OTHER MEASURES OF RESTRAINED EATING

Given the difficulties raised with the RS, other scales were developed in the attempt to assess restrained eating in a “purer” form, without including factors such as weight fluctuation. Notably, this includes the Three Factor Eating Questionnaire (TFEQ; Stunkard & Messick, 1985) and the Dutch Eating Behaviour Questionnaire (van Strien, Frijters, Bergers, & Defares, 1986). The TFEQ was designed to assess three distinct factors: 1) cognitive restraint of eating, 2) disinhibition, and 3) (susceptibility to) hunger. It must be noted, however, that the authors do not give a specific definition for what they consider to be “cognitive restraint”; however, the items (e.g., “Life is too short to worry about dieting” and “I consciously hold back at meals in order not to gain weight”) mostly pertain to the respondent’s attitudes towards weight loss and

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dieting, and the tendency to exercise conscious control over their eating behaviour (the questions in this sub-scale were shown to reliably load on a single factor by Stunkard and Messick in the original paper). The scale was initially designed to assess eating behaviours and cognition in overweight individuals. The cognitive restraint subscale (TFEQ-CR) was found to be negatively correlated with BMI in a sample of obese individuals (Cappelleri et al., 2009), and the disinhibition scale (TFEQ-D) reliably differentiated between obese and non-obese women (Lindroos et al., 1997). This is in contrast to the RS, which is positively correlated with BMI (Tiggemann, 1994) but cannot be used to reliably discriminate obese participants from normal weight, as 90% of the former and 30% of the latter could be classified as “restrained”

(Drewnowski et al., 1982). However, the TFEQ has also been found to reliably discriminate between different dietary behaviours in normal weight samples (de Lauzon et al., 2004): e.g., higher scores on both the Restraint subscale and the Disinhibition subscale were positively correlated with actual caloric (energy) intake, and participants who scored higher on the Emotional subscale also reported greater snacking frequency.

The DEBQ is a 33-item questionnaire which consists of three sub-scales:1) restrained eating (deliberately limiting food intake with the intention of weight loss), 2) emotional eating (eating in response to negative emotional states or mood) and 3) external eating (the extent to which eating behaviour is triggered by external cues). Overall, the measure was found to have good discriminant validity (Wardle, 1987) and internal consistency (Halvarsson & Sjödén, 1998). (Laessle, Tuschl, Kotthaus, and Prike (1989) found stronger correlations between the RS and the DEBQ (r=.59) than between the RS and the TFEQ (r=.35), which suggests that the array of behaviours and cognitions assessed by the DEBQ may be closer to the RS’s assessment of restriction and weight fluctuation than the TFEQ.

Heatherton, Herman, Polivy, King, and McGree (1988) argued for the distinction between “restraint” and “restriction”. The RS is designed to assess broader cognitive aspects of restraint, as well as its consequences, such as weight fluctuation. By contrast, the DEBQ-R and TFEQ-CR are intended as a narrower assessment of the “restriction” aspect of restraint: i.e., intended or

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actual limiting of food intake for the purpose of weight loss. For example, “When I have eaten my quota of calories, I am usually good about not eating any more” (TFEQ-CR), or “Do you deliberately eat foods which are slimming?” (DEBQ-R). The scales are significantly correlated with each other (r=.66, Laessle et al., 1989). However, this could partially be due to the fact that both were loosely modelled on Pudel’s Latent Obesity Scale (Pudel, Metzdorff, & Oetting, 1975), which was designed to assess obese-like eating behaviours in normal weight individuals.

Unlike the RS, “restrained eaters” identified using the DEBQ-R or the TFEQ-CR do not show the same counter-regulatory behaviour following a caloric preload, or manipulation of negative affect (Lowe, 1993; Stroebe, 2008). Also unlike the RS, factor analyses found that while RS loaded on all three restraint factors (overeating, dieting, and body dissatisfaction), the DEBQ and TFEQ Restraint subscales loaded on the dieting factor only (van Strien, Herman, Engels, Larsen, & van Leeuwe, 2007): i.e., an exploratory factor analysis yielded a single-factor solution for the DEBQ and TFEQ, and a three-factor solution for the RS. Laessle et al. (1989) similarly found that while the RS was an appropriate measure of the “disinhibition” and “weight fluctuation” aspects of restrained eating, the TFEQ-CR and DEBQ-R were more suitable for assessment of the restriction of caloric intake.

However, the assumption that elevated scores on the TFEQ-CR and DEBQ-R are

associated with a smaller caloric intake do not appear to be supported by evidence. Laessle et al. (1989) did find a significant correlation between TFEQ-CR and DEBQ-R scores, and self- reported caloric intake over a 7-day period. No such correlation was found with scores on the RS. By contrast, Stice and colleagues carried out a series of studies (Stice, Fisher, & Lowe, 2004; Stice, Cooper, Schoeller, Tappe, & Lowe, 2007; Stice, Sysko, Roberto, & Allison, 2010) in which participants’ food intake was assessed using doubly labelled water, allowing for a more accurate assessment of metabolic rate and thus caloric intake. Neither TFEQ-CR nor DEBQ-R scores were correlated with actual caloric intake, either under laboratory, or naturalistic conditions. This was true for both short-term observation (e.g., one meal) and medium-to-long term (e.g., 2 weeks). The authors propose that the scales measure caloric restriction relative to

