as well as perception of body weight (C2, C3). Body dissatisfaction is measured with Stunkard’s Figure Rating Scale; respondents are asked to select the silhouette that best indicates his or her current body size and the silhouette that reflects his or her ideal body size (C4, C5) (15). Please note that Stunkard’s Scale is asked at earlier regular waves. In addition, five items of the Short Nutritional Assessment Questionnaire 65+ (SNAQ65+) are included about unintentional weight loss change in past 6 months, appetite and physical functioning (C6 to C10) (16). Last, three items from the Simplified Nutritional Appetite Questionnaire (SNAQ) are asked about appetite and satiety; the fourth SNAQ-item is asked in ‘Meals and snacks’ as question H1 (17).

 

Instead of self-reported body weight (C1), measured body weight and height from the regular waves before (wave H/3B) and after (wave I) this side study can be used. For example, BMI can be calculated from measured body weight. This has been done by using the mean weight of wave H/3B and wave I, and the height of wave I. The mean of these two waves was chosen because the side study was performed between them (see Availability of information, elsewhere on this page). The computation of BMI - including syntax - is explained in this file (pdf).  

 

Mindful eating (G. Eten met aandacht)

This subtopic can be divided into ‘mindful eating’ (G1 to G20) and ‘routine’ (G21 to G25). All answer categories range from ‘never’ (1) to ‘very often’ (5).

 

Mindful eating is measured with the Mindful Eating Behaviour Scale (MEBS) (18). This scale consists of 17 items on four domains: ‘Focused Eating’, ‘Hunger and Satiety Cues’, ‘Eating with Awareness’ and ‘Eating without Distraction’. Because of low inter-factor correlations, a total score combining the four domains should not be computed. More information on the development and psychometric properties can be found in Winkens et al. (18).

 

The questions on routine are not part of the Winkens Mindful Eating Behaviour Scale. ‘Eating routine’ is measured with four items from the subscale ‘Routine’ (G21 to G24) and one item (‘I need to eat like clockwork’ G25) from the subscale ‘Non-reactivity’ of the Mindful Eating Scale (19).

 

Meals and snacks (H. Maaltijdgebruik en tussendoortjes)

Next to the fourth SNAQ item about the number of meals per day (H1, see ‘Weight (loss) and appetite’), there are questions about the frequency of eating a warm meal and replacing the warm meal with something easy to prepare (H2, H3). The next five questions are about the frequency of eating snacks at specific times during the day (H4-8).

 

Interoceptive awareness of hunger and satiety (I. Honger en verzadiging)

Respondents are asked about the frequency of a feeling of have eaten too much/less during the day at the end of the day (I1, I2). Poor interoceptive awareness (IA) is measured with two items of the 10-item IA-scale of the Revised Eating Disorder Inventory-II (I3, I4) (20, Dutch version: 21). The wording of one item (I3) was adjusted based on results of a pilot study; the answer categories range from ‘never’ (1) to ‘very often’ (5).

 

Alexithymia (J. Gevoelens)

Alexithymia is a personality construct characterized by the subclinical inability to identify and describe emotions in the self. It is measured with the scales ‘Difficulty Identifying Feelings’ (7 items) and ‘Difficulty Describing Feelings’ (5 items) from the Toronto Alexithymia Scale-20 (TAS-20; 22). The third scale ‘Externally Oriented Thinking’ was not included because it appears to be unreliable (23).

 

Binge eating (K. Eetbuien)

It is asked whether the respondent experiences binge eating episodes. If the respondent’s answer is ‘yes’, (s)he needed to indicate the frequency of these episodes in the past three months and the frequency of loss of control during an episode. This item is an additional question from the Dutch Eating Behaviour Questionnaire (see ‘Eating styles’).

 

Eating styles (L. Eetgedrag)

The eating styles emotional, external and restrained eating are measured with the brief 20-item version of the 33-item Dutch Eating Behaviour Questionnaire (DEBQ) (24, Dutch version: 25). Six items of the DEBQ-20 are on emotional eating; the scales on external and restrained eating have seven items each.

 

The 33-item DEBQ has been rated as ‘up to the mark’ or ‘good’ by the Dutch Committee on Tests and Testing (COTAN) on all European Federation of Psychologists' Association (EFPA) criteria (e.g. norms, reliability (internal consistency, test-re-test) and validity (dimensional validity, construct validity and criterion validity) (26). The psychometric properties of the brief 20-item version has yet to be determined.

