Physical activity in women attending a dissonance-based intervention after Roux-en-Y Gastric Bypass: A 2-year follow-up of a randomized controlled trial

Sofie Possmark; Fanny Sellberg; Ata Ghaderi; Per Tynelius; Mikaela Willmer; Finn Rasmussen; Margareta Persson; Daniel Berglind

doi:10.1371/journal.pone.0255556

. 2021 Nov 4;16(11):e0255556. doi: 10.1371/journal.pone.0255556

Physical activity in women attending a dissonance-based intervention after Roux-en-Y Gastric Bypass: A 2-year follow-up of a randomized controlled trial

Sofie Possmark ¹, Fanny Sellberg ¹, Ata Ghaderi ², Per Tynelius ^1,³, Mikaela Willmer ⁴, Finn Rasmussen ¹, Margareta Persson ⁵, Daniel Berglind ^1,^3,^*

Editor: Dario Ummarino⁶

PMCID: PMC8568166 PMID: 34735452

Abstract

Background

The majority of Roux-en-Y gastric bypass (RYGB) patients are not sufficiently physically active post-surgery, yet little support from the Swedish healthcare system is offered. We investigated if a dissonance-based group intervention, aiming to increase health-related quality of life after surgery, had any effect on patients’ physical activity two years post-RYGB.

Methods

Women undergoing RYGB surgery were recruited from five Swedish hospitals and randomized to intervention or control group (standard post-surgery care). The dissonance-based intervention was conducted three months post-RYGB and consisted of four group sessions, each with a specific topic, of which one addressed physical activity. ActiGraph GT3X+ accelerometers were used to measure physical activity at pre-RYGB, one- and two-years post-surgery.

Results

At pre-RYGB, 259 women were recruited and randomized (intervention n = 156 and control n = 103). Participants had a mean age of 44.7 years (SD 10.3) and pre-RYGB body mass index of 40.8 (SD 4.5) kg/m². At two-years follow-up, 99 participants (63.5%) in intervention group and 68 (66.0%) in control group had valid accelerometer-measurements. Pre- to post-surgery increases were seen in all physical activity outcomes, but no statistically significant differences between the groups were observed at the two-years follow-up, and intervention effects were poor (d = 0.02–0.35).

Conclusion

To our knowledge, this is the first dissonance-based intervention targeting women undergoing RYGB surgery. At two-years follow-up, we did not observe any differences in physical activity levels between the intervention group and control group.

Trial registration number: ISRCTN16417174.

Introduction

Bariatric surgery has shown significant weight loss with successful long-term weight maintenance [1, 2]. Physical activity, especially moderate-to-vigorous physical activity (MVPA), is important as it can help to maintain post-bariatric surgery weight loss, improve body composition [3–5], increase cardiorespiratory fitness [3], increase muscle strength, and limit the loss of fat-free mass [6, 7]. A systematic review has shown that exercise interventions performed after bariatric surgery resulted in improved physical fitness and optimized fat mass loss, as well as weight loss [8]. In contrast, a more recent systematic review examining the effect of exercise on weight loss concluded that exercise post-surgery does not contribute to greater weight loss compared to the usual post-surgery care. However, this review only examined weight loss (not loss of fat mass per se) as an outcome [9]. Despite all established health benefits associated with physical activity, and global physical activity guidelines recommending ≥150 min of MVPA per week [10, 11], most patients are not sufficiently physically active pre-surgery and continue to be inactive post-surgery despite large weight loss. However, data remains limited on this issue [12–14]. According to a systematic review and meta-analysis, where physical activity was measured objectively post-surgery, patients do not increase their physical activity [12]. In contrast, another meta-analysis has shown significant increases in objectively measured physical activity after six months and up to three years post-bariatric surgery [13]. Exercise interventions could have beneficial effect on physical activity post-surgery [14, 15]; A randomized controlled trial (RCT), investigating if exercise after surgery could increase health-related quality of life (HRQoL), has reported a small increase in step counts, light physical activity (LPA), MVPA and general health in the intervention group, but improvements were not maintained long-term [14]. Also, individualized physical activity counseling may increase physical activity post-bariatric surgery [15].

Dissonance-based interventions are built on cognitive dissonance theory and aim to change a person’s behavior by altering their cognitions [16, 17]. A systematic review has shown that the effectiveness of dissonance-based interventions on non-clinical health behavior change (i.e. changes in health behavior, attitude and intention in non-clinical settings, and not for example pathological behavior such as eating disorder symptomatology) seems positive, even though the included studies were prone to bias [18]. Dissonance-based interventions have shown effects in behavioral change; for healthy physical activity behaviors [19], smoking cessation [20] and the prevention of eating disorders and unhealthy weight gain [19–21]. Moreover, the intervention effects were greater when there were more dissonance-inducing activities, larger group sizes and more group sessions [22]. However, the effect of an already existing program to prevent unhealthy weight-gain increased when additional dissonance-based activities were added [23]. To the best of our knowledge, dissonance-based interventions have never previously been conducted in patients undergoing RYGB-surgery.

In Sweden, hospitals performing bariatric surgery procedures have standard post-surgery care that includes health check-ups by physicians, nurses and/or dieticians (check-ups are approximately scheduled at six months, one-, two- and five-years post-surgery). However, there is no additional psychosocial or behavioral change support offered in standard care. For this reason, together with the knowledge about the dissonance-based interventions’ positive effects on several health outcomes [18–23], we hypothesized that such an intervention could also have an effect on various wellbeing-related outcomes after RYGB surgery. We therefore developed a dissonance-based group intervention program targeting RYGB-treated women, aiming to prevent a decline in various long-term wellbeing-related outcomes, with the expectation that physical activity might be positively affected as well. The aim of this study was to examine if there were any differences in objectively-measured physical activity levels, between the intervention group and control group, two years after RYGB-surgery.

Material and methods

The Wellbeing after Gastric Bypass (WELL-GBP) trial has been approved by the Stockholm Ethical Review Board (registration number: 2013/1847-31/2. Date at which the ethics committee approved the study: December 10^th 2013). The trial was registered in February 2015 (ISRCTN16417174) and the enrollment started in January 2015. However, the enrollment that was done before the trial was registered only consisted of informing the participating hospitals and to determine the details of the recruitment of participants. No analyses or outcomes have been affected or changed during or after the registration of the trial. The authors confirm that all ongoing and related trials for this drug/intervention are registered. Written consent was obtained from all participants before they entered the trial. A protocol paper with more detailed description of the WELL-GBP trial has been published elsewhere [24], as well as one-year intervention effects [25]. In this paper we analyzed how the intervention affected physical activity two years after RYGB surgery.

Recruitment and participants

Participants were recruited between January 2015 and June 2017, from five hospitals located in three counties in Sweden. The two-year follow-up measures were finalized in August 2019. At the time of recruitment, RYGB accounted for more than 80% of all bariatric procedures in Sweden, and 75% of the patients were women [26]. Patients were included in the trial if they were female, eligible for RYGB surgery (body mass index (BMI) ≥40 kg/m², or if comorbidities were present: a BMI ≥35 kg/m²) and able to understand and speak Swedish. In total, 259 eligible participants provided written consent and were randomized to intervention group (60%, n = 156) or control group (40%, n = 103). Both groups received standard follow-up care from the hospitals. All participants (intervention group and controls) were offered to wear an accelerometer for seven consecutive days, sent to their homes by mail, approximately one-month pre- and one and two years post-RYGB surgery. To wear the accelerometer was optional for the participants. A CONSORT flow-chart of the recruitment and the follow-up measurements is presented in Fig 1.

