3. Results
3.1 Characteristics of identified studies
Fourteen studies with ten samples (n = 693) were included in this review, presented in Table 2. The majority of studies were conducted in the USA (N = 10 studies, based on seven samples). The remainder of studies were conducted in Sweden (N = two studies, based on one sample), Australia (N = 1) and the UK (N
=1). The number of participants across all studies ranged from 39 to 128. The majority of participants were females (n= 369). Mean ages ranged from 23.1 (3.8) to 50.6 (11). Studies focused on a mixture of outcomes and often overlapped. A range of variables including eating behaviour, activity and weight-related outcomes were measured. The specific number of studies for each of the outcomes were as follows:
weight-related outcomes (n = five), eating behaviours (n = five) and physical activity (n= five). The duration of interventions varied in all studies from two to ten hours.
The majority of participants were recruited from community settings, with the exception of one study (Weineland, Arvidsson, Kakoulidis & Dahl, 2012) which
recruited bariatric patients from a clinical centre for minimally invasive surgery. Other treatment settings included a university campus (Pearson, Follette & Hayes, 2012;
Butryn, Forman, Hoffman, Shaw & Juarascio, 2011; Juarascio, Forman & Herbert, 2010; Katterman et al., 2014), general public (Forman et al., 2013); clients with type II diabetes who attended a low income community centre (Gregg, Callaghan, Hayes
& Glenn-Lawson, 2007); community weight loss clinic (Lillis, Hayes, Bunting &
Masuda, 2009); and general community (Tapper et al., 2009). Eating behaviours targeted by the ACT interventions included emotional eating (Tapper et al., 2009;
Katterman, Goldstein, Butryn, Forman & Lowe, 2014; Forman et al, 2013) ; binge eating (Tapper et al., 2009; Juarascio, Forman & Herbert, 2010; Lillis, Hayes &
Levin, 2011) and external eating (Tapper et al., 2009); and a range of measures were used for each.
32
Table 2: Characteristics of studies Author(s),
year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings American (7.4%), Hispanic (1.9%), Asian (13%); Native American (1.9%), Other (18.6%)
Evaluation of an exercise intervention. Increase in physical activity and DDS scores for the ACT group.
For both groups, follow-up analysis showed increases in the PAAAQ and awareness subscale of the PHLMS between baseline and
Weight loss in both groups, but more so when treatment was delivered by experts. More
↓Emotional eating (EES):
ACT > C (r = .20)
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Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings
Post- treatment effect size (r)
Caucasian (62.3%); African American (24.6%); Asian (1.6%) Hispanic (3.8%)
weight loss in ABT (ACT) than SBT group (13.17% vs 7.54%) and at 6 month follow-up (10.98% vs 4.83%).
Improvements in emotional eating, disinhibition and responsivity to food cues.
↓Disinhibition (EI):
Community centre, Type II diabetes Ethnicity
Caucasian (23.5%); African
American (9.9%); Hispanic (28.4%);
Native American (1.2%);
Explored the impact of ACT on diabetes self-management
34
Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings
Post- treatment effect size (r)
Asian Pacific Islander (29.6%);
Arabic (3.7%); Other (3.7%).
n (% female)
At three month follow-up, those in the ACT condition were able to use coping strategies and reported better diabetes self-care, and glycated haemoglobin values in the target range.
Juarascio et
Caucasian (71%); African American (5%); Asian (13%); Latino (2%)
CT led to decreases in eating pathology but ACT produced larger decreases.
↓Eating pathology (EPI):
ACT > C (r = .28)
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Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings
University, female college students Ethnicity
Caucasian (62%); African American (11%); Asian American (11%);
Pacific Islander (7%); Other (9%) n (% female)
Examined the efficacy of ACT-based treatment in facilitating weight gain prevention.
ACT-based group produced reductions in BMI and weight which was maintained at one year follow-up.
36
Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings Community weight loss clinic, previously on a diet.
Ethnicity
For ACT: Caucasian (95%);
Hispanic Latino (5%)
Examined the effectiveness of ACT for improving the lives of obese individuals.
At follow-up there were improvements in obesity-related stigma, quality of life, psychological distress, body mass, distress tolerance and general and weight specific acceptance and psychological flexibility.
↓BMI
(3 month follow-up):
ACT > C (r = .30)
Further data presented in:
37
Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings
BMI, AIS Reductions in avoidance and inflexibility for ACT, useful for weight control
Lillis et al.
(2008)8
AAQ-W, ORWELLS
Examining the impact of ACT on avoidance and inflexibility.
The AAQ tool shows promise.
Lillis et al.
(2011)*9
BMI, AAQ Examined the effectiveness of ACT on binge eating and weight reduction and
psychological processes. ACT condition reported less binge eating leading to weight loss reductions.
Examined the effectiveness of an ACT DVD for physical activity initiation.
↑Physical activity (IPAQ):
ACT > C (r = .31)
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Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings
ACT led to greater increases in physical activity and a higher average step count.
39
Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings attempting to lose weight Ethnicity increases in physical activity, compared to controls but no difference in weight loss.