 

The DEBQ (all language versions) is protected by copyright by the publisher of the manual and questionnaire: Hogrefe, Amsterdam. Since the DEBQ-20 consists of a selection of the items of the 33-item DEBQ, also the DEBQ-20 is protected by copyright.

 

Problems food intake (M. Problemen voedingsinname)

Ten questions address potential nutritional problems, such as problems with chewing, swallowing, autonomously eating, doing groceries and preparing a meal. For each problem – if answering yes – it is asked how often this problem leads to a lower intake than what is preferred.

 

Use of amenities (N. Gebruik voorzieningen)

The frequency of using several amenities concerning groceries and meals are asked, such as groceries delivery, Meals on Wheels (“Tafeltje-dek-je”), eating ready-to-eat meals and eating outdoors at a care home or at family/friends’ homes.

 

Food products for older adults (O. Voedingsmiddelen voor ouderen)

In the future, more food products specifically developed for older adults may become available in the supermarkets. Five potential reasons to buy such products are asked for, such as to eat healthily and to prevent a disease. Answer categories range from to ‘strongly disagree’ (1) to ‘strongly agree’ (5).

 

Dietary recommendations (P. Voedingsadviezen)

For eight dietary recommendations, it is asked how important this recommendation is for the respondent. Answer categories range from to ‘not important’ (1) to ‘very important’ (5).

 

Sustainable behaviour (Q. Duurzaamheid)

Six questions address sustainable food-related behaviour, such as bringing your own shopping bag, buying locally produced products and using food left-overs. Answer categories range from to ‘never’ (1) to ‘very often’ (5). The English items were translated to Dutch and back-translated to English (US) by a US native speaker.

 

Change in sleep and appetite (D. Slaap en eetlust)

Questions about change in sleep and change in appetite during the past 4 weeks are asked. If the respondent’s answer is ‘yes’, (s)he need to indicate whether (s)he sleeps/eats less or more. These questions are based on two items of the Beck Depression Inventory II (BDI-II) (27).

 

Depressive symptoms (E. Stemming)

Depressive symptoms in the past week are measured with the Center for Epidemiological Studies Depression Scale (CES-D), a self-report symptoms-rating scale consisting of 20 items (28). Please note that the CES-D is also assessed at each regular LASA wave using an interviewer-administered questionnaire (see documentation on Depressive Symptoms). Please be aware of the mode difference between self-completed questionnaires and interviewer-administered CES-D assessments, which affects the CES-D scores (29).

 

Mental health problems (F. Psychische problemen)

Questions on previous and current mental health problems are asked: type of problems, being under treatment of a doctor/psychologist and the use of medication for mental health problems prescribed by a doctor (in the past three years and currently). 

 

24-hour dietary recalls

Twenty-four-hour dietary recalls were collected by telephone in a subsample of 93 respondents (response rate 95.9%; see the variable ‘selectionrecalls’). These respondents, who had filled out the questionnaire and had indicated to be willing to participate in a supplementary study, were randomly selected stratified for type of questionnaire (paper or online) and receipt date. The participants were sent a booklet with colour pictures of various food products (ranging from a buttered slice of bread to a plate with vegetables or pasta sauce) using different portion sizes. They were also instructed to measure the content of frequently used glasses, cups, bowls and serving spoons. To exclude the influence of season on food intake between the FFQ and the three recalls, the first recall was performed within 3 weeks after the researchers received the completed questionnaire; a second and third recall were performed within 3 weeks after the first recall.

 

All recalls (two weekdays and one weekend day per respondent) were performed from November 14th until December 22nd 2014. Specifically trained researchers and students telephoned the participants unexpectedly to recall their food intake of the previous day covering all foods and beverages consumed from waking up until the next morning. The weight of the reported food products was estimated by the respondent (used portion of the total packaging), or by use of the portion size booklet, the measured content of commonly used kitchenware and used recipes. Data were also collected on eating moment (ranging from before breakfast (1) to after dinner (7)), normal or special day (e.g. birthday), and special diets (e.g. energy restricted). To minimize daily variation, the 24-hour recalls were performed all days of the week.

 

The dataset with the recall information will be released in 2018.