Fig 1 — Participant flow-chart according to CONSORT standards. Of the included participants in the two-year follow-up belonging to the intervention group, 61 of them (61.6%) had attended the session about physical activity. Two participants did not want to participate in the one-year follow-up, but wanted to be contacted for the two-year follow-up.

Randomization

Approximately two months post-RYGB, participants who had provided informed consent and pre-RYGB data (questionnaires about HRQoL, among others (not included in this study)) were block randomized (in blocks of 5 participants) within their county to either group, by using the SAS 9.4 procedure Proc Plan (SAS Institute Inc., Cary, NC, USA). The random allocation sequence was computer generated into 60% to intervention and 40% to control group. An investigator not involved in the data collection randomized the participants to their allocated group. Blinding of participants or investigators was not possible.

Intervention

The intervention in the WELL-GBP trial was based on a model by Stice et al. [20] and consisted of four dissonance-based group sessions post-RYGB. The sessions started approximately three months post-RYGB, were conducted once a week for four weeks, lasted around 1.5 hours/session and were led by a facilitator who had been trained in dissonance-based theory (individual readings on the topic together with informational meetings with a psychologist) and followed an intervention manual. The intervention manual was developed by researchers (AG, DB, MW, FS and FR) who were involved in the development of the intervention. Each session covered a topic known to be problematic for many patients after RYGB surgery: (i) physical activity, (ii) eating behavior, (iii) social relationships and (iv) sexual and intimate relationships. Within each topic, the participants discussed how one should think and act in order to be able to meet future challenges, to optimize health and wellbeing, as well as to maintain the positive outcomes of surgery. The aim of the intervention was to induce dissonance and to increase the probability of healthy actions and attitudes. If a participant had attended at least three out of any of the four sessions, she was considered as having received the intervention. This threshold was set as there is a widely used threshold of <80% adherence to an intervention or medication in order to distinguish adherent from non-adherent patients [27]. Before the intervention started, we conducted a pilot study in order to get feed-back from the pilot participants and to test the intervention manual. Minor changes were done to the manuscript after the feed-back. A description of the pilot study has been published elsewhere [24]. During the session on physical activity, discussions were focused on what sedentary behavior and physical activity is, how one can increase their daily physical activity, difficulties and barriers of physical activity after bariatric surgery and how to overcome these barriers.

Outcomes

At pre-, one- and two years post-RYGB, all participants were asked to wear the ActiGraph GT3X+ accelerometer on the right hip during all waking hours for seven consecutive days, in order to objectively measure their physical activity levels. Valid accelerometer measurements were set to a minimum wear time of at least 10 hours/day for at least three days. Vector magnitude (V_m) was recorded and analyzed in 10-second epochs and converted to counts per minute (cpm). For wear time, an algorithm by Choi et al. [28] was used where non-wear time was classified as non-zero counts for at least 60 minutes, with a maximum break of two minutes. We classified sedentary time as <100 cpm, LPA as 100–3208 cpm and MVPA >3208 cpm [29]. Wear time and classification of bouts were computed using ActiLife v.6.13.3 (ActiGraph, Pensacola, USA).

Power calculation

The initial power calculations were calculated with HRQoL as main outcome. To attain a statistical power of 0.90 with a significance level of 5% and an expected moderate effect size (Cohen’s d = 0.5), estimated participating patients was a sample size of 240, with a 20% expected drop-out rate. Of the original sample of 259, a total number of 167 participants had valid accelerometer measurements at the two-year follow-up (intervention group n = 99, control group n = 68), resulting in a statistical power of more than 90% to detect the pre-planned effect size of d = 0.5.

Statistical analysis

As one-year differences between the groups already have been published elsewhere [25], this study focused on the two-year follow-up. All participants with valid accelerometer measurements at the two-year follow-up were included in the intention-to-treat analysis, regardless of whether they had valid measurements at pre-RYGB or not. When recruiting participants at pre-RYGB, not all participants had enough time to wear the accelerometer before their surgery, resulting in fewer valid accelerometer measurements at pre-RYGB than at the follow-ups.

Primary analysis was intention-to-treat analysis [30], in order to see if there were any differences in physical activity levels between the intervention and control group at two-years post-RYGB surgery. Normal distribution was evaluated graphically and tested with Shapiro-Wilk test. The variables were approximately normally distributed, however not perfectly. We therefore present the results as means and use Cohen’s d to quantify intervention effect sizes [31], but because of the lack of complete normality, we also used Kruskal-Wallis H test to test for group differences, which assuming the same distribution in both groups tests whether the medians differ. Also, additional analysis of all outcomes at the two-years follow-up in the intention-to-treat analysis were adjusted for wear time. Chi-square test was used for dichotomous variables, for example if a participant smoked or not, had university level of education or not, and meeting the physical activity recommendations or not. BMI was calculated as weight (kg)/height (m)².

Furthermore, per protocol analysis was performed to compare the control group to the participants in intervention group who had received the intervention according to protocol (attended ≥3 group sessions). Per protocol analysis was also performed to compare the participants in the intervention group who had participated in the session about physical activity, to the participants who had not participated in that session. Sensitivity analysis was conducted for the participants with valid accelerometer measurements from all three time points, conducted with a regression analysis adjusted for pre-RYGB measures and presented as differences of the means between the groups at one- and two-years follow-up. Additionally, a sensitivity analysis was conducted for all participants who had ≥5 valid days of accelerometer measurements. All statistical analyses were performed using Stata 14.1 (StataCorp) software.

Results

Descriptive statistics analysis

A total of 259 women were recruited to the trial, with a mean pre-surgery BMI of 40.8 (SD 4.5) and a mean age of 44.7 years (SD 10.3) at pre-RYGB. Pre-surgery, 54% met the recommended physical activity guidelines of ≥150 minutes of MVPA per week (non-bouts) [10, 11]. At pre-RYGB, 174 of the initial 259 participants had valid accelerometer measurements. However, not all of them where included in the analysis of this study, as only participants with valid measurements at the two-year follow-up were included, regardless if they had valid measurements at pre-RYGB or not (Fig 1). At the two-year follow-up, 167 of the 259 participants had valid accelerometer measurements (intervention group n = 99 and control group n = 68), thus resulting in a loss to follow-up rate of 35.5% (36.5% in intervention group and 34.0% in control group). Of the participants in the intervention group, 61.6% (n = 61) had attended the session where physical activity had been discussed. The only pre-RYGB characteristic that were significantly different between those included in the two-year follow-up (n = 167) compared to those not included (n = 92) were age at surgery (p = 0.0097). The women who were included were somewhat older (45.5 years, SD = 10.1) compared to the women not included in this study (41.4 years, SD = 10.6). Table 1 shows pre-RYGB characteristics of the original cohort (n = 259) and of the participants included in this study. No significant differences in pre-RYGB characteristics between intervention group and control group were detected. Seventy-three percent of included participants in the intervention group (of the n = 99 who had valid accelerometer measurements at the two-year follow-up) had attended at least one group session (any of the four sessions), and 51% had received the intervention according to protocol (i.e. attended ≥3 group sessions). There were no statistical differences in pre-RYGB characteristics between those receiving the intervention compared to both control group and participants in the intervention group who did not receive the intervention.

Table 1. Pre-surgery characteristics of total sample, intervention group and control group of the women undergoing Roux-en-Y Gastric Bypass (RYGB) surgery and included in the two-year follow-up, as well as the original cohort.

