Fewer studies were identified investigating the effect of self-regulation on weight control, compared to the effect of self-regulation on diet. All of the studies had a cross-sectional design and most of them used different measures to assess self- regulation. Price, Higgs, and Lee (2017) administered the SCS with 218
undergraduate students in the UK (17.4% male) and showed that self-regulation was weakly and negatively correlated with self-reported BMI (r=-0.15). They also found that self-control mediated the relationship between future time perspective (which refers to how individuals look at their future, as opposed to their present or past (Brothers, Chui, & Diehl, 2014)) and BMI. This suggests that having a higher
expectation and consideration of future goals and values (e.g. maintaining a healthy weight) was related to lower BMI, among people with higher self-control. However, due to the cross-sectional design of this study, no conclusions about the direction of the relationship can be made. Although weight and height were self-reported, the results of this study were in line with other studies using objectively measured BMI. For example, Kinnunen, Suihko, Hankonen, Absetz, and Jallinoja (2012) found a negative and weak correlation between SCS and objectively measured BMI (r=-0.15) in a male adult sample (N=482) in Finland. However, in this cross-sectional study the SCS was shortened to match the age group’s situation in life, that is – young male adults taking part in compulsory military service. These changes to the original scale may have compromised the validity and reliability of the SCS. A study administering a similar measure of self-control, the Habitual Self-control Questionnaire (HSCQ), with 2224 undergraduate students (42.3% male) in the US also found a weak, but positive correlation (r=0.22 to 0.35) between successful weight loss (≥10 pounds or 4.5kg) and self-control (Schroder, Ollis, & Davies, 2013). But it is important to note that data on successful weight loss were self-reported, which may have
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compromised the validity of this information. A recent study administering the Barrat Impulsiveness Scale (BIS-11) with a large cross-sectional sample from a French web-based prospective cohort (the NutriNet-Santé study, N=51,043) found that individuals with high impulsivity trait were more likely to be obese (Benard et al., 2017). However, similar to the previous studies, this cross-sectional study used a general measure and did not assess all the components of self-regulation.
Studies using scales that have been developed to assess self-regulatory strategies for eating and weight control, have demonstrated conflicting results for the
relationship between self-regulation and BMI. Keller and Siegrist (2015) administered the 63-item Weight Management Strategies Inventory (WMSI) to assess eating and weight self-regulatory strategies within an online sample composed of 616 adults (51% female) from the German-speaking region of Switzerland. The results showed that inhibition and attention control strategies were related to higher self-reported BMI. The authors argued that people with a higher BMI might be trying to regulate their weight, while people with a lower BMI might not. However, the study did not compare self-regulation between weight status groups (e.g. overweight vs normal weight) and did not provide the sample’s mean BMI, limiting the understanding of the results. Another study applied the 43-item Behavioural Objective for Weight
Management Scale (BOWM) with 407 adults in the US (Nothwehr, Dennis, & Wu, 2007). The scores for the subscales relating only to eating self-regulation were positively but not significantly correlated to BMI. Therefore, this scale might also be assessing strategies for weight loss and not for a healthy diet and weight
maintenance. As not everyone has weight issues, these scales may neither be adequate to be applied in the general population, nor to explore self-regulatory skills that help individuals to maintain a healthy weight and diet.
In contrast, other studies have found an inverse relationship between eating self- regulatory strategies and BMI. A study conducted with 120 Dutch adults (53% male) administered a 32-item Behavioural Strategies in Weight Management Scale
(BSWM) to explore individuals’ behavioural strategies to control the amount of food selected and consumed. This scale only included items related to eating regulation. The findings indicated that as eating behavioural strategies increased, self-report
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BMI decreased (Poelman, de Vet, Velema, Seidell, & Steenhuis, 2014). However, when the same study was repeated in a different sample (N=278, 15.5% male) of people with a BMI ≥ 25 kg/m2
, no significant relationship between behavioural
strategies and objectively measured BMI was found. The authors suggested that the use of the 32 eating behavioural strategies may be an indication of weight control efficacy, as it only discriminates normal weight from overweight and obese but not overweight from obese (Poelman et al., 2014). However, this interpretation might have been biased by the fact that self-report data was used in the first study and objective measures of BMI were used in the second one.
Another study also found an inverse relationship between self-regulation and self- reported BMI (r=-0.42 to -0.44) when applying the 3-item Perceived Self-regulatory Success in Dieting Scale (PSSDS) with 480 adults (Meule et al., 2012) in Germany. The administration of this scale in Dutch students produced similar results (Papies, Stroebe, & Aarts, 2008) for the relationship between self-regulation and self-report BMI (r=-0.48), although this sample included only 50 students. However, it is
important to note that the PSSDS mainly assesses how confident people are about their ability to regulate their eating behaviour and weight, and people’s reports of what they think they can do may not always represent what they actually do (De Ridder et al., 2012). Additionally, two items are about preventing weight gain (e.g. How successful are you in watching your weight?), and one item about losing weight (e.g. How successful are you in losing extra weight?), making this measure again only applicable to people who want to control their weight.
The evidence presented in this section showed conflicting results for the relationship between self-regulation and weight control. The studies varied in terms of the
measures used to assess self-regulation, and no study used a comprehensive and valid measure to assess eating-specific self-regulatory skills. Due to the lack of longitudinal studies, no conclusions about the direction of the relationships could be made. Additionally, the impact of self-regulatory skills on weight changes and on the maintenance of a healthy weight has not been explored. Intervention studies could potentially enhance the understanding of the impact of self-regulatory skills on weight loss and dietary changes.
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