 

Selection and response

In Figure 1, the selection and response of this side study is shown. Briefly, of the persons who participated in the LASA measurement wave of 2011/2012 (cohort 1 and 2) and 2012/2013 (cohort 3), 2089 persons were eligible to participate and were approached. Of them, 1439 (response rate 68.9%) persons took part in the side study; they (partly) completed the questionnaire either online (n=666; 46.3%) or on paper (n=773; 53.7%). The selection for the 24-hour recalls is shown in the lowest part of Figure 1. (open this figure in jpg here).

 

 

 

Figure 1. Flow chart of the selection and response of the Nutrition and Food-related Behaviour study

Blocks in dashed lines refer to the substudy with 24-hour recalls.

* For example: respondent has indicated to participate at LASA regular waves only, severe vision problems, etc.

 

Variable information

The questionnaire is available, as well as its codebook, which includes a list of all questions and the computed variables (see above under ‘Food intake’) in the datasets. Both questionnaire and codebook can be retrieved from the data manager. An overview of the variables of the 24-hour recalls will become available after data cleaning and processing.

 

Availability of information1:

The Nutrition and Food-related Behaviour study was conducted from October 2014 until April 2015. This was between wave H (2011/2012) and wave I (2015/2016) for the first and second cohort, and between wave 3B (2012/2013, baseline) and wave I (2015/2016) for the third cohort.

 

1 More information about the regular LASA data collection waves is available on:

  http://www.lasa-vu.nl/data/lasa/sampleLASAdatacollection.html

 

Recommendations and remarks regarding the use of the data

 

General recommendations and remarks: for FFQ dataset and Food-related Behaviour (FRB) dataset

 

  1. Date of completion: Many respondents who filled out the paper version did not fill in the date of completion (‘invuldatumpapier’, n=172). The receipt date of the completed questionnaire at the Vrije Universiteit (‘ontvangenpapier’) can be used as an alternative (e.g. invuldatumpapier = ontvangenpapier - 345600 (=4 days)). The latter was done for calculating the respondent’s age (‘mfage’) if the date of completion was missing.
  2. Late questionnaires: please note that questionnaires of four respondents were received more than a year after the start of the study (‘verlatevrl’). Two (R31909 and R71857) filled in the questionnaire within the study period (winter of 2015), one (R41498) at March 1st, 2016, and from one (R41366) the date of completion is unknown.
  3. Written comments: some respondents wrote a comment in the questionnaire. This not-specifically asked, extra information is summarized in 7 variables: deviating eating pattern ('afwijkend eetpatroon'), non-community dwelling ('onzelfstandig wonen'), use of prednisone or levothyroxine ('gebruik van prednison of Thyrax'), disease affecting body weight ('ziekte van invloed op lichaamsgewicht'), negative event or disease ('nare gebeurtenis of ziekte'), diabetes mellitus ('diabetes mellitus') and wheelchair user ('rolstoelgebruiker'). These variables may have an influence on food intake, eating behaviour or mood. Depending on the research question, it might be important to treat these persons differently.
    • Note for the variable ‘Deviating eating pattern’ ('afwijkend eetpatroon'): some persons indicated that their eating pattern differed from their habitual diet due to circumstances, such as illness (cancer), medical surgery, loss of sense of taste and smell, ileostoma, diabetes mellitus, on a diet (and using Modifast products, protein shakes or meal replacement shakes), or unintentional weight loss/gain. The duration or reason of this deviation is given in the answer categories. If the research question includes dietary data (from the FFQ), it might be important to treat these persons differently, for example exclude (some of) them.

 

Recommendations and remarks: for FFQ dataset

 