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the individual’s subjective needs, rather than restriction in absolute terms. This is consistent with the “set point” theory presented by Nisbett (1972); people who score high on the TFEQ-CR or DEBQ-R can be assumed to exercise restraint over their eating, yet because their satiety boundary is high, Stice et al. (2007) argue, they do not appear to be consuming fewer calories compared to unrestrained eaters. This is corroborated by findings which suggest that restrained eaters consume more calories than the unrestrained, yet do not subjectively feel that they have (Jansen, 1996). Lowe and Levine (Lowe & Levine, 2005) also argue that homeostatic

mechanisms underlie hedonic craving, as well as physiological hunger, which makes deprivation (or restriction of) palatable food as subjectively “real” as the deprivation of hunger.

The Eating Disorder Examination Questionnaire (EDE-Q), developed from the Eating Disorder Examination (Cooper & Fairburn, 1987), is another measure which includes a “restraint” subscale. The measure was developed within the context of the “transdiagnostic” model of eating disorders (Fairburn, Cooper, & Shafran, 2003) The Fairburn et al. model was developed as cognitive behavioural theory, in which the symptoms and behaviours associated with BN interact with its cognitive aspects, which together act as an obstacle to change and/or treatment. However, the authors define “dietary restraint” as “persistent attempts to restrict food intake” (Fairburn et al., 2003; p.510). This is a conflation of cognitive and behavioural restraint with caloric restriction. The term “dietary restraint” (or “restraint”) is therefore used throughout to refer to, for example, periods of deprivation within the BN binge-purge cycle. This conflation is problematic, as it has contributed to the blending of the two terms and their interchangeable use in literature. For instance, in Hoiles, Egan and Kane’s (2012) assessment of the model’s validity, “restraint” is implied to be both the mechanism through which weight loss is achieved, and the behaviour which perpetuates the ED symptomatology – both of which can be more accurately described as caloric restriction. As a consequence of the interchangeable terminology used in the model, subsequent measures developed along side it also suffer from similar conflations.

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The EDE-Q was adapted from the Eating Disorders Examination (Cooper & Fairburn, 1987), a semi-structured interview used to aid clinical eating disorder diagnosis. The EDE-Q is a 36-item questionnaire is scored on the basis of behaviour and thought frequency over the last 28 days and comprises of four sub-scales relating to different facets of ED pathology: dietary restraint, weight concern, shape concern and eating concern. The restraint subscale consists of five questions which pertain to both attempted restraint (e.g., “Have you tried to avoid eating any foods which you like in order to influence your shape or weight?”), and actual restraint behaviour (“Have you gone for long periods of time without eating anything in order to influence your shape or weight?”). A factor analysis carried out in a predominantly bulimic female population supports the intended factor structure of the restraint subscale: all items were found to load on a single factor (Peterson et al., 2007). Another study which carried out an exploratory factor analysis using a mixed ED sample (AN, BN, BED and EDNOS) found that all five of the Restraint items loaded on a single factor, but that the factor also included two items from the Eating Concern subscale and one from the Weight and Shape subscales (Aardoom, Dingemans, Landt, & Van Furth, 2012). Similar findings were made in a clinical study which found that four of the five Restraint items loaded on one factor, but also included three items from other subscales (Machado et al., In Press). In a study of healthy female athletes, three items from the Restraint subscale were found to comprise a single factor; another factor consisted of mostly Eating Concern subscale items, and a third of a mix of Shape and Weight Concern items (Darcy, Hardy, Crosby, Lock, & Peebles, 2013). White, Haycraft, Goodwin and Meyer (2014) also found a three-factor solution to the EDE-Q in a study of healthy adolescents, one of which included four of the Restraint sub-scale items, and one item from the Shape Concern sub-scale. Overall, factor analyses suggest that the factorial structure of the EDE-Q-R is mostly, but not completely, consistent with its intended design as a measure of restriction only.

Lowe and Thomas (2009) argue that the EDE-Q-R is not suitable for the assessment of restraint in a non-clinical population, as it was intended for diagnostic use. However, using the sub-scale has been used to assess elevated, but pre-clinical, levels of attempted restraint. For

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example, Delinsky and Wilson (2008) used the EDE-Q-R to assess changes in ED pathology following weight gain in women in their first year of college. Ross and Wade (2004) also used the scale in the assessment of dietary restraint in university students to test the cognitive model of bulimia nervosa in a non-clinical sample. However, the factor structure of the sub- scale in a non-clinical sample appears to be multifactorial: an exploratory factor analysis yielded a two-factor solution: dietary restriction (accounting for 36% of the variance) and dietary restraint (accounting for 25%) (Dakanalis et al., in press); however, only the restriction factor was found to be relevant, which suggests that it is more important in the context of ED symptomatology, compared to restraint. Nevertheless, researchers should bear in mind that the EDE-Q-R and the DEBQ/TFEQ were developed for different research purposes and therefore assess different types of restraint: specifically, the EDE-Q-R assesses the types of cognitive and behavioural restriction which are common in clinical ED contexts.

1.3. “DIETERS” VS. “RESTRAINED EATERS” AND DIETING SUCCESS