The methodological quality of the evidence was generally good considering the typically high ratings in each of the quality assessment domains overall. However considering the heterogeneity of studies, the generalisability of the findings is questionable. The quality assessment also revealed methodological limitations of some studies. These related to poor or no description of whether samples were adequately powered, poor description of assignment to treatment, little or no follow-up, lack of detail regarding how attrition was handled, little description (if any) of checks for therapist competence and treatment fidelity. These shortcomings could be easily overcome by more transparent reporting by researchers. These biases
undermine the quality of studies which in turn creates ambiguity in interpreting the findings because it is not known whether the results adequately reflected the
methods employed. Nevertheless, two of the included studies (Forman et al., 2013;
Gregg et al., 2007) controlled for concomitant treatments in their design which is a strength. This is especially important considering how other treatment (psychological or pharmacological) could impact on outcomes. Therefore it is important that future studies control for this as doing so would strengthen the inferences which could be made.
53 4.3 Critique
This review is timely considering the government initiative and NHS drive to tackle obesity (Department of Health, 2011),as well as the recent surge of research using ACT. A strength of the review is the breath of the search as expert authors in the area were contacted via the ACBS website to enquire about research to help identify all references.
The limitations of this review should also be considered. First, as ACT is a fairly new approach, there is a scarcity of studies in comparison to other treatment modalities. In addition, the research mostly consists of small sample sizes, females, Caucasian samples, little or no follow-up, failure to either check or report checks for treatment adherence and therapist competence and a lack of an active treatment comparator. Therefore, this limits the generalisability of the findings and so cautious interpretation about the usefulness of ACT treatment (Öst, 2014) should be
considered. However, it is important to note that the low methodological quality of some of the studies may reflect the preliminary state of research investigating the efficacy of ACT. In order to attract funding required for long-term, definitive trials, it is necessary to conduct initial investigations which may be limited in scope (for
example, sample size, length of follow-up) due to resource constraints and the exploratory nature associated with preliminary work. Although ACT studies have been critiqued for not showing improvement over time (refer to Öst, 2014), this impression may be explained by the broadening of ACT applications (in terms of ACT exploring new problem areas, each following a new development cycle, such that early studies are unlikely to be definitive). With current (ACT for weight
management) studies, it’s notable that all have been published in the past ten years and so are subsequently still in the early phase of identifying possible utility of ACT in this domain.
Secondly, this review focused on studies which had a randomised control.
Although RCTs are considered the highest standard in research, it would have been valuable to consider other types of research design when answering this question – notwithstanding difficulties of comparing findings and effect-sizes across studies where different designs and standards of control have been used. Furthermore RCT’s have been criticised for treatment being delivered by highly competent staff, which has implications for the findings as although found to be effective in that
54 context, this may not be the case if conducted in a standard treatment environment (Ferriter, 2011). However, this review compared and synthesised the findings across a wide-ranging area, which should be acknowledged.
Thirdly, only English peer-reviewed articles were included in this review, which means it may be subject to missing relevant articles in other languages as well as vulnerable to publication bias because it is known that studies with significant effects tend to be more readily published (Ferriter, 2011; Chan, Hróbjartsson, Haahr, Gøtzsche & Altman, 2004). This point serves as an important reminder when
drawing conclusions about the effectiveness of ACT in this area. As ACT is an emerging area, there may be smaller service-evaluation or small scale studies
available using ACT within the grey literature- this is perhaps an area worth exploring in future reviews.
Fourthly, ACT research is typically carried out by those who have a strong allegiance in the area which could be a confounding variable in skewing the findings (Wampold et al., 1997). Finally, although comprehensive, the quality rating scale did not include a criterion looking at ethical issues (e.g. right to withdraw) in each of the studies. This is an oversight which may have influenced the modal number of scores and differentiated the subjective rating for each study.
4.4 Implications
The evidence reviewed suggests that ACT is effective at addressing problematic eating behaviours to enable positive lifestyle changes. However, the current view is an interim perspective and therefore strong conclusions cannot be drawn but the evidence to date indicates that ACT has been useful across a range of populations and so may be transferable to other areas considering its
transdiagnostic approach.
The reviewed studies highlight the following implications for clinical practice:
Regardless of the type of eating behaviour, over or under eating, both may be addressed within the remit of ACT to influence weight management and lifestyle change. This highlights the need for training in ACT-based
approaches for clinicians working in this area of clinical practice. In addition, the finding that ACT proves promising for weight management has ethical
55 implications in that it provides scope to potentially offer another evidence-based treatment option for clients to choose from.
Another factor which may influence clinical practice is considering the
experience of therapists when working with more challenging presentations. It was acknowledged that expert therapists enabled more change resulting in larger effect sizes (Forman et al., 2013). However, this was based on one study in this area and so further evidence is needed.
An ACT DVD was found to be effective for increasing exercise (Moffitt &
Mohr, 2014). This has implications for clinical practice due to pressures to develop cost-effective interventions with maximal ease of access (Cavanagh, Strauss, Forder & Jones, 2014). Therefore, such self-help interventions are appealing because they increase access and availability to reach those who may be inclined to decline standard treatment and they also allow the client autonomy (Cavanagh et al., 2014). There was only one such intervention method included within the scope of this review and more are needed to increase understanding of this area. It is particularly important to examine the format of treatment delivery, especially when considering that the therapeutic alliance is considered the main influential component of therapeutic change (Lambert & Barley, 2001). However, given the increase in such therapy formats, it is timely that their effectiveness is researched, and arguably by independent investigators such as clinical psychologists.