  1. Missing values or stopped halfway: Not all respondents filled out the FFQ completely: they skipped questions (not possible for online version) or stopped halfway (i.e. did not complete the FFQ). Missings on questions about amount, portion size and product type (b, c, d, e questions) are imputed if the reported frequency was at least ‘1 day per 4 weeks’. The imputed values are the means of respondents who filled out the specific question. The total number of missing FFQ-items (before imputation) is calculated for each respondent (‘totaalmissing’, range 0-131). It is recommended to exclude respondents with 11 or more missings (n=18); see the variable ‘morethan10missings’ (0/1).
    In total, 8 respondents stopped halfway the FFQ, of which 7 also have 11 or more missing values. So, one respondent, with less than 11 missings on the FFQ, stopped ‘halfway’: at question N74 (soft drinks). Depending on the research question it is recommended to exclude these persons as their nutrient intakes are based on less food items; see the variable ‘stoppedhalfwayFFQ’ (0/1). For example, if total energy intake is needed as a covariate, then it is advised to exclude these persons; while exclusion may not be needed if intake of one food product is investigated (and total energy intake is not).
  2. Inconsistency in answers: For some food products, it is checked for inconsistencies in respondents’ answers. Fifteen ‘inconsistency variables’ (in Dutch: foutvariabelen) are made covering the following 5 food groups: margarine/butter versus bread, spreads on bread versus bread, cooked and raw vegetables, meat and alcohol. Persons showing an inconsistency are marked on the specific inconsistency variable (0/1) and a sum score is calculated (‘totaalfout’, range 0-15). In Table 3, the meaning of a value of ‘1’ on each inconsistency variable is explained. Depending on the research question, it might be important to check persons scoring on a specific ‘inconsistency variable’. For example, when studying meat intake, exclusion of persons scoring ‘1’ on the inconsistency variables ‘vleestotgroter’, ‘vleessrtgroter’ or ‘vleessrtgroter2LASA’ should be considered.
  3. Implausible energy intake: Depending on the research question, it might be important to exclude respondents whose total energy intake estimated from the FFQ is very low or very high. For this, Willett’s cut off values are often used: females: <500 kcal/d (n=2), >3500 kcal/d (n=7); and males: <800 kcal/d (n=5), >4000 kcal/d (n=15), see the variable ‘implEintakeWillett’ (0/1) (30).

 

Recommendations and remarks: for Food-related Behaviour (FRB) dataset

 

  1. Skipped subtopics. Not all respondents filled out all subtopics of the questionnaire (see Table 1). If a respondent skipped a subtopic completely, this is indicated with the variable ‘skippedpartX’.

 

Previous use in LASA

N.A.

 

References

 