Variables	Original cohort (n = 259)	Cohort included in 2-year follow-up (n = 167)	Intervention group (n = 99)	Control group (n = 68)	p-value
BMI pre-RYGB (kg/m²) (SD)	40.9 (4.8)	40.8 (4.4)	40.8 (4.1)	41.0 (4.7)	.859
BMI (kg/ m²) at 2y post-surgery (SD)	27.2 (4.1)	27.0 (3.8)	26.6 (3.5)	27.6 (4.2)	.070
% total body weight loss (SD) (from pre- to 2y post-RYGB)	33.2 (8.8)	33.6 (8.7)	34.5 (8.4)	32.2 (9.0)	.184
% excess BMI loss (excess BMI > 25 kg/m²) (SD) (from pre- to 2y post-RYGB)	88.1 (23.7)	89.1 (22.9)	91.1 (21.1)	86.1 (25.3)	.103
Age pre-RYGB, in years (SD)	44.0 (10.4)	45.5 (10.1)	44.7 (10.4)	46.7 (9.5)	.148
Education pre-RYGB, university level, n (%)	75 (29.1)	51 (30.5)	32 (32.3)	19 (27.9)	.546
Smokers pre-RYGB, n (%)	17 (6.6)	9 (5.4)	4 (4.0)	5 (7.4)	.352

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BMI = body mass index.

Presented as mean (standard deviation) or percentage (numbers).

Intention-to-treat analysis

We observed no statistically significant differences in any of the physical activity levels between intervention and control group at the two-year follow-up, and intervention effects were poor (d = 0.02–0.35). Table 2 shows a detailed description of the outcomes of physical activity intensities at pre-RYGB, one- and two-years follow-up for the intervention and control group. Only the participants who had valid accelerometer measurements at the two-year follow-up (intervention group n = 99 and control group n = 68) were included in the analysis. Of those, 77 in the intervention group and 46 in the control group had valid measurements at pre-RYGB, and 85 and 56 in intervention and control group, respectively, had measures at the one-year follow-up. At two-years, the intervention group spent 29.0 min/day (SE = 1.8) in MVPA and the control group 27.1 min/day (SE = 2.5). Participants were sedentary for 493.3 min/day (SE = 12.0) and 458.8 min/day (SE = 12.3) in the intervention group and control group, respectively. Percentage of women who met the recommended physical activity guidelines (non-bouts) were 66.7% in the intervention group and 54.4% in the control group. No difference between groups were statistically significant.

Table 2. Intention-to-treat analysis of the different physical activity intensities, measured by the GT3X+ accelerometers and divided by intervention and control group, in women pre-, one- and two-years post-Roux-en-Y Gastric Bypass (RYGB) surgery.

Accelerometer outcomes	Pre-RYGB, Intervention (n = 77)	Pre-RYGB, Control (n = 46)	p- value	1y post-RYGB, Intervention (n = 85)	1y post-RYGB, Control (n = 56)	p- value	2y post-RYGB, Intervention (n = 99)	2y post-RYGB, Control (n = 68)	p- value	Cohen’s d (95% CI)
Mean wear time, mean hours/d (SE)	14.3 (0.1)	14.0 (0.2)	.154	15.0 (0.2)	14.9 (0.2)	.858	15.2 (0.2)	14.7 (0.2)	.195	.35 (.03 to .66)^*
Mean counts, mean min/d (SE)	558.0 (23.6)	564.1 (28.1)	.714	576.1 (20.3)	596.8 (24.3)	.541	570.1 (17.6)	579.9 (22.9)	.858	-.05 (-.36 to .25)
MVPA, mean min/d (SE)	26.7 (2.1)	24.5 (3.1)	.327	27.9 (1.9)	30.0 (3.1)	.936	29.0 (1.8)	27.1 (2.5)	.302	.10 (-.21 to .41)^*
LPA, mean min/d (SE)	356.3 (10.6)	359.3 (11.1)	.854	390.3 (9.3)	401.6 (10.6)	.351	392.4 (9.2)	394.0 (11.2)	.916	-.02 (-.33 to .29)
Sedentary time, mean min/d (SE)	476.7 (11.9)	455.5 (12.2)	.235	481.0 (12.7)	462.9 (13.1)	.362	493.3 (12.0)	458.8 (12.3)	.075	.31 (-.00 to .62)^*
Mean steps, mean counts/d (SE)	6176.6 (282.1)	5971.5 (397.9)	.548	7518.5 (300.9)	7571.6 (396.3)	.792	7700.3 (268.5)	7387.8 (366.5)	.268	.11 (-.20 to .42)^*
Meeting PA-recommendations ^ , n (%)**	43 (55.8)	20 (43.5)	.184	48 (56.5)	32 (57.1)	.937	66 (66.7)	37 (54.4)	.110	.25 (-.06 to .56)
Meeting PA-recommendations in ≥10-min bouts ^ , n (%)**	7 (9.1)	4 (8.7)	.941	12 (14.1)	9 (16.1)	.750	17 (17.2)	13 (19.1)	.748	-.05 (-.36 to .26)

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MVPA = moderate-to-vigorous physical activity; LPA = light physical activity; PA = physical activity. Presented as mean scores (standard errors) or frequency (percent) for each subscale, p-value for the difference in medians between the two groups (Kruskal-Wallis H test) at pre-RYGB, one- and two-years post-RYGB surgery. Effect sizes at two years measured with Cohen’s d (95% CI).

*Normal distribution assumption rejected according to Shapiro-Wilk test (p<0.05). Participants with valid accelerometer measurements at the two-year follow-up were included in the analysis. There are fewer participants with valid measurements at pre-RYGB than at the follow-ups, because not all participants had enough time to wear the accelerometer before their surgery.

**PA-recommendations: ≥150 minutes of MVPA per week in non-bouts and 10-minute bouts.

Per protocol analysis

Per protocol analysis between participants in intervention group who received the intervention (n = 50) and control group (n = 68) showed no statistically significant differences between the groups, except for sedentary time. Those who received the intervention were more sedentary (522.5 min/day, SE = 17.2) than the control group (458.8 min/day, SE = 12.3) (p = 0.002, d = -0.58) at two-years post-RYGB (S1 Appendix). However, this difference was also significantly different at pre-RYGB (p = 0.039), and therefore this difference may not be relevant from a clinical perspective.

Per protocol analysis of the participants attending the session about physical activity (n = 61) versus participants in the intervention group who did not attend that session (n = 38), showed no significant differences of clinical importance in any of the physical activity outcomes that changed any of the conclusions. There were also no differences in any of the pre-RYGB characteristics between these two groups.

Sensitivity analysis

All outcomes at two years post-RYGB in the intention-to-treat analysis were adjusted for accelerometer wear time, but there were still no differences between the groups (p>0.05) (Table 2 shows the results from the non-adjusted analysis). Moreover, we performed sensitivity analysis for the women who had valid accelerometer measurements from all measurement time points (pre-RYGB, one- and two-year follow-up, n = 68 in intervention group and n = 36 in control group) and adjusted all outcomes at one- and two years for pre-RYGB measurements, but no statistical differences between the intervention and control group were observed (p>0.05). Figs 2 and 3 graphically show the mean daily minutes of MVPA and sedentary time from pre-RYGB to two years, for the women who had valid measurements at all time points (not adjusted for pre-RYGB measures). Fig 4 shows the percentage of women with valid measurements at all time points in intervention group (n = 68) and control group (n = 36) who meet current physical activity guidelines of doing at least 150 minutes of MVPA per week in non-bouts.

Fig 2 — Means of daily minutes of moderate-to-vigorous physical activity (MVPA) with 95% confidence intervals of the women in the intervention group (n = 68) and control group (n = 36) who had valid accelerometer measures at all three assessment time points at pre-, one- and two-years post-Roux-en-Y Gastric Bypass (RYGB) surgery.

Fig 3 — Means of daily minutes of sedentary time with 95% confidence intervals of the women in the intervention group (n = 68) and control group (n = 36) who had valid accelerometer measures at all three assessment time points at pre-, one- and two-years post-Roux-en-Y Gastric Bypass (RYGB) surgery.