Results showed improvements in physical activity and weight reduction when those who did not use ACT were excluded.
↓External (DEBQ):
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Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings
Clinical centre for minimal invasive surgery, bariatric patients
RCT of ACT for bariatric patients. Improvements in eating disordered behaviour, body dissatisfaction and quality of life for those in the ACT condition.
Further data presented in;
Weineland et al. (2012b)14
Follow-up six months later
Examined the maintenance of behaviour change at six month follow-up.
↓Eating disorders (EDE-Q total):
ACT> C (r = .26)
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Author(s), year and location
Sample characteristics Study design
Treatment length (hours)
Outcomes Summary and key findings
Post- treatment effect size (r)
ACT participants maintained gains in quality of life and body dissatisfaction.
Both groups maintained improvements in eating disordered behaviours.
↓Binge eating (SBEQ):
ACT = C (r = .18)
Note: Vertical arrows (↓/↑) indicate direction of desired change for each outcome measure. For comparative effect sizes (i.e., ACT vs. C), positive values of r
favour ACT: Indicating that ACT produced relatively larger effects in the desired direction of change. Relational operators (</=/>) signify statistical conclusions reported in the original study: “ACT = C” denotes statistical equivalence; “ACT > C” denotes a statistically significant difference favouring ACT. r values indicate effect sizes, where r =0.1 indicates a small effect size, r =0.30 indicates a medium effect size, and r =0.50 indicates a large effect size; T (Total); ACT (Acceptance and Commitment Therapy condition); C (Control condition); NR (Not Reported); TX (Treatment); NA (Not Available); EES (Emotional Eating Scale); EI (Eating Inventory); EPI (Eating Pathology Inventory);DEBQ (Dutch Eating Behaviour Questionnaire); EEQ (Emotional Eating Questionnaire); BES (Binge Eating Scale); EDE-Q (Eating Disorders Examination Questionnaire); SBEQ (Subjective Binge Eating Questionnaire); BMI (Body Mass Index); PHLMS (Philadelphia Mindfulness Scale); DDS (Drexel Defusion Scale); EPI (Easting Pathology Inventory); AIS (Avoidance and Inflexibility Scale); AAQ-W
(Acceptance and Action Questionnaire for weight); VLQ (Value Living Questionnaire); PAAAQ (Physical Activity Acceptance and Action Questionnaire); ABT (Acceptance Based Therapy); SBT (Standard Behavioural Treatment); CT (Cognitive Therapy).
42 3.2 Treatment outcomes
Treatment outcomes included changes in eating behaviour, exercise and weight. Effect size calculations between treatment and control groups are outlined below according to differences in these outcomes. Heterogeneity of studies (e.g., variability in terms of outcomes, control conditions, and intervention characteristics) precluded meaningful use of formal meta-analysis; we instead used effect size estimates for individual studies to enable descriptive comparisons.
3.2.1 Effect of ACT-informed interventions on weight outcomes
A total of six papers based on five studies focused on weight or BMI as an outcome (Tapper et al., 2009; Lillis et al., 2009; Katterman et al., 2014; Forman et al., 2013; Gifford & Lillis, 2009; Moffitt & Mohr, 2014). In all studies, weight changed in a direction favouring ACT over control conditions. The largest effect size was medium (r = .38) (Katterman et al., 2014) in this case ACT was more beneficial than an assessment only control group. In another study (Forman et al., 2013)the effect sizes differed for weight depending on whether the intervention was delivered by an experienced therapist (r = .31), in comparison to when delivered by a novice (r = .12).
3.2.2 Effect of ACT-informed interventions on eating-related outcomes
A total of five studies measured a range of eating behaviours using a variety of measures: including emotional eating (EES, DEBQ, EEQ), binge eating (BES, SBEQ), eating pathology (EPI), and maladaptive eating attitudes (EAT-26). Effect sizes in the area of eating-related outcomes ranged from rs = -.13 (Tapper et al., 2009) to .28 (Juarascio et al., 2010). (Refer to Table 2 for the effect sizes for each individual measure). The effect sizes ranged from .18 (Weineland et al., 2012b)to .42 (Weineland et al., 2012) for measures of binge eating. Most studies observed effects in a direction favouring ACT, although effect sizes were variable and generally in a range of small magnitude.
3.2.3 Effect of ACT-informed interventions on activity-related outcomes A total of five studies examined the effect of an ACT intervention on physical activity; all identified changes in a direction favouring ACT over control conditions (Tapper et al., 2009; Butryn et al., 2011; Katterman et al., 2014; Gregg et al., 2007;
43 Weineland et al., 2012b).The effect sizes ranged from .21 (Katterman et al., 2014) to .43 (Moffitt & Mohr, 2014). The largest effect size was found in a study which used step-count (i.e. the number of steps taken in a day) as the means of measurement in comparison to treatment as usual which consisted of a pedometer based walking programme (Moffitt & Mohr, 2014). Other studies used self-report questionnaires such as the BPAT (.34) (Tapper et al., 2009) or the IPAQ (r = .31) (Moffitt & Mohr, 2014).