  1. World Health Organization. Global strategy on diet, physical activity and health. Geneva: 2004.
  2. Ley SH, Hamdy O, Mohan V, Hu FB. Prevention and management of type 2 diabetes: dietary components and nutritional strategies. Lancet (London, England). 2014;383(9933):1999-2007.
  3. Ravera A, Carubelli V, Sciatti E, Bonadei I, Gorga E, Cani D, et al. Nutrition and cardiovascular disease: finding the perfect recipe for cardiovascular health. Nutrients. 2016;8(6):363.
  4. Schwingshackl L, Hoffmann G, Kalle-Uhlmann T, Arregui M, Buijsse B, Boeing H. Fruit and vegetable consumption and changes in anthropometric variables in adult populations: a systematic review and meta-analysis of prospective cohort studies. PLoS ONE. 2015;10(10):e0140846.
  5. Anderson AL, Harris TB, Tylavsky FA, Perry SE, Houston DK, Hue TF, et al. Dietary patterns and survival of older adults. Journal of the American Dietetic Association. 2011;111(1):84-91.
  6. Kiefte-de Jong JC, Mathers JC, Franco OH. Nutrition and healthy ageing: the key ingredients. Proceedings of the Nutrition Society. 2014;73(02):249-59.
  7. Quirk SE, Williams LJ, O'Neil A, Pasco JA, Jacka FN, Housden S, et al. The association between diet quality, dietary patterns and depression in adults: a systematic review. BMC psychiatry. 2013;13:175.
  8. Lai JS, Hiles S, Bisquera A, Hure AJ, McEvoy M, Attia J. A systematic review and meta-analysis of dietary patterns and depression in community-dwelling adults. Am J Clin Nutr. 2014;99(1):181-97.
  9. Rahe C, Unrath M, Berger K. Dietary patterns and the risk of depression in adults: a systematic review of observational studies. Eur J Nutr. 2014:1-17.
  10. Van de Rest O, Berendsen AAM, Haveman-Nies A, de Groot LC. Dietary patterns, cognitive decline, and dementia: a systematic review. Advances in Nutrition. 2015;6(2):154-68.
  11. Dutch Food Composition Table 2011. National Institute for Public Health and the Netherlands Nutrition Centre, The Hague; 2011.
  12. Beukers MH, Dekker LH, de Boer EJ, Perenboom CWM, Meijboom S, Nicolaou M, et al. Development of the HELIUS food frequency questionnaires: ethnic-specific questionnaires to assess the diet of a multiethnic population in The Netherlands. Eur J Clin Nutr. 2015;69(5):579-84.
  13. National Institute for Public Health and the Environment (RIVM). Dutch National Food Consumption Survey 2007-2010. Part 1 Food groups, based on dataset FCS_2010_core_20111125 2010.
  14. Netherlands Nutrition Centre (Voedingscentrum). Richtlijnen Voedselkeuze 2011.
  15. Stunkard A.J., Sorensen T., Schulsinger F. Use of the Danish Adoption Register for the study of obesity and thinness. In: Kety S.S., Rowland L.P., Sidman R.L., Matthysse S.W., editors. The genetics of neurological and psychiatric disorders. New York: Raven; 1983. p. 115-20.
  16. Wijnhoven HAH, Schilp J, van Bokhorst-de van der Schueren MAE, de Vet HCW, Kruizenga HM, Deeg DJH, et al. Development and validation of criteria for determining undernutrition in community-dwelling older men and women: The Short Nutritional Assessment Questionnaire 65+. Clinical Nutrition. 2012;31(3):351-8.
  17. Wilson M-MG, Thomas DR, Rubenstein LZ, Chibnall JT, Anderson S, Baxi A, et al. Appetite assessment: simple appetite questionnaire predicts weight loss in community-dwelling adults and nursing home residents. The American Journal of Clinical Nutrition. 2005;82(5):1074-81.
  18. Winkens LHH, van Strien T, Barrada JR, Brouwer IA, Penninx BWJH, Visser M. The Mindful Eating Behaviour Scale: Development and psychometric properties. in revision.
  19. Hulbert-Williams L, Nicholls W, Joy J, Hulbert-Williams N. Initial validation of the Mindful Eating Scale. Mindfulness. 2014;5(6):719-29.
  20. Garner DM. Eating disorder inventory-2. manual. Odessa, Fl: Psychological Assessment Resources Inc.; 1991.
  21. Van Strien T. Eating Disorder Inventory-II : Nederlandse versie (EDI-II-NL). Manual. In: Testuitgevers H, editor. Amsterdam: Pearson; 2002. p. 58.
  22. Bagby RM, Parker JDA, Taylor GJ. The twenty-item Toronto Alexithymia scale—I. Item selection and cross-validation of the factor structure. Journal of Psychosomatic Research. 1994;38(1):23-32.
  23. Kooiman CG, Spinhoven P, Trijsburg RW. The assessment of alexithymia: A critical review of the literature and a psychometric study of the Toronto Alexithymia Scale-20. Journal of Psychosomatic Research. 2002;53(6):1083-90.
  24. Van Strien T, Frijters JER, Bergers GPA, Defares PB. The Dutch Eating Behavior Questionnaire (DEBQ) for assessment of restrained, emotional, and external eating behavior. International Journal of Eating Disorders. 1986;5(2):295-315.
  25. Van Strien T. Nederlandse vragenlijst voor eetgedrag (NVE). Handleiding. (Dutch eating behaviour Questionnaire. Manual). Amsterdam Hogrefe; 2015. p. 80.
  26. COTAN. Beoordeling Nederlandse Vragenlijst voor Eetgedrag, NVE (in English: Review Dutch Eating Behaviour Questionnaire, DEBQ). COTAN, 2013.
  27. Beck AT, Steer RA, Brown GK. Beck depression inventory-II. San Antonio. 1996;78(2):490-8.
  28. Radloff LS. The CES-D scale: a self-report depression scale for research in the general population. Appl Psychol Meas. 1977;1(3):385-401.
  29. Geerlings SW, Beekman ATF, Deeg DJH, Tilburg WV, Smit JH. The Center for Epidemiologic Studies Depression scale (CES-D) in a mixed-mode repeated measurements design: sex and age effects in older adults. International Journal of Methods in Psychiatric Research. 1999;8(2):102-9.
  30. Willett WC. Issues in analysis and presentation of dietary data. In: Willett WC, ed. Nutritional Epidemiology. 2nd ed. New York, USA: Oxford University Press; 1998. p. 321-46.