Fig 4 — Percentage of women in intervention group (n = 68) and control group (n = 36) who had valid accelerometer measures at all three assessment time points at pre-, one- and two-years post-Roux-en-Y Gastric Bypass (RYGB) surgery who meet current physical activity guidelines of doing at least 150 minutes of moderate-to-vigorous physical activity (MVPA) per week in non-bouts.

We also performed sensitivity analysis for women who had ≥5 valid accelerometer measurement days at pre-RYGB and two-year follow-up (intervention group n = 92 and control group n = 64). No statistically significant between-group differences were observed, except for sedentary time, where the intervention group was significantly more sedentary than the control group (p = 0.047), with a mean of 500.6 min/day (SE = 12.5) compared to 460.8 min/day (SE = 2.8), respectively (d = 0.35) (S2 Appendix).

Discussion

Main findings

No statistically significant differences in any of the physical activity outcomes were observed between the dissonance-based intervention group and control group at two years post RYGB.

Previous research

Some interventions investigating different counselling interventions to improve physical activity before or after bariatric surgery have been conducted [14, 15, 19, 32, 33]. A review from 2013 showed that individualized counselling directed toward physical activity can help bariatric patients to increase their physical activity post-surgery [15]. The interventions included in that review started pre-surgery or between three to 102 months post-surgery and the lengths of the interventions were between six and 12 weeks long [15]. In addition, a previous study has shown an association between meeting the physical activity recommendations of at least 150 min of MVPA per week and a higher score for HRQoL both pre- and one-year post-surgery [34]. A pre-surgery intervention consisting of six counselling sessions with the aim to increase physical activity reported that the intervention group increased their MVPA and also reported better HRQoL scores post-intervention compared with the control group [32]. Further, an intervention where participants were randomized to either standard care, receiving pedometers only, or receiving pedometers as well as counselling sessions, showed that the combined pedometer and counselling group increased physical activity from pre-surgery up to 6.5 months post-surgery (counselling and pedometers = 6 787 steps/day, pedometers only = 5 325 steps/day and standard care = 5253 steps/day) [33]. These results are not in line with our findings, as we did not observe any differences in physical activity between intervention and control groups. However, most of these studies were conducted pre-surgery [32, 33] and with shorter follow-up time and may thus not be quite comparable to our study. For instance, a recent physical activity intervention has shown increases in physical activity levels and step counts at one year post-RYGB, but the effects were not maintained at two-year follow-up [14]; thus, in line with our findings at two-years. However, the main aim of our WELL-GBP intervention was to maintain the increased HRQoL post-RYGB, as HRQoL, for some bariatric patients, starts decreasing around one to two years post-RYGB [35, 36], where we anticipated that physical activity might be positively affected as well. A dissonance-based intervention aiming to increase physical activity among female college students, showed that the participants receiving the dissonance-based intervention had greater increases in physical activity directly at post-test, but not at the follow-up at six months post-intervention [19]. This may indicate that dissonance-based interventions might increase physical activity in the short-term but are not as effective for long-term maintenance of physical activity.

To the best of our knowledge, the WELL-GBP trial is the first dissonance-based intervention for post-RYGB support to women, with the aim to prevent a decline in HRQoL and also possibly increase physical activity. The way the intervention was delivered is of importance to discuss. Of the total participants randomized to intervention and included in this study, 73% attended at least one session (any of the four sessions) and 51% received the intervention according to protocol (Fig 1), despite the fact that all times and dates for the sessions were decided in agreement with the participants. This may indicate that another type of delivery, such as various online-based group sessions, might be more suitable and enable more RYGB patients to attend all sessions. Previous research, conducted on both men and women, have shown that reasons and barriers for not attending support groups after bariatric surgery are due to inconvenient times and locations, responsibilities towards family, work or school, as well as travel time and distance [37]. Also, more group sessions have been observed to be more effective, where four to five sessions seem to be optimal [22]. Therefore, maybe our intervention consisting of four dissonance-based sessions, where only one of them elaborate on physical activity, is too little to show any long-term impact on physical activity behavior post-surgery.

Strengths and limitations

First, the RCT-design, which is the main strength of the study, enables us to compare the intervention group’s results to the standard follow-up care provided by the hospitals. Second, we also pre-registered the trial (ISRCTN16417174) and followed the initial analysis plan. Third, physical activity was objectively measured at pre-RYGB and all follow-ups, with ActiGraph GT3X+ accelerometers, a validated research tool which accurately estimates physical activity in free-living subjects [38]. We chose objective measures as self-reported physical activity among bariatric patients have proven not to be a reliable method [39–41]. Inclusion criterion for valid wear time was set to at least three days with a minimum of 10-hour wear time per day, as three to four wear time days has shown to be sufficient for achieving 80% reliability of MVPA [42]. Fourth, we based the intervention on Stice’s dissonance-based intervention model [20], which has previously shown positive effects on physical activity behaviors [19] and on non-clinical health behavior change [18]. Fifth, the study results have generalizability as we recruited participants from five hospitals from different geographical areas of Sweden, and our participants have similar age and BMI as the typical female RYGB-patient in Sweden [43]. However, the sample of participants included in our study might be somewhat selected, as our participants, compared to the general bariatric surgery patients, may have had higher motivation and interest for health behavior change and therefore be more prone to participate. Thus, when generalizing our results, it is of importance to take this into consideration. Globally, bariatric surgery patients are somewhat older and have higher pre-surgery BMI [44] than the women in this study. Also, the post-surgery care might vary between countries, and therefore our findings should be generalized to other countries with caution. Sixth, few studies have objectively measured bariatric surgery patients’ physical activity levels both before and after surgery. The majority of those have only conducted follow-up 6–12 months post-surgery [4, 33, 39–41, 45–47], while some have conducted follow-up assessments after two to four years [14, 48, 49]. Our study therefore adds further knowledge on physical activity patterns among women from before to long-term post-RYGB. Finally, the WELL-GBP trial can easily be implemented in healthcare settings, as various healthcare personnel, such as nurses, dietitians and physiotherapists would be able to deliver the intervention after appropriate training [20].

There are some limitations to the current study that need to be addressed. First, any comparisons or generalizations to men are not possible, as only women were included. We also only included patients who underwent RYGB, therefore any comparisons with other types of bariatric surgeries might be done with some caution. Second, smaller sample sizes were used when conducting per protocol and sensitivity analyses. Consequently, the power might be too small to detect between-group differences. Third, participants were recruited from different hospitals where the follow-up routines differed slightly, which may have influenced the outcomes. Fourth, of the total 259 participants included in the trial at pre-RYGB, 167 (64%) had valid accelerometer measurements at the two-year follow-up, which might have affected the findings as a result of selection bias: i.e. participants who already are more physically active choose to wear an accelerometer, while inactive participants refrained. Though, no differences in pre-RYGB characteristics were observed, except that the 167 women with valid accelerometer measurements were older than those women without valid measurements (45.5 years (SD 10.1) versus 41.4 years (SD 10.6), respectively, p = 0.0097). Fifth, only 61.6% of the participants in the intervention group attended the session about physical activity, which might have had impact on the results. Sixth, one limitation of the ActiGraph GT3X+ is that it cannot distinguish between sitting or standing, which might result in inaccurate estimations of sedentary time [50]. Seventh, the power calculation in this RCT was performed to detect group differences at the two years follow-up for the primary outcome (HRQoL) and not secondary outcomes such as physical activity. Finally, the ActiGraph GT3X+ has not been validated in RYGB patients.

Conclusion

To our best knowledge, this is the first dissonance-based intervention aiming to influence physical activity among women post-RYGB surgery. However, no differences in any of the physical activity outcomes were observed between the intervention group and control group two-years post-RYGB. Dissonance-based interventions focusing exclusively on the topic of physical activity might be more suitable and should be considered for future dissonance-based interventions aiming to increase physical activity levels among bariatric patients.

Supporting information

S1 Checklist. CONSORT 2010 checklist.

(DOC)

Click here for additional data file.^{(218KB, doc)}

S1 Appendix. Per protocol analysis of the physical activity intensities two years post-Roux-en-Y Gastric Bypass (RYGB) surgery for the women in the intervention group who received the intervention (attended ≥3 of 4 sessions) versus control group (standard care).

MVPA = moderate-to-vigorous physical activity; LPA = light physical activity. Presented as mean scores (standard errors) or numbers (percentage) for each variable, p-value for the difference between the groups at the two-year follow-up. Effect sizes at two years measured with Cohen’s d (95% CI). There are fewer participants with valid measurements at pre-RYGB than at the follow-ups, because not all participants had enough time to wear the accelerometer before their surgery. *PA-recommendations: ≥150 minutes of MVPA per week in non-bouts and 10-minute bouts.

(DOCX)

Click here for additional data file.^{(15.9KB, docx)}

S2 Appendix. Sensitivity analysis for pre-surgery and two-years follow-up measures of the physical activity intensities (measured by the GT3X+ accelerometers) among the women, undergoing Roux-en-Y Gastric Bypass (RYGB) surgery, in the intervention group and control group who had ≥5 valid accelerometer measurement days.

MVPA = moderate-to-vigorous physical activity; LPA = light physical activity. Presented as mean scores (standard errors) or numbers (percent) for each subscale, p-value for the difference between the two groups at pre-RYGB and two-years post-RYGB surgery. Effect sizes at 2 years measured with Cohen’s d (95% CI). There are fewer participants with valid measurements at pre-RYGB than at the follow-ups, because not all participants had enough time to wear the accelerometer before their surgery. *PA-recommendations: ≥150 minutes of MVPA per week in non-bouts and 10-minute bouts.

(DOCX)

Click here for additional data file.^{(15.7KB, docx)}

S1 File. The protocol study plan for the conduct and analysis of the trial that the ethics committee (the Stockholm Ethical Review Board) approved before the trial began.

(DOC)

Click here for additional data file.^{(122.5KB, doc)}

Acknowledgments

We would like to thank the staff involved in this study from the five hospitals for their help in recruiting study participants and to the study participants who participated in the data collection.

Data Availability

Swedish secrecy law prohibits us from making register data publicly available. The data supporting our findings were used under license and ethical approval for the current study. Readers interested in obtaining microdata or replicating our study may seek similar approvals and inquire through Statistics Sweden. For further advice see: https://www.scb.se/en/services/guidance-for-researchers-and-universities/.

Funding Statement

This study was funded by: the Swedish Research Council (Vetenskapsrådet) grant number 2015-02621 to DB and FR (https://www.government.se/government-agencies/the-swedish-research-council-vetenskapsradet/); the Stockholm County Council (ALF Medicine) grant number 20180266 to DB (https://ki.se/en/nvs/about-the-research-school-in-health-science); and the Research School of Caring Sciences at Karolinska Institutet (NVF), grant number 2-14672016 to DB (https://ki.se/en/nvs/about-the-research-school-in-health-science). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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PLoS One. doi: 10.1371/journal.pone.0255556.r001

Decision Letter 0

Dario Ummarino

8 May 2020

PONE-D-20-01663

Physical activity in women attending a dissonance-based intervention after Roux-en-Y Gastric Bypass: A 2-year follow-up of a randomized controlled trial

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Reviewer #1: General comments

In this paper, authors assessed the effect of a dissonance-based intervention conducted in the first months after RYGB on habitual physical activity up to two years after surgery. They conclude that no difference was observed between physical activity at the two-year follow-up between intervention and control groups. A previous paper by the same group described the effect of the intervention at the 1-year follow-up. Strengths of the study were to use a randomized design and to assess physical activity with accelerometers. The study is well written, and the references are up to date.

My only concern is about the statistical methods used. Authors compared physical activity outcomes between the two groups at each time point (pre-surgery, one-year and two-year post-surgery) instead of comparing longitudinal changes in physical activity. By doing so, they included only participants with valid data at the 2-year follow-up and therefore excluded many participants who had valid data at baseline but not at 2 years. Mixed models might be more appropriate when several time points are available.

Specific comments

Abstract

- Line 28: Is “baseline” a pre-surgery measure? If so, “before surgery” might be more precise than “at baseline”

Introduction

- Line 58-67: the references are up to date but the message of this paragraph is not clear to me. The expression “In addition” (line 65) does not seem appropriate to me, “In contrast” might be more appropriate here.

What I understand from this paragraph is that: 1) exercise training has been shown effective after bariatric surgery, 2) mixed results are found regarding the spontaneous change in physical activity after bariatric surgery, 3) exercise training leads to a small and transient increase in habitual physical activity, 3) physical activity counselling might be effective to increase physical activity.

I would suggest to make a clearer distinction between changes in physical activity related to bariatric surgery and those related to exercise training after bariatric surgery.

- Line 91: “objectively-measured” rather than “objective measured”

Methods

- Line 98-99: “we analysed how the intervention affected physical activity”

Results

- Tables do not fit in the pdf. I cannot comment the tables.

- The authors compared physical activity outcomes between intervention and control group at all times (Table 2). This method results in the exclusion of many participants who do no hate valid measures at the 2-year follow-up. It would have been more appropriate to compare changes in physical activity between groups. Mixed models are usually used in this situation.

Discussion

- Lines 307-309: Are the results similar in other contexts (eg in the studies cited in the introduction)?

Reviewer #2: Thank you for the opportunity to review the manuscript entitled ‘Physical activity in women attending a dissonance-based intervention after Roux-en-Y- Gastric Bypass: A 2-year follow-up of a randomized controlled trial’. This is an interesting paper looking at objectively measured physical activity in a sample of women whom have undergone RYGB, this is a large sample given the population and topic area (physical activity) that the authors are researching in. It is also an area of research which is in its infancy and a useful addition to the literature.

Please see my comments in the document attached

Reviewer #3: Two-year follow-up results on patients activity levels were summarized from a two-arm randomized controlled clinical trial which aimed to increase quality of life following Roux-en-Y gastric bypass surgery through dissonance-based group intervention. At two-years follow-up, no significant differences in physical activity levels were observed between the intervention and control arms.

Minor revisions:

1- Cohen’s d is valid when the distribution of the data is normal. Indicate if the normality assumption was met.

2- Line 172: Technically the Kruskal-Wallis H test is used for comparing ranks rather than means for data that is not normally distributed. Additionally, non-normally distributed data is generally summarized using median, first and third quartiles.

3- Line 173 states, “Chi-square test was used for dichotomous variables.” Provide further clarity by indicating the comparisons which are being tested by the chi-square test.

4- Line 177 would be clarified by stating, “Sensitivity analysis was conducted for the participants with valid accelerometer measurements from all three time points, conducted with a regression analysis adjusted for baseline measures and presented as differences of the means between the groups at one- and two-years follow-up.”

5- Line 180: Again replace “calculated” with “conducted.”

6- Table 2: Clarify the statistical methods used to calculate the p-values in Table 2.

7- Line 232: Replace “numbers” with “frequency” to improve clarity.

8- Clarify if SE represents standard error or standard error of the mean.

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PLoS One. 2021 Nov 4;16(11):e0255556. doi: 10.1371/journal.pone.0255556.r002

Author response to Decision Letter 0

15 Jun 2020

Dear Associate Editor Dario Ummarino,

Thank you for the opportunity to revise our paper entitled “Physical activity in women attending a dissonance-based intervention after Roux-en-Y Gastric Bypass: A 2-year follow-up of a randomized controlled trial”. Below, please see a detailed description of our responses and ways to address each comment from the reviewers. In the manuscript, all changes performed have been highlighted with red text. In this document, all citations from the manuscript are in quotes with changes highlighted with red text.

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Response: Thank you for providing this information! However, we believe that we have followed the style requirements. If we have not done so, please let us know.

As per the journal’s editorial policy, please include in the Methods section of your paper:

a) your reasons for your delay in registering this study (after enrolment of participants started);

b) confirmation that all related trials are registered by stating: “The authors confirm that all ongoing and related trials for this drug/intervention are registered”.

Response: Thank you for giving us the chance to clarify this! The trial was registered in February 2015 and the enrollment of participants started in January 2015. However, the enrollment that was done before the trial was registered only consisted of informing the hospitals that was participating in the trial and to start the planning of the details on how and where to recruit the participants. No analyses or outcomes have been affected or changed during or after the registration of the trial. We have now added a couple of sentences in the method section to clarify this (lines 95-101):

“The Wellbeing after Gastric Bypass (WELL-GBP) trial has been approved by the Stockholm Ethical Review Board (registration number: 2013/1847-31/2. Date at which the ethics committee approved the study: December 10th 2013). The trial was registered in February 2015 (ISRCTN16417174) and the enrollment of participants started in January 2015. However, the enrollment that was done before the trial was registered only consisted of informing the participating hospitals and to determine the details of the recruitment of participants. No analyses or outcomes have been affected or changed during or after the registration of the trial. The authors confirm that all ongoing and related trials for this drug/intervention are registered.”

Response: Thank you for the feedback! Swedish secrecy law prohibits us from making register data publicly available. The data supporting our findings were used under license and ethical approval for the current study. Readers interested in obtaining microdata or replicating our study may seek similar approvals and inquire through Statistics Sweden. For further advice see: https://www.scb.se/en/services/guidance-for-researchers-anduniversities/. However, the part where we stated “data not shown” is not a core part of the research, so we have now removed the statement “(data not shown)”.

Reviewer #1:

General comments

Response: Thank you for your comment! The reason we only measured the outcomes between the groups at each time-point, and not the longitudinal changes, is because we do not investigate the longitudinal changes in this study. We are interested to see if this intervention we have conducted had any beneficial effects on physical activity at (primarily) two years post-RYGB, which is the aim of this study, and therefore we are primarily interested in any differences between the groups at the two-year follow-up. Therefore, the longitudinal changes are of less interest for this article. We show the data for the pre- and one-year post-RYGB follow-up to show all available data for the reader, but the main aim is to look at the differences between intervention- and control groups at two years follow-up.

Specific comments

Abstract

- Line 28: Is “baseline” a pre-surgery measure? If so, “before surgery” might be more precise than “at baseline”

Response: Thank you for the comment! We have now changed all “baseline” to “pre-RYGB” in the whole manuscript, to make it clearer.

Introduction

I would suggest to make a clearer distinction between changes in physical activity related to bariatric surgery and those related to exercise training after bariatric surgery.

Response: Thank you for the comment! We have now included a sentence to distinguish between physical activity (spontaneous) after surgery and interventions aiming to increase physical activity after surgery (lines 62-63): “Exercise interventions could have beneficial effect on physical activity post-surgery [14, 15]; A randomized controlled trial (RCT), investigating if exercise after surgery could increase health…”.

We then changed “in addition” to “also” on line 66 (previous line 65), because of the change we made to the paragraph shown above: “Also, individualized physical activity counseling may increase physical activity post-bariatric surgery [15].”

- Line 91: “objectively-measured” rather than “objective measured”

Response: Thank you for letting us improve the grammar! We have now changed it according to your suggestions (line 91): “The aim of this study was to examine if there were any differences in objectively-measured physical activity levels…”.

Methods

- Line 98-99: “we analysed how the intervention affected physical activity”

Response: Thank you for letting us improve the grammar! We have now changed it according to your suggestions (line 104): “In this paper we analyzed how the intervention affected physical activity…”.

Results

- Tables do not fit in the pdf. I cannot comment the tables.

Response: Thank you for acknowledging this! We assumed it would be able to see the tables anyway. But now we have changed the set of the pages in the document to “landscape” where all the tables are, in order for you to be able to see them. We hope that will work.

Response: Thank you for the comment! However, we do not show data for the participants who had valid measurements at all time points. As stated in the first row of the table, number of participants with valid measurements are seen (n=77 for example) for each time-point. As you can see, there are more participants who have valid data at the two-year follow-up than at pre-RYGB. This is because not all participants had time to wear an accelerometer at pre-RYGB, and we have stated that in the text under the table. The aim was to analyze differences between groups at two-years follow-up, which is why we included only participants who had valid measurements at the two-years follow-up. Thus, table 2 shows participants who had valid measurements at the two-year follow-up, and if those participants also had valid measurements at pre- and one-year post-RYGB, they were included in the pre- and one-year analyses as well. This was so we would not exclude participants who had valid measurements at two-years, but not at the pre- or one-year follow-up. This is, as mentioned, described in the text under table 2, as well as in the method section (statistical analysis) on lines 179-182.

Discussion

- Lines 307-309: Are the results similar in other contexts (eg in the studies cited in the introduction)?

Response: Thank you for the comment! However, we are not sure what you mean. There have not been many previous studies investigating dissonance-based interventions on physical activity (the ones we know of is what we have cited and includes female college students) and it has never, to our best knowledge, been conducted on bariatric surgery patients. We have stated this in the manuscript (on lines 37-38, 79-80, 343-345 and 411-412) and therefore we cannot conclude whether or not the results are similar in other contexts.

Reviewer #2:

Thank you for the opportunity to review the manuscript entitled ‘Physical activity in women attending a dissonance-based intervention after Roux-en-Y- Gastric Bypass: A 2-year follow-up of a randomized controlled trial’. This is an interesting paper looking at objectively measured physical activity in a sample of women whom have undergone RYGB, this is a large sample given the population and topic area (physical activity) that the authors are researching in. It is also an area of research which is in its infancy and a useful addition to the literature.

Please see my comments in the document attached.

General comments

Overall a good well written manuscript, I have the following questions I would like you to consider;

1. You have undertaken a dissonance-based intervention comprising four sessions that focus on different topic areas. One of these focus on physical activity, nowhere in this manuscript can I see how many of the individuals analysed attended this physical activity session. Surely it is important to know how many attended the physical activity session; you wouldn’t typically expect physical activity to increase when compared to normal care if they have not been given an additional physical activity intervention. Did you look at data from those who attended the physical activity session?

Response: Thank you for this excellent comment! Of course, you are right, it is of importance to look at how many of the patients attended the physical activity session. We have now done such an analysis, and 61.6% (n=61) of the participants in the intervention group attended the session about physical activity. However, it did not change any of the results. We did per protocol analysis and included a few sentences about this in the manuscript:

In the section Methods – Statistical analysis (lines 196-198): “Per protocol analysis was also performed to compare the participants in the intervention group who had participated in the session about physical activity, to the participants who had not participated in that session.”

In the section Results – descriptive statistics (lines 215-216): “Of the participants in the intervention group, 61.6% (n=61) had attended the session where physical activity had been discussed.”

In the section Results – Per protocol analysis (lines 269-273): “Per protocol analysis of the participants attending the session about physical activity (n=61) versus participants in the intervention group who did not attend that session (n=38), showed no significant differences of clinical importance in any of the physical activity outcomes that changed any of the results. There were also no differences in any of the pre-RYGB characteristics between these two groups.”

2. All tables were cut off so I was unable to read half of the table.

Response: Thank you for letting us know! We have now adjusted this, so the pages where the tables are, are now set into “landscape” in order for the whole tables to be seen.

Specific comments

Page 1 line 58 – instead of ‘inconclusive’ should this be ‘limited’

Response: Thank you for the comment! We have now changed the sentence according to your suggestion (line 58): “However, data remains limited on this issue.”

Page 2 line 74 – remove for example

Response: Thank you for this comment! We have now removed the words and the sentence is now (Lines 73-75): “Dissonance-based interventions have shown effects in behavioral change; for healthy physical activity behaviors [19], smoking cessation….”

Page 2 line 77 – instead of ‘Also’ should this be ‘However’

Response: Thank you for the comment! We have now changed the sentence according to your suggestion (line 77): “However, the effect of an already existing program….”

Page 2 line 81 – change ‘surgeries’ to ‘surgery procedures’

Response: Thank you for the comment! We have now changed the sentence according to your suggestion (line 81): “In Sweden, hospitals performing bariatric surgery procedures have standard…”

Page 2 lines 87-90 – instead of ‘with the aim to’ potentially change to ‘aiming to’, this is a long sentence.

Response: Thank you for the comment! We have now changed the sentence according to your suggestion (line 89): “…a dissonance-based group intervention program targeting RYGB-treated women, aiming to prevent a decline in…”

Page 5 line 98-99 – this sentence needs to be slightly reworded or add how after ‘analyse’

Response: Thank you for the comment! We have now changed the sentence according to your suggestion (line 104): “In this paper we analyzed how the intervention affected….”

Page 5 line 109 – Was wearing the accelerometer optional? ‘ were offered to wear’ makes it sound optional

Response: Thank you for the comment! It was optional to wear the accelerometer, as the questionnaires measuring HRQoL (among others) were the main thing for this intervention (questionnaires are not included in this study. We have now added a sentence about this in the section Method – Recruitment and participants (lines 117-118): “To wear the accelerometer was optional for the participants.”

Page 6 line 117 Re-wording suggestion ‘ participants who had provided informed consent and baseline data…’

Response: Thank you for letting us improve the wording! We have now changed the sentence according to your suggestion, as well as clarified the pre-RYGB data (lines 126-127):

“Approximately two months post-RYGB, participants who had provided informed consent and pre-RYGB data (questionnaires about HRQoL, among others (not included in this study)) were…”

Page 6 line 127 Trained facilitators – include what the training comprised of and in what ‘teaching’ style was the programme delivered?

Response: Thank you for the opportunity to clarify this! We have now added a paragraph in that sentence to describe what the training contained (line 138):

“…led by a facilitator who had been trained in dissonance-based theory (individual readings on the topic together with informational meetings with a psychologist) and followed an intervention manual.”

Page 6 line 135-136 – the participant was considered as having received the intervention if they attended three sessions was it any three sessions? If so state this.

Response: Thank you for letting us clarify this! Yes, it was at least three of any of the four sessions. We have now clarified this in that sentence (line 147): “If a participant had attended at least three out of any of the four sessions…”

Page 6 line 139-140 – I think it would be useful to mention the topics covered in the physical activity session.

Response: Thank you for your valuable input! We have now included a sentence about what were discussed during the physical activity session in the section Methods – intervention (lines 152-155): “During the session on physical activity, discussions were focused on what sedentary behavior and physical activity is, how one can increase their daily physical activity, difficulties and barriers of physical activity after bariatric surgery and how to overcome these barriers.”

Page 6 line 139-140 - Did you refine the programme based on the pilot feedback – this may also be worth mentioning

Response: Thank you for letting us clarify this! Yes, we did some minor changes after the feed-back from the pilot study. We have now included a sentence about this in the section Method – Intervention (line 151): “Minor changes were done to the manuscript after the feed-back.”

Page 7 line 144 – was the accelerometer worn on the dominant or non-dominant wrist? This should be reported.

Response: Thank you for this input in clarifying the manuscript! The accelerometer was worn on the right hip, and we have now added this information to the sentence you are referring to, in section Method – Outcomes (line 158): “…were asked to wear the ActiGraph GT3X+ accelerometer on the right hip during all waking hours…”

Page 7 line 146 – why the 10 hour threshold? Is there a reference for this?

Response: When having the criteria for using the accelerometer during all waking hours, a threshold of at least 10 hours is common, as it is a majority of the hours of the day spent awake. There is already a reference on this in the section Discussion – Strengths and limitations (lines 367-369): “Inclusion criterion for valid wear time was set to at least three days with a minimum of 10-hour wear time per day, as three to four wear time days has shown to be sufficient for achieving 80% reliability of MVPA [43].”

Page 9 table half missing and the variables in the table are not clear if they are baseline or 2 years post.

Response: Thank you for the comment! The pages where the tables are, are now set into “landscape”, in order for the whole tables to be seen. As stated in the heading of the table 1, it is pre-RYGB measures that are stated in the table. To clarify, we have now added more information in the table to make it clearer that it is pre-RYGB measures (if not stated otherwise) in Table 1 (page 11, lines 231-232).

Page 10 line 225 – what do you mean by non bouts? 1 minute bouts?

Response: Thank you for letting us clarify this! In the manuscript we use both 10-min bouts and non-bouts, where non-bouts mean just like it sounds: the MVPA have been measured as it is and do not have any requirement that the MVPA should have been going on for any set amount of time to be counted as MVPA, where 10-min bouts mean the participants had to be active for at least 10-min in MVPA-level to be counted in that outcome. We therefore write “non-bouts” in the manuscript to distinguish which outcome we are referring to, in order to not make any confusing. Therefore, non-bouts mean that there are no bouts whatsoever in that outcome, but that all time spent in MVPA have been accounted for.

Page 10-11 Table 2 format

Response: Thank you for letting us know about the tables! As mentioned above, we have now set the pages where the tables are into “landscape”, hopefully you will be able to see the tables now.

Page 11 line 232 – the sentence starts with presented – what is this sentence referring to?

Response: Thank you for letting us clarify this section! The sentence belongs to the description of Table 2 (the text under the table). To make it clearer, we have now moved up that sentence to the line above, so it is clearer that it is a part of the Table 2 (line 253).

Page 11 line 244 – a sedentary time difference between groups of 64 minutes per day seems large, you have stated that it is not relevant from a clinical perspective… if this is correct you need to reference this. This is implying that the individuals are more sedentary as a result of attending the programme, is this correct?

Response: Thank you for the comment! What we meant was that this difference between the groups was also significant at pre-RYGB, and therefore may not be relevant or something to put too much emphasis on. We also already have stated in the section Discussion – Limitations (lines 392-394): “Second, smaller sample sizes were used when conducting per protocol and sensitivity analyses. Consequently, the power might be too small to detect between-group differences.”

But, to clarify this in the manuscript, we have added to section Results – Per protocol analysis that the significant difference was there also at pre-RYGB, and we added that it may not be relevant from a clinical perspective (lines 264-268): “Those who received the intervention were more sedentary (522.5 min/day, SE=17.2) than the control group (458.8 min/day, SE=12.3) (p=0.002, d=-0.58) at two-years post-RYGB (Table 2 in S2 Appendix). However, this difference was also significantly different at pre-RYGB (p=0.039), and therefore this difference may not be relevant from a clinical perspective.”

Page 13 discussion – I think the difference in sedentary time (increase in intervention group) should be mentioned in the results and justified.

Response: Thank you for the comment! Do you refer to the section of main results (lines 309-310)? In that case, unfortunately, we do not agree with you. The main results are the Intention-to-treat analysis, Table 2 (as those analysis have enough power, which the per protocol analysis do not have due to small sample sizes, which, as already mentioned above, are stated in the Discussion-section (lines 392-394)), and this study focuses on the differences between the groups at the two-years follow-up (as we want to see if our intervention had have any effect), and not the longitudinal differences from the time-points. There is no statistically significant difference between the groups in sedentary time at the two-year follow-up in the ITT-analysis in Table 2. And if you are referring to the difference in the intervention group from pre-RYGB to two-years post-RYGB in Table 2 (the ITT-analysis), it is only a difference if 16 min.

Page 13 line 286 – when referring to the other research, it would be useful to know when these studies were undertaken post-surgery was it 2 years or 6 months etc?

Response: Thank you for your valuable input! We have now included in that sentence the time of the start and the length of the interventions right after the sentence you are referring to in section Discussion – Previous research (lines 315-317): “The interventions included in that review started pre-surgery or between three to 102 months post-surgery and the lengths of the interventions were between six and 12 weeks long [15].”

Page 13 line 294 – physical activity increased by how much?

Response: Thank you for this input! We have now added that information in a paragraph right after the end of that sentence you are referring to (lines 326-327): “…(counselling and pedometers = 6 787 steps/day, pedometers only = 5 325 steps/day and standard care = 5253 steps/day) [34].”

Page 14 line 314 – attendance at at least one session, was this one session the physical activity session or not? If not why not? If not how many of those included attended that session?

If they did not attend the physical activity session this is likely why you didn’t see a change and previous research in this population reports exercise education alone is insufficient for increasing physical activity.

Response: Thank you for this comment! This comment is in line with a previous comment from you above, about how many attended the session about physical activity. When “at least one session” is mentioned in the manuscript, it is at least one of any of the four sessions in the intervention. We have added, after input from you in the comment above, information and per protocol analysis on how many participants attended the session about physical activity and the results from the per protocol analysis. We therefore refer to our answer on that question above where we have stated all the changes we made to the manuscript according to your comment. We have now, after this comment, also clarified that we mean at least any of the four sessions (line 347): “… 73% attended at least one session (any of the four sessions)…”

The same addition (any of the four sessions) have been added in the section Results – Descriptive analysis (line 225): “…had attended at least one group session (any of the four sessions),…”.

Limitation – may not have attended the physical activity session

Response: Thank you for this valuable input! You are right, we have not mentioned that as a limitation. We have now added that to the section Discussion – Limitations (lines 402-404): “Fifth, only 61.6% of the participants in the intervention group attended the session about physical activity, which might have had impact on the results.”

You have mentioned you were likely not powered, have you looked at your data to see how many individuals you would have needed to be powered?

Response: Thank you for this comment! However, no we have not looked at that data, as we calculated the power of the intervention according to HRQoL (which is part of another yet not published article) as the initial aim of this intervention was to try to maintain/prevent the decline in HRQoL post-surgery.

Fig 1 – include amount of individuals who attended the physical activity session

Response: Thank you for this input! We have now included this information in the figure caption of Figure 1 (lines 120-122): “Of the included participants in the two-year follow-up belonging to the intervention group, 61 of them (61.6%) had attended the session about physical activity.”

Reviewer #3:

Two-year follow-up results on patients activity levels were summarized from a two-arm randomized controlled clinical trial which aimed to increase quality of life following Roux-en-Y gastric bypass surgery through dissonance-based group intervention. At two-years follow-up, no significant differences in physical activity levels were observed between the intervention and control arms.

Minor revisions:

1- Cohen’s d is valid when the distribution of the data is normal. Indicate if the normality assumption was met.

Response: Thank you for these comments! As these two comments are related, we will answer them together. We have now added a paragraph in the section Method – Statistical analysis on information about normality assumptions and why we chose to use Kruskal-Wallis H test and Cohen’s D (lines 185-189): “Normal distribution was evaluated graphically and tested with Shapiro-Wilk test. The variables were approximately normally distributed, however not perfectly. We therefore present the results as means and use Cohen’s d to quantify intervention effect sizes [31], but because of the lack of complete normality, we also used Kruskal-Wallis H test to test for differences in medians between the groups.”

We also added information under Table 2 (lines 254-256): “…p-value for the difference in medians between the two groups (Kruskal-Wallis H test) at pre-RYGB, one- and two-years post-RYGB surgery. Effect sizes at two years measured with Cohen’s d (95 % CI). *Normal distribution assumption rejected according to Shapiro-Wilk test (p<0.05).”

3- Line 173 states, “Chi-square test was used for dichotomous variables.” Provide further clarity by indicating the comparisons which are being tested by the chi-square test.

Response: Thank you for the opportunity to clarify this! Variables that were dichotomous were for example “smokers or not”, “university level or not” and “meeting physical activity recommendations or not”. We have now included thin in the section Method – Statistical analysis (lines 191-192): “Chi-square test was used for dichotomous variables, for example if a participant smoked or not, had university level of education or not, and meeting the physical activity recommendations or not.”

Response: Thank you for letting us clarify this sentence! We have now changed it according to your suggestion (line 198-201): “Sensitivity analysis was conducted for the participants with valid accelerometer measurements from all three time points, conducted with a regression analysis adjusted for pre-RYGB measures and presented as differences of the means between the groups at one- and two-years follow-up.”

5- Line 180: Again replace “calculated” with “conducted.”

Response: Thank you for letting us improve the sentence! We have now changed it according to your suggestion (line 202): “Additionally, a sensitivity analysis was conducted for all participants who had ≥5 valid days…”

6- Table 2: Clarify the statistical methods used to calculate the p-values in Table 2.

Response: Thank you for the comment! We have now clarified this under Table 2 and added how we calculated the p-value (line 254): “p-value for the difference in medians between the two groups (Kruskal-Wallis H test) at pre-RYGB, one- and two-years post-RYGB surgery.”

We have also added the same information under S2 Appendix and S3 Appendix.

7- Line 232: Replace “numbers” with “frequency” to improve clarity.

Response: Thank you for the comment! We have now changed the sentence according to your suggestion in the text under Table 2 (line 254): “…or frequency (percent) for each subscale…”

We have also added that same information under S2 Appendix and S3 Appendix.

8- Clarify if SE represents standard error or standard error of the mean.

Response: Thank you for the comment! We do mean Standard Error of the mean.

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PLoS One. doi: 10.1371/journal.pone.0255556.r003

Decision Letter 1

Dario Ummarino

17 Aug 2020

PONE-D-20-01663R1

Physical activity in women attending a dissonance-based intervention after Roux-en-Y Gastric Bypass: A 2-year follow-up of a randomized controlled trial

PLOS ONE

Dear Dr. Berglind,

As you can see from the comments included at the end of this letter, I am pleased to say that the reviewers are satisfied that the previously raised concerns have been adequately addressed. There is just one minor point from reviewer 3 regarding the statistical test used.

In addition, in order to fully comply with our editorial requirements for clinical trial submissions, please upload the full clinical trial protocol in the original language that was submitted to your local ethics committee.

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We look forward to receiving your revised manuscript.

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Dario Ummarino, Ph.D.

Associate Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #3: (No Response)

Reviewer #4: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Partly

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #1: Yes

Reviewer #3: No

Reviewer #4: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #1: Yes

Reviewer #3: Yes

Reviewer #4: Yes

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6. Review Comments to the Author

Reviewer #1: (No Response)

Reviewer #3: Technically, the Kruskal-Wallis test compares ranks rather than medians.

Reviewer #4: The authors should be commended for their thorough responses to detailed critiques, in particular the explicit stating of the study limitations.

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Reviewer #1: No

Reviewer #3: No

Reviewer #4: No

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2021 Nov 4;16(11):e0255556. doi: 10.1371/journal.pone.0255556.r004

Author response to Decision Letter 1

10 Sep 2020

PLOS ONE

Manuscript number PONE-D-